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Sample records for solar white-light flares

  1. CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Kuhar, Matej; Krucker, Säm; Battaglia, Marina; Kleint, Lucia; Casadei, Diego [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland); Oliveros, Juan Carlos Martinez; Hudson, Hugh S. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

    2016-01-01

    A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and Helioseismic and Magnetic Imager. We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 Å summed over the hard X-ray flare ribbons with an integration time of 45 s around the peak hard-X ray time. We find a good correlation between hard X-ray fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ∼50 keV. At higher electron energies the correlation decreases gradually while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy ∼50 keV are the main source for white light production.

  2. Solar flare impulsivity and its relationship with white-light flares and with CMEs

    Science.gov (United States)

    Watanabe, K.; Masuda, S.

    2017-12-01

    There are many types of classification in solar flares. One of them is a classification by flare duration in soft X-rays; so-called impulsive flare and long duration event (LDE). Typically, the duration of an impulsive flare is shorter than 1 hour, and that of an LDE is longer than 1 hour. These two types of flare show different characteristics. In soft X-rays, impulsive flares usually have a compact loop structure. On the other hand, LDEs show a large-scale loop, sometimes a large arcade structure. In hard X-rays (HXRs), the difference appears clear, too. The former shows a strong and short-time (10 minutes) emissions and show a large coronal source. These facts suggest that HXR observation becomes one of a good indicator to classify solar flares, especially for the study on the particle acceleration and the related phenomena. However, HXR data do not always exist due to the satellite orbit and the small sensitivity of HXR instruments. So, in this study, based on the concept of the Neupert effect (Neupert, 1968), we use soft X-ray derivative data as the proxy of HXR. From this data, we define impulsivity (IP) for each flare. Then we investigate solar flares using this new index. First we apply IP index to white-light flare (WLF) research. We investigate how WL enhancement depends on IP, then it is found that WLF tend to have large IP values. So the flare impulsivity (IP) is one of the important factors if WL enhancement appears or not in a solar flare. Next we investigate how CME itself and/or its physical parameters depend on IP index. It has been believed that most of CMEs are associated with LDEs, but we found that there is only a weak correlation between the existence of CME and IP index. Finally, we also search for the relationship between WLF and CME as a function of IP and discuss the physical condition of WLF.

  3. Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars

    Science.gov (United States)

    Namekata, Kosuke; Sakaue, Takahito; Watanabe, Kyoko; Asai, Ayumi; Maehara, Hiroyuki; Notsu, Yuta; Notsu, Shota; Honda, Satoshi; Ishii, Takako T.; Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari

    2017-12-01

    Recently, many superflares on solar-type stars have been discovered as white-light flares (WLFs). The statistical study found a correlation between their energies (E) and durations (τ): τ \\propto {E}0.39, similar to those of solar hard/soft X-ray flares, τ \\propto {E}0.2{--0.33}. This indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. We here carried out statistical research on 50 solar WLFs observed with Solar Dynamics Observatory/HMI and examined the correlation between the energies and durations. As a result, the E–τ relation on solar WLFs (τ \\propto {E}0.38) is quite similar to that on stellar superflares (τ \\propto {E}0.39). However, the durations of stellar superflares are one order of magnitude shorter than those expected from solar WLFs. We present the following two interpretations for the discrepancy: (1) in solar flares, the cooling timescale of WLFs may be longer than the reconnection one, and the decay time of solar WLFs can be elongated by the cooling effect; (2) the distribution can be understood by applying a scaling law (τ \\propto {E}1/3{B}-5/3) derived from the magnetic reconnection theory. In the latter case, the observed superflares are expected to have 2–4 times stronger magnetic field strength than solar flares.

  4. Suppression of Hydrogen Emission in an X-class White-light Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Procházka, Ondrej; Milligan, Ryan O.; Mathioudakis, Mihalis [Astrophysics Research Centre, Queen’s University Belfast, Northern Ireland (United Kingdom); Allred, Joel C. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Kowalski, Adam F. [Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, 2000 Colorado Avenue, Boulder, CO 80305 (United States); Kotrč, Pavel, E-mail: oprochazka01@qub.ac.uk [Astronomical Institute, The Czech Academy of Sciences, 25165 Ondřejov (Czech Republic)

    2017-03-01

    We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at the Ondřejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. Reuven Ramaty High-Energy Solar Spectroscopic Imager and Fermi observations indicate an extremely hard X-ray spectrum and γ -ray emission. We use the RADYN radiative hydrodynamic code to perform two types of simulations: one where an energy of 3 × 10{sup 11} erg cm{sup −2} s{sup −1} is deposited by an electron beam with a spectral index of ≈3, and a second where the same energy is applied directly to the photosphere. The combination of observations and simulations allows us to conclude that the white-light emission and the suppression or complete lack of hydrogen emission lines is best explained by a model where the dominant energy deposition layer is located in the lower layers of the solar atmosphere, rather than the chromosphere.

  5. EMISSION HEIGHT AND TEMPERATURE DISTRIBUTION OF WHITE-LIGHT EMISSION OBSERVED BY HINODE/SOT FROM THE 2012 JANUARY 27 X-CLASS SOLAR FLARE

    International Nuclear Information System (INIS)

    Watanabe, Kyoko; Shimizu, Toshifumi; Masuda, Satoshi; Ichimoto, Kiyoshi; Ohno, Masanori

    2013-01-01

    White-light emissions were observed from an X1.7 class solar flare on 2012 January 27, using three continuum bands (red, green, and blue) of the Solar Optical Telescope on board the Hinode satellite. This event occurred near the solar limb, and so differences in the locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penetrated down to near the photosphere, and deposited heat into the ambient lower layers of the atmosphere

  6. Lower atmosphere of solar flares; Proceedings of the Solar Maximum Mission Symposium, Sunspot, NM, Aug. 20-24, 1985

    International Nuclear Information System (INIS)

    Neidig, D.F.

    1986-01-01

    The topics discussed by the present conference encompass the chromospheric flare phenomenon, white light flares, UV emission and the flare transition region, the flare corona and high energy emissions, stellar flares, and flare energy release and transport. Attention is given to radiative shocks and condensation in flares, impulsive brightening of H-alpha flare points, the structure and response of the chromosphere to radiation backwarming during solar flares, the interpretation of continuum emissions in white light flares, and the radiation properties of solar plasmas. Also discussed are EUV images of a solar flare and C III intensity, an active region survey in H-alpha and X-rays, dynamic thermal plasma conditions in large flares, the evolution of the flare mechanism in dwarf stars, the evidence concerning electron beams in solar flares, the energetics of the nonlinear tearing mode, macroscopic electric fields during two-ribbon flares, and the low temperature signatures of energetic particles

  7. A TWO-RIBBON WHITE-LIGHT FLARE ASSOCIATED WITH A FAILED SOLAR ERUPTION OBSERVED BY ONSET, SDO, AND IRIS

    International Nuclear Information System (INIS)

    Cheng, X.; Hao, Q.; Ding, M. D.; Chen, P. F.; Fang, C.; Liu, K.; Liu, Y. D.

    2015-01-01

    Two-ribbon brightenings are one of the most remarkable characteristics of an eruptive solar flare and are often used to predict the occurrence of coronal mass ejections (CMEs). Nevertheless, it was recently called into question whether all two-ribbon flares are eruptive. In this paper, we investigate a two-ribbon-like white-light (WL) flare that is associated with a failed magnetic flux rope (MFR) eruption on 2015 January 13, which has no accompanying CME in the WL coronagraph. Observations by the Optical and Near-infrared Solar Eruption Tracer and the Solar Dynamics Observatory reveal that with the increase of the flare emission and the acceleration of the unsuccessfully erupting MFR, two isolated kernels appear at the WL 3600 Å passband and quickly develop into two elongated ribbon-like structures. The evolution of the WL continuum enhancement is completely coincident in time with the variation of Fermi hard X-ray 26–50 keV flux. An increase of continuum emission is also clearly visible at the whole FUV and NUV passbands observed by the Interface Region Imaging Spectrograph. Moreover, in one WL kernel, the Si iv, C ii, and Mg ii h/k lines display significant enhancement and non-thermal broadening. However, their Doppler velocity pattern is location-dependent. At the strongly bright pixels, these lines exhibit a blueshift, while at moderately bright ones, the lines are generally redshifted. These results show that the failed MFR eruption is also able to produce a two-ribbon flare and high-energy electrons that heat the lower atmosphere, causing the enhancement of the WL and FUV/NUV continuum emissions and chromospheric evaporation

  8. KEPLER FLARES. II. THE TEMPORAL MORPHOLOGY OF WHITE-LIGHT FLARES ON GJ 1243

    Energy Technology Data Exchange (ETDEWEB)

    Davenport, James R. A.; Hawley, Suzanne L.; Johnson, Emily C.; Peraza, Jesus; Jansen, Tiffany C.; Larsen, Daniel M. [Department of Astronomy, University of Washington, P.O. Box 351580, Seattle, WA 98195 (United States); Hebb, Leslie [Department of Physics, Hobart and William Smith Colleges, 300 Pulteney Street, Geneva, NY 14456 (United States); Wisniewski, John P.; Malatesta, Michael; Keil, Marcus; Silverberg, Steven M.; Scheffler, Matthew S.; Berdis, Jodi R. [HL Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks Street, Norman, OK 73019 (United States); Kowalski, Adam F. [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Hilton, Eric J., E-mail: jrad@astro.washington.edu [Universe Sandbox, 911 E. Pike Street #333, Seattle, WA 98122 (United States)

    2014-12-20

    We present the largest sample of flares ever compiled for a single M dwarf, the active M4 star GJ 1243. Over 6100 individual flare events, with energies ranging from 10{sup 29} to 10{sup 33} erg, are found in 11 months of 1 minute cadence data from Kepler. This sample is unique for its completeness and dynamic range. We have developed automated tools for finding flares in short-cadence Kepler light curves, and performed extensive validation and classification of the sample by eye. From this pristine sample of flares we generate a median flare template. This template shows that two exponential cooling phases are present during the white-light flare decay, providing fundamental constraints for models of flare physics. The template is also used as a basis function to decompose complex multi-peaked flares, allowing us to study the energy distribution of these events. Only a small number of flare events are not well fit by our template. We find that complex, multi-peaked flares occur in over 80% of flares with a duration of 50 minutes or greater. The underlying distribution of flare durations for events 10 minutes and longer appears to follow a broken power law. Our results support the idea that sympathetic flaring may be responsible for some complex flare events.

  9. KEPLER FLARES. II. THE TEMPORAL MORPHOLOGY OF WHITE-LIGHT FLARES ON GJ 1243

    International Nuclear Information System (INIS)

    Davenport, James R. A.; Hawley, Suzanne L.; Johnson, Emily C.; Peraza, Jesus; Jansen, Tiffany C.; Larsen, Daniel M.; Hebb, Leslie; Wisniewski, John P.; Malatesta, Michael; Keil, Marcus; Silverberg, Steven M.; Scheffler, Matthew S.; Berdis, Jodi R.; Kowalski, Adam F.; Hilton, Eric J.

    2014-01-01

    We present the largest sample of flares ever compiled for a single M dwarf, the active M4 star GJ 1243. Over 6100 individual flare events, with energies ranging from 10 29 to 10 33 erg, are found in 11 months of 1 minute cadence data from Kepler. This sample is unique for its completeness and dynamic range. We have developed automated tools for finding flares in short-cadence Kepler light curves, and performed extensive validation and classification of the sample by eye. From this pristine sample of flares we generate a median flare template. This template shows that two exponential cooling phases are present during the white-light flare decay, providing fundamental constraints for models of flare physics. The template is also used as a basis function to decompose complex multi-peaked flares, allowing us to study the energy distribution of these events. Only a small number of flare events are not well fit by our template. We find that complex, multi-peaked flares occur in over 80% of flares with a duration of 50 minutes or greater. The underlying distribution of flare durations for events 10 minutes and longer appears to follow a broken power law. Our results support the idea that sympathetic flaring may be responsible for some complex flare events

  10. Solar flare effects on the zodiacal light

    International Nuclear Information System (INIS)

    Misconi, N.Y.

    1975-01-01

    An observational and theoretical study was carried out of possible solar flare effects on the zodiacal light. A total of 38 nights (February, March and April 1966, March 1967, and March 1968) of ground based observations, which were taken from Mt. Haleakala, Hawaii by Weinberg, were searched for solar flare effects. No changes were found in the shape of the main cone of the zodiacal light at elongations greater than 23 degrees from the sun to a limit of approximately 20 S 10 (V) units, and none were found in the level of brightness from night to night to a limit of approximately 100 S 10 (V) units. The earlier reported enhancement in the zodiacal light due to a large solar flare by Blackwell and Ingham (1961) is considered doubtful for two reasons: probable contamination of their observations by enhanced atmospheric emission, and detailed geometry of that event shows that it is unlikely that the plasma/dust interaction could have caused a 40 percent enhancement in the zodiacal light. Whether or not the plasma/dust interaction can be effective in causing a brightness change, a knowledge of the brightness contribution along the lines of sight and as a function of heliocentric distance is needed. For this purpose models of dielectric and metallic particles with spatial distribution of the form r/sup -ν/, ν = 0,1,2, and size distribution of the form a/sup -p/, p = 2.5,4, were computed using the Mie scattering theory. Dynamical processes affecting the dust particle's heliocentric orbit were considered in relation to brightness changes

  11. Observations of white-light flares in NOAA active region 11515: high occurrence rate and relationship with magnetic transients

    Science.gov (United States)

    Song, Y. L.; Tian, H.; Zhang, M.; Ding, M. D.

    2018-06-01

    Aims: There are two goals in this study. One is to investigate how frequently white-light flares (WLFs) occur in a flare-productive active region (NOAA active region 11515). The other is to investigate the relationship between WLFs and magnetic transients (MTs). Methods: We used the high-cadence (45 s) full-disk continuum filtergrams and line-of-sight magnetograms taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to identify WLFs and MTs, respectively. Images taken by the Atmospheric Imaging Assembly (AIA) on board SDO were also used to show the flare morphology in the upper atmosphere. Results: We found at least 20 WLFs out of a total of 70 flares above C class (28.6%) in NOAA active region 11515 during its passage across the solar disk (E45°-W45°). Each of these WLFs occurred in a small region, with a short duration of about 5 min. The enhancement of the white-light continuum intensity is usually small, with an average enhancement of 8.1%. The 20 WLFs we observed were found along an unusual configuration of the magnetic field that was characterized by a narrow ribbon of negative field. Furthermore, the WLFs were found to be accompanied by MTs, with radical changes in magnetic field strength (or even a sign reversal) observed during the flare. In contrast, there is no obvious signature of MTs in the 50 flares without white-light enhancements. Conclusions: Our results suggest that WLFs occur much more frequently than previously thought, with most WLFs being fairly weak enhancements. This may explain why WLFs are reported rarely. Our observations also suggest that MTs and WLFs are closely related and appear cospatial and cotemporal, when considering HMI data. A greater enhancement of WL emission is often accompanied by a greater change in the line-of-sight component of the unsigned magnetic field. Considering the close relationship between MTs and WLFs, many previously reported flares with MTs may be WLFs. The movie

  12. Solar flares as harbinger of new physics

    CERN Document Server

    Zioutas, K; Semertzidis, Y.; Papaevangelou, T.; Georgiopoulou, E.; Gardikiotis, A.; Dafni, T.; Tsagri, M.; Semertzidis, Y.; Papaevangelou, T.; Dafni, T.

    2011-01-01

    This work provides additional evidence on the involvement of exotic particles like axions and/or other WISPs, following recent measurements during the quietest Sun and flaring Sun. Thus, SPHINX mission observed a minimum basal soft X-rays emission in the extreme solar minimum in 2009. The same scenario (with ~17 meV axions) fits also the dynamical behaviour of white-light solar flares, like the measured spectral components in the visible and in soft X-rays, and, the timing between them. Solar chameleons remain a viable candidate, since they may preferentially convert to photons in outer space.

  13. Impulsive phase of solar flares: theory

    International Nuclear Information System (INIS)

    Mackinnon, A.L.

    1986-01-01

    The paper reviews the theoretical interpretation of impulsive phase phenomena in solar flares. The impulsive phase is defined to be that period of approx. 10 - 100s duration, during which the flare radiative output undergoes its most rapid, dramatic increase and decrease. The interpretation of the various impulsive phase radiation signatures are examined, including the i) hard x-ray emission, ii) radio emission, iii) UV, Hα and white light emissions and iv) gamma-ray emission. The acceleration mechanisms are discussed with respect to candidate acceleration mechanisms, and the synthesis of the theory and observations. (UK)

  14. WHITE-LIGHT FLARES ON CLOSE BINARIES OBSERVED WITH KEPLER

    International Nuclear Information System (INIS)

    Gao, Qing; Xin, Yu; Liu, Ji-Feng; Zhang, Xiao-Bin; Gao, Shuang

    2016-01-01

    Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies (“detachedness”). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%–20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period ( P orb ) and rotation period ( P rot , calculated for only detached binaries). We find that the AL increases with decreasing P orb or P rot , up to the critical values at P orb ∼ 3 days or P rot ∼ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.

  15. THE HEIGHT OF A WHITE-LIGHT FLARE AND ITS HARD X-RAY SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Oliveros, Juan-Carlos; Hudson, Hugh S.; Hurford, Gordon J.; Krucker, Saem; Lin, R. P. [Space Sciences Laboratory, UC Berkeley, Berkeley, CA 94720 (United States); Lindsey, Charles [North West Research Associates, CORA Division, Boulder, CO (United States); Couvidat, Sebastien; Schou, Jesper [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA (United States); Thompson, W. T. [Adnet Systems, Inc., NASA Goddard Space Flight Center, code 671, Greenbelt, MD (United States)

    2012-07-10

    We describe observations of a white-light (WL) flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray (HXR) sources. For this purpose, we use HXR images from the Reuven Ramaty High Energy Spectroscopic Imager and optical images at 6173 A from the Solar Dynamics Observatory. We find that the centroids of the impulsive-phase emissions in WL and HXRs (30-80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0.''2. This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 Angstrom-Sign image from the Solar-Terrestrial RElations Observatory spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; {tau} = 1 at 5000 A) of 305 {+-} 170 km and 195 {+-} 70 km, respectively, for the centroids of the HXR and WL footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of {tau} = 1 for the 6173 Angstrom-Sign and the {approx}40 keV photons observed, respectively.

  16. The Height of a White-Light Flare and its Hard X-Ray Sources

    Science.gov (United States)

    Oliveros, Juan-Carlos Martinez; Hudson, Hugh S.; Hurford, Gordon J.; Kriucker, Saem; Lin, R. P.; Lindsey, Charles; Couvidat, Sebastien; Schou, Jesper; Thompson, W. T.

    2012-01-01

    We describe observations of a white-light (WL) flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray (HXR) sources. For this purpose, we use HXR images from the Reuven Ramaty High Energy Spectroscopic Imager and optical images at 6173 Ang. from the Solar Dynamics Observatory.We find that the centroids of the impulsive-phase emissions in WL and HXRs (30 -80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0".2. This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 Ang. image from the Solar-Terrestrial RElations Observatory spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; tau = 1 at 5000 Ang.) of 305 +/- 170 km and 195 +/- 70 km, respectively, for the centroids of the HXR and WL footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of tau = 1 for the 6173 Ang and the approx 40 keV photons observed, respectively.

  17. On the possibility of detecting solar flare effects in the zodiacal light

    International Nuclear Information System (INIS)

    Misconi, N.Y.; Hanner, M.S.

    1975-01-01

    To evaluate possible effects of solar flares on the brightness of the inner zodiacal light, it is necessary to consider the brightness contribution along the line of sight and as a function of Sun-particle distance. For this purpose, models of the brightness contribution along the line of sight are presented for both dielectric and metallic particles with a spatial distribution of the form rsup(-ν), ν=0, 1, 2. These models are discussed in terms of the geometry of shock front interaction. A reported zodiacal light enhancement following a solar flare (Blackwell and Ingham (Mon. Not. R. Astr. Soc.; 122:143 (1961)) is analysed on the basis of the shock front geometry. (auhtor)

  18. Flare Characteristics from X-ray Light Curves

    Science.gov (United States)

    Gryciuk, M.; Siarkowski, M.; Sylwester, J.; Gburek, S.; Podgorski, P.; Kepa, A.; Sylwester, B.; Mrozek, T.

    2017-06-01

    A new methodology is given to determine basic parameters of flares from their X-ray light curves. Algorithms are developed from the analysis of small X-ray flares occurring during the deep solar minimum of 2009, between Solar Cycles 23 and 24, observed by the Polish Solar Photometer in X-rays (SphinX) on the Complex Orbital Observations Near-Earth of Activity of the Sun-Photon (CORONAS- Photon) spacecraft. One is a semi-automatic flare detection procedure that gives start, peak, and end times for single ("elementary") flare events under the assumption that the light curve is a simple convolution of a Gaussian and exponential decay functions. More complex flares with multiple peaks can generally be described by a sum of such elementary flares. Flare time profiles in the two energy ranges of SphinX (1.16 - 1.51 keV, 1.51 - 15 keV) are used to derive temperature and emission measure as a function of time during each flare. The result is a comprehensive catalogue - the SphinX Flare Catalogue - which contains 1600 flares or flare-like events and is made available for general use. The methods described here can be applied to observations made by Geosynchronous Operational Environmental Satellites (GOES), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and other broad-band spectrometers.

  19. K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs

    Science.gov (United States)

    Gizis, John E.; Paudel, Rishi R.; Mullan, Dermott; Schmidt, Sarah J.; Burgasser, Adam J.; Williams, Peter K. G.

    2017-08-01

    We use Kepler K2 Campaign 4 short-cadence (one-minute) photometry to measure white light flares in the young, moving group brown dwarfs 2MASS J03350208+2342356 (2M0335+23) and 2MASS J03552337+1133437 (2M0355+11), and report on long-cadence (thirty-minute) photometry of a superflare in the Pleiades M8 brown dwarf CFHT-PL-17. The rotation period (5.24 hr) and projected rotational velocity (45 km s-1) confirm 2M0335+23 is inflated (R≥slant 0.20 {R}⊙ ) as predicted for a 0.06 {M}⊙ , 24 Myr old brown dwarf βPic moving group member. We detect 22 white light flares on 2M0335+23. The flare frequency distribution follows a power-law distribution with slope -α =-1.8+/- 0.2 over the range 1031 to 1033 erg. This slope is similar to that observed in the Sun and warmer flare stars, and is consistent with lower-energy flares in previous work on M6-M8 very-low-mass stars; taking the two data sets together, the flare frequency distribution for ultracool dwarfs is a power law over 4.3 orders of magnitude. The superflare (2.6× {10}34 erg) on CFHT-PL-17 shows higher-energy flares are possible. We detect no flares down to a limit of 2× {10}30 erg in the nearby L5γ AB Dor moving group brown dwarf 2M0355+11, consistent with the view that fast magnetic reconnection is suppressed in cool atmospheres. We discuss two multi-peaked flares observed in 2M0335+23, and argue that these complex flares can be understood as sympathetic flares, in which fast-mode magnetohydrodynamic waves similar to extreme-ultraviolet waves in the Sun trigger magnetic reconnection in different active regions.

  20. A SOLAR FLARE DISTURBING A LIGHT WALL ABOVE A SUNSPOT LIGHT BRIDGE

    International Nuclear Information System (INIS)

    Hou, Yijun; Zhang, Jun; Li, Ting; Yang, Shuhong; Li, Leping; Li, Xiaohong

    2016-01-01

    With the high-resolution data from the Interface Region Imaging Spectrograph , we detect a light wall above a sunspot light bridge in the NOAA active region (AR) 12403. In the 1330 Å slit-jaw images, the light wall is brighter than the ambient areas while the wall top and base are much brighter than the wall body, and it keeps oscillating above the light bridge. A C8.0 flare caused by a filament activation occurred in this AR with the peak at 02:52 UT on 2015 August 28, and the flare’s one ribbon overlapped the light bridge, which was the observational base of the light wall. Consequently, the oscillation of the light wall was evidently disturbed. The mean projective oscillation amplitude of the light wall increased from 0.5 to 1.6 Mm before the flare and decreased to 0.6 Mm after the flare. We suggest that the light wall shares a group of magnetic field lines with the flare loops, which undergo a magnetic reconnection process, and they constitute a coupled system. When the magnetic field lines are pushed upward at the pre-flare stage, the light wall turns to the vertical direction, resulting in the increase of the light wall’s projective oscillation amplitude. After the magnetic reconnection takes place, a group of new field lines with smaller scales are formed underneath the reconnection site, and the light wall inclines. Thus, the projective amplitude notably decrease at the post-flare stage.

  1. A SOLAR FLARE DISTURBING A LIGHT WALL ABOVE A SUNSPOT LIGHT BRIDGE

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Yijun; Zhang, Jun; Li, Ting; Yang, Shuhong; Li, Leping; Li, Xiaohong, E-mail: yijunhou@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2016-10-01

    With the high-resolution data from the Interface Region Imaging Spectrograph , we detect a light wall above a sunspot light bridge in the NOAA active region (AR) 12403. In the 1330 Å slit-jaw images, the light wall is brighter than the ambient areas while the wall top and base are much brighter than the wall body, and it keeps oscillating above the light bridge. A C8.0 flare caused by a filament activation occurred in this AR with the peak at 02:52 UT on 2015 August 28, and the flare’s one ribbon overlapped the light bridge, which was the observational base of the light wall. Consequently, the oscillation of the light wall was evidently disturbed. The mean projective oscillation amplitude of the light wall increased from 0.5 to 1.6 Mm before the flare and decreased to 0.6 Mm after the flare. We suggest that the light wall shares a group of magnetic field lines with the flare loops, which undergo a magnetic reconnection process, and they constitute a coupled system. When the magnetic field lines are pushed upward at the pre-flare stage, the light wall turns to the vertical direction, resulting in the increase of the light wall’s projective oscillation amplitude. After the magnetic reconnection takes place, a group of new field lines with smaller scales are formed underneath the reconnection site, and the light wall inclines. Thus, the projective amplitude notably decrease at the post-flare stage.

  2. Solar flares through electric current interaction

    International Nuclear Information System (INIS)

    De Jager, C.

    1988-01-01

    The fundamental hypothesis by Alfven and Carlqvist (1967) that solar flares are related to electrical currents in the solar chromosphere and low corona is investigated in the light of modern observations. The authors confirm the important role of currents in solar flares. There must be tens of such current loops (flux threads) in any flare, and this explains the hierarchy of bursts in flares. The authors summarize quantitative data on energies, numbers of particles involved and characteristic times. A special case is the high-energy flare: this one may originate in the same way as less energetic ones, but it occurs in regions with higher magnetic field strength. Because of the high particle energies involved their emission seats live only very briefly; hence the area of emission coincides virtually with the seat of the instability. These flares are therefore the best examples for studying the primary instability leading to the flare. Finally, the authors compare the merits of the original Alfven-Carlqvist idea (that flares originate by current interruption) with the one that they are due to interaction (reconnection) between two or more fluxthreads. The authors conclude that a final decision cannot yet by made, although the observed extremely short time constants of flare bursts seem to demand a reconnection-type instability rather than interruption of a circuit

  3. Global Energetics of Solar Flares. VI. Refined Energetics of Coronal Mass Ejections

    Science.gov (United States)

    Aschwanden, Markus J.

    2017-09-01

    In this study, we refine the coronal mass ejection (CME) model that was presented in an earlier study of the global energetics of solar flares and associated CMEs and apply it to all (860) GOES M- and X-class flare events observed during the first seven years (2010-2016) of the Solar Dynamics Observatory (SDO) mission. The model refinements include (1) the CME geometry in terms of a 3D volume undergoing self-similar adiabatic expansion, (2) the solar gravitational deceleration during the propagation of the CME, which discriminates between eruptive and confined CMEs, (3) a self-consistent relationship between the CME center-of-mass motion detected during EUV dimming and the leading-edge motion observed in white-light coronagraphs, (4) the equipartition of the CME’s kinetic and thermal energies, and (5) the Rosner-Tucker-Vaiana scaling law. The refined CME model is entirely based on EUV-dimming observations (using Atmospheric Imager Assembly (AIA)/SDO data) and complements the traditional white-light scattering model (using Large-Angle and Spectrometric Coronagraph Experiment (LASCO)/Solar and Heliospheric Observatory data), and both models are independently capable of determining fundamental CME parameters. Comparing the two methods, we find that (1) LASCO is less sensitive than AIA in detecting CMEs (in 24% of the cases), (2) CME masses below {m}{cme}≲ {10}14 g are underestimated by LASCO, (3) AIA and LASCO masses, speeds, and energies agree closely in the statistical mean after the elimination of outliers, and (4) the CME parameters speed v, emission measure-weighted flare peak temperature T e , and length scale L are consistent with the following scaling laws: v\\propto {T}e1/2, v\\propto {({m}{cme})}1/4, and {m}{cme}\\propto {L}2.

  4. Solar flares

    International Nuclear Information System (INIS)

    Kaastra, J.S.

    1985-01-01

    In this thesis an electrodynamic model for solar flares is developed. The main theoretical achievements underlying the present study are treated briefly and the observable flare parameters are described within the framework of the flare model of this thesis. The flare model predicts large induced electric fields. Therefore, acceleration processes of charged particles by direct electric fields are treated. The spectrum of the accelerated particles in strong electric fields is calculated, 3 with the electric field and the magnetic field perpendicular and in the vicinity of an X-type magnetic neutral line. An electromagnetic field configuration arises in the case of a solar flare. A rising current filament in a quiescent background bipolar magnetic field causes naturally an X-type magnetic field configuration below the filament with a strong induced electric field perpendicular to the ambient magnetic field. This field configuration drives particles and magnetic energy towards the neutral line, where a current sheet is generated. The global evolution of the fields in the flare is determined by force balance of the Lorentz forces on the filament and the force balance on the current sheet. The X-ray, optical and radio observations of a large solar flare on May 16, 1981 are analyzed. It is found that these data fit the model very well. (Auth.)

  5. Sun and solar flares

    Energy Technology Data Exchange (ETDEWEB)

    McKenna-Lawlor, S. (Saint Patrick' s Coll., Maynooth (Ireland))

    1982-07-01

    The subject is discussed under the headings: the sun's core (thermonuclear reactions, energy transfer from core through radiation zone, convection zone, photosphere, chromosphere and corona); the photosphere (convection, granulation, sunspots, magnetic fields, solar cycle, rotation of the sun); solar variability and paleoclimatic records (correlation of low solar activity with increased /sup 14/C production in atmosphere); the chromosphere and corona (turbulence, temperature, coronal streamers, energy transfer); solar flares (cosmic rays, aurorae, spectra, velocity of flares, prominences, mechanisms of flares); the solar wind.

  6. Solar Flares and Their Prediction

    Science.gov (United States)

    Adams, Mitzi L.

    1999-01-01

    Solar flares and coronal mass ejection's (CMES) can strongly affect the local environment at the Earth. A major challenge for solar physics is to understand the physical mechanisms responsible for the onset of solar flares. Flares, characterized by a sudden release of energy (approx. 10(exp 32) ergs for the largest events) within the solar atmosphere, result in the acceleration of electrons, protons, and heavier ions as well as the production of electromagnetic radiation from hard X-rays to km radio waves (wavelengths approx. = 10(exp -9) cm to 10(exp 6) cm). Observations suggest that solar flares and sunspots are strongly linked. For example, a study of data from 1956-1969, reveals that approx. 93 percent of major flares originate in active regions with spots. Furthermore, the global structure of the sunspot magnetic field can be correlated with flare activity. This talk will review what we know about flare causes and effects and will discuss techniques for quantifying parameters, which may lead to a prediction of solar flares.

  7. X-ray observations of solar flares with the Einstein Observatory

    International Nuclear Information System (INIS)

    Schmitt, J.H.M.M.; Fink, H.; Harnden, F.R. Jr.; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)

    1987-01-01

    The first Einstein Observatory Imaging Proportional Counter (IPC) observations of solar flares are presented. These flares were detected in scattered X-ray light when the X-ray telescope was pointed at the sunlit earth. The propagation and scattering of solar X-rays in the earth's atmosphere are discussed in order to be able to deduce the solar X-ray flux incident on top of the atmosphere from scattered X-ray intensity measurements. After this correction, the scattered X-ray data are interpreted as full-disk observations of the sun obtained with the same instrumentation used for observations of flares on other stars. Employing the same data analysis and interpretation techniques, extremely good agreement is found between the physical flare parameters deduced from IPC observations and known properties of compact loop flares. This agreement demonstrates that flare observations with the IPC can reveal physical parameters such as temperature and density quite accurately in the solar case and therefore suggests that the interpretations of stellar X-ray flare observations are on a physically sound basis. 26 references

  8. Global Energetics in Solar Flares and Coronal Mass Ejections

    Science.gov (United States)

    Aschwanden, Markus J.

    2017-08-01

    We present a statistical study of the energetics of coronal mass ejections (CME) and compare it with the magnetic, thermal, and nonthermal energy dissipated in flares. The physical parameters of CME speeds, mass, and kinetic energies are determined with two different independent methods, i.e., the traditional white-light scattering method using LASCO/SOHO data, and the EUV dimming method using AIA/SDO data. We analyze all 860 GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the SDO mission. The new ingredients of our CME modeling includes: (1) CME geometry in terms of a self-similar adiabatic expansion, (2) DEM analysis of CME mass over entire coronal temperature range, (3) deceleration of CME due to gravity force which controls the kinetic and potentail CME energy as a function of time, (4) the critical speed that controls eruptive and confined CMEs, (5) the relationship between the center-of-mass motion during EUV dimming and the leading edge motion observed in white-light coronagraphs. Novel results are: (1) Physical parameters obtained from both the EUV dimming and white-light method can be reconciled; (2) the equi-partition of CME kinetic and thermal flare energy; (3) the Rosner-Tucker-Vaiana scaling law. We find that the two methods in EUV and white-light wavelengths are highly complementary and yield more complete models than each method alone.

  9. Variation of the solar wind velocity following solar flares

    International Nuclear Information System (INIS)

    Huang, Y.; Lee, Y.

    1975-01-01

    By use of the superposed epoch method, changes in the solar wind velocity following solar flares have been investigated by using the solar wind velocity data obtained by Pioneer 6 and 7 and Vela 3, 4, and 5 satellites. A significant increase of the solar wind velocity has been found on the second day following importance 3 solar flares and on the third day following importance 2 solar flares. No significant increase of the solar wind velocity has been found for limb flares. (auth)

  10. Proton solar flares

    International Nuclear Information System (INIS)

    Shaposhnikova, E.F.

    1979-01-01

    The observations of proton solar flares have been carried out in 1950-1958 using the extrablackout coronograph of the Crimea astrophysical observatory. The experiments permit to determine two characteristic features of flares: the directed motion of plasma injection flux from the solar depths and the appearance of a shock wave moving from the place of the injection along the solar surface. The appearance of the shock wave is accompanied by some phenomena occuring both in the sunspot zone and out of it. The consistent flash of proton flares in the other groups of spots, the disappearance of fibres and the appearance of eruptive prominences is accomplished in the sunspot zone. Beyond the sunspot zone the flares occur above spots, the fibres disintegrate partially or completely and the eruptive prominences appear in the regions close to the pole

  11. Solar flares

    International Nuclear Information System (INIS)

    Zirin, H.

    1974-01-01

    A review of the knowledge about solar flares which has been obtained through observations from the earth and from space by various methods is presented. High-resolution cinematography is best carried out at H-alpha wavelengths to reveal the structure, time history, and location of flares. The classification flares in H alpha according to either physical or morphological criteria is discussed. The study of flare morphology, which shows where, when, and how flares occur, is important for evaluating theories of flares. Consideration is given to studies of flares by optical spectroscopy, radio emissions, and at X-ray and XUV wavelengths. Research has shown where and possibly why flares occur, but the physics of the instability involved, of the particle acceleration, and of the heating are still not understood. (IAA)

  12. CHROMOSPHERIC AND CORONAL OBSERVATIONS OF SOLAR FLARES WITH THE HELIOSEISMIC AND MAGNETIC IMAGER

    Energy Technology Data Exchange (ETDEWEB)

    Martínez Oliveros, Juan-Carlos; Krucker, Säm; Hudson, Hugh S.; Saint-Hilaire, Pascal; Bain, Hazel [Space Sciences Laboratory, UC Berkeley, Berkeley, CA 94720 (United States); Lindsey, Charles [North West Research Associates, CORA Division, Boulder, CO 80301 (United States); Bogart, Rick; Couvidat, Sebastien; Scherrer, Phil [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Schou, Jesper [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2014-01-10

    We report observations of white-light ejecta in the low corona, for two X-class flares on 2013 May 13, using data from the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory. At least two distinct kinds of sources appeared (chromospheric and coronal), in the early and later phases of flare development, in addition to the white-light footpoint sources commonly observed in the lower atmosphere. The gradual emissions have a clear identification with the classical loop-prominence system, but are brighter than expected and possibly seen here in the continuum rather than line emission. We find the HMI flux exceeds the radio/X-ray interpolation of the bremsstrahlung produced in the flare soft X-ray sources by at least one order of magnitude. This implies the participation of cooler sources that can produce free-bound continua and possibly line emission detectable by HMI. One of the early sources dynamically resembles {sup c}oronal rain{sup ,} appearing at a maximum apparent height and moving toward the photosphere at an apparent constant projected speed of 134 ± 8 km s{sup –1}. Not much literature exists on the detection of optical continuum sources above the limb of the Sun by non-coronagraphic instruments and these observations have potential implications for our basic understanding of flare development, since visible observations can in principle provide high spatial and temporal resolution.

  13. GLOBAL ENERGETICS OF SOLAR FLARES. IV. CORONAL MASS EJECTION ENERGETICS

    International Nuclear Information System (INIS)

    Aschwanden, Markus J.

    2016-01-01

    This study entails the fourth part of a global flare energetics project, in which the mass m cme , kinetic energy E kin , and the gravitational potential energy E grav of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The model derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r ≳ 2 R ⊙ , while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.

  14. THE THERMAL PROPERTIES OF SOLAR FLARES OVER THREE SOLAR CYCLES USING GOES X-RAY OBSERVATIONS

    International Nuclear Information System (INIS)

    Ryan, Daniel F.; Gallagher, Peter T.; Milligan, Ryan O.; Dennis, Brian R.; Kim Tolbert, A.; Schwartz, Richard A.; Alex Young, C.

    2012-01-01

    Solar flare X-ray emission results from rapidly increasing temperatures and emission measures in flaring active region loops. To date, observations from the X-Ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES) have been used to derive these properties, but have been limited by a number of factors, including the lack of a consistent background subtraction method capable of being automatically applied to large numbers of flares. In this paper, we describe an automated Temperature and Emission measure-Based Background Subtraction method (TEBBS), that builds on the methods of Bornmann. Our algorithm ensures that the derived temperature is always greater than the instrumental limit and the pre-flare background temperature, and that the temperature and emission measure are increasing during the flare rise phase. Additionally, TEBBS utilizes the improved estimates of GOES temperatures and emission measures from White et al. TEBBS was successfully applied to over 50,000 solar flares occurring over nearly three solar cycles (1980-2007), and used to create an extensive catalog of the solar flare thermal properties. We confirm that the peak emission measure and total radiative losses scale with background subtracted GOES X-ray flux as power laws, while the peak temperature scales logarithmically. As expected, the peak emission measure shows an increasing trend with peak temperature, although the total radiative losses do not. While these results are comparable to previous studies, we find that flares of a given GOES class have lower peak temperatures and higher peak emission measures than previously reported. The TEBBS database of flare thermal plasma properties is publicly available at http://www.SolarMonitor.org/TEBBS/.

  15. The sun and solar flares

    International Nuclear Information System (INIS)

    McKenna-Lawlor, S.

    1982-01-01

    The subject is discussed under the headings: the sun's core (thermonuclear reactions, energy transfer from core through radiation zone, convection zone, photosphere, chromosphere and corona); the photosphere (convection, granulation, sunspots, magnetic fields, solar cycle, rotation of the sun); solar variability and paleoclimatic records (correlation of low solar activity with increased 14 C production in atmosphere); the chromosphere and corona (turbulence, temperature, coronal streamers, energy transfer); solar flares (cosmic rays, aurorae, spectra, velocity of flares, prominences, mechanisms of flares); the solar wind. (U.K.)

  16. Quasi-periodic Pulsations in the Most Powerful Solar Flare of Cycle 24

    Science.gov (United States)

    Kolotkov, Dmitrii Y.; Pugh, Chloe E.; Broomhall, Anne-Marie; Nakariakov, Valery M.

    2018-05-01

    Quasi-periodic pulsations (QPPs) are common in solar flares and are now regularly observed in stellar flares. We present the detection of two different types of QPP signals in the thermal emission light curves of the X9.3-class solar flare SOL2017-09-06T12:02, which is the most powerful flare of Cycle 24. The period of the shorter-period QPP drifts from about 12 to 25 s during the flare. The observed properties of this QPP are consistent with a sausage oscillation of a plasma loop in the flaring active region. The period of the longer-period QPP is about 4 to 5 minutes. Its properties are compatible with standing slow magnetoacoustic oscillations, which are often detected in coronal loops. For both QPP signals, other mechanisms such as repetitive reconnection cannot be ruled out, however. The studied solar flare has an energy in the realm of observed stellar flares, and the fact that there is evidence of a short-period QPP signal typical of solar flares along with a long-period QPP signal more typical of stellar flares suggests that the different ranges of QPP periods typically observed in solar and stellar flares is likely due to observational constraints, and that similar physical processes may be occurring in solar and stellar flares.

  17. Parameterization of solar flare dose

    International Nuclear Information System (INIS)

    Lamarche, A.H.; Poston, J.W.

    1996-01-01

    A critical aspect of missions to the moon or Mars will be the safety and health of the crew. Radiation in space is a hazard for astronauts, especially high-energy radiation following certain types of solar flares. A solar flare event can be very dangerous if astronauts are not adequately shielded because flares can deliver a very high dose in a short period of time. The goal of this research was to parameterize solar flare dose as a function of time to see if it was possible to predict solar flare occurrence, thus providing a warning time. This would allow astronauts to take corrective action and avoid receiving a dose greater than the recommended limit set by the National Council on Radiation Protection and Measurements (NCRP)

  18. A Catalog of Solar White-Light Flares (1859-1982), Including Their Statistical Properties and Associated Emissions.

    Science.gov (United States)

    1983-09-20

    comprehensively studied. Among those aspects in need of further observational descriptions are (1) morphology (a description of the various WLF forms in terms of...Sacramento Peak, we compiled the list O ourselves. To the best of our knowledge the final list of events is comprehensive , although we have recently...and Conway, M. (1950) The solar, flare of 1949 November 19, Observatory .70.77. 33. Porret, M. (1952) Communications Ecrites : Soelil, I’Astronomie

  19. Influences of misprediction costs on solar flare prediction

    Science.gov (United States)

    Huang, Xin; Wang, HuaNing; Dai, XingHua

    2012-10-01

    The mispredictive costs of flaring and non-flaring samples are different for different applications of solar flare prediction. Hence, solar flare prediction is considered a cost sensitive problem. A cost sensitive solar flare prediction model is built by modifying the basic decision tree algorithm. Inconsistency rate with the exhaustive search strategy is used to determine the optimal combination of magnetic field parameters in an active region. These selected parameters are applied as the inputs of the solar flare prediction model. The performance of the cost sensitive solar flare prediction model is evaluated for the different thresholds of solar flares. It is found that more flaring samples are correctly predicted and more non-flaring samples are wrongly predicted with the increase of the cost for wrongly predicting flaring samples as non-flaring samples, and the larger cost of wrongly predicting flaring samples as non-flaring samples is required for the higher threshold of solar flares. This can be considered as the guide line for choosing proper cost to meet the requirements in different applications.

  20. Solar Flares: Magnetohydrodynamic Processes

    Directory of Open Access Journals (Sweden)

    Kazunari Shibata

    2011-12-01

    Full Text Available This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10^32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence, local enhancement of electric current in the corona (formation of a current sheet, and rapid dissipation of electric current (magnetic reconnection that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely, while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

  1. Coronal mass ejection kinematics deduced from white light (Solar Mass Ejection Imager) and radio (Wind/WAVES) observations

    Science.gov (United States)

    Reiner, M. J.; Jackson, B. V.; Webb, D. F.; Mizuno, D. R.; Kaiser, M. L.; Bougeret, J.-L.

    2005-09-01

    White-light and radio observations are combined to deduce the coronal and interplanetary kinematics of a fast coronal mass ejection (CME) that was ejected from the Sun at about 1700 UT on 2 November 2003. The CME, which was associated with an X8.3 solar flare from W56°, was observed by the Mauna Loa and Solar and Heliospheric Observatory (SOHO) Large-Angle Spectrometric Coronograph (LASCO) coronagraphs to 14 R⊙. The measured plane-of-sky speed of the LASCO CME was 2600 km s-1. To deduce the kinematics of this CME, we use the plane-of-sky white light observations from both the Solar Mass Ejection Imager (SMEI) all-sky camera on board the Coriolis spacecraft and the SOHO/LASCO coronagraph, as well as the frequency drift rate of the low-frequency radio data and the results of the radio direction-finding analysis from the WAVES experiment on the Wind spacecraft. In agreement with the in situ observations for this event, we find that both the white light and radio observations indicate that the CME must have decelerated significantly beginning near the Sun and continuing well into the interplanetary medium. More specifically, by requiring self-consistency of all the available remote and in situ data, together with a simple, but not unreasonable, assumption about the general characteristic of the CME deceleration, we were able to deduce the radial speed and distance time profiles for this CME as it propagated from the Sun to 1 AU. The technique presented here, which is applicable to mutual SMEI/WAVES CME events, is expected to provide a more complete description and better quantitative understanding of how CMEs propagate through interplanetary space, as well as how the radio emissions, generated by propagating CME/shocks, relate to the shock and CME. This understanding can potentially lead to more accurate predictions for the onset times of space weather events, such as those that were observed during this unique period of intense solar activity.

  2. Solar Flare Aimed at Earth

    Science.gov (United States)

    2002-01-01

    At the height of the solar cycle, the Sun is finally displaying some fireworks. This image from the Solar and Heliospheric Observatory (SOHO) shows a large solar flare from June 6, 2000 at 1424 Universal Time (10:24 AM Eastern Daylight Savings Time). Associated with the flare was a coronal mass ejection that sent a wave of fast moving charged particles straight towards Earth. (The image was acquired by the Extreme ultaviolet Imaging Telescope (EIT), one of 12 instruments aboard SOHO) Solar activity affects the Earth in several ways. The particles generated by flares can disrupt satellite communications and interfere with power transmission on the Earth's surface. Earth's climate is tied to the total energy emitted by the sun, cooling when the sun radiates less energy and warming when solar output increases. Solar radiation also produces ozone in the stratosphere, so total ozone levels tend to increase during the solar maximum. For more information about these solar flares and the SOHO mission, see NASA Science News or the SOHO home page. For more about the links between the sun and climate change, see Sunspots and the Solar Max. Image courtesy SOHO Extreme ultaviolet Imaging Telescope, ESA/NASA

  3. Statistical and observational research of solar flare for total spectra and geometrical features

    Science.gov (United States)

    Nishimoto, S.; Watanabe, K.; Imada, S.; Kawate, T.; Lee, K. S.

    2017-12-01

    Impulsive energy release phenomena such as solar flares, sometimes affect to the solar-terrestrial environment. Usually, we use soft X-ray flux (GOES class) as the index of flare scale. However, the magnitude of effect to the solar-terrestrial environment is not proportional to that scale. To identify the relationship between solar flare phenomena and influence to the solar-terrestrial environment, we need to understand the full spectrum of solar flares. There is the solar flare irradiance model named the Flare Irradiance Spectral Model (FISM) (Chamberlin et al., 2006, 2007, 2008). The FISM can estimate solar flare spectra with high wavelength resolution. However, this model can not express the time evolution of emitted plasma during the solar flare, and has low accuracy on short wavelength that strongly effects and/or controls the total flare spectra. For the purpose of obtaining the time evolution of total solar flare spectra, we are performing statistical analysis of the electromagnetic data of solar flares. In this study, we select solar flare events larger than M-class from the Hinode flare catalogue (Watanabe et al., 2012). First, we focus on the EUV emission observed by the SDO/EVE. We examined the intensities and time evolutions of five EUV lines of 55 flare events. As a result, we found positive correlation between the "soft X-ray flux" and the "EUV peak flux" for all EVU lines. Moreover, we found that hot lines peaked earlier than cool lines of the EUV light curves. We also examined the hard X-ray data obtained by RHESSI. When we analyzed 163 events, we found good correlation between the "hard X-ray intensity" and the "soft X-ray flux". Because it seems that the geometrical features of solar flares effect to those time evolutions, we also looked into flare ribbons observed by SDO/AIA. We examined 21 flare events, and found positive correlation between the "GOES duration" and the "ribbon length". We also found positive correlation between the "ribbon

  4. Hard X-Ray Emission from Partially Occulted Solar Flares: RHESSI Observations in Two Solar Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Effenberger, Frederic; Costa, Fatima Rubio da; Petrosian, Vahé [Department of Physics and KIPAC, Stanford University, Stanford, CA 94305 (United States); Oka, Mitsuo; Saint-Hilaire, Pascal; Krucker, Säm [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States); Liu, Wei [Bay Area Environmental Research Institute, 625 2nd Street, Suite 209, Petaluma, CA 94952 (United States); Glesener, Lindsay, E-mail: feffen@stanford.edu, E-mail: frubio@stanford.edu [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)

    2017-02-01

    Flares close to the solar limb, where the footpoints are occulted, can reveal the spectrum and structure of the coronal looptop source in X-rays. We aim at studying the properties of the corresponding energetic electrons near their acceleration site, without footpoint contamination. To this end, a statistical study of partially occulted flares observed with Reuven Ramaty High-Energy Solar Spectroscopic Imager is presented here, covering a large part of solar cycles 23 and 24. We perform detailed spectra, imaging, and light curve analyses for 116 flares and include contextual observations from SDO and STEREO when available, providing further insights into flare emission that were previously not accessible. We find that most spectra are fitted well with a thermal component plus a broken power-law, non-thermal component. A thin-target kappa distribution model gives satisfactory fits after the addition of a thermal component. X-ray imaging reveals small spatial separation between the thermal and non-thermal components, except for a few flares with a richer coronal source structure. A comprehensive light curve analysis shows a very good correlation between the derivative of the soft X-ray flux (from GOES ) and the hard X-rays for a substantial number of flares, indicative of the Neupert effect. The results confirm that non-thermal particles are accelerated in the corona and estimated timescales support the validity of a thin-target scenario with similar magnitudes of thermal and non-thermal energy fluxes.

  5. Flare colours and luminosities

    International Nuclear Information System (INIS)

    Cristaldi, S.; Rodono, M.

    1975-01-01

    Flare colours determined from simultaneous UBV observations made at Catania Observatory and from sequential UBV observations made at McDonald Observatory are presented. They fit fairly well with the theoretical colours computed according to the Gurzadian's (1970) non-thermal model. Only part of the observed flare colours are consistent with the solar type models by Gershberg (1967) and Kunkel (1970). From a B-band patrol of UV Cet-type stars carried out from 1967 to 1972, some quantitative estimates of flare frequencies and luminosities and their average contributions to the stellar radiation are given. The corresponding parameters for the Sun, which were estimated from 'white light' flare activity, are also given for comparison. The Sun and V 1216 Sgr can be regarded as low-activity flare stars of the type found by Kunkel (1973). (Auth.)

  6. An Interactive Multi-instrument Database of Solar Flares

    Energy Technology Data Exchange (ETDEWEB)

    Sadykov, Viacheslav M; Kosovichev, Alexander G; Oria, Vincent; Nita, Gelu M [Center for Computational Heliophysics, New Jersey Institute of Technology, Newark, NJ 07102 (United States)

    2017-07-01

    Solar flares are complicated physical phenomena that are observable in a broad range of the electromagnetic spectrum, from radio waves to γ -rays. For a more comprehensive understanding of flares, it is necessary to perform a combined multi-wavelength analysis using observations from many satellites and ground-based observatories. For an efficient data search, integration of different flare lists, and representation of observational data, we have developed the Interactive Multi-Instrument Database of Solar Flares (IMIDSF, https://solarflare.njit.edu/). The web-accessible database is fully functional and allows the user to search for uniquely identified flare events based on their physical descriptors and the availability of observations by a particular set of instruments. Currently, the data from three primary flare lists ( Geostationary Operational Environmental Satellites , RHESSI , and HEK) and a variety of other event catalogs ( Hinode , Fermi GBM, Konus- W IND, the OVSA flare catalogs, the CACTus CME catalog, the Filament eruption catalog) and observing logs ( IRIS and Nobeyama coverage) are integrated, and an additional set of physical descriptors (temperature and emission measure) is provided along with an observing summary, data links, and multi-wavelength light curves for each flare event since 2002 January. We envision that this new tool will allow researchers to significantly speed up the search of events of interest for statistical and case studies.

  7. Solar neighbourhood flare stars - a review

    International Nuclear Information System (INIS)

    Kunkel, W.E.

    1975-01-01

    The review concentrates on 'astronomical' aspects of flare activity, such as where, and under what circumstances flare activity is found in the solar vicinity. Non-classical activity is briefly described (without regard for completeness) and the influence of detection effects on flare observations is treated. Flare stars discovered during the last four years are described and flare activity of local dMe stars is compared. The BY Draconis syndrome is discussed followed by some remarks about rotation. Pleiades flare activity is compared to that of the solar neighbourhood and evidence for the evolution of flare activity in stars is examined. (Auth.)

  8. Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

    NARCIS (Netherlands)

    Lucarelli, G.; Di Giacomo, F.; Zardetto, V.; Creatore, M.; Brown, T.M.

    2017-01-01

    This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx, values typically found in indoor environments. Flexible cells were developed using either

  9. Solar Flares and the High Energy Solar Spectroscopic Imager (HESSI)

    Science.gov (United States)

    Holman, Gordon D.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Solar flares are the biggest explosions in the solar system. They are important both for understanding explosive events in the Universe and for their impact on human technology and communications. The satellite-based HESSI is designed to study the explosive release of energy and the acceleration of electrons, protons, and other charged particles to high energies in solar flares. HESSI produces "color" movies of the Sun in high-energy X rays and gamma rays radiated by these energetic particles. HESSI's X-ray and gamma-ray images of flares are obtained using techniques similar to those used in radio interferometry. Ground-based radio observations of the Sun provide an important complement to the HESSI observations of solar flares. I will describe the HESSI Project and the high-energy aspects of solar flares, and how these relate to radio astronomy techniques and observations.

  10. Detecting Solar Neutrino Flare in Megaton and km3 detectors

    International Nuclear Information System (INIS)

    Fargion, Daniele; Di Giacomo, Paola

    2009-01-01

    To foresee a solar flare neutrino signal we infer its upper and lower bound. The upper bound was derived since a few years by general energy equipartition arguments on observed solar particle flare. The lower bound, the most compelling one for any guarantee neutrino signal, is derived by most recent records of hard Gamma bump due to solar flare on January 2005 (by neutral pion decay). Because neutral and charged pions (made by hadron scattering in the flare) are born on the same foot, their link is compelling: the observed gamma flux [Grechnev V.V. et al., (arXiv:0806.4424), Solar Physics, Vol. 1, October, (2008), 252] reflects into a corresponding one for the neutrinos, almost one to one. Moreover while gamma photons might be absorbed (in deep corona) or at least reduced inside the flaring plasma, the secondaries neutrino are not. So pion neutrinos should be even more abundant than gamma ones. Tens-hundred MeV neutrinos may cross undisturbed the whole Sun, doubling at least their rate respect a unique solar-side for gamma flare. Therefore we obtain minimal bounds opening a windows for neutrino astronomy, already at the edge of present but quite within near future Megaton neutrino detectors. Such detectors are considered mostly to reveal cosmic supernova background or rare Local Group (few Mpc) Supernovas events [Matthew D. Kistler et al. (0810.1959v1)]. However rarest (once a decade), brief (a few minutes) powerful solar neutrino 'flare' may shine and they may overcome by two to three order of magnitude the corresponding steady atmospheric neutrino noise on the Earth, leading in largest Neutrino detector at least to one or to meaning-full few events clustered signals. The voice of such a solar anti-neutrino flare component at a few tens MeVs may induce an inverse beta decay over a vanishing anti-neutrino solar background. Megaton or even inner ten Megaton Ice Cube detector at ten GeV threshold may also reveal traces in hardest energy of solar flares. Icecube

  11. X-ray Emission from Solar Flares

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Solar flares; X-ray detectors; X-ray line emission and continuum; break energy; microflares. Abstract. Solar X-ray Spectrometer (SOXS), the first space-borne solar astronomy experiment of India was designed to improve our current understanding of X-ray emission from the Sun in general and solar flares in ...

  12. RADIO EMISSION FROM ACCELERATION SITES OF SOLAR FLARES

    International Nuclear Information System (INIS)

    Li Yixuan; Fleishman, Gregory D.

    2009-01-01

    This Letter takes up the question of what radio emission is produced by electrons at the very acceleration site of a solar flare. Specifically, we calculate incoherent radio emission produced within two competing acceleration models-stochastic acceleration by cascading MHD turbulence and regular acceleration in collapsing magnetic traps. Our analysis clearly demonstrates that radio emission from acceleration sites (1) has sufficiently strong intensity to be observed by currently available radio instruments, and (2) has spectra and light curves that are distinctly different in these two competing models, which makes them observationally distinguishable. In particular, we suggest that some of the narrowband microwave and decimeter continuum bursts may be a signature of the stochastic acceleration in solar flares.

  13. Fast electrons in small solar flares

    International Nuclear Information System (INIS)

    Lin, R.P.

    1975-01-01

    Because approximately 5-100 keV electrons are frequently accelerated and emitted by the Sun in small flares, it is possible to define a detailed characteristic physical picture of these events. The review summarizes both the direct spacecraft observations of non-relativistic solar electrons, and observations of the X-ray and radio emission generated by these particles at the Sun and in the interplanetary medium. These observations bear on the basic astrophysical process of particle acceleration in tenuous plasmas. It is found that in many small solar flares the approximately 5-100 keV electrons accelerated during flash phase constitute the bulk of the total flare energy. Thus the basic flare mechanism in these flares essentially converts the available flare energy into fast electrons. These electrons may produce the other flare electromagnetic emissions through their interactions with the solar atmosphere. In large proton flares these electrons may provide the energy to eject material from the Sun and to create a shock wave which could then accelerate nuclei and electrons to much higher energies. (Auth.)

  14. Anti-neutrino imprint in solar neutrino flare

    Science.gov (United States)

    Fargion, D.

    2006-10-01

    A future neutrino detector at megaton mass might enlarge the neutrino telescope thresholds revealing cosmic supernova background and largest solar flares (SFs) neutrinos. Indeed the solar energetic (Ep>100 MeV) flare particles (protons, α), while scattering among themselves on solar corona atmosphere must produce prompt charged pions, whose chain decays are source of a solar (electron muon) neutrino 'flare' (at tens or hundreds MeV energy). These brief (minutes) neutrino 'bursts' at largest flare peak may overcome by three to five orders of magnitude the steady atmospheric neutrino noise on the Earth, possibly leading to their detection above detection thresholds (in a full mixed three flavour state). Moreover the birth of anti-neutrinos at a few tens of MeV very clearly flares above a null thermal 'hep' anti-neutrino solar background and also above a tiny supernova relic and atmospheric noise. The largest prompt solar anti-neutrino 'burst' may be well detected in future Super Kamikande (gadolinium implemented) anti-neutrino \\bar\

  15. The High Energy Photons Emission from Solar Flares Observed by SZ2-XD

    Science.gov (United States)

    Wang, Huanyu; Li, Xinqiao; Ma, Yuqian; Zhang, Chengmo; Xu, Yupeng; Wang, Jingzhou; Chen, Guoming

    The spectra and light curve of near a hundred Solar X-ray Flare events, which were observed by SZ2/XD in the energy band of 10-800 keV during 2001, have been investigated. The events covered from C to X-class flares, which are shown different characters of high energy photons emission. The results will be presented in this paper. The discussions will be made especially for 3 of the brightest X-class solar flares SF010402(X20),SF010406(X5.6) and SF010415 (X14.4, a GLE event).

  16. Measurements and modeling of total solar irradiance in X-class solar flares

    International Nuclear Information System (INIS)

    Moore, Christopher Samuel; Chamberlin, Phillip Clyde; Hock, Rachel

    2014-01-01

    The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

  17. Solar and stellar flares and their impact on planets

    Science.gov (United States)

    Shibata, Kazunari

    Recent observations of the Sun revealed that the solar atmosphere is full of flares and flare-like phenomena, which affect terrestrial environment and our civilization. It has been established that flares are caused by the release of magnetic energy through magnetic reconnection. Many stars show flares similar to solar flares, and such stellar flares especially in stars with fast rotation are much more energetic than solar flares. These are called superflares. The total energy of a solar flare is 1029 - 1032 erg, while that of a superflare is 1033 - 1038 erg. Recently, it was found that superflares (with 1034 - 1035 erg) occur on Sun-like stars with slow rotation with frequency once in 800 - 5000 years. This suggests the possibility of superflares on the Sun. We review recent development of solar and stellar flare research, and briefly discuss possible impacts of superflares on the Earth and exoplanets.

  18. Solar Features - Solar Flares

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A solar flare is a short-lived sudden increase in the intensity of radiation emitted in the neighborhood of sunspots. For many years it was best monitored in the...

  19. Solar flare loops observations and interpretations

    CERN Document Server

    Huang, Guangli; Ji, Haisheng; Ning, Zongjun

    2018-01-01

    This book provides results of analysis of typical solar events, statistical analysis, the diagnostics of energetic electrons and magnetic field, as well as the global behavior of solar flaring loops such as their contraction and expansion. It pays particular attention to analyzing solar flare loops with microwave, hard X-ray, optical and EUV emissions, as well as the theories of their radiation, and electron acceleration/transport. The results concerning influence of the pitch-angle anisotropy of non-thermal electrons on their microwave and hard X-ray emissions, new spectral behaviors in X-ray and microwave bands, and results related to the contraction of flaring loops, are widely discussed in the literature of solar physics. The book is useful for graduate students and researchers in solar and space physics.

  20. Solar flares

    International Nuclear Information System (INIS)

    Brown, J.C.; Smith, D.F.

    1980-01-01

    The current observational and theoretical status of solar flares as a typical astrophysical problem is reviewed with especial reference to the intense and complex energy release in large flares. Observations and their diagnostic applications are discussed in three broad areas: thermal radiation at temperatures T 5 K; thermal radiation at T > approximately 10 5 K; and non-thermal radiation and particles. Particular emphasis is given to the most recent observational discoveries such as flare γ-rays, interplanetary Langmuir waves, and the ubiquitous association of soft x-ray loops with flares, and also the progress in particle diagnostics of hard x-ray and radio bursts. The theoretical problems of primary energy release are considered in terms of both possible magnetic configuration and in plasma instabilities and the question of achieving the necessary flash power discussed. The credibility of models for the secondary redistribution through the atmosphere of the primary magnetic energy released in terms of conduction, convection, radiation and particle transport is examined. Progress made in the flare problem in the past decade is assessed and some possible reasons why no convincing solution has yet been found are considered. 296 references. (U.K.)

  1. Active Longitude and Solar Flare Occurrences

    Science.gov (United States)

    Gyenge, N.; Ludmány, A.; Baranyi, T.

    2016-02-01

    The aim of the present work is to specify the spatio-temporal characteristics of flare activity observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Geostationary Operational Environmental Satellite (GOES) in connection with the behavior of the longitudinal domain of enhanced sunspot activity known as active longitude (AL). By using our method developed for this purpose, we identified the AL in every Carrington Rotation provided by the Debrecen Photoheliographic Data. The spatial probability of flare occurrence has been estimated depending on the longitudinal distance from AL in the northern and southern hemispheres separately. We have found that more than 60% of the RHESSI and GOES flares is located within +/- 36^\\circ from the AL. Hence, the most flare-productive active regions tend to be located in or close to the active longitudinal belt. This observed feature may allow for the prediction of the geo-effective position of the domain of enhanced flaring probability. Furthermore, we studied the temporal properties of flare occurrence near the AL and several significant fluctuations were found. More precisely, the results of the method are the following fluctuations: 0.8, 1.3, and 1.8 years. These temporal and spatial properties of the solar flare occurrence within the active longitudinal belts could provide us with an enhanced solar flare forecasting opportunity.

  2. Flare Observations

    Directory of Open Access Journals (Sweden)

    Benz Arnold O.

    2008-02-01

    Full Text Available Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays at 100 MeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio waves. Space missions such as RHESSI, Yohkoh, TRACE, and SOHO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections (CMEs, electrons, and ions may be accelerated at different sites, there are at least 3 different magnetic topologies, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s of energy release, tests of energy release scenarios and particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting reconnection of magnetic field lines as the basic cause. While this process has become generally accepted as the trigger, it is still controversial how it converts a considerable fraction of the energy into non-thermal particles. Flare-like processes may be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth’s lower ionosphere. While flare scenarios have slowly converged over the past decades, every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain a complex problem of astrophysics including major unsolved questions.

  3. Flare Observations

    Science.gov (United States)

    Benz, Arnold O.

    2017-12-01

    Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays beyond 1 GeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio waves. Space missions such as RHESSI, Yohkoh, TRACE, SOHO, and more recently Hinode and SDO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections, electrons, and ions may be accelerated at different sites, there are at least 3 different magnetic topologies, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s) of energy release, tests of energy release scenarios and particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting magnetic reconnection as the basic cause. While this process has become generally accepted as the trigger, it is still controversial how it converts a considerable fraction of the energy into non-thermal particles. Flare-like processes may be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth's ionosphere. Flare scenarios have slowly converged over the past decades, but every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain a complex problem of astrophysics including major unsolved questions.

  4. Statistical properties of solar flares and coronal mass ejections through the solar cycle

    International Nuclear Information System (INIS)

    Telloni, Daniele; Antonucci, Ester; Carbone, Vincenzo; Lepreti, Fabio

    2016-01-01

    Waiting Time Distributions (WTDs) of solar flares are investigated all through the solar cycle. The same approach applied to Coronal Mass Ejections (CMEs) in a previous work is considered here for flare occurrence. Our analysis reveals that flares and CMEs share some common statistical properties, which result dependent on the level of solar activity. Both flares and CMEs seem to independently occur during minimum solar activity phases, whilst their WTDs significantly deviate from a Poisson function at solar maximum, thus suggesting that these events are correlated. The characteristics of WTDs are constrained by the physical processes generating those eruptions associated with flares and CMEs. A scenario may be drawn in which different mechanisms are actively at work during different phases of the solar cycle. Stochastic processes, most likely related to random magnetic reconnections of the field lines, seem to play a key role during solar minimum periods. On the other hand, persistent processes, like sympathetic eruptions associated to the variability of the photospheric magnetism, are suggested to dominate during periods of high solar activity. Moreover, despite the similar statistical properties shown by flares and CMEs, as it was mentioned above, their WTDs appear different in some aspects. During solar minimum periods, the flare occurrence randomness seems to be more evident than for CMEs. Those persistent mechanisms generating interdependent events during maximum periods of solar activity can be suggested to play a more important role for CMEs than for flares, thus mitigating the competitive action of the random processes, which seem instead strong enough to weaken the correlations among flare event occurrence during solar minimum periods. However, it cannot be excluded that the physical processes at the basis of the origin of the temporal correlation between solar events are different for flares and CMEs, or that, more likely, more sophisticated effects are

  5. Solar Features - Solar Flares - Patrol

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The H-alpha Flare Patrol identifies time periods each day when the sun is being continuously monitored by select ground-based solar observatories.

  6. Solar and Stellar Flares and Their Effects on Planets

    Science.gov (United States)

    Shibata, Kazunari

    2015-08-01

    Recent space observations of the Sun revealed that the solar atmosphere is full of explosions, such as flares and flare-like phenomena. These flares generate not only strong electromagnetic emissions but also nonthermal particles and bulk plasma ejections, which sometimes lead to geomagnetic storms and affect terrestrial environment and our civilization, damaging satellite, power-grids, radio communication etc. Solar flares are prototype of various explosions in our universe, and hence are important not only for geophysics and environmental science but also for astrophysics. The energy source of solar flares is now established to be magnetic energy stored near sunspots. There is now increasing observational evidence that solar flares are caused by magnetic reconnection, merging of anti-parallel magnetic field lines and associated magneto-plasma dynamics (Shibata and Magara 2011, Living Review). It has also been known that many stars show flares similar to solar flares, and often such stellar flares are much more energetic than solar flares. The total energy of a solar flare is typically 10^29 - 10^32 erg. On the other hand, there are much more energetic flares (10^33 - 10^38 erg) in stars, especially in young stars. These are called superflares. We argue that these superflares on stars can also be understood in a unified way based on the reconnection mechanism. Finally we show evidence of occurrence of superflares on Sun-like stars according to recent stellar observations (Maehara et al. 2012, Nature, Shibayama et al. 2013), which revealed that superflares with energy of 10^34 - 10^35 erg (100 - 1000 times of the largest solar flares) occur with frequency of once in 800 - 5000 years on Sun-like stars which are very similar to our Sun. Against the previous belief, these new observations as well as theory (Shibata et al. 2013) suggest that we cannot deny the possibility of superflares on the present Sun. Finally, we shall discuss possible impacts of these superflares

  7. Solar flares, CMEs and solar energetic particle events during solar cycle 24

    Science.gov (United States)

    Pande, Bimal; Pande, Seema; Chandra, Ramesh; Chandra Mathpal, Mahesh

    2018-01-01

    We present here a study of Solar Energetic Particle Events (SEPs) associated with solar flares during 2010-2014 in solar cycle 24. We have selected the flare events (≥GOES M-class), which produced SEPs. The SEPs are classified into three categories i.e. weak (proton intensity ≤ 1 pfu), minor (1 pfu pfu) and major (proton intensity ≥ 10 pfu). We used the GOES data for the SEP events which have intensity greater than one pfu and SOHO/ERNE data for the SEP event less than one pfu intensity. In addition to the flare and SEP properties, we have also discussed different properties of associated CMEs.

  8. Solar flare irradiation records in Antarctic meteorites

    International Nuclear Information System (INIS)

    Goswami, J.N.

    1981-01-01

    Observations of solar flare heavy nuclei tracks in eight Antartic meteorite samples are reported. Two of these were interior specimens from an L-3 chondrite which contained track-rich grains (olivine) indicating their exposure to solar flare irradiation before compaction of the meteorite. Preliminary noble gas data also indicate the presence of solar-type gases. (U.K.)

  9. High-energy particles associated with solar flares

    International Nuclear Information System (INIS)

    Sakurai, K.; Klimas, A.J.

    1974-05-01

    High energy particles, the so-called solar cosmic rays, are often generated in association with solar flares, and then emitted into interplanetary space. These particles, consisting of electrons, protons, and other heavier nuclei, including the iron-group, are accelerated in the vicinity of the flare. By studying the temporal and spatial variation of these particles near the earth's orbit, their storage and release mechanisms in the solar corona and their propagation mechanism can be understood. The details of the nuclear composition and the rigidity spectrum for each nuclear component of the solar cosmic rays are important for investigating the acceleration mechanism in solar flares. The timing and efficiency of the acceleration process can also be investigated by using this information. These problems are described in some detail by using observational results on solar cosmic rays and associated phenomena. (U.S.)

  10. Interactive Multi-Instrument Database of Solar Flares

    Science.gov (United States)

    Ranjan, Shubha S.; Spaulding, Ryan; Deardorff, Donald G.

    2018-01-01

    The fundamental motivation of the project is that the scientific output of solar research can be greatly enhanced by better exploitation of the existing solar/heliosphere space-data products jointly with ground-based observations. Our primary focus is on developing a specific innovative methodology based on recent advances in "big data" intelligent databases applied to the growing amount of high-spatial and multi-wavelength resolution, high-cadence data from NASA's missions and supporting ground-based observatories. Our flare database is not simply a manually searchable time-based catalog of events or list of web links pointing to data. It is a preprocessed metadata repository enabling fast search and automatic identification of all recorded flares sharing a specifiable set of characteristics, features, and parameters. The result is a new and unique database of solar flares and data search and classification tools for the Heliophysics community, enabling multi-instrument/multi-wavelength investigations of flare physics and supporting further development of flare-prediction methodologies.

  11. Implications of NRL/ATM solar flare observations on flare theories

    International Nuclear Information System (INIS)

    Cheng, C.C.; Spicer, D.S.

    1975-01-01

    During the Skylab mission, many solar flares were observed with the NRL XUV spectroheliogram in the wavelength region from 150 to 650 A. Because of its high spatial resolution (approximately 2ins.) the three-dimensional structures of the flare emission regions characterized by temperatures from 10 4 K to 20 x 10 6 K can be resolved. Thus the spatial relationship between the relatively cool plasma and the hot plasma components of a flare, and the associated magnetic field structure can be inferred. The implications for various flare models are discussed. (Auth.)

  12. Thermodynamics of supra-arcade downflows in solar flares

    Science.gov (United States)

    Chen, Xin; Liu, Rui; Deng, Na; Wang, Haimin

    2017-10-01

    Context. Supra-arcade downflows (SADs) have been frequently observed during the gradual phase of solar flares near the limb. In coronal emission lines sensitive to flaring plasmas, they appear as tadpole-like dark voids against the diffuse fan-shaped "haze" above, flowing toward the well-defined flare arcade. Aims: We aim to investigate the evolution of SADs' thermal properties, and to shed light on the formation mechanism and physical processes of SADs. Methods: We carefully studied several selected SADs from two flare events and calculated their differential emission measures (DEMs) as well as DEM-weighted temperatures using data obtained by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory. Results: Our analysis shows that SADs are associated with a substantial decrease in DEM above 4 MK, which is 1-3 orders of magnitude smaller than the surrounding haze as well as the region before or after the passage of SADs, but comparable to the quiet corona. There is no evidence for the presence of the SAD-associated hot plasma (>20 MK) in the AIA data, and this decrease in DEM does not cause any significant change in the DEM distribution as well as the DEM-weighted temperature, which supports this idea that SADs are density depletion. This depression in DEM rapidly recovers in the wake of the SADs studied, generally within a few minutes, suggesting that they are discrete features. In addition, we found that SADs in one event are spatio-temporally associated with the successive formation of post-flare loops along the flare arcade. Movies associated to Figs. A.1 and A.2 are available at http://www.aanda.org

  13. Solar Flares Observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

    Science.gov (United States)

    Holman, Gordon D.

    2004-01-01

    Solar flares are impressive examples of explosive energy release in unconfined, magnetized plasma. It is generally believed that the flare energy is derived from the coronal magnetic field. However, we have not been able to establish the specific energy release mechanism(s) or the relative partitioning of the released energy between heating, particle acceleration (electrons and ions), and mass motions. NASA's RHESSI Mission was designed to study the acceleration and evolution of electrons and ions in flares by observing the X-ray and gamma-ray emissions these energetic particles produce. This is accomplished through the combination of high-resolution spectroscopy and spectroscopic imaging, including the first images of flares in gamma rays. RHESSI has observed over 12,000 solar flares since its launch on February 5, 2002. I will demonstrate how we use the RHESSI spectra to deduce physical properties of accelerated electrons and hot plasma in flares. Using images to estimate volumes, w e typically find that the total energy in accelerated electrons is comparable to that in the thermal plasma. I will also present flare observations that provide strong support for the presence of magnetic reconnection in a large-scale, vertical current sheet in the solar corona. RHESSI observations such as these are allowing us to probe more deeply into the physics of solar flares.

  14. Millimeter and X-Ray Emission from the 5 July 2012 Solar Flare

    Science.gov (United States)

    Tsap, Y. T.; Smirnova, V. V.; Motorina, G. G.; Morgachev, A. S.; Kuznetsov, S. A.; Nagnibeda, V. G.; Ryzhov, V. S.

    2018-03-01

    The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39 - 11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager, Solar Dynamics Observatory (SDO), Geostationary Operational Environmental Satellite, Radio Solar Telescope Network, and Bauman Moscow State Technical University millimeter radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the Atmospheric Imaging Assembly/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (≳ 300 keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.

  15. Deep Flare Net (DeFN) Model for Solar Flare Prediction

    Science.gov (United States)

    Nishizuka, N.; Sugiura, K.; Kubo, Y.; Den, M.; Ishii, M.

    2018-05-01

    We developed a solar flare prediction model using a deep neural network (DNN) named Deep Flare Net (DeFN). This model can calculate the probability of flares occurring in the following 24 hr in each active region, which is used to determine the most likely maximum classes of flares via a binary classification (e.g., ≥M class versus statistically predict flares, the DeFN model was trained to optimize the skill score, i.e., the true skill statistic (TSS). As a result, we succeeded in predicting flares with TSS = 0.80 for ≥M-class flares and TSS = 0.63 for ≥C-class flares. Note that in usual DNN models, the prediction process is a black box. However, in the DeFN model, the features are manually selected, and it is possible to analyze which features are effective for prediction after evaluation.

  16. Solar flare hard and soft x ray relationship determined from SMM HXRBS and BCS data

    Science.gov (United States)

    Toot, G. David

    1989-01-01

    The exact nature of the solar flare process is still somewhat a mystery. A key element to understanding flares if the relationship between the hard x rays emitted by the most energetic portions of the flare and the soft x rays from other areas and times. This relationship was studied by comparing hard x ray light curved from the Hard X-Ray Burst Spectrometer (HXRBS) with the soft x ray light curve and its derivation from the Bent Crystal Spectrometer (BCS) which is part of the X-Ray Polychrometer (XRP), these instruments being on the Solar Maximum Mission spacecraft (SMM). Data sample was taken from flares observed with the above instruments during 1980, the peak of the previous maximum of solar activity. Flares were chosen based on complete coverage of the event by several instruments. The HXRBS data covers the x ray spectrum from about 25 keV to about 440 keV in 15 spectral channels, while the BCS data used covers a region of the Spectrum around 3 angstroms including emission from the Ca XIX ion. Both sets of data were summed over their spectral ranges and plotted against time at a maximum time resolution of around 3 seconds. The most popular theory of flares holds that a beam of electrons produces the hard x rays by bremsstrahlung while the soft x rays are the thermal response to this energy deposition. The question is whether the rate of change of soft x ray emission might reflect the variability of the electron beam and hence the variability of the hard x rays. To address this, we took the time derivative of the soft x ray light curve and compared it to the hard flares, 12 of them showed very closed agreement between the soft x ray derivative and the hard x ray light curve. The other five did not show this behavior but were similar to each other in general soft x ray behavior. Efforts to determine basic differences between the two kinds of flares continue. In addition the behavior of soft x ray temperature of flares was examined.

  17. Suppression of Hydrogen Emission in an X-class White-light Solar Flare

    Czech Academy of Sciences Publication Activity Database

    Procházka, O.; Milligan, R.O.; Allred, J.C.; Kowalski, A.F.; Kotrč, Pavel; Mathioudakis, M.

    2017-01-01

    Roč. 837, č. 1 (2017), 46/1-46/9 ISSN 0004-637X R&D Projects: GA ČR(CZ) GA16-18495S Grant - others:EC(XE) 606862 Program:FP7 Institutional support: RVO:67985815 Keywords : Sun * atmosphere * flares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.533, year: 2016

  18. Explosive Chromospheric Evaporation Driven by Nonthermal Electrons around One Footpoint of a Solar Flare Loop

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.; Ning, Z. J.; Huang, Y.; Zhang, Q. M., E-mail: lidong@pmo.ac.cn [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, CAS, Nanjing 210008 (China)

    2017-05-20

    We explore the temporal relationship between microwave/hard X-ray (HXR) emission and Doppler velocity during the impulsive phase of a solar flare on 2014 October 27 (SOL2014-10-27) that displays a pulse on the light curves in the microwave (34 GHz) and HXR (25–50 keV) bands before the flare maximum. Imaging observation shows that this pulse mainly comes from one footpoint of a solar flare loop. The slit of the Interface Region Imaging Spectrograph ( IRIS ) stays at this footpoint during this solar flare. The Doppler velocities of Fe xxi 1354.09 Å and Si iv 1402.77 Å are extracted from the Gaussian fitting method. We find that the hot line of Fe xxi 1354.09 Å (log T ∼ 7.05) in the corona exhibits blueshift, while the cool line of Si iv 1402.77 Å (log T ∼ 4.8) in the transition region exhibits redshift, indicating explosive chromospheric evaporation. Evaporative upflows along the flare loop are also observed in the AIA 131 Å image. To our knowledge, this is the first report of chromospheric evaporation evidence from both spectral and imaging observations in the same flare. Both microwave and HXR pulses are well correlated with the Doppler velocities, suggesting that the chromospheric evaporation is driven by nonthermal electrons around this footpoint of a solar flare loop.

  19. Solar flare leaves sun quaking

    Science.gov (United States)

    1998-05-01

    Dr. Alexander G. Kosovichev, a senior research scientist from Stanford University, and Dr. Valentina V. Zharkova from Glasgow (United Kingdom) University found the tell-tale seismic signature in data on the Sun's surface collected by the Michelson Doppler Imager onboard the Solar and Heliospheric Observatory (SOHO) spacecraft immediately following a moderate-sized flare on July 9, 1996. "Although the flare was a moderate one, it still released an immense amount of energy," said Dr. Craig Deforest, a researcher with the SOHO project. "The energy released is equal to completely covering the Earth's continents with a yard of dynamite and detonating it all at once." SOHO is a joint project of the European Space Agency and NASA. The finding is reported in the May 28 issue of the journal Nature, and is the subject of a press conference at the spring meeting of the American Geophysical Union in Boston, Mass., May 27. The solar quake that the science team recorded looks much like ripples spreading from a rock dropped into a pool of water. But over the course of an hour, the solar waves traveled for a distance equal to 10 Earth diameters before fading into the fiery background of the Sun's photosphere. Unlike water ripples that travel outward at a constant velocity, the solar waves accelerated from an initial speed of 22,000 miles per hour to a maximum of 250,000 miles per hour before disappearing. "People have looked for evidence of seismic waves from flares before, but they didn't have a theory so they didn't know where to look," says Kosovichev. Several years ago Kosovichev and Zharkova developed a theory that can explain how a flare, which explodes in space above the Sun's surface, can generate a major seismic wave in the Sun's interior. According to the currently accepted model of solar flares, the primary explosion creates high-energy electrons (electrically charged subatomic particles). These are funneled down into a magnetic flux tube, an invisible tube of magnetic

  20. Search for correlation of neutrino events with solar flares in Kamiokande

    International Nuclear Information System (INIS)

    Hirata, K.S.; Kajita, T.; Kifune, T.

    1988-10-01

    A search has been made for a correlation between large solar flares and neutrino events observed in Kamiokande for the period of July 1983 - July 1988. No significant neutrino signal was found at the time of a solar flare, giving a limit on the time integrated 'solar-flare' ν e flux 7 (2.5 x 10 9 )/cm 2 per flare at 90 % confidence level, for E ν = 100 (50) MeV. These limits are 2000 (60) times smaller than the value required for neutrinos with those energies to account for the excess of signal in the 37 Cl solar neutrino experiment at some of the corresponding solar flare times. (author)

  1. MAGNETIC PROPERTIES OF SOLAR ACTIVE REGIONS THAT GOVERN LARGE SOLAR FLARES AND ERUPTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Toriumi, Shin [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Schrijver, Carolus J. [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, CA 94304 (United States); Harra, Louise K. [UCL-Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Surrey, RH5 6NT (United Kingdom); Hudson, Hugh [SUPA School of Physics and Astronomy, University of Glasgow (United Kingdom); Nagashima, Kaori, E-mail: shin.toriumi@nao.ac.jp [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2017-01-01

    Solar flares and coronal mass ejections (CMEs), especially the larger ones, emanate from active regions (ARs). With the aim of understanding the magnetic properties that govern such flares and eruptions, we systematically survey all flare events with Geostationary Orbiting Environmental Satellite levels of ≥M5.0 within 45° from disk center between 2010 May and 2016 April. These criteria lead to a total of 51 flares from 29 ARs, for which we analyze the observational data obtained by the Solar Dynamics Observatory . More than 80% of the 29 ARs are found to exhibit δ -sunspots, and at least three ARs violate Hale’s polarity rule. The flare durations are approximately proportional to the distance between the two flare ribbons, to the total magnetic flux inside the ribbons, and to the ribbon area. From our study, one of the parameters that clearly determine whether a given flare event is CME-eruptive or not is the ribbon area normalized by the sunspot area, which may indicate that the structural relationship between the flaring region and the entire AR controls CME productivity. AR characterization shows that even X-class events do not require δ -sunspots or strong-field, high-gradient polarity inversion lines. An investigation of historical observational data suggests the possibility that the largest solar ARs, with magnetic flux of 2 × 10{sup 23} Mx, might be able to produce “superflares” with energies of the order of 10{sup 34} erg. The proportionality between the flare durations and magnetic energies is consistent with stellar flare observations, suggesting a common physical background for solar and stellar flares.

  2. Sixty-Year Career in Solar Physics

    Science.gov (United States)

    Fang, C.

    2018-05-01

    This memoir reviews my academic career in solar physics for 60 years, including my research on non-LTE modeling, white-light flares, and small-scale solar activities. Through this narrative, the reader can catch a glimpse of the development of solar physics research in mainland China from scratch. In the end, some prospects for future development are given.

  3. The solar-flare infrared continuum: observational techniques and upper limits

    International Nuclear Information System (INIS)

    Hudson, H.S.

    1975-01-01

    Exploratory observations at 20μ and 350 μ have determined detection thresholds for solar flares in these wavelengths. In the 20μ range solar atmospheric fluctuations (the 'temperature field') set the basic limits on flare detectability at approximately 5K; at 350μ the extinction in the Earth's atmosphere provides the basic limitation of approximately 30 K. These thresholds are low enough for the successful detection of several infrared-emitting components of large flares. Limited observing time and lack of solar activity have prevented observations of large flares up to the present, but the techniques promise to be extremely useful in the future. The upper limits obtained thus far, for subflares, indicate that the thickness of the Hα flare region does not exceed approximately 10 km. This result confirms the conclusion of Suemoto and Hiei (1959) regarding the small effective thickness of the Hα-emitting regions in solar flares. (Auth.)

  4. Reconnection in Solar Flares: Outstanding Questions Hiroaki Isobe ...

    Indian Academy of Sciences (India)

    Although the idea of magnetic reconnection for explaining the energy release in solar flares had been proposed many decades ago (Parker 1957; Sweet. 1958) it was after Yohkoh (Ogawara et al. 1991) observations that the reality of mag- netic reconnection occurring during solar flares was established. Examples of evi-.

  5. The radiated energy budget of chromospheric plasma in a major solar flare deduced from multi-wavelength observations

    Energy Technology Data Exchange (ETDEWEB)

    Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Kerr, Graham S.; Hudson, Hugh S.; Fletcher, Lyndsay [School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Dennis, Brian R.; Allred, Joel C.; Chamberlin, Phillip C.; Ireland, Jack, E-mail: r.milligan@qub.ac.uk [Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-10-01

    This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form of nonthermal electrons. Hard X-ray observations from RHESSI were used to track the evolution of the parameters of the nonthermal electron distribution to reveal the total power contained in flare accelerated electrons. By integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be >2 × 10{sup 31} erg. The response of the lower solar atmosphere was measured in the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304 Å and H I (Lyα) at 1216 Å by SDO/EVE, the UV continua at 1600 Å and 1700 Å by SDO/AIA, and the white light continuum at 4504 Å, 5550 Å, and 6684 Å, along with the Ca II H line at 3968 Å using Hinode/SOT. The summed energy detected by these instruments amounted to ∼3 × 10{sup 30} erg; about 15% of the total nonthermal energy. The Lyα line was found to dominate the measured radiative losses. Parameters of both the driving electron distribution and the resulting chromospheric response are presented in detail to encourage the numerical modeling of flare heating for this event, to determine the depth of the solar atmosphere at which these line and continuum processes originate, and the mechanism(s) responsible for their generation.

  6. The Solar Flare: A Strongly Turbulent Particle Accelerator

    Science.gov (United States)

    Vlahos, L.; Krucker, S.; Cargill, P.

    The topics of explosive magnetic energy release on a large scale (a solar flare) and particle acceleration during such an event are rarely discussed together in the same article. Many discussions of magnetohydrodynamic (MHD) mod- eling of solar flares and/or CMEs have appeared (see [143] and references therein) and usually address large-scale destabilization of the coronal mag- netic field. Particle acceleration in solar flares has also been discussed exten- sively [74, 164, 116, 166, 87, 168, 95, 122, 35] with the main emphasis being on the actual mechanisms for acceleration (e.g., shocks, turbulence, DC electric fields) rather than the global magnetic context in which the acceleration takes place.

  7. K2 Ultracool Dwarfs Survey. III. White Light Flares Are Ubiquitous in M6-L0 Dwarfs

    Science.gov (United States)

    Paudel, Rishi R.; Gizis, John E.; Mullan, D. J.; Schmidt, Sarah J.; Burgasser, Adam J.; Williams, Peter K. G.; Berger, Edo

    2018-05-01

    We report the white light flare rates for 10 ultracool dwarfs using Kepler K2 short-cadence data. Among our sample stars, two have spectral type M6, three are M7, three are M8, and two are L0. Most of our targets are old low-mass stars. We identify a total of 283 flares in all of the stars in our sample, with Kepler energies in the range log E Kp ∼ (29–33.5) erg. Using the maximum-likelihood method of line fitting, we find that the flare frequency distribution (FFD) for each star in our sample follows a power law with slope ‑α in the range ‑(1.3–2.0). We find that cooler objects tend to have shallower slopes. For some of our targets, the FFD follows either a broken power law, or a power law with an exponential cutoff. For the L0 dwarf 2MASS J12321827-0951502, we find a very shallow slope (‑α = ‑1.3) in the Kepler energy range (0.82–130) × 1030 erg: this L0 dwarf has flare rates which are comparable to those of high-energy flares in stars of earlier spectral types. In addition, we report photometry of two superflares: one on the L0 dwarf 2MASS J12321827-0951502 and another on the M7 dwarf 2MASS J08352366+1029318. In the case of 2MASS J12321827-0951502, we report a flare brightening by a factor of ∼144 relative to the quiescent photospheric level. Likewise, for 2MASS J08352366+1029318, we report a flare brightening by a factor of ∼60 relative to the quiescent photospheric level. These two superflares have bolometric (ultraviolet/optical/infrared) energies 3.6 × 1033 erg and 8.9 × 1033 erg respectively, while the full width half maximum timescales are very short, ∼2 min. We find that the M8 star TRAPPIST-1 is more active than the M8.5 dwarf 2M03264453+1919309, but less active than another M8 dwarf (2M12215066-0843197).

  8. Spots and White Light Flares in an L Dwarf

    Science.gov (United States)

    2013-01-01

    Program GN-2012A-Q-37) GMOS spectrograph (Hook et al. 2004) when a series of flares occurred. A spectrum of the most powerful flare in its impulsive...10:14 Hα HeI HeI HeI OI Fig. 4. Gemini-North GMOS spectra of W1906+40 in quiescence (below) and in flare. Note the broad Hα, atomic emission lines

  9. PREDICTION OF SOLAR FLARES USING UNIQUE SIGNATURES OF MAGNETIC FIELD IMAGES

    Energy Technology Data Exchange (ETDEWEB)

    Raboonik, Abbas; Safari, Hossein; Alipour, Nasibe [Department of Physics, University of Zanjan, P.O. Box 45195-313, Zanjan (Iran, Islamic Republic of); Wheatland, Michael S., E-mail: raboonik@alumni.znu.ac.ir, E-mail: safari@znu.ac.ir [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia)

    2017-01-01

    Prediction of solar flares is an important task in solar physics. The occurrence of solar flares is highly dependent on the structure and topology of solar magnetic fields. A new method for predicting large (M- and X-class) flares is presented, which uses machine learning methods applied to the Zernike moments (ZM) of magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory for a period of six years from 2010 June 2 to 2016 August 1. Magnetic field images consisting of the radial component of the magnetic field are converted to finite sets of ZMs and fed to the support vector machine classifier. ZMs have the capability to elicit unique features from any 2D image, which may allow more accurate classification. The results indicate whether an arbitrary active region has the potential to produce at least one large flare. We show that the majority of large flares can be predicted within 48 hr before their occurrence, with only 10 false negatives out of 385 flaring active region magnetograms and 21 false positives out of 179 non-flaring active region magnetograms. Our method may provide a useful tool for the prediction of solar flares, which can be employed alongside other forecasting methods.

  10. The X-ray signature of solar coronal mass

    Science.gov (United States)

    Harrison, R. A.; Waggett, P. W.; Bentley, R. D.; Phillips, K. J. H.; Bruner, M.

    1985-01-01

    The coronal response to six solar X-ray flares has been investigated. At a time coincident with the projected onset of the white-light coronal mass ejection associated with each flare, there is a small, discrete soft X-ray enhancement. These enhancements (precursors) precede by typically about 20 m the impulsive phase of the solar flare which is dominant by the time the coronal mass ejection has reached an altitude above 0.5 solar radii. Motions of hot X-ray emitting plasma, during the precursors, which may well be a signature of the mass ejection onsets, are identified. Further investigations have also revealed a second class of X-ray coronal transient, during the main phase of the flare. These appear to be associated with magnetic reconnection above post-flare loop systems.

  11. A Novel Forecasting System for Solar Particle Events and Flares (FORSPEF)

    International Nuclear Information System (INIS)

    Papaioannou, A; Anastasiadis, A; Sandberg, I; Tsiropoula, G; Tziotziou, K; Georgoulis, M K; Jiggens, P; Hilgers, A

    2015-01-01

    Solar Energetic Particles (SEPs) result from intense solar eruptive events such as solar flares and coronal mass ejections (CMEs) and pose a significant threat for both personnel and infrastructure in space conditions. In this work, we present FORSPEF (Forecasting Solar Particle Events and Flares), a novel dual system, designed to perform forecasting of SEPs based on forecasting of solar flares, as well as independent SEP nowcasting. An overview of flare and SEP forecasting methods of choice is presented. Concerning SEP events, we make use for the first time of the newly re-calibrated GOES proton data within the energy range 6.0-243 MeV and we build our statistics on an extensive time interval that includes roughly 3 solar cycles (1984-2013). A new comprehensive catalogue of SEP events based on these data has been compiled including solar associations in terms of flare (magnitude, location) and CME (width, velocity) characteristics. (paper)

  12. Some evidence on the evolution of the flare mechanism in dwarf stars

    Energy Technology Data Exchange (ETDEWEB)

    Skumanich, A.

    1986-10-01

    White-light flare parameters are estimated for the sun as a star. It is found that these parameters fall in the same domain as those for the dMe flare stars. In particular, it is found that the time-averaged flare power loss and quiescent coronal soft X-ray power loss at solar maximum satisfies the recently proposed flare power-coronal X-ray relation for dMe stars (Doyle and Butler; Skumanich). In addition, one finds that dM stars, which are believed to be magnetically evolved dMe stars, also satisfy the same relation. On this basis, an evolutionary scenario is suggested for the flare mechanism in which the total flare rate remains, more or less, constant but the mean flare yield decreases linearly with coronal X-ray strength. It is also suggested that the flare mechanism is universal in all magnetically active dwarfs. 48 references.

  13. Observation of solar flare by Hinotori SXT/HXM

    International Nuclear Information System (INIS)

    Ohki, Ken-ichiro; Takakura, Tatsuo; Tsuneta, Sukehisa; Nitta, Nariaki; Makishima, Kazuo.

    1982-01-01

    Solar flares were observed by SXT (hard X-ray two-dimensional observation system) and HXM (hard X-ray spectrometer) on Hinotori. The results of two-dimensional analysis of 20 flares are reported in this paper. Various images of hard X-ray were observed. Hard X-ray bursts with relatively long duration may be generated in corona. The hard X-ray flare generated on the solar disc gives information on the relative position to the H flare. The examples of this hard X-ray images are presented. The HXM can observe the hard X-ray spectra up to 350 keV. The flares with duration less than 5 min have the spectra coninciding with the thermal radiation from a single temperature before the peak, and power law type non-thermal radiation spectra after the peak. The hard X-ray flares with duration longer than 10 min have power law type spectra. (Kato, T.)

  14. Radiative hazard of solar flares in the nearterrestrial cosmic space

    International Nuclear Information System (INIS)

    Kolomenskij, A.V.; Petrov, V.M.; Zil', M.V.; Eremkina, T.M.

    1978-01-01

    Simulation of radiation enviroment due to solar cosmic rays was carried out in the near-terrestrial space. Systematized are the data on cosmic ray flux and spectra detected during 19-th and 20-th cycles of solar activity. 127 flares are considered with proton fluxes of more than 10 proton/cm 2 at energies higher than 30 MeV. Obtained are distribution functions of intervals between flares, flux distribution of flares and characteristic rigidity, and also distribution of magnetic disturbances over Dsub(st)-variation amplitude. The totality of these distributions presents the statistic model of radiation enviroment caused by solar flare protons for the period of maximum solar .activity. This model is intended for estimation of radiation hazard at manned cosmic flights

  15. Motion of matter in flare loops of the solar disc

    International Nuclear Information System (INIS)

    Xu Ao-ao

    1987-01-01

    By using the optical observation data of a Class 3B double-ribbon flare obtained on July 14, 1980 at the Yunan Observatory, and the x-ray result from the SMM satellite for the same flare, the law of motion of matter in the flare loops of the solar disc is discussed. First, the solar disc positions from the Hα and x-ray images for the flare were compared, and the altitude of the flare loop was determined according to projection effects. Second, the line-of-sight velocity distribution in the region of flare activity due to the falling of matter in the flare loop was estimated theoretically. The result agreed with the observed data

  16. White light coronagraph in OSO-7

    International Nuclear Information System (INIS)

    Koomen, M.J.; Detwiler, C.R.; Brueckner, G.E.; Cooper, H.W.; Tousey, R.

    1975-01-01

    A small, externally occulted Lyot-type coronagraph, designated for use in the seventh unmanned Orbiting Solar Observatory (OSO-7), is described. Optical configuration, suppression of stray light, SEC vidicon detector, and data system are discussed, as well as integration of the instrument into the spacecraft and operation in orbit. Orbital operation produced daily images of the white light corona, from 2.8 to 10 solar radii, at least once per day for 2 3/4 yr. The first records of white light coronal transient events were obtained, and the corona was shown to be constantly changing

  17. Modelling Quasi-Periodic Pulsations in Solar and Stellar Flares

    Science.gov (United States)

    McLaughlin, J. A.; Nakariakov, V. M.; Dominique, M.; Jelínek, P.; Takasao, S.

    2018-02-01

    Solar flare emission is detected in all EM bands and variations in flux density of solar energetic particles. Often the EM radiation generated in solar and stellar flares shows a pronounced oscillatory pattern, with characteristic periods ranging from a fraction of a second to several minutes. These oscillations are referred to as quasi-periodic pulsations (QPPs), to emphasise that they often contain apparent amplitude and period modulation. We review the current understanding of quasi-periodic pulsations in solar and stellar flares. In particular, we focus on the possible physical mechanisms, with an emphasis on the underlying physics that generates the resultant range of periodicities. These physical mechanisms include MHD oscillations, self-oscillatory mechanisms, oscillatory reconnection/reconnection reversal, wave-driven reconnection, two loop coalescence, MHD flow over-stability, the equivalent LCR-contour mechanism, and thermal-dynamical cycles. We also provide a histogram of all QPP events published in the literature at this time. The occurrence of QPPs puts additional constraints on the interpretation and understanding of the fundamental processes operating in flares, e.g. magnetic energy liberation and particle acceleration. Therefore, a full understanding of QPPs is essential in order to work towards an integrated model of solar and stellar flares.

  18. VERY LONG-PERIOD PULSATIONS BEFORE THE ONSET OF SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Baolin; Huang, Jing; Tan, Chengming; Zhang, Yin [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China); Yu, Zhiqiang, E-mail: bltan@nao.cas.cn [School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, Beijing 100049 (China)

    2016-12-20

    Solar flares are the most powerful explosions occurring in the solar system, which may lead to disastrous space weather events and impact various aspects of our Earth. It remains a big challenge in modern astrophysics to understand the origin of solar flares and predict their onset. Based on the analysis of soft X-ray emission observed by the Geostationary Operational Environmental Satellite , this work reports a new discovery of very long-periodic pulsations occurring in the preflare phase before the onset of solar flares (preflare-VLPs). These pulsations typically have periods of 8–30 min and last for about 1–2 hr. They are possibly generated from LRC oscillations of plasma loops where electric current dominates the physical process during magnetic energy accumulation in the source region. Preflare-VLPs provide essential information for understanding the triggering mechanism and origin of solar flares, and may be a convenient precursory indicator to help us respond to solar explosions and the corresponding disastrous space weather events.

  19. DOES A SCALING LAW EXIST BETWEEN SOLAR ENERGETIC PARTICLE EVENTS AND SOLAR FLARES?

    International Nuclear Information System (INIS)

    Kahler, S. W.

    2013-01-01

    Among many other natural processes, the size distributions of solar X-ray flares and solar energetic particle (SEP) events are scale-invariant power laws. The measured distributions of SEP events prove to be distinctly flatter, i.e., have smaller power-law slopes, than those of the flares. This has led to speculation that the two distributions are related through a scaling law, first suggested by Hudson, which implies a direct nonlinear physical connection between the processes producing the flares and those producing the SEP events. We present four arguments against this interpretation. First, a true scaling must relate SEP events to all flare X-ray events, and not to a small subset of the X-ray event population. We also show that the assumed scaling law is not mathematically valid and that although the flare X-ray and SEP event data are correlated, they are highly scattered and not necessarily related through an assumed scaling of the two phenomena. An interpretation of SEP events within the context of a recent model of fractal-diffusive self-organized criticality by Aschwanden provides a physical basis for why the SEP distributions should be flatter than those of solar flares. These arguments provide evidence against a close physical connection of flares with SEP production.

  20. Common SphinX and RHESSI observations of solar flares

    Science.gov (United States)

    Mrozek, T.; Gburek, S.; Siarkowski, M.; Sylwester, B.; Sylwester, J.; Gryciuk, M.

    The Polish X-ray spectrofotometer SphinX has observed a great number of solar flares in the year 2009 - during the most quiet solar minimum almost over the last 100 years. Hundreds of flares have been recorded due to excellent sensitivity of SphinX's detectors. The Si-PIN diodes are about 100 times more sensitive to X-rays than GOES X-ray Monitors. SphinX detectors were absolutely calibrated on Earth with a use of the BESSY synchrotron. In space observations were made in the range 1.2-15~keV with 480~eV energy resolution. SphinX data overlap with the low-energy end of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data. RHESSI detectors are quite old (7 years in 2009), but still sensitive enough to provide us with observations of extremely weak solar flares such as those which occurred in 2009. We have selected a group of flares simultaneously observed by RHESSI and SphinX and performed a spectroscopic analysis of the data. Moreover, we compared the physical parameters of these flares plasma. Preliminary results of the comparison show very good agreement between both instruments.

  1. Strong Transverse Photosphere Magnetic Fields and Twist in Light Bridge Dividing Delta Sunspot of Active Region 12673

    OpenAIRE

    Wang, Haimin; Yurchyshyn, Vasyl; Liu, Chang; Ahn, Kwangsu; Toriumi, Shin; Cao, Wenda

    2018-01-01

    Solar Active Region (AR) 12673 is the most flare productive AR in the solar cycle 24. It produced four X-class flares including the X9.3 flare on 06 September 2017 and the X8.2 limb event on 10 September. Sun and Norton (2017) reported that this region had an unusual high rate of flux emergence, while Huang et al. (2018) reported that the X9.3 flare had extremely strong white-light flare emissions. Yang at al. (2017) described the detailed morphological evolution of this AR. In this report, w...

  2. Wavelength Dependence of Solar Flare Irradiation and its Influence on the Thermosphere

    Science.gov (United States)

    Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Qian, L.; Solomon, S.; Chamberlin, P.

    2012-01-01

    The wavelength dependence of solar flare enhancement is one of the important factors determining how the Thermosphere-Ionosphere (T-I) system response to flares. To investigate the wavelength dependence of solar flare, the Flare Irradiance Spectral Model (FISM) has been run for 34 X-class flares. The results show that the percentage increases of solar irradiance at flare peak comparing to pre-flare condition have a clear wavelength dependence. In the wavelength range between 0 - 195 nm, it can vary from 1% to 10000%. The solar irradiance enhancement is largest ( 1000%) in the XUV range (0 - 25 nm), and is about 100% in EUV range (25 - 120 nm). The influence of different wavebands on the T-I system during the October 28th, 2003 flare (X17.2-class) has also been examined using the latest version of National Center for Atmospheric Research (NCAR) Thermosphere- Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). While the globally integrated solar energy deposition is largest in the 0 - 14 nm waveband, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for 25 - 105 nm waveband. The effect of 122 - 195 nm is small in magnitude, but it decays slowly.

  3. AUTOMATED SOLAR FLARE STATISTICS IN SOFT X-RAYS OVER 37 YEARS OF GOES OBSERVATIONS: THE INVARIANCE OF SELF-ORGANIZED CRITICALITY DURING THREE SOLAR CYCLES

    International Nuclear Information System (INIS)

    Aschwanden, Markus J.; Freeland, Samuel L.

    2012-01-01

    We analyzed the soft X-ray light curves from the Geostationary Operational Environmental Satellites over the last 37 years (1975-2011) and measured with an automated flare detection algorithm over 300,000 solar flare events (amounting to ≈5 times higher sensitivity than the NOAA flare catalog). We find a power-law slope of α F = 1.98 ± 0.11 for the (background-subtracted) soft X-ray peak fluxes that is invariant through three solar cycles and agrees with the theoretical prediction α F = 2.0 of the fractal-diffusive self-organized criticality (FD-SOC) model. For the soft X-ray flare rise times, we find a power-law slope of α T = 2.02 ± 0.04 during solar cycle minima years, which is also consistent with the prediction α T = 2.0 of the FD-SOC model. During solar cycle maxima years, the power-law slope is steeper in the range of α T ≈ 2.0-5.0, which can be modeled by a solar-cycle-dependent flare pile-up bias effect. These results corroborate the FD-SOC model, which predicts a power-law slope of α E = 1.5 for flare energies and thus rules out significant nanoflare heating. While the FD-SOC model predicts the probability distribution functions of spatio-temporal scaling laws of nonlinear energy dissipation processes, additional physical models are needed to derive the scaling laws between the geometric SOC parameters and the observed emissivity in different wavelength regimes, as we derive here for soft X-ray emission. The FD-SOC model also yields statistical probabilities for solar flare forecasting.

  4. Periodic Recurrence Patterns In X-Ray Solar Flare Appearances

    Science.gov (United States)

    Gyenge, N.; Erdélyi, R.

    2018-06-01

    The temporal recurrence of micro-flare events is studied for a time interval before and after of major solar flares. Our sample is based on the X-ray flare observations by the Geostationary Operational Environmental Satellite (GOES) and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The analyzed data contain 1330/301 M-class and X-class GOES/RHESSI energetic solar flares and 4062/4119 GOES/RHESSI micro-flares covering the period elapse since 2002. The temporal analysis of recurrence, by Fast Fourier Transform, of the micro-flares, shows multiple significant periods. Based on the GOES and RHESSI data, the temporal analysis also demonstrates that multiple periods manifest simultaneously in both statistical samples without any significant shift over time. In the GOES sample, the detected significant periods are: 11.33, 5.61, 3.75, 2.80, and 2.24 minutes. The RHESSI data show similar significant periods at 8.54, 5.28, 3.66, 2.88, and 2.19 minutes. The periods are interpreted as signatures of standing oscillations, with the longest period (P 1) being the fundamental and others being higher harmonic modes. The period ratio of the fundamental and higher harmonics (P 1/P N ) is also analyzed. The standing modes may be signatures of global oscillations of the entire solar atmosphere encompassing magnetized plasma from the photosphere to the corona in active regions.

  5. Magnetohydrodynamic and thermal processes in solar flare energy build-up and release

    International Nuclear Information System (INIS)

    Tend, W. van.

    1979-01-01

    A solar flare can be described as an instability in the upper solar atmosphere that converts 10 28 ergs to 10 32 ergs of magnetic energy into other forms of energy, mainly kinetic energy. The solar flare gives rise to a wealth of observable phenomena. The author develops a fairly simple model to explain many of these apparently very diverse features of solar flares. (Auth.)

  6. Imaging Observations of Magnetic Reconnection in a Solar Eruptive Flare

    International Nuclear Information System (INIS)

    Li, Y.; Ding, M. D.; Sun, X.; Qiu, J.; Priest, E. R.

    2017-01-01

    Solar flares are among the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of which are probably driven by the eruption of a magnetic flux rope (MFR). Here we report an eruptive flare on 2016 March 23 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory . The extreme-ultraviolet imaging observations exhibit the clear rise and eruption of an MFR. In particular, the observations reveal solid evidence of magnetic reconnection from both the corona and chromosphere during the flare. Moreover, weak reconnection is observed before the start of the flare. We find that the preflare weak reconnection is of tether-cutting type and helps the MFR to rise slowly. Induced by a further rise of the MFR, strong reconnection occurs in the rise phases of the flare, which is temporally related to the MFR eruption. We also find that the magnetic reconnection is more of 3D-type in the early phase, as manifested in a strong-to-weak shear transition in flare loops, and becomes more 2D-like in the later phase, as shown by the apparent rising motion of an arcade of flare loops.

  7. Imaging Observations of Magnetic Reconnection in a Solar Eruptive Flare

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.; Ding, M. D. [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China); Sun, X. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Qiu, J. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Priest, E. R., E-mail: yingli@nju.edu.cn [School of Mathematics and Statistics, University of St Andrews, Fife KY16 9SS, Scotland (United Kingdom)

    2017-02-01

    Solar flares are among the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of which are probably driven by the eruption of a magnetic flux rope (MFR). Here we report an eruptive flare on 2016 March 23 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory . The extreme-ultraviolet imaging observations exhibit the clear rise and eruption of an MFR. In particular, the observations reveal solid evidence of magnetic reconnection from both the corona and chromosphere during the flare. Moreover, weak reconnection is observed before the start of the flare. We find that the preflare weak reconnection is of tether-cutting type and helps the MFR to rise slowly. Induced by a further rise of the MFR, strong reconnection occurs in the rise phases of the flare, which is temporally related to the MFR eruption. We also find that the magnetic reconnection is more of 3D-type in the early phase, as manifested in a strong-to-weak shear transition in flare loops, and becomes more 2D-like in the later phase, as shown by the apparent rising motion of an arcade of flare loops.

  8. A magnetic bald-patch flare in solar active region 11117

    Science.gov (United States)

    Jiang, Chao-Wei; Feng, Xue-Shang; Wu, Shi-Tsan; Hu, Qiang

    2017-09-01

    With SDO observations and a data-constrained magnetohydrodynamics (MHD) model, we identify a confined multi-ribbon flare that occurred on 2010 October 25 in solar active region 11117 as a magnetic bald patch (BP) flare with strong evidence. From the photospheric magnetic field observed by SDO/HMI, we find there are indeed magnetic BPs on the polarity inversion lines (PILs) which match parts of the flare ribbons. From the 3D coronal magnetic field derived from an MHD relaxation model constrained by the vector magnetograms, we find strikingly good agreement of the BP separatrix surface (BPSS) footpoints with the flare ribbons, and the BPSS itself with the hot flaring loop system. Moreover, the triggering of the BP flare can be attributed to a small flux emergence under the lobe of the BPSS, and the relevant change of coronal magnetic field through the flare is reproduced well by the pre-flare and post-flare MHD solutions, which match the corresponding pre- and post-flare AIA observations, respectively. Our work contributes to the study of non-typical flares that constitute the majority of solar flares but which cannot be explained by the standard flare model.

  9. Studies of solar flares: Homology and X-ray line broadening

    Science.gov (United States)

    Ranns, Neale David Raymond

    This thesis starts with an introduction to the solar atmosphere and the physics that governs its behaviour. The formation processes of spectral lines are presented followed by an explanation of employed plasma diagnostic techniques and line broadening mechanisms. The current understanding on some principle concepts of flare physics are reviewed and the topics of flare homology and non-thermal line broadening are introduced. The many solar satellites and instrumentation that were utilised during this thesis are described. Analysis techniques for some instruments are also presented. A series of solar flares that conform to the literature definition for homologous flares are examined. The apparent homology is shown to be caused by emerging flux rather than continual stressing of a single, or group of, magnetic structure's. The implications for flare homology are discussed. The analysis of a solar flare with a rise and peak in the observed non-thermal X-ray line broadening (Vnt) is then performed. The location of the hot plasma within the flare area is determined and consequently the source of Vnt is located to be within and above the flare loops. The flare footpoints are therefore discarded as a possible source location. Viable source locations are discussed with a view to determining the dominant mechanism for the generation of line broadening. The timing relationships between the hard X-ray (HXR) flux and Vnt in many solar flares are then examined. I show that there is a causal relationship between these two parameters and that the HXR rise time is related to the time delay between the maxima of HXR flux and Vnt. The temporal evolution of Vnt is shown to be dependent upon the shape of the HXR burst. The implications of these results are discussed in terms of determining the line broadening mechanism and the limitations of the data. A summary of the results in this thesis is then presented together with suggestions for future research.

  10. Second-stage acceleration in solar flares

    International Nuclear Information System (INIS)

    Mullan, D.J.

    1976-01-01

    A model proposed by Chevalier and Scott to account for cosmic ray acceleration in an expanding supernova remnant is applied to the case of a shock wave injected into the solar corona by a flare. Certain features of solar cosmic rays can be explained by this model. (orig.) [de

  11. A New Relationship Between Soft X-Rays and EUV Flare Light Curves

    Science.gov (United States)

    Thiemann, Edward

    2016-05-01

    Solar flares are the result of magnetic reconnection in the solar corona which converts magnetic energy into kinetic energy resulting in the rapid heating of solar plasma. As this plasma cools, it emits radiation at different EUV wavelengths when the dropping temperature passes a line’s temperature of formation. This results in a delay in the emissions from cooler EUV lines relative to hotter EUV lines. Therefore, characterizing how this hot plasma cools is important for understanding how the corresponding geo-effective extreme ultraviolet (EUV) irradiance evolves in time. I present a simple new framework in which to study flare cooling by using a Lumped Element Thermal Model (LETM). LETM is frequently used in science and engineering to simplify a complex multi-dimensional thermal system by reducing it to a 0-D thermal circuit. For example, a structure that conducts heat out of a system is simplified with a resistive element and a structure that allows a system to store heat is simplified with a capacitive element. A major advantage of LETM is that the specific geometry of a system can be ignored, allowing for an intuitive analysis of the major thermal processes. I show that LETM is able to accurately reproduce the temporal evolution of cooler flare emission lines based on hotter emission line evolution. In particular, it can be used to predict the evolution of EUV flare light curves using the NOAA X-Ray Sensor (XRS).

  12. Magnetic transients in flares

    International Nuclear Information System (INIS)

    Zirin, H.; Tanaka, K.

    1981-01-01

    We present data on magnetic transients (mgtr's) observed in flares on 1980 July 1 and 5 with Big Bear videomagnetograph (VMG). The 1980 July 1 event was a white light flare in which a strong bipolar mgtr was observed, and a definite change in the sunspots occurred at the time of the flare. In the 1980 July 5 flare, a mgtr was observed in only one polarity, and, although no sunspot changes occurred simultaneous with the flare, major spot changes occurred in a period of hours

  13. Spatially inhomogeneous acceleration of electrons in solar flares

    Science.gov (United States)

    Stackhouse, Duncan J.; Kontar, Eduard P.

    2018-04-01

    The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.

  14. Lyman continuum observations of solar flares

    Science.gov (United States)

    Machado, M. E.; Noyes, R. W.

    1978-01-01

    A study is made of Lyman continuum observations of solar flares, using data obtained by the EUV spectroheliometer on the Apollo Telescope Mount. It is found that there are two main types of flare regions: an overall 'mean' flare coincident with the H-alpha flare region, and transient Lyman continuum kernels which can be identified with the H-alpha and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density .000005 g/sq cm in the quiet sun to .0003 g/sq cm in the mean flare, and to .001 g/sq cm in kernels. From these results the amount of chromospheric material 'evaporated' into the high temperature region is derived, which is found to be approximately 10 to the 15th g, in agreement with observations of X-ray emission measures.

  15. The coalescence instability in solar flares

    Science.gov (United States)

    Tajima, T.; Brunel, F.; Sakai, J.-I.; Vlahos, L.; Kundu, M. R.

    1985-01-01

    The nonlinear coalescence instability of current carrying solar loops can explain many of the characteristics of the solar flares such as their impulsive nature, heating and high energy particle acceleration, amplitude oscillations of electromagnetic and emission as well as the characteristics of two-dimensional microwave images obtained during a flare. The plasma compressibility leads to the explosive phase of loop coalescence and its overshoot results in amplitude oscillations in temperatures by adiabatic compression and decompression. It is noted that the presence of strong electric fields and super-Alfvenic flows during the course of the instability play an important role in the production of nonthermal particles. A qualitative explanation on the physical processes taking place during the nonlinear stages of the instability is given.

  16. The coalescence instability in solar flares

    International Nuclear Information System (INIS)

    Tajima, T.; Brunel, F.; Sakai, J.I.; Vlahos, L.; Kundu, M.R.

    1984-01-01

    The non-linear coalescence instability of current carrying solar loops can explain many of the characteristics of the solar flares such as their impulsive nature, heating and high energy particle acceleration, amplitude oscillations of electromagnetic emission as well as the characteristics of 2-D microwave images obtained during a flare. The plasma compressibility leads to the explosive phase of loop coalescence and its overshoot results in amplitude oscillations in temperatures by adiabatic compression and decompression. We note that the presence of strong electric fields and super-Alfvenic flows during the course of the instabilty paly an important role in the production of non-thermal particles. A qualitative explanation on the physical processes taking place during the non-linear stages of the instability is given. (author)

  17. Comparison of emission properties of two homologous flares in AR 11283

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yan; Jing, Ju; Wang, Shuo; Wang, Haimin, E-mail: yx2@njit.edu [Space Weather Research Lab, Center for Solar-Terrestrial Research, New Jersey Institute of Technology 323 Martin Luther King Boulevard, Newark, NJ 07102-1982 (United States)

    2014-05-20

    Large, complex, active regions may produce multiple flares within a certain period of one or two days. These flares could occur in the same location with similar morphologies, commonly referred to as 'homologous flares'. In 2011 September, active region NOAA 11283 produced a pair of homologous flares on the 6th and 7th, respectively. Both of them were white-light (WL) flares, as captured by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory in visible continuum at 6173 Å which is believed to originate from the deep solar atmosphere. We investigate the WL emission of these X-class flares with HMI's seeing-free imaging spectroscopy. The durations of impulsive peaks in the continuum are about 4 minutes. We compare the WL with hard X-ray (HXR) observations for the September 6 flare and find a good correlation between the continuum and HXR both spatially and temporally. In absence of RHESSI data during the second flare on September 7, the derivative of the GOES soft X-ray is used and also found to be well correlated temporally with the continuum. We measure the contrast enhancements, characteristic sizes, and HXR fluxes of the twin flares, which are similar for both flares, indicating analogous triggering and heating processes. However, the September 7 flare was associated with conspicuous sunquake signals whereas no seismic wave was detected during the flare on September 6. Therefore, this comparison suggests that the particle bombardment may not play a dominant role in producing the sunquake events studied in this paper.

  18. ON THE NON-KOLMOGOROV NATURE OF FLARE-PRODUCTIVE SOLAR ACTIVE REGIONS

    Energy Technology Data Exchange (ETDEWEB)

    Mandage, Revati S. [Physics and Astronomy Department, Rice University, 6100 Main MS-61, Houston, TX 77005-1827 (United States); McAteer, R. T. James, E-mail: mcateer@nmsu.edu [Department of Astronomy, New Mexico State University, MSC 4500, Las Cruces, NM 88001 (United States)

    2016-12-20

    A magnetic power spectral analysis is performed on 53 solar active regions, observed from 2011 August to 2012 July. Magnetic field data obtained from the Helioseismic and Magnetic Imager, inverted as Active Region Patches, are used to study the evolution of the magnetic power index as each region rotates across the solar disk. Active regions are classified based on the numbers and sizes of solar flares they produce in order to study the relationship between flare productivity and the magnetic power index. The choice of window size and inertial range plays a key role in determining the correct magnetic power index. The overall distribution of magnetic power indices has a range of 1.0–2.5. Flare-quiet regions peak at a value of 1.6. However, flare-productive regions peak at a value of 2.2. Overall, the histogram of the distribution of power indices of flare-productive active regions is well separated from flare-quiet active regions. Only 12% of flare-quiet regions exhibit an index greater than 2, whereas 90% of flare-productive regions exhibit an index greater than 2. Flare-quiet regions exhibit a high temporal variance (i.e., the index fluctuates between high and low values), whereas flare-productive regions maintain an index greater than 2 for several days. This shows the importance of including the temporal evolution of active regions in flare prediction studies, and highlights the potential of a 2–3 day prediction window for space weather applications.

  19. Energy Release in Solar Flares,

    Science.gov (United States)

    1982-10-01

    Plasma Research, Stanford University P. Kaufmanu CRAA/CNPq -Conseiho lacional de Desenvolvimento Cientifico e Tecnologico, Slo Paulo, SP, Brasil D.F...three phases of energy release in solar flares (Sturrock, 1980). However, a recent article by Feldman e a.. (1982) points to a significant

  20. Center-to-Limb Variability of Hot Coronal EUV Emissions During Solar Flares

    Science.gov (United States)

    Thiemann, E. M. B.; Chamberlin, P. C.; Eparvier, F. G.; Epp, L.

    2018-02-01

    It is generally accepted that densities of quiet-Sun and active region plasma are sufficiently low to justify the optically thin approximation, and this is commonly used in the analysis of line emissions from plasma in the solar corona. However, the densities of solar flare loops are substantially higher, compromising the optically thin approximation. This study begins with a radiative transfer model that uses typical solar flare densities and geometries to show that hot coronal emission lines are not generally optically thin. Furthermore, the model demonstrates that the observed line intensity should exhibit center-to-limb variability (CTLV), with flares observed near the limb being dimmer than those occurring near disk center. The model predictions are validated with an analysis of over 200 flares observed by the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO), which uses six lines, with peak formation temperatures between 8.9 and 15.8 MK, to show that limb flares are systematically dimmer than disk-center flares. The data are then used to show that the electron column density along the line of sight typically increases by 1.76 × 10^{19} cm^{-2} for limb flares over the disk-center flare value. It is shown that the CTLV of hot coronal emissions reduces the amount of ionizing radiation propagating into the solar system, and it changes the relative intensities of lines and bands commonly used for spectral analysis.

  1. MAGNETIC FIELD STRUCTURES TRIGGERING SOLAR FLARES AND CORONAL MASS EJECTIONS

    International Nuclear Information System (INIS)

    Kusano, K.; Bamba, Y.; Yamamoto, T. T.; Iida, Y.; Toriumi, S.; Asai, A.

    2012-01-01

    Solar flares and coronal mass ejections, the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL. In addition, we analyzed two large flares, the X-class flare on 2006 December 13 and the M-class flare on 2011 February 13, using imaging data provided by the Hinode satellite, and we demonstrated that they conform to the simulation predictions. These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

  2. North–South Distribution of Solar Flares during Cycle 23 Bhuwan ...

    Indian Academy of Sciences (India)

    in the SGD (Solar Geophysical Data) during the time span of 01 May 1996 to 31. December 2003, covering almost 8 years of solar cycle 23. During this period, the occurrence of 20235 Hα flares is reported. In Hα, flares are classified according to their importance and brightness classes. The important class (S = subflare, ...

  3. Characteristic studies on solar x-ray flares and solar radio bursts during descending phases of solar cycles 22 and 23

    International Nuclear Information System (INIS)

    Bhattacharya, J.; De, B.K.; Guha, A.

    2014-01-01

    In this paper, a comparative study between the solar X-ray flares and solar radio bursts in terms of their duration and energy has been done. This has been done by analyzing the data in a statistical way covering the descending phase of the 22nd and 23rd solar cycles. It has been observed that the most probable value of duration of both solar X-ray flares and solar radio bursts remain same for a particular cycle. There is a slight variation in the most probable value of duration in going from 22nd cycle to 23rd cycle in the case of both kinds of events. This small variation may be due to the variation of polar field. A low correlation has been observed between energy fluxes in solar X-ray flares and in solar radio bursts. This has been attributed to the non symmetric contribution of energy to the solar radio and X-ray band controlled by solar magnetic field

  4. Solar flares and the cosmic ray intensity

    International Nuclear Information System (INIS)

    Hatton, C.J.

    1980-01-01

    The relationship between the cosmic ray intensity and solar activity during solar cycle 20 is discussed. A model is developed whereby it is possible to simulate the observed cosmic ray intensity from the observed number of solar flares of importance >= 1. This model leads to a radius for the modulation region of 60-70 AU. It is suggested that high speed solar streams also made a small contribution to the modulation of cosmic rays during solar cycle 20. (orig.)

  5. SIZE DISTRIBUTIONS OF SOLAR FLARES AND SOLAR ENERGETIC PARTICLE EVENTS

    International Nuclear Information System (INIS)

    Cliver, E. W.; Ling, A. G.; Belov, A.; Yashiro, S.

    2012-01-01

    We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast (≥1000 km s –1 ) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (α values) of power-law size distributions of the peak 1-8 Å fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes ≥1 pr cm –2 s –1 sr –1 ) and (b) fast CMEs were ∼1.3-1.4 compared to ∼1.2 for the peak proton fluxes of >10 MeV SEP events and ∼2 for the peak 1-8 Å fluxes of all SXR flares. The difference of ∼0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.

  6. Foretelling Flares and Solar Energetic Particle Events: the FORSPEF tool

    Science.gov (United States)

    Anastasiadis, Anastasios; Papaioannou, Athanasios; Sandberg, Ingmar; Georgoulis, Manolis K.; Tziotziou, Kostas; Jiggens, Piers

    2017-04-01

    A novel integrated prediction system, for both solar flares (SFs) and solar energetic particle (SEP) events is being presented. The Forecasting Solar Particle Events and Flares (FORSPEF) provides forecasting of solar eruptive events, such as SFs with a projection to coronal mass ejections (CMEs) (occurrence and velocity) and the likelihood of occurrence of a SEP event. In addition, FORSPEF, also provides nowcasting of SEP events based on actual SF and CME near real-time data, as well as the complete SEP profile (peak flux, fluence, rise time, duration) per parent solar event. The prediction of SFs relies on a morphological method: the effective connected magnetic field strength (Beff); it is based on an assessment of potentially flaring active-region (AR) magnetic configurations and it utilizes sophisticated analysis of a large number of AR magnetograms. For the prediction of SEP events new methods have been developed for both the likelihood of SEP occurrence and the expected SEP characteristics. In particular, using the location of the flare (longitude) and the flare size (maximum soft X-ray intensity), a reductive statistical method has been implemented. Moreover, employing CME parameters (velocity and width), proper functions per width (i.e. halo, partial halo, non-halo) and integral energy (E>30, 60, 100 MeV) have been identified. In our technique warnings are issued for all > C1.0 soft X-ray flares. The prediction time in the forecasting scheme extends to 24 hours with a refresh rate of 3 hours while the respective prediction time for the nowcasting scheme depends on the availability of the near real-time data and falls between 15-20 minutes for solar flares and 6 hours for CMEs. We present the modules of the FORSPEF system, their interconnection and the operational set up. The dual approach in the development of FORPSEF (i.e. forecasting and nowcasting scheme) permits the refinement of predictions upon the availability of new data that characterize changes on

  7. An operational integrated short-term warning solution for solar radiation storms: introducing the Forecasting Solar Particle Events and Flares (FORSPEF) system

    Science.gov (United States)

    Anastasiadis, Anastasios; Sandberg, Ingmar; Papaioannou, Athanasios; Georgoulis, Manolis; Tziotziou, Kostas; Jiggens, Piers; Hilgers, Alain

    2015-04-01

    We present a novel integrated prediction system, of both solar flares and solar energetic particle (SEP) events, which is in place to provide short-term warnings for hazardous solar radiation storms. FORSPEF system provides forecasting of solar eruptive events, such as solar flares with a projection to coronal mass ejections (CMEs) (occurrence and velocity) and the likelihood of occurrence of a SEP event. It also provides nowcasting of SEP events based on actual solar flare and CME near real-time alerts, as well as SEP characteristics (peak flux, fluence, rise time, duration) per parent solar event. The prediction of solar flares relies on a morphological method which is based on the sophisticated derivation of the effective connected magnetic field strength (Beff) of potentially flaring active-region (AR) magnetic configurations and it utilizes analysis of a large number of AR magnetograms. For the prediction of SEP events a new reductive statistical method has been implemented based on a newly constructed database of solar flares, CMEs and SEP events that covers a large time span from 1984-2013. The method is based on flare location (longitude), flare size (maximum soft X-ray intensity), and the occurrence (or not) of a CME. Warnings are issued for all > C1.0 soft X-ray flares. The warning time in the forecasting scheme extends to 24 hours with a refresh rate of 3 hours while the respective warning time for the nowcasting scheme depends on the availability of the near real-time data and falls between 15-20 minutes. We discuss the modules of the FORSPEF system, their interconnection and the operational set up. The dual approach in the development of FORPSEF (i.e. forecasting and nowcasting scheme) permits the refinement of predictions upon the availability of new data that characterize changes on the Sun and the interplanetary space, while the combined usage of solar flare and SEP forecasting methods upgrades FORSPEF to an integrated forecasting solution. This

  8. Neutrino fluxes produced by high energy solar flare particles

    International Nuclear Information System (INIS)

    Kolomeets, E.V.; Shmonin, V.L.

    1975-01-01

    In this work the calculated differential energy spectra of neutrinos poduced by high energy protons accelerated during 'small' solar flares are presented. The muon flux produced by neutrino interactions with the matter at large depths under the ground is calculated. The obtained flux of muons for the total number of solar flare accelerated protons of 10 28 - 10 32 is within 10 9 - 10 13 particles/cm 2 X s x ster. (orig.) [de

  9. An essay on sunspots and solar flares

    International Nuclear Information System (INIS)

    Akasofu, S.-I.

    1984-01-01

    The presently prevailing theories of sunspots and solar flares rely on the hypothetical presence of magnetic flux tubes beneath the photosphere and the two subsequent hypotheses, their emergence above the photosphere and explosive magnetic reconnection, converting magnetic energy carried by the flux tubes for solar flare energy. In this paper, attention is paid to the fact that there are large-scale magnetic fields which divide the photosphere into positive and negative (line-of-sight) polarity regions and that they are likely to be more fundamental than sunspot fields, as emphasized most recently by McIntosh. A new phenomenological model of the sunspot pair formation is then constructed by considering an amplification process of these large-scale fields near their boundaries by shear flows, including localized vortex motions. The amplification results from a dynamo process associated with such vortex flows and the associated convergence flow in the large-scale fields. This dynamo process generates also some of the familiar ''force-free'' fields or the ''sheared'' magnetic fields in which the magnetic field-aligned currents are essential. Upward field-aligned currents generated by the dynamo process are carried by downward streaming electrons which are expected to be accelerated by an electric potential structure; a similar structure is responsible for accelerating auroral electrons in the magnetosphere. Depending on the magnetic field configuration and the shear flows, the current-carrying electrons precipitate into different geometrical patterns, causing circular flares, umbral flares, two-ribbon flares, etc. Thus, it is suggested that ''low temperature flares'' are directly driven by the photospheric dynamo process. (author)

  10. Space radiation dose analysis for solar flare of August 1989

    International Nuclear Information System (INIS)

    Nealy, J.E.; Simonsen, L.C.; Sauer, H.H.; Wilson, J.W.; Townsend, L.W.

    1990-12-01

    Potential dose and dose rate levels to astronauts in deep space are predicted for the solar flare event which occurred during the week of August 13, 1989. The Geostationary Operational Environmental Satellite (GOES-7) monitored the temporal development and energy characteristics of the protons emitted during this event. From these data, differential fluence as a function of energy was obtained in order to analyze the flare using the Langley baryon transport code, BRYNTRN, which describes the interactions of incident protons in matter. Dose equivalent estimates for the skin, ocular lens, and vital organs for 0.5 to 20 g/sq cm of aluminum shielding were predicted. For relatively light shielding (less than 2 g/sq cm), the skin and ocular lens 30-day exposure limits are exceeded within several hours of flare onset. The vital organ (5 cm depth) dose equivalent is exceeded only for the thinnest shield (0.5 g/sq cm). Dose rates (rem/hr) for the skin, ocular lens, and vital organs are also computed

  11. The Dependence of Solar Flare Limb Darkening on Emission Peak Formation Temperature

    Science.gov (United States)

    Thiemann, Edward; Epp, Luke; Eparvier, Francis; Chamberlin, Phillip C.

    2017-08-01

    Solar limb effects are local brightening or darkening of an emission that depend on where in the Sun's atmosphere it forms. Near the solar limb, optically thick (thin) emissions will darken (brighten) as the column of absorbers (emitters) along the line-of-sight increases. Note that in limb brightening, emission sources are re-arranged whereas in limb darkening they are obscured. Thus, only limb darkening is expected to occur in disk integrated observations. Limb darkening also results in center-to-limb variations of disk-integrated solar flare spectra, with important consequences for how planetary atmospheres are affected by flares. Flares are typically characterized by their flux in the optically thin 0.1-0.8 nm band measured by the X-ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES). On the other hand, Extreme Ultraviolet (EUV) line emissions can limb darken because they are sensitive to resonant scattering, resulting in a flare's location on the solar disk controlling the amount of ionizing radiation that reaches a planet. For example, an X-class flare originating from disk center may significantly heat a planet's thermosphere, whereas the same flare originating near the limb may have no effect because much of the effective emissions are scattered in the solar corona.To advance the relatively poor understanding of flare limb darkening, we use over 300 M-class or larger flares observed by the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) to characterize limb darkening as a function of emission peak formation temperature, Tf. For hot coronal emissions (Tf>2 MK), these results show a linear relationship between the degree of limb darkening and Tf where lines with Tf=2 MK darken approximately 7 times more than lines with Tf=16 MK. Because the extent of limb darkening is dependent on the height of the source plasma, we use simple Beer-Lambert radiative transfer analysis to interpret these results

  12. NEW SOLAR EXTREME-ULTRAVIOLET IRRADIANCE OBSERVATIONS DURING FLARES

    International Nuclear Information System (INIS)

    Woods, Thomas N.; Hock, Rachel; Eparvier, Frank; Jones, Andrew R.; Chamberlin, Phillip C.; Klimchuk, James A.; Didkovsky, Leonid; Judge, Darrell; Mariska, John; Warren, Harry; Schrijver, Carolus J.; Webb, David F.; Bailey, Scott; Tobiska, W. Kent

    2011-01-01

    New solar extreme-ultraviolet (EUV) irradiance observations from the NASA Solar Dynamics Observatory (SDO) EUV Variability Experiment provide full coverage in the EUV range from 0.1 to 106 nm and continuously at a cadence of 10 s for spectra at 0.1 nm resolution and even faster, 0.25 s, for six EUV bands. These observations can be decomposed into four distinct characteristics during flares. First, the emissions that dominate during the flare's impulsive phase are the transition region emissions, such as the He II 30.4 nm. Second, the hot coronal emissions above 5 MK dominate during the gradual phase and are highly correlated with the GOES X-ray. A third flare characteristic in the EUV is coronal dimming, seen best in the cool corona, such as the Fe IX 17.1 nm. As the post-flare loops reconnect and cool, many of the EUV coronal emissions peak a few minutes after the GOES X-ray peak. One interesting variation of the post-eruptive loop reconnection is that warm coronal emissions (e.g., Fe XVI 33.5 nm) sometimes exhibit a second large peak separated from the primary flare event by many minutes to hours, with EUV emission originating not from the original flare site and its immediate vicinity, but rather from a volume of higher loops. We refer to this second peak as the EUV late phase. The characterization of many flares during the SDO mission is provided, including quantification of the spectral irradiance from the EUV late phase that cannot be inferred from GOES X-ray diagnostics.

  13. Study of the behaviour of the equatorial ionization anomaly (EIA) during solar flares

    Science.gov (United States)

    Aggarwal, Malini; Astafyeva, Elvira

    2014-05-01

    A solar flare occurring in the sun's chromosphere is observed in various wavebands (radio to x-rays). The response of the solar flare which causes sudden changes in the earth's ionosphere is not yet well understood though investigations suggested that its impact depends on the size and location of occurrence of solar flare on sun. Considering this, we have carried an investigation to study the response of two strong and gradual solar flares: 2 Apr 2001 (X20, limb) and 7 Feb 2010 (M6.4, disk) on the earth's equatorial-low latitude regions using multi-technique observations of satellite and ground-based instruments. We found a weakening of strength of equatorial ionization anomaly (EIA) in total electron content during both the flares as observed by TOPEX, JASON-1 and JASON-2 altimeter measurements. The H component of the geomagnetic field also shows a sudden change at equatorial and low latitude stations in the sunlit hemisphere during the flare. The observations of ionosonde at low-latitudes indicate a strong absorption of higher-frequency radio signals. The detail response of these flare on EIA of the earth's ionosphere will be presented and discussed.

  14. Impulsiveness and energetics in solar flares with and without type II radio bursts - A comparison of hard X-ray characteristics for over 2500 solar flares

    Science.gov (United States)

    Pearson, Douglas H.; Nelson, Robert; Kojoian, Gabriel; Seal, James

    1989-01-01

    The hard X-ray characteristics of more than 2500 solar flares are used to study the relative size, impulsiveness, and energetics of flares with and without type II radio bursts. A quantitative definition of the hard X-ray impulsiveness is introduced, which may be applied to a large number of events unambiguously. It is found that the flares with type II bursts are generally not significantly larger, more impulsive, or more energetic than those without type II bursts. Also, no evidence is found to suggest a simple classification of the flares as either 'impulsive' or 'gradual'. Because type II bursts are present even in small flares with relatively unimpulsive energy releases, it is concluded that changes in the ambient conditions of the solar atmosphere causing an unusually low Alfven speed may be important in the generation of the shock wave that produces type II radio bursts.

  15. Statistical study of spatio-temporal distribution of precursor solar flares associated with major flares

    Science.gov (United States)

    Gyenge, N.; Ballai, I.; Baranyi, T.

    2016-07-01

    The aim of the present investigation is to study the spatio-temporal distribution of precursor flares during the 24 h interval preceding M- and X-class major flares and the evolution of follower flares. Information on associated (precursor and follower) flares is provided by Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Flare list, while the major flares are observed by the Geostationary Operational Environmental Satellite (GOES) system satellites between 2002 and 2014. There are distinct evolutionary differences between the spatio-temporal distributions of associated flares in about one-day period depending on the type of the main flare. The spatial distribution was characterized by the normalized frequency distribution of the quantity δ (the distance between the major flare and its precursor flare normalized by the sunspot group diameter) in four 6 h time intervals before the major event. The precursors of X-class flares have a double-peaked spatial distribution for more than half a day prior to the major flare, but it changes to a lognormal-like distribution roughly 6 h prior to the event. The precursors of M-class flares show lognormal-like distribution in each 6 h subinterval. The most frequent sites of the precursors in the active region are within a distance of about 0.1 diameter of sunspot group from the site of the major flare in each case. Our investigation shows that the build-up of energy is more effective than the release of energy because of precursors.

  16. Table-top solar flares produced with laser driven magnetic reconnections

    Directory of Open Access Journals (Sweden)

    Zhong J.Y.

    2013-11-01

    Full Text Available The American Nuclear Society (ANS has presented the prestigious Edward Teller award to Dr. Bruce A. Remington during the 2011 IFSA conference due to his “pioneering scientific work in the fields of inertial confinement fusion (ICF, and especially developing an international effort in high energy density laboratory astrophysics” [1,2]. This is a great acknowledgement to the subject of high energy density laboratory astrophysics. In this context, we report here one experiment conducted to model solar flares in the laboratory with intense lasers [3]. The mega-gauss –scale magnetic fields produced by laser produced plasmas can be used to make magnetic reconnection topology. We have produced one table-top solar flare in our laboratory experiment with the same geometric setup as associated with solar flares.

  17. High-energy particle production in solar flares (SEP, gamma-ray and neutron emissions). [solar energetic particles

    Science.gov (United States)

    Chupp, E. L.

    1987-01-01

    Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near earth, consist of electrons and ions that range in energy from 10 keV to about 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while X-ray, gamma-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism. The paper reviews the physics of gamma-rays and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. Particular attention is given to energetic particle production in the large flare on June 3, 1982.

  18. Deep Learning Based Solar Flare Forecasting Model. I. Results for Line-of-sight Magnetograms

    Science.gov (United States)

    Huang, Xin; Wang, Huaning; Xu, Long; Liu, Jinfu; Li, Rong; Dai, Xinghua

    2018-03-01

    Solar flares originate from the release of the energy stored in the magnetic field of solar active regions, the triggering mechanism for these flares, however, remains unknown. For this reason, the conventional solar flare forecast is essentially based on the statistic relationship between solar flares and measures extracted from observational data. In the current work, the deep learning method is applied to set up the solar flare forecasting model, in which forecasting patterns can be learned from line-of-sight magnetograms of solar active regions. In order to obtain a large amount of observational data to train the forecasting model and test its performance, a data set is created from line-of-sight magnetogarms of active regions observed by SOHO/MDI and SDO/HMI from 1996 April to 2015 October and corresponding soft X-ray solar flares observed by GOES. The testing results of the forecasting model indicate that (1) the forecasting patterns can be automatically reached with the MDI data and they can also be applied to the HMI data; furthermore, these forecasting patterns are robust to the noise in the observational data; (2) the performance of the deep learning forecasting model is not sensitive to the given forecasting periods (6, 12, 24, or 48 hr); (3) the performance of the proposed forecasting model is comparable to that of the state-of-the-art flare forecasting models, even if the duration of the total magnetograms continuously spans 19.5 years. Case analyses demonstrate that the deep learning based solar flare forecasting model pays attention to areas with the magnetic polarity-inversion line or the strong magnetic field in magnetograms of active regions.

  19. The energetic relationship among geoeffective solar flares, associated CMEs and SEPs

    International Nuclear Information System (INIS)

    Bhatt Nipa J; Jain Rajmal; Awasthi Arun Kumar

    2013-01-01

    Major solar eruptions (flares, coronal mass ejections (CMEs) and solar energetic particles (SEPs)) strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares (observed by RHESSI), followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship (r ∼ 0.79) between the hard X-ray (HXR) spectral index (before flare-peak) and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law (r ∼ 0.9) between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event (r ∼ 0.96). We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics

  20. Excitation of helium resonance lines in solar flares

    International Nuclear Information System (INIS)

    Porter, J.G.; Gebbie, K.B.; November, L.J.; Joint Institute for Laboratory Astrophysics, Boulder, CO; National Solar Observatory, Sunspot, NM)

    1985-01-01

    Helium resonance line intensities are calculated for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. The differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra are examined. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining which of these models most nearly represents the density vs temperature structure and soft X-ray flux in the flaring solar transition region, and the temperature and dominant mechanaism of formation of the helium line spectrum during a flare. 26 references

  1. ANATOMY OF A SOLAR FLARE: MEASUREMENTS OF THE 2006 DECEMBER 14 X-CLASS FLARE WITH GONG, HINODE, AND RHESSI

    International Nuclear Information System (INIS)

    Matthews, S. A.; Zharkov, S.; Zharkova, V. V.

    2011-01-01

    Some of the most challenging observations to explain in the context of existing flare models are those related to the lower atmosphere and below the solar surface. Such observations, including changes in the photospheric magnetic field and seismic emission, indicate the poorly understood connections between energy release in the corona and its impact in the photosphere and the solar interior. Using data from Hinode, TRACE, RHESSI, and GONG we study the temporal and spatial evolution of the 2006 December 14 X-class flare in the chromosphere, photosphere, and the solar interior. We investigate the connections between the emission at various atmospheric depths, including acoustic signatures obtained by time-distance and holography methods from the GONG data. We report the horizontal displacements observed in the photosphere linked to the timing and locations of the acoustic signatures we believe to be associated with this flare, their vertical and horizontal displacement velocities, and their potential implications for current models of flare dynamics.

  2. Thermodynamic Spectrum of Solar Flares Based on SDO/EVE Observations: Techniques and First Results

    Science.gov (United States)

    Wang, Yuming; Zhou, Zhenjun; Zhang, Jie; Liu, Kai; Liu, Rui; Shen, Chenglong; Chamberlin, Phillip C.

    2016-01-01

    The Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) provides rich information on the thermodynamic processes of solar activities, particularly on solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could potentially be useful for extreme ultraviolet (EUV) astronomy to learn about the eruptive activities on distant astronomical objects. Through several cases, we illustrate what we can learn from the TDS charts. Furthermore, we apply the TDS method to 74 flares equal to or greater than the M5.0 class, and reach the following statistical results. First, EUV peaks are always behind the soft X-ray (SXR) peaks and stronger flares tend to have faster cooling rates. There is a power-law correlation between the peak delay times and the cooling rates, suggesting a coherent cooling process of flares from SXR to EUV emissions. Second, there are two distinct temperature drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperature like a quadrilateral, whereas for Type II flares the drift pattern looks like a triangle. Statistical analysis suggests that Type II flares are more impulsive than Type I flares. Third, for late-phase flares, the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class, and the flares with a strong late phase are all confined. We believe that the re-deposition of the energy carried by a flux rope, which unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Furthermore, we show the signatures of the flare thermodynamic process in the chromosphere and transition region in the TDS charts. These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associated solar eruptions, e.g., coronal mass ejections.

  3. THERMODYNAMIC SPECTRUM OF SOLAR FLARES BASED ON SDO/EVE OBSERVATIONS: TECHNIQUES AND FIRST RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuming; Zhou, Zhenjun; Liu, Kai; Liu, Rui; Shen, Chenglong [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zhang, Jie [School of Physics, Astronomy and Computational Sciences, George Mason University, 4400 University Drive, MSN 6A2, Fairfax, VA 22030 (United States); Chamberlin, Phillip C., E-mail: ymwang@ustc.edu.cn [Solar Physics Laboratory, Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-03-15

    The Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) provides rich information on the thermodynamic processes of solar activities, particularly on solar flares. Here, we develop a method to construct thermodynamic spectrum (TDS) charts based on the EVE spectral lines. This tool could potentially be useful for extreme ultraviolet (EUV) astronomy to learn about the eruptive activities on distant astronomical objects. Through several cases, we illustrate what we can learn from the TDS charts. Furthermore, we apply the TDS method to 74 flares equal to or greater than the M5.0 class, and reach the following statistical results. First, EUV peaks are always behind the soft X-ray (SXR) peaks and stronger flares tend to have faster cooling rates. There is a power-law correlation between the peak delay times and the cooling rates, suggesting a coherent cooling process of flares from SXR to EUV emissions. Second, there are two distinct temperature drift patterns, called Type I and Type II. For Type I flares, the enhanced emission drifts from high to low temperature like a quadrilateral, whereas for Type II flares the drift pattern looks like a triangle. Statistical analysis suggests that Type II flares are more impulsive than Type I flares. Third, for late-phase flares, the peak intensity ratio of the late phase to the main phase is roughly correlated with the flare class, and the flares with a strong late phase are all confined. We believe that the re-deposition of the energy carried by a flux rope, which unsuccessfully erupts out, into thermal emissions is responsible for the strong late phase found in a confined flare. Furthermore, we show the signatures of the flare thermodynamic process in the chromosphere and transition region in the TDS charts. These results provide new clues to advance our understanding of the thermodynamic processes of solar flares and associated solar eruptions, e.g., coronal mass ejections.

  4. The soft X-ray telescope for the SOLAR-A mission

    Science.gov (United States)

    Tsuneta, S.; Acton, L.; Bruner, M.; Lemen, J.; Brown, W.; Caravalho, R.; Catura, R.; Freeland, S.; Jurcevich, B.; Owens, J.

    1991-01-01

    The Soft X-ray Telescope (SXT) of the SOLAR-A mission is designed to produce X-ray movies of flares with excellent angular and time resolution as well as full-disk X-ray images for general studies. A selection of thin metal filters provide a measure of temperature discrimination and aid in obtaining the wide dynamic range required for solar observing. The co-aligned SXT aspect telescope will yield optical images for aspect reference, white-light flare and sunspot studies, and, possibly, helioseismology. This paper describes the capabilities and characteristics of the SXT for scientific observing.

  5. Automated Solar Flare Detection and Feature Extraction in High-Resolution and Full-Disk Hα Images

    Science.gov (United States)

    Yang, Meng; Tian, Yu; Liu, Yangyi; Rao, Changhui

    2018-05-01

    In this article, an automated solar flare detection method applied to both full-disk and local high-resolution Hα images is proposed. An adaptive gray threshold and an area threshold are used to segment the flare region. Features of each detected flare event are extracted, e.g. the start, peak, and end time, the importance class, and the brightness class. Experimental results have verified that the proposed method can obtain more stable and accurate segmentation results than previous works on full-disk images from Big Bear Solar Observatory (BBSO) and Kanzelhöhe Observatory for Solar and Environmental Research (KSO), and satisfying segmentation results on high-resolution images from the Goode Solar Telescope (GST). Moreover, the extracted flare features correlate well with the data given by KSO. The method may be able to implement a more complicated statistical analysis of Hα solar flares.

  6. Evidence for solar flare rare gases in the Khor Temiki aubrite.

    Science.gov (United States)

    Rajan, R. S.; Price, P. B.

    1973-01-01

    It has been found by studying a number of gas-rich meteorites, including Khor Temiki that there is a correlation between the abundance of 'track-rich' grains and the concentration of trapped rare gases. The amount of solar flare gas in Khor Temiki is examined. It is pointed out that the Khor Temiki enstatite is an ideal sample in which to look for evidence of solar flare gases because there has been little or no diffusion loss of solar wind gases.

  7. Multifractality as a Measure of Complexity in Solar Flare Activity

    Science.gov (United States)

    Sen, Asok K.

    2007-03-01

    In this paper we use the notion of multifractality to describe the complexity in H α flare activity during the solar cycles 21, 22, and 23. Both northern and southern hemisphere flare indices are analyzed. Multifractal behavior of the flare activity is characterized by calculating the singularity spectrum of the daily flare index time series in terms of the Hölder exponent. The broadness of the singularity spectrum gives a measure of the degree of multifractality or complexity in the flare index data. The broader the spectrum, the richer and more complex is the structure with a higher degree of multifractality. Using this broadness measure, complexity in the flare index data is compared between the northern and southern hemispheres in each of the three cycles, and among the three cycles in each of the two hemispheres. Other parameters of the singularity spectrum can also provide information about the fractal properties of the flare index data. For instance, an asymmetry to the left or right in the singularity spectrum indicates a dominance of high or low fractal exponents, respectively, reflecting a relative abundance of large or small fluctuations in the total energy emitted by the flares. Our results reveal that in the even (22nd) cycle the singularity spectra are very similar for the northern and southern hemispheres, whereas in the odd cycles (21st and 23rd) they differ significantly. In particular, we find that in cycle 21, the northern hemisphere flare index data have higher complexity than its southern counterpart, with an opposite pattern prevailing in cycle 23. Furthermore, small-scale fluctuations in the flare index time series are predominant in the northern hemisphere in the 21st cycle and are predominant in the southern hemisphere in the 23rd cycle. Based on these findings one might suggest that, from cycle to cycle, there exists a smooth switching between the northern and southern hemispheres in the multifractality of the flaring process. This new

  8. Probing the Production of Extreme-ultraviolet Late-phase Solar Flares Using the Model Enthalpy-based Thermal Evolution of Loops

    Science.gov (United States)

    Dai, Yu; Ding, Mingde

    2018-04-01

    Recent observations in extreme-ultraviolet (EUV) wavelengths reveal an EUV late phase in some solar flares that is characterized by a second peak in warm coronal emissions (∼3 MK) several tens of minutes to a few hours after the soft X-ray (SXR) peak. Using the model enthalpy-based thermal evolution of loops (EBTEL), we numerically probe the production of EUV late-phase solar flares. Starting from two main mechanisms of producing the EUV late phase, i.e., long-lasting cooling and secondary heating, we carry out two groups of numerical experiments to study the effects of these two processes on the emission characteristics in late-phase loops. In either of the two processes an EUV late-phase solar flare that conforms to the observational criteria can be numerically synthesized. However, the underlying hydrodynamic and thermodynamic evolutions in late-phase loops are different between the two synthetic flare cases. The late-phase peak due to a long-lasting cooling process always occurs during the radiative cooling phase, while that powered by a secondary heating is more likely to take place in the conductive cooling phase. We then propose a new method for diagnosing the two mechanisms based on the shape of EUV late-phase light curves. Moreover, from the partition of energy input, we discuss why most solar flares are not EUV late flares. Finally, by addressing some other factors that may potentially affect the loop emissions, we also discuss why the EUV late phase is mainly observed in warm coronal emissions.

  9. A solar tornado triggered by flares?

    OpenAIRE

    Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C.

    2013-01-01

    Context. Solar tornados are dynamical, conspicuously helical magnetic structures that are mainly observed as a prominence activity. Aims. We investigate and propose a triggering mechanism for the solar tornado observed in a prominence cavity by SDO/AIA on September 25, 2011. Methods. High-cadence EUV images from the SDO/AIA and the Ahead spacecraft of STEREO/EUVI are used to correlate three flares in the neighbouring active-region (NOAA 11303) and their EUV waves with the dynamical de...

  10. Study of s-component of the solar radio emission and short-term quantitative prediction of powerful solar flares

    International Nuclear Information System (INIS)

    Guseynov, Sh; Gakhramanov, I.G.

    2012-01-01

    Full text : All living and non-living things on Earth is dependent on the processes occurring in the Sun. Therefore the study of the Sun with the aim to predict powerful solar flares is of great scientific and practical importance. It is known that the main drawback of modern forecasting of solar flares and the low reliability of forecasts is the lack of use of the physical concepts of the mechanism of flares

  11. Coordinated soft X-ray and H-alpha observation of solar flares

    Science.gov (United States)

    Zarro, D. M.; Canfield, R. C.; Metcalf, T. R.; Lemen, J. R.

    1988-01-01

    Soft X-ray, Ca XIX, and H-alpha observations obtained for a set of four solar flares in the impulsive phase are analyzed. A blue asymmetry was observed in the coronal Ca XIX line during the soft-Xray rise phase in all of the events. A red asymmetry was observed simultaneously in chromospheric H-alpha at spatial locations associated with enhanced flare heating. It is shown that the impulsive phase momentum of upflowing soft X-ray plasma equalled that of the downflowing H-alpha plasma to within an order of magnitude. This supports the explosive chromospheric evaporation model of solar flares.

  12. SLIPPING MAGNETIC RECONNECTIONS WITH MULTIPLE FLARE RIBBONS DURING AN X-CLASS SOLAR FLARE

    International Nuclear Information System (INIS)

    Zheng, Ruisheng; Chen, Yao; Wang, Bing

    2016-01-01

    With the observations of the Solar Dynamics Observatory , we present the slipping magnetic reconnections with multiple flare ribbons (FRs) during an X1.2 eruptive flare on 2014 January 7. A center negative polarity was surrounded by several positive ones, and three FRs appeared. The three FRs showed apparent slipping motions, and hook structures formed at their ends. Due to the moving footpoints of the erupting structures, one tight semi-circular hook disappeared after the slippage along its inner and outer edges, and coronal dimmings formed within the hook. The east hook also faded as a result of the magnetic reconnection between the arcades of a remote filament and a hot loop that was impulsively heated by the under flare loops. Our results are accordant with the slipping magnetic reconnection regime in three-dimensional standard model for eruptive flares. We suggest that the complex structures of the flare are likely a consequence of the more complex flux distribution in the photosphere, and the eruption involves at least two magnetic reconnections.

  13. The impact of solar flares and magnetic storms on humans

    Energy Technology Data Exchange (ETDEWEB)

    Joselyn, J.A. (NOAA, Space Environment Laboratory, Boulder, CO (United States))

    1992-03-01

    Three classes of solar emanations, namely, photon radiation from solar flares, solar energetic particles, and inhomogeneities in the solar wind that drive magnetic storms, are examined, and their effects on humans and technological systems are discussed. Solar flares may disrupt radio communications in the HF and VLF ranges. Energetic particles pose a special hazard at low-earth orbit and above, where they can penetrate barriers such as spacesuits and aluminum and destroy cells and solid state electronics. Energetic solar particles also influence terrestrial radio waves propagating through polar regions. Magnetic storms may disturb the operation of navigation instruments, power lines and pipelines, and satellites; they give rise to ionospheric storms which affect radio communication at all latitudes. There is also a growing body of evidence that changes in the geomagnetic field affect biological systems. 3 refs.

  14. The impact of solar flares and magnetic storms on humans

    International Nuclear Information System (INIS)

    Joselyn, J.A.

    1992-01-01

    Three classes of solar emanations, namely, photon radiation from solar flares, solar energetic particles, and inhomogeneities in the solar wind that drive magnetic storms, are examined, and their effects on humans and technological systems are discussed. Solar flares may disrupt radio communications in the HF and VLF ranges. Energetic particles pose a special hazard at low-earth orbit and above, where they can penetrate barriers such as spacesuits and aluminum and destroy cells and solid state electronics. Energetic solar particles also influence terrestrial radio waves propagating through polar regions. Magnetic storms may disturb the operation of navigation instruments, power lines and pipelines, and satellites; they give rise to ionospheric storms which affect radio communication at all latitudes. There is also a growing body of evidence that changes in the geomagnetic field affect biological systems. 3 refs

  15. Toward an Efficient Prediction of Solar Flares: Which Parameters, and How?

    Directory of Open Access Journals (Sweden)

    Manolis K. Georgoulis

    2013-11-01

    Full Text Available Solar flare prediction has become a forefront topic in contemporary solar physics, with numerous published methods relying on numerous predictive parameters, that can even be divided into parameter classes. Attempting further insight, we focus on two popular classes of flare-predictive parameters, namely multiscale (i.e., fractal and multifractal and proxy (i.e., morphological parameters, and we complement our analysis with a study of the predictive capability of fundamental physical parameters (i.e., magnetic free energy and relative magnetic helicity. Rather than applying the studied parameters to a comprehensive statistical sample of flaring and non-flaring active regions, that was the subject of our previous studies, the novelty of this work is their application to an exceptionally long and high-cadence time series of the intensely eruptive National Oceanic and Atmospheric Administration (NOAA active region (AR 11158, observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Aiming for a detailed study of the temporal evolution of each parameter, we seek distinctive patterns that could be associated with the four largest flares in the AR in the course of its five-day observing interval. We find that proxy parameters only tend to show preflare impulses that are practical enough to warrant subsequent investigation with sufficient statistics. Combining these findings with previous results, we conclude that: (i carefully constructed, physically intuitive proxy parameters may be our best asset toward an efficient future flare-forecasting; and (ii the time series of promising parameters may be as important as their instantaneous values. Value-based prediction is the only approach followed so far. Our results call for novel signal and/or image processing techniques to efficiently utilize combined amplitude and temporal-profile information to optimize the inferred solar-flare probabilities.

  16. Flare stars

    International Nuclear Information System (INIS)

    Nicastro, A.J.

    1981-01-01

    The least massive, but possibly most numerous, stars in a galaxy are the dwarf M stars. It has been observed that some of these dwarfs are characterized by a short increase in brightness. These stars are called flare stars. These flare stars release a lot of energy in a short amount of time. The process producing the eruption must be energetic. The increase in light intensity can be explained by a small area rising to a much higher temperature. Solar flares are looked at to help understand the phenomenon of stellar flares. Dwarfs that flare are observed to have strong magnetic fields. Those dwarf without the strong magnetic field do not seem to flare. It is believed that these regions of strong magnetic fields are associated with star spots. Theories on the energy that power the flares are given. Astrophysicists theorize that the driving force of a stellar flare is the detachment and collapse of a loop of magnetic flux. The mass loss due to stellar flares is discussed. It is believed that stellar flares are a significant contributor to the mass of interstellar medium in the Milky Way

  17. On the Importance of the Flare's Late Phase for the Solar Extreme Ultraviolet Irradiance

    Science.gov (United States)

    Woods, Thomas N.; Eparvier, Frank; Jones, Andrew R.; Hock, Rachel; Chamberlin, Phillip C.; Klimchuk, James A.; Didkovsky, Leonid; Judge, Darrell; Mariska, John; Bailey, Scott; hide

    2011-01-01

    The new solar extreme ultraviolet (EUV) irradiance observations from NASA Solar Dynamics Observatory (SDO) have revealed a new class of solar flares that are referred to as late phase flares. These flares are characterized by the hot 2-5 MK coronal emissions (e.g., Fe XVI 33.5 nm) showing large secondary peaks that appear many minutes to hours after an eruptive flare event. In contrast, the cool 0.7-1.5 MK coronal emissions (e.g., Fe IX 17.1 nm) usually dim immediately after the flare onset and do not recover until after the delayed second peak of the hot coronal emissions. We refer to this period of 1-5 hours after the fl amrea sin phase as the late phase, and this late phase is uniquely different than long duration flares associated with 2-ribbon flares or large filament eruptions. Our analysis of the late phase flare events indicates that the late phase involves hot coronal loops near the flaring region, not directly related to the original flaring loop system but rather with the higher post-eruption fields. Another finding is that space weather applications concerning Earth s ionosphere and thermosphere need to consider these late phase flares because they can enhance the total EUV irradiance flare variation by a factor of 2 when the late phase contribution is included.

  18. The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29

    Energy Technology Data Exchange (ETDEWEB)

    Kowalski, Adam F. [Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, 2000 Colorado Ave, Boulder, CO 80305 (United States); Allred, Joel C.; Daw, Adrian [NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Cauzzi, Gianna [INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy); Carlsson, Mats, E-mail: Adam.Kowalski@lasp.colorado.edu [Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, NO-0315 Oslo (Norway)

    2017-02-10

    The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright continuum emission in the far- and near-ultraviolet (NUV) and highly asymmetric chromospheric emission lines, providing long-sought constraints on the heating mechanisms of the lower atmosphere in solar flares. We analyze the continuum and emission line data from the Interface Region Imaging Spectrograph (IRIS) of the brightest flaring magnetic footpoints in this flare. We compare the NUV spectra of the brightest pixels to new radiative-hydrodynamic predictions calculated with the RADYN code using constraints on a nonthermal electron beam inferred from the collisional thick-target modeling of hard X-ray data from Reuven Ramaty High Energy Solar Spectroscopic Imager . We show that the atmospheric response to a high beam flux density satisfactorily achieves the observed continuum brightness in the NUV. The NUV continuum emission in this flare is consistent with hydrogen (Balmer) recombination radiation that originates from low optical depth in a dense chromospheric condensation and from the stationary beam-heated layers just below the condensation. A model producing two flaring regions (a condensation and stationary layers) in the lower atmosphere is also consistent with the asymmetric Fe ii chromospheric emission line profiles observed in the impulsive phase.

  19. A Large-scale Plume in an X-class Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Fleishman, Gregory D.; Nita, Gelu M.; Gary, Dale E. [Physics Department, Center for Solar-Terrestrial Research, New Jersey Institute of Technology Newark, NJ, 07102-1982 (United States)

    2017-08-20

    Ever-increasing multi-frequency imaging of solar observations suggests that solar flares often involve more than one magnetic fluxtube. Some of the fluxtubes are closed, while others can contain open fields. The relative proportion of nonthermal electrons among those distinct loops is highly important for understanding energy release, particle acceleration, and transport. The access of nonthermal electrons to the open field is also important because the open field facilitates the solar energetic particle (SEP) escape from the flaring site, and thus controls the SEP fluxes in the solar system, both directly and as seed particles for further acceleration. The large-scale fluxtubes are often filled with a tenuous plasma, which is difficult to detect in either EUV or X-ray wavelengths; however, they can dominate at low radio frequencies, where a modest component of nonthermal electrons can render the source optically thick and, thus, bright enough to be observed. Here we report the detection of a large-scale “plume” at the impulsive phase of an X-class solar flare, SOL2001-08-25T16:23, using multi-frequency radio data from Owens Valley Solar Array. To quantify the flare’s spatial structure, we employ 3D modeling utilizing force-free-field extrapolations from the line of sight SOHO /MDI magnetograms with our modeling tool GX-Simulator. We found that a significant fraction of the nonthermal electrons that accelerated at the flare site low in the corona escapes to the plume, which contains both closed and open fields. We propose that the proportion between the closed and open fields at the plume is what determines the SEP population escaping into interplanetary space.

  20. Simulating the Mg II NUV Spectra & C II Resonance Lines During Solar Flares

    Science.gov (United States)

    Kerr, Graham Stewart; Allred, Joel C.; Leenaarts, Jorrit; Butler, Elizabeth; Kowalski, Adam

    2017-08-01

    The solar chromosphere is the origin of the bulk of the enhanced radiative output during solar flares, and so comprehensive understanding of this region is important if we wish to understand energy transport in solar flares. It is only relatively recently, however, with the launch of IRIS that we have routine spectroscopic flarea observations of the chromsphere and transition region. Since several of the spectral lines observed by IRIS are optically thick, it is necessary to use forward modelling to extract the useful information that these lines carry about the flaring chromosphere and transition region. We present the results of modelling the formation properties Mg II resonance lines & subordinate lines, and the C II resonance lines during solar flares. We focus on understanding their relation to the physical strucutre of the flaring atmosphere, exploiting formation height differences to determine if we can extract information about gradients in the atmosphere. We show the effect of degrading the profiles to the resolution of the IRIS, and that the usual observational techniques used to identify the line centroid do a poor job in the early stages of the flare (partly due to multiple optically thick line components). Finally, we will tentatively comment on the effects that 3D radiation transfer may have on these lines.

  1. Decrease of the solar flare/solar wind flux ratio in the past several aeons from solar neon and tracks in lunar soil plagioclases

    International Nuclear Information System (INIS)

    Wieler, R.; Etique, Ph.; Signer, P.; Poupeau, G.

    1982-08-01

    The He, Ne, and Ar concentrations and isotopic compositions of mineral separates of six lunar subsurface samples and of two regolith breccias which were exposed to the sun as early as 2 - 3 billion years ago are determined. The results are compared with our noble gas data obtained previously on mineral separates of lunar surface soil samples most of which contain recently implanted solar gases. The mean solar flare track densities were determined on aliquots of several of the plagioclase separates analyzed for noble gases. Solar wind retentive mafic minerals and ilmenites show that a possible secular increase of the 20 Ne/ 22 Ne ratio in the solar wind during the last 2 - 3 Ga. is 20 Ne/ 22 Ne of approximately 11.3 - 11.8, reported for solar flare Ne retained in plagioclase separates from lunar soils. The solar flare track data and the Ne data independently show that plagioclases exposed to the sun over the last 10 8 years recorded a lower mean ratio of solar flare to solar wind intensities than samples exposed about 1 - 3 billion years ago. On the basis of track data these ratios are estimated to differ by a factor approximately 2. (Author) [pt

  2. X-Ray Source Heights in a Solar Flare: Thick-Target Versus Thermal Conduction Front Heating

    Science.gov (United States)

    Reep, J. W.; Bradshaw, S. J.; Holman, G. D.

    2016-01-01

    Observations of solar flares with RHESSI have shown X-ray sources traveling along flaring loops, from the corona down to the chromosphere and back up. The 2002 November 28 C1.1 flare, first observed with RHESSI by Sui et al. and quantitatively analyzed by O'Flannagain et al., very clearly shows this behavior. By employing numerical experiments, we use these observations of X-ray source height motions as a constraint to distinguish between heating due to a non-thermal electron beam and in situ energy deposition in the corona. We find that both heating scenarios can reproduce the observed light curves, but our results favor non-thermal heating. In situ heating is inconsistent with the observed X-ray source morphology and always gives a height dispersion with photon energy opposite to what is observed.

  3. A LARGE-SCALE SEARCH FOR EVIDENCE OF QUASI-PERIODIC PULSATIONS IN SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Inglis, A. R.; Ireland, J.; Dennis, B. R. [Solar Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Hayes, L; Gallagher, P. [Trinity College Dublin, Dublin (Ireland)

    2016-12-20

    The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1–300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 1–8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi /Gamma-ray Burst Monitor (GBM) 15–25 keV X-ray data for each of these flares associated with a Fermi /GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that ∼30% of GOES events and ∼8% of Fermi /GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of ∼5–30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.

  4. A Large-Scale Search for Evidence of Quasi-Periodic Pulsations in Solar Flares

    Science.gov (United States)

    Inglis, A. R.; Ireland, J.; Dennis, B. R..; Hayes, L.; Gallagher, P.

    2016-01-01

    The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 18 soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi/Gamma-ray Burst Monitor (GBM) 1525 keV X-ray data for each of these flares associated with a Fermi/GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that approx. 30% of GOES events and approx. 8% of Fermi/GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic time-scale of approx. 5-30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic time-scales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.

  5. A LARGE-SCALE SEARCH FOR EVIDENCE OF QUASI-PERIODIC PULSATIONS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L; Gallagher, P.

    2016-01-01

    The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1–300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 1–8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi /Gamma-ray Burst Monitor (GBM) 15–25 keV X-ray data for each of these flares associated with a Fermi /GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that ∼30% of GOES events and ∼8% of Fermi /GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of ∼5–30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.

  6. Flares on dMe stars: IUE and optical observations of At Mic, and comparison of far-ultraviolet stellar and solar flares

    International Nuclear Information System (INIS)

    Bromage, G.E.; Phillips, K.J.H.; Dufton, P.L.; Kingston, A.E.

    1986-01-01

    The paper concerns observations of a large flare event on the dMe star At Mic, detected by the International Ultraviolet Explorer. The far-ultraviolet spectra of the flare is compared with those of other stellar flares, and also with a large solar flare recorded by the Skylab mission in 1973. The quiescent-phase optical and ultraviolet spectrum of the same dMe flare star is discussed. (U.K.)

  7. Proton Flares in Solar Activity Complexes: Possible Origins and Consequences

    Science.gov (United States)

    Isaeva, E. S.; Tomozov, V. M.; Yazev, S. A.

    2018-03-01

    Solar flares observed during the 24th solar-activity cycle and accompanied by fluxes of particles detected at the Earth's orbit with intensities exceeding 10 particles cm-2 s-1 and energies of more than 10 MeV per particle mainly occurred in activity complexes (82% of cases), with 80% of these occurring no more than 20 heliographic degrees from the nearest coronal holes. The correlation between the X-ray classes of flares and the proton fluxes detected at the Earth's orbit is weak. The work presented here supports the hypothesis that the leakage of particles into the heliosphere is due to the existence of long-lived magnetic channels, which facilitate the transport of flare-accelerated particles into the boundary regions of open magnetic structures of coronal holes. The possible contribution of exchange reconnection in the formation of such channels and the role of exchange reconnection in the generation of flares are discussed.

  8. Energy storage and deposition in a solar flare

    Science.gov (United States)

    Vorpahl, J. A.

    1976-01-01

    X-ray pictures of a solar flare taken with the S-056 X-ray telescope aboard Skylab are interpreted in terms of flare energy deposition and storage. The close similarity between calculated magnetic-field lines and the overall structure of the X-ray core is shown to suggest that the flare occurred in an entire arcade of loops. It is found that different X-ray features brightened sequentially as the flare evolved, indicating that some triggering disturbance moved from one side to the other in the flare core. A propagation velocity of 180 to 280 km/s is computed, and it is proposed that the geometry of the loop arcade strongly influenced the propagation of the triggering disturbance as well as the storage and site of the subsequent energy deposition. Some possible physical causes for the sequential X-ray brightening are examined, and a magnetosonic wave is suggested as the triggering disturbance. 'Correct' conditions for energy release are considered

  9. Thermal Structure of Supra-Arcade Plasma in Two Solar Flares

    Science.gov (United States)

    Reeves, Katharine K.; Savage, Sabrina; McKenzie, David E.; Weber, Mark A.

    2012-01-01

    In this work, we use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra-arcade plasma in two solar flares. The first flare is a Ml.2 flare that occurred on November 5, 2010 on the east limb. This flare was one of a series of flares from AR 11121, published in Reeves & Golub (2011). The second flare is an XI.7 flare that occurred on January 27, 2012 on the west limb. This flare exhibits visible supra-arcade downflows (SADs), where the November 2010 flare does not. For these two flares we combine XRT and AlA data to calculate DEMs of each pixel in the supra-arcade plasma, giving insight into the temperature and density structures in the fan of plasma above the post-flare arcade. We find in each case that the supra-arcade plasma is around 10 MK, and there is a marked decrease in the emission measure in the SADs. We also compare the DEMs calculated with the combined AIA/XRT dataset to those calculated using AIA alone.

  10. MOST OBSERVATIONS OF OUR NEAREST NEIGHBOR: FLARES ON PROXIMA CENTAURI

    Energy Technology Data Exchange (ETDEWEB)

    Davenport, James R. A. [Department of Physics and Astronomy, Western Washington University, 516 High Street, Bellingham, WA 98225 (United States); Kipping, David M. [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Sasselov, Dimitar [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Matthews, Jaymie M. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Cameron, Chris [Department of Mathematics, Physics and Geology, Cape Breton University, 1250 Grand Lake Road, Sydney, NS B1P 6L2 (Canada)

    2016-10-01

    We present a study of white-light flares from the active M5.5 dwarf Proxima Centauri using the Canadian microsatellite Microvariability and Oscillations of STars . Using 37.6 days of monitoring data from 2014 to 2015, we have detected 66 individual flare events, the largest number of white-light flares observed to date on Proxima Cen. Flare energies in our sample range from 10{sup 29} to 10{sup 31.5} erg. The flare rate is lower than that of other classic flare stars of a similar spectral type, such as UV Ceti, which may indicate Proxima Cen had a higher flare rate in its youth. Proxima Cen does have an unusually high flare rate given its slow rotation period, however. Extending the observed power-law occurrence distribution down to 10{sup 28} erg, we show that flares with flux amplitudes of 0.5% occur 63 times per day, while superflares with energies of 10{sup 33} erg occur ∼8 times per year. Small flares may therefore pose a great difficulty in searches for transits from the recently announced 1.27 M {sub ⊕} Proxima b, while frequent large flares could have significant impact on the planetary atmosphere.

  11. Flares: solar and stellar. Rutherford Appleton Laboratory workshop on astronomy and astrophysics, Abingdon, 19-21 May 1986

    International Nuclear Information System (INIS)

    Gondhalekar, P.M.

    1986-05-01

    The paper concerns solar and stellar flare phenomena reported at the Rutherford Appleton Laboratory Workshop on Astronomy and Astrophysics, May 1986. Eleven papers were presented at the Workshop on: the solar-stellar connection, observational evidence for solar and stellar flares, and flare models; and all are indexed separately. (UK)

  12. On line profile asymmetries in a solar flare

    Czech Academy of Sciences Publication Activity Database

    Prosecký, Tomáš; Kotrč, Pavel; Berlicki, A.

    2006-01-01

    Roč. 30, č. 1 (2006), s. 31-41 ISSN 1845-8319. [Central European Solar Physics Meeting /2./. Bairisch Kölldorf, 19.05.2005-21.05.2005] R&D Projects: GA AV ČR IAA3003203 Institutional research plan: CEZ:AV0Z10030501 Keywords : sun * solar flares * spectrum Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  13. Forecasting Solar Flares Using Magnetogram-based Predictors and Machine Learning

    Science.gov (United States)

    Florios, Kostas; Kontogiannis, Ioannis; Park, Sung-Hong; Guerra, Jordan A.; Benvenuto, Federico; Bloomfield, D. Shaun; Georgoulis, Manolis K.

    2018-02-01

    We propose a forecasting approach for solar flares based on data from Solar Cycle 24, taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) mission. In particular, we use the Space-weather HMI Active Region Patches (SHARP) product that facilitates cut-out magnetograms of solar active regions (AR) in the Sun in near-realtime (NRT), taken over a five-year interval (2012 - 2016). Our approach utilizes a set of thirteen predictors, which are not included in the SHARP metadata, extracted from line-of-sight and vector photospheric magnetograms. We exploit several machine learning (ML) and conventional statistics techniques to predict flares of peak magnitude {>} M1 and {>} C1 within a 24 h forecast window. The ML methods used are multi-layer perceptrons (MLP), support vector machines (SVM), and random forests (RF). We conclude that random forests could be the prediction technique of choice for our sample, with the second-best method being multi-layer perceptrons, subject to an entropy objective function. A Monte Carlo simulation showed that the best-performing method gives accuracy ACC=0.93(0.00), true skill statistic TSS=0.74(0.02), and Heidke skill score HSS=0.49(0.01) for {>} M1 flare prediction with probability threshold 15% and ACC=0.84(0.00), TSS=0.60(0.01), and HSS=0.59(0.01) for {>} C1 flare prediction with probability threshold 35%.

  14. X-ray line coincidence photopumping in a solar flare

    Science.gov (United States)

    Keenan, F. P.; Poppenhaeger, K.; Mathioudakis, M.; Rose, S. J.; Flowerdew, J.; Hynes, D.; Christian, D. J.; Nilsen, J.; Johnson, W. R.

    2018-03-01

    Line coincidence photopumping is a process where the electrons of an atomic or molecular species are radiatively excited through the absorption of line emission from another species at a coincident wavelength. There are many instances of line coincidence photopumping in astrophysical sources at optical and ultraviolet wavelengths, with the most famous example being Bowen fluorescence (pumping of O III 303.80 Å by He II), but none to our knowledge in X-rays. However, here we report on a scheme where a He-like line of Ne IX at 11.000 Å is photopumped by He-like Na X at 11.003 Å, which predicts significant intensity enhancement in the Ne IX 82.76 Å transition under physical conditions found in solar flare plasmas. A comparison of our theoretical models with published X-ray observations of a solar flare obtained during a rocket flight provides evidence for line enhancement, with the measured degree of enhancement being consistent with that expected from theory, a truly surprising result. Observations of this enhancement during flares on stars other than the Sun would provide a powerful new diagnostic tool for determining the sizes of flare loops in these distant, spatially unresolved, astronomical sources.

  15. Simulation of GRIS spectrometer response to the solar gamma-ray flare of 23 July 2002

    International Nuclear Information System (INIS)

    Trofimov, Yu A; Kotov, Yu D; Yurov, V N; Lupar, E E; Faradzhaev, R M; Glyanenko, A S

    2017-01-01

    GRIS is a prospective experiment designed to measure hard X-rays and γ-rays of solar flares in the energy range from 50 keV to 200 MeV as well as solar neutrons > 30 MeV. This study considers results of GEANT 4 simulation of GRIS detectors response to cosmic background radiation and to the solar flare SOL2002-07-23 (X4.8). It is shown that the GRIS spectrometers have enough sensitivity and energy resolution to measure redshifts of some narrow γ-rays in flare spectra, that the low energy thresholds of the detectors can be lowered considerably without a risk of counting rate saturation during high magnitude flares and that at a choice between LaBr 3 (Ce) and CeBr 3 the second one is a preferable scintillator for a hard X-ray and γ-ray spectrometer of solar flares. (paper)

  16. Solar flare neon and solar cosmic ray fluxes in the past using gas-rich meteorites

    International Nuclear Information System (INIS)

    Nautiyal, C.M.; Rao, M.N.

    1986-01-01

    Methods were developed earlier to deduce the composition of solar flare neon and to determine the solar cosmic ray proton fluxes in the past using etched lunar samples and at present, these techniques are extended to gas rich meteorites. By considering high temperature Ne data points for Pantar, Fayetteville and other gas rich meteorites and by applying the three component Ne-decomposition methods, the solar cosmic ray and galactic cosmic ray produced spallation Ne components from the trapped SF-Ne was resolved. Using appropiate SCR and GCR production rates, in the case of Pantar, for example, a GCR exposure age of 2 m.y. was estimated for Pantar-Dark while Pantar-Light yielded a GCR age of approx. 3 m.y. However the SCR exposure age of Pantar-Dark is two orders of magnitude higher than the average surface exposure ages of lunar soils. The possibility of higher proton fluxes in the past is discussed

  17. Solar Flare Termination Shock and Synthetic Emission Line Profiles of the Fe xxi 1354.08 Å Line

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Lijia [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA (United States); Li, Gang [Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL (United States); Reeves, Kathy; Raymond, John, E-mail: gang.li@uah.edu [Harvard-Smithsonian Center for Astrophysics, Boston, MA (United States)

    2017-09-01

    Solar flares are among the most energetic phenomena that occur in the solar system. In the standard solar flare model, a fast mode shock, often referred to as the flare termination shock (TS), can exist above the loop-top source of hard X-ray emissions. The existence of the TS has been recently related to spectral hardening of a flare’s hard X-ray spectra at energies >300 keV. Observations of the Fe xxi 1354.08 Å line during solar flares by the Interface Region Imaging Spectrograph ( IRIS ) spacecraft have found significant redshifts with >100 km s{sup −1}, which is consistent with a reconnection downflow. The ability to detect such a redshift with IRIS suggests that one may be able to use IRIS observations to identify flare TSs. Using a magnetohydrodynamic simulation to model magnetic reconnection of a solar flare and assuming the existence of a TS in the downflow of the reconnection plasma, we model the synthetic emission of the Fe xxi 1354.08 line in this work. We show that the existence of the TS in the solar flare may manifest itself in the Fe xxi 1354.08 Å line.

  18. Solar Flare Super-Events: When they Can Occur and the Energy Limits of their Realization

    Science.gov (United States)

    Ishkov, Vitaly N.

    2015-03-01

    For the successful development of terrestrial civilization it is necessary to estimate the space factors, including phenomena on Sun, which can ruin it or cause such catastrophic loss, that the restoration to the initial level can take unacceptably long time. Super-powerful solar flares are the only such phenomena. Therefore an attempt is undertaken to estimate the possibility of such super-event occurrence at this stage of our star evolution. Since solar flare events are the consequence of the newly emerging magnetic fluxes interacting with the already existing magnetic fields of active regions, are investigated the observed cases which lead to the realization of such super-events. From the observations of the maximal magnetic fluxes during the period of reliable solar observations, the conclusion is made that the super- extreme solar flares cannot significantly exceed the most powerful solar flares which have already been observed. On the statistics of the reliable solar cycles the sunspot groups, in which occurred the most powerful solar super-events (August- September 1859 - solar cycle 10; June 1991 - SC 22; October-November 2003 - SC 23) appeared in the periods of the solar magnetic field reorganization between the epochs of "increased" and "lowered" solar activity.

  19. IRIS , Hinode , SDO , and RHESSI Observations of a White Light Flare Produced Directly by Non-thermal Electrons

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung-Sun [Hinode Science Center, National Astronomical Observatory of Japan (NAOJ), 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Imada, Shinsuke [Institute for Space–Earth Environmental Research (ISEE), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 466-8550 (Japan); Watanabe, Kyoko [National Defense Academy of Japan, 1-10-20 Hashirimizu, Yokosuka 239-8686 (Japan); Bamba, Yumi [Hinode team, ISAS/JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Brooks, David H., E-mail: ksun.lee@nao.ac.jp [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2017-02-20

    An X1.6 flare occurred in active region AR 12192 on 2014 October 22 at 14:02 UT and was observed by Hinode , IRIS , SDO , and RHESSI . We analyze a bright kernel that produces a white light (WL) flare with continuum enhancement and a hard X-ray (HXR) peak. Taking advantage of the spectroscopic observations of IRIS and Hinode /EIS, we measure the temporal variation of the plasma properties in the bright kernel in the chromosphere and corona. We find that explosive evaporation was observed when the WL emission occurred, even though the intensity enhancement in hotter lines is quite weak. The temporal correlation of the WL emission, HXR peak, and evaporation flows indicates that the WL emission was produced by accelerated electrons. To understand the WL emission process, we calculated the energy flux deposited by non-thermal electrons (observed by RHESSI ) and compared it to the dissipated energy estimated from a chromospheric line (Mg ii triplet) observed by IRIS . The deposited energy flux from the non-thermal electrons is about (3–7.7) × 10{sup 10} erg cm{sup −2} s{sup −1} for a given low-energy cutoff of 30–40 keV, assuming the thick-target model. The energy flux estimated from the changes in temperature in the chromosphere measured using the Mg ii subordinate line is about (4.6–6.7) × 10{sup 9} erg cm{sup −2} s{sup −1}: ∼6%–22% of the deposited energy. This comparison of estimated energy fluxes implies that the continuum enhancement was directly produced by the non-thermal electrons.

  20. Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Flare

    Science.gov (United States)

    Barghouty, A. F.; Mewaldt, R. A.; Leske, R. A.; Shih, A. Y.; Stone, E. C.; Cohen, C. M. S.; Cummings, A. C.; Labrador, A. W.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2009-01-01

    We discuss observations of energetic neutral hydrogen atoms (ENAs) from a solar flare/coronal mass ejection event reported by Mewaldt et al. (2009). The observations were made during the 5 December 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV particles arriving from the Sun. The derived solar emission profile, arrival directions, and energy spectrum all show that the atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV gamma-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. CME-driven shock acceleration is also considered. Taking into account ENA losses, we conclude that the observed ENAs must have been produced in the high corona at heliocentric distances .2 solar radii.

  1. He I D3 OBSERVATIONS OF THE 1984 MAY 22 M6.3 SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Liu Chang; Xu Yan; Deng Na; Lee, Jeongwoo; Zhang Jifeng; Wang Haimin [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Prasad Choudhary, Debi, E-mail: chang.liu@njit.edu [Physics and Astronomy Department, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330-0001 (United States)

    2013-09-01

    The He I D3 line has a unique response to a flare impact on the low solar atmosphere and can be a powerful diagnostic tool for energy transport processes. Using images obtained from the recently digitized films of the Big Bear Solar Observatory, we report D3 observations of the M6.3 flare on 1984 May 22, which occurred in an active region with a circular magnetic polarity inversion line (PIL). The impulsive phase of the flare starts with a main elongated source that darkens in D3, inside of which bright emission kernels appear at the time of the initial small peak in hard X-rays (HXRs). These flare cores subsequently evolve into a sharp emission strand lying within the dark halo; this evolution occurs at the same time as the main peak in HXRs, reversing the overall source contrast from -5% to 5%. The radiated energy in D3 during the main peak is estimated to be about 10{sup 30} erg, which is comparable to that carried by nonthermal electrons above 20 keV. Afterward, the flare proceeds along the circular PIL in the counterclockwise direction to form a dark circular ribbon in D3, which apparently mirrors the bright ribbons in H{alpha} and He I 10830 A. All of these ribbons last for over one hour in the late gradual phase. We suggest that the present event resembles the so-called black-light flare that was proposed based on continuum images, and that D3 darkening and brightening features herein may be due to thermal conduction heating and the direct precipitation of high-energy electrons, respectively.

  2. Solar flares: invited review at the Royal Astronomical Society's meeting at Armagh, April 5, 1991

    International Nuclear Information System (INIS)

    Phillips, K.J.H.

    1991-04-01

    A solar flare may be defined to be the sudden release of stored magnetic energy in an active region and all the associated radiation, particle, mass-motion, wave and shock-wave phenomena directly resulting from it or triggered by it. In the last few years, solar flares have taken on an extra significance in respect of the fact that outbursts on cool dwarf stars seem to have the same characteristics and are widely assumed to be the same type of phenomenon. The physical mechanism that leads to solar flares, most likely the reconnection of magnetic fields, may well be the one that operates in stellar flares also. In this review, I shall deal with the chief observational facts about flares and associated phenomena, then deal with both interpretations and magnetic field reconnection theories. (Author)

  3. Statistical relationship between the succeeding solar flares detected by the RHESSI satellite

    Science.gov (United States)

    Balázs, L. G.; Gyenge, N.; Korsós, M. B.; Baranyi, T.; Forgács-Dajka, E.; Ballai, I.

    2014-06-01

    The Reuven Ramaty High Energy Solar Spectroscopic Imager has observed more than 80 000 solar energetic events since its launch on 2002 February 12. Using this large sample of observed flares, we studied the spatiotemporal relationship between succeeding flares. Our results show that the statistical relationship between the temporal and spatial differences of succeeding flares can be described as a power law of the form R(t) ˜ tp with p = 0.327 ± 0.007. We discuss the possible interpretations of this result as a characteristic function of a supposed underlying physics. Different scenarios are considered to explain this relation, including the case where the connectivity between succeeding events is realized through a shock wave in the post Sedov-Taylor phase or where the spatial and temporal relationship between flares is supposed to be provided by an expanding flare area in the sub-diffusive regime. Furthermore, we cannot exclude the possibility that the physical process behind the statistical relationship is the reordering of the magnetic field by the flare or it is due to some unknown processes.

  4. Association of solar flares with coronal mass ejections accompanied by Deca-Hectometric type II radio burst for two solar cycles 23 and 24

    Science.gov (United States)

    Kharayat, Hema; Prasad, Lalan; Pant, Sumit

    2018-05-01

    The aim of present study is to find the association of solar flares with coronal mass ejections (CMEs) accompanied by Deca-Hectometric (DH) type II radio burst for the period 1997-2014 (solar cycle 23 and ascending phase of solar cycle 24). We have used a statistical analysis and found that 10-20∘ latitudinal belt of northern region and 80-90∘ longitudinal belts of western region of the sun are more effective for flare-CME accompanied by DH type II radio burst events. M-class flares (52%) are in good association with the CMEs accompanied by DH type II radio burst. Further, we have calculated the flare position and found that most frequent flare site is at the center of the CME span. However, the occurrence probability of all flares is maximum outside the CME span. X-class flare associated CMEs have maximum speed than that of M, C, and B-class flare associated CMEs. We have also found a good correlation between flare position and central position angle of CMEs accompanied by DH type II radio burst.

  5. STUDY OF RAPID FORMATION OF A δ SUNSPOT ASSOCIATED WITH THE 2012 JULY 2 C7.4 FLARE USING HIGH-RESOLUTION OBSERVATIONS OF THE NEW SOLAR TELESCOPE

    International Nuclear Information System (INIS)

    Wang Haimin; Liu Chang; Wang Shuo; Deng Na; Xu Yan; Jing Ju; Cao Wenda

    2013-01-01

    Rapid, irreversible changes of magnetic topology and sunspot structure associated with flares have been systematically observed in recent years. The most striking features include the increase of the horizontal field at the polarity inversion line (PIL) and the co-spatial penumbral darkening. A likely explanation of the above phenomenon is the back reaction to the coronal restructuring after eruptions: a coronal mass ejection carries the upward momentum while the downward momentum compresses the field lines near the PIL. Previous studies could only use low-resolution (above 1'') magnetograms and white-light images. Therefore, the changes are mostly observed for X-class flares. Taking advantage of the 0.''1 spatial resolution and 15 s temporal cadence of the New Solar Telescope at the Big Bear Solar Observatory, we report in detail the rapid formation of sunspot penumbra at the PIL associated with the C7.4 flare on 2012 July 2. It is unambiguously shown that the solar granulation pattern evolves to an alternating dark and bright fibril structure, the typical pattern of penumbra. Interestingly, the appearance of such a penumbra creates a new δ sunspot. The penumbral formation is also accompanied by the enhancement of the horizontal field observed using vector magnetograms from the Helioseismic and Magnetic Imager. We explain our observations as being due to the eruption of a flux rope following magnetic cancellation at the PIL. Subsequently, the re-closed arcade fields are pushed down toward the surface to form the new penumbra. NLFFF extrapolation clearly shows both the flux rope close to the surface and the overlying fields

  6. Mid-term periodicities and heliospheric modulation of coronal index and solar flare index during solar cycles 22-23

    Science.gov (United States)

    Singh, Prithvi Raj; Saxena, A. K.; Tiwari, C. M.

    2018-04-01

    We applied fast Fourier transform techniques and Morlet wavelet transform on the time series data of coronal index, solar flare index, and galactic cosmic ray, for the period 1986-2008, in order to investigate the long- and mid-term periodicities including the Rieger ({˜ }130 to {˜ }190 days), quasi-period ({˜ }200 to {˜ }374 days), and quasi-biennial periodicities ({˜ }1.20 to {˜ }3.27 years) during the combined solar cycles 22-23. We emphasize the fact that a lesser number of periodicities are found in the range of low frequencies, while the higher frequencies show a greater number of periodicities. The rotation rates at the base of convection zone have periods for coronal index of {˜ }1.43 years and for solar flare index of {˜ }1.41 year, and galactic cosmic ray, {˜ }1.35 year, during combined solar cycles 22-23. In relation to these two solar parameters (coronal index and solar flare index), for the solar cycles 22-23, we found that galactic cosmic ray modulation at mid cut-off rigidity (Rc = 2.43GV) is anti-correlated with time-lag of few months.

  7. Magnetic Properties of Solar Active Regions that Govern Large Solar Flares and Eruptions

    Science.gov (United States)

    Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise; Hudson, Hugh S.; Nagashima, Kaori

    2017-08-01

    Strong flares and CMEs are often produced from active regions (ARs). In order to better understand the magnetic properties and evolutions of such ARs, we conducted statistical investigations on the SDO/HMI and AIA data of all flare events with GOES levels >M5.0 within 45 deg from the disk center for 6 years from May 2010 (from the beginning to the declining phase of solar cycle 24). Out of the total of 51 flares from 29 ARs, more than 80% have delta-sunspots and about 15% violate Hale’s polarity rule. We obtained several key findings including (1) the flare duration is linearly proportional to the separation of the flare ribbons (i.e., scale of reconnecting magnetic fields) and (2) CME-eruptive events have smaller sunspot areas. Depending on the magnetic properties, flaring ARs can be categorized into several groups, such as spot-spot, in which a highly-sheared polarity inversion line is formed between two large sunspots, and spot-satellite, where a newly-emerging flux next to a mature sunspot triggers a compact flare event. These results point to the possibility that magnetic structures of the ARs determine the characteristics of flares and CMEs. In the presentation, we will also show new results from the systematic flux emergence simulations of delta-sunspot formation and discuss the evolution processes of flaring ARs.

  8. He-like spectra from laboratory plasmas and solar flares

    International Nuclear Information System (INIS)

    Kato, Takako

    1990-01-01

    The X-ray spectra of He-like ions from tokamaks and solar flares have been measured. Several physical parameters of plasma can be derived from the X-ray spectra of He-like ions. The ion temperature can be derived from the doppler width of a resonance line. The electron temperature is obtained from the intensity ratio of dielectronic satellite lines to a resonance line. The energy level for the prominent lines is shown. The line q is produced mainly by the inner-shell excitation of Li-like ions, and line beta is produced by the inner-shell excitation of Be-like ions. The intensity ratios give the ion density ratios. The intensities of the intercombination and the forbidden lines are affected by the recombination from H-like ions. The synthetic spectra including excitation, ionization and recombination processes are fitted to the measurement. In this paper, the He-like X-ray spectra of the titanium ions from TFTR tokamak plasma and of the iron ions from solar flares are discussed, paying attention to the presence of high energy electrons which affect the spectra and ionization balance. Atomic data, the spectra from the TFTR tokamak, the spectra from solar flares and so on are described. (K.I.)

  9. Optical-to-Radio Continua in Solar Flares

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Avrett, E.H.

    2012-01-01

    Roč. 227, č. 1 (2012), s. 31-44 ISSN 0038-0938 R&D Projects: GA ČR GAP209/10/1680 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * spectral continua * diagnostics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.256, year: 2012

  10. Solar flares observed simultaneously with SphinX, GOES and RHESSI

    Science.gov (United States)

    Mrozek, Tomasz; Gburek, Szymon; Siarkowski, Marek; Sylwester, Barbara; Sylwester, Janusz; Kępa, Anna; Gryciuk, Magdalena

    2013-07-01

    In February 2009, during recent deepest solar minimum, Polish Solar Photometer in X-rays (SphinX) begun observations of the Sun in the energy range of 1.2-15 keV. SphinX was almost 100 times more sensitive than GOES X-ray Sensors. The silicon PIN diode detectors used in the experiment were carefully calibrated on the ground using Synchrotron Radiation Source BESSY II. The SphinX energy range overlaps with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) energy range. The instrument provided us with observations of hundreds of very small flares and X-ray brightenings. We have chosen a group of solar flares observed simultaneously with GOES, SphinX and RHESSI and performed spectroscopic analysis of observations wherever possible. The analysis of thermal part of the spectra showed that SphinX is a very sensitive complementary observatory for RHESSI and GOES.

  11. Beam heating in solar flares - Electrons or protons?

    International Nuclear Information System (INIS)

    Brown, J.C.; Karlicky, M.; Mackinnon, A.L.; Van Den Oord, G.H.J.

    1990-01-01

    The current status of electron and proton beam models as candidates for the impulsive phase heating of solar flares is discussed in relation to observational constants and theoretical difficulties. It is concluded that, while the electron beam model for flare heating still faces theoretical and observational problems, the problems faced by low and high energy proton beam models are no less serious, and there are facets of proton models which have not yet been studied. At the present, the electron beam model remains the most viable and best developed of heating model candidates. 58 refs

  12. Anomalous Temporal Behaviour of Broadband Ly Alpha Observations During Solar Flares from SDO/EVE

    Science.gov (United States)

    Milligan, Ryan O.; Chamberlin, Phillip C.

    2016-01-01

    Although it is the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly-alpha) emission during solar flares in recent years. However, the few examples that do exist have shown Ly-alpha emission to be a substantial radiator of the total energy budget of solar flares (of the order of 10 percent). It is also a known driver of fluctuations in the Earth's ionosphere. The EUV (Extreme Ultra-Violet) Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) now provides broadband, photometric Ly-alpha data at 10-second cadence with its Multiple EUV Grating Spectrograph-Photometer (MEGS-P) component, and has observed scores of solar flares in the 5 years since it was launched. However, the MEGS-P time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H-alpha, Ly-beta, LyC, C III, etc.). Furthermore, the emission detected by MEGS-P peaks around the time of the peak of thermal soft X-ray emission and not during the impulsive phase when energy deposition in the chromosphere (often assumed to be in the form of non-thermal electrons) is greatest. The time derivative of Ly-alpha lightcurves also appears to resemble that of the time derivative of soft X-rays, reminiscent of the Neupert effect. Given that spectrally-resolved Ly-alpha observations during flares from SORCE / SOLSTICE (Solar Radiation and Climate Experiment / Solar Stellar Irradiance Comparison Experiment) peak during the impulsive phase as expected, this suggests that the atypical behaviour of MEGS-P data is a manifestation of the broadband nature of the observations. This could imply that other lines andor continuum emission that becomes enhanced during flares could be contributing to the passband. Users are hereby urged to exercise caution when interpreting

  13. Fermi -LAT Observations of High-energy Behind-the-limb Solar Flares

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Allafort, A.; Bottacini, E.; Cameron, R. A.; Charles, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bissaldi, E.; Caragiulo, M.; Costanza, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Bonino, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, I-10125 Torino (Italy); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, F-34095 Montpellier (France); Bruel, P. [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); Caraveo, P. A. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Cavazzuti, E.; Ciprini, S. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00133 Roma (Italy); Cecchi, C., E-mail: nicola.omodei@stanford.edu, E-mail: vahep@stanford.edu, E-mail: melissa.pesce.rollins@pi.infn.it [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); and others

    2017-02-01

    We report on the Fermi -LAT detection of high-energy emission from the behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014 January 6 and September 1. The Fermi -LAT observations are associated with flares from active regions originating behind both the eastern and western limbs, as determined by STEREO . All three flares are associated with very fast coronal mass ejections (CMEs) and strong solar energetic particle events. We present updated localizations of the >100 MeV photon emission, hard X-ray (HXR) and EUV images, and broadband spectra from 10 keV to 10 GeV, as well as microwave spectra. We also provide a comparison of the BTL flares detected by Fermi -LAT with three on-disk flares and present a study of some of the significant quantities of these flares as an attempt to better understand the acceleration mechanisms at work during these occulted flares. We interpret the HXR emission to be due to electron bremsstrahlung from a coronal thin-target loop top with the accelerated electron spectra steepening at semirelativistic energies. The >100 MeV gamma-rays are best described by a pion-decay model resulting from the interaction of protons (and other ions) in a thick-target photospheric source. The protons are believed to have been accelerated (to energies >10 GeV) in the CME environment and precipitate down to the photosphere from the downstream side of the CME shock and landed on the front side of the Sun, away from the original flare site and the HXR emission.

  14. A Model of Solar Flares Based on Arcade Field Reconnection and Merging of Magnetic Islands

    International Nuclear Information System (INIS)

    Choe, G.S.; Cheng, C.Z.

    2001-01-01

    Solar flares are intense, abrupt releases of energy in the solar corona. In the impulsive phase of a flare, the intensity of hard X-ray emission reaches a sharp peak indicating the highest reconnection rate. It is often observed that an X-ray emitting plasma ejecta (plasmoid) is launched before the impulsive phase and accelerated throughout the phase. Thus, the plasmoid ejection may not be an effect of fast magnetic reconnection as conventionally assumed, but a cause of fast reconnection. Based on resistive magnetohydrodynamic simulations, a solar flare model is presented, which can explain these observational characteristics of flares. In the model, merging of a newly generated magnetic island and a pre-existing island results in stretching and thinning of a current sheet, in which fast magnetic reconnection is induced. Recurrence of homologous flares naturally arises in this model. Mechanisms of magnetic island formation are also discussed

  15. Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-Flaring Active Regions

    Science.gov (United States)

    Kilcik, A.; Yurchyshyn, V.; Donmez, B.; Obridko, V. N.; Ozguc, A.; Rozelot, J. P.

    2018-04-01

    We analyzed temporal and periodic variations of sunspot counts (SSCs) in flaring (C-, M-, or X-class flares), and non-flaring active regions (ARs) for nearly three solar cycles (1986 through 2016). Our main findings are as follows: i) temporal variations of monthly means of the daily total SSCs in flaring and non-flaring ARs behave differently during a solar cycle and the behavior varies from one cycle to another; during Solar Cycle 23 temporal SSC profiles of non-flaring ARs are wider than those of flaring ARs, while they are almost the same during Solar Cycle 22 and the current Cycle 24. The SSC profiles show a multi-peak structure and the second peak of flaring ARs dominates the current Cycle 24, while the difference between peaks is less pronounced during Solar Cycles 22 and 23. The first and second SSC peaks of non-flaring ARs have comparable magnitude in the current solar cycle, while the first peak is nearly absent in the case of the flaring ARs of the same cycle. ii) Periodic variations observed in the SSCs profiles of flaring and non-flaring ARs derived from the multi-taper method (MTM) spectrum and wavelet scalograms are quite different as well, and they vary from one solar cycle to another. The largest detected period in flaring ARs is 113± 1.6 days while we detected much longer periodicities (327± 13, 312 ± 11, and 256± 8 days) in the non-flaring AR profiles. No meaningful periodicities were detected in the MTM spectrum of flaring ARs exceeding 55± 0.7 days during Solar Cycles 22 and 24, while a 113± 1.3 days period was detected in flaring ARs of Solar Cycle 23. For the non-flaring ARs the largest detected period was only 31± 0.2 days for Cycle 22 and 72± 1.3 days for the current Cycle 24, while the largest measured period was 327± 13 days during Solar Cycle 23.

  16. Enhancement in electron and ion temperatures due to solar flares as measured by SROSS-C2 satellite

    Directory of Open Access Journals (Sweden)

    D. K. Sharma

    2004-06-01

    Full Text Available The observations on the ionospheric electron and ion temperatures (Te and Ti measured by the RPA payload aboard the SROSS-C2 satellite have been used to study the effect of solar flares on ionospheric heating. The data on solar flare has been obtained from the National Geophysical Data Center (NGDC Boulder, Colorado (USA. It has been found that the electron and ion temperatures have a consistent enhancement during the solar flares on the dayside Earth's ionosphere. The estimated enhancement for the average electron temperature is from 1.3 to 1.9 times whereas for ion temperature it is from 1.2 to 1.4 times to the normal days average temperature. The enhancement of ionospheric temperatures due to solar flares is correlated with the diurnal variation of normal days' ionospheric temperatures. The solar flare does not have any significant effect on the nightside ionosphere. A comparison with the temperature obtained from the IRI-95 model also shows a similar enhancement.

  17. Radiation dose from solar flares at ground level

    International Nuclear Information System (INIS)

    O'Brien, K.

    1979-01-01

    Wdowczyk and Wolfendale (Nature, 268, 510, 1977) concluded that a very large solar flare producing exposure of 10 4 rad at ground level (lethal to almost any organism) has a possible frequency of once per 10 5 -10 8 yr. In the work reported similar results were obtained using a more elaborate model. Flares occuring from February 1956 to August 1972 were analyzed. The flare size distribution above the earth's atmosphere, and neutron flux, dose and dose equivalent at ground level at the latitude of Deep River, Canada, were calculated. The probable frequency of flares delivering various doses are given. Doses larger than 100 rad which have significant somatic effects on man and other animals may be delivered once in 10 6 years. The probability of 10 4 rad was found to be 10 -8 /yr. These calculations apply only to high geomagnetic latitudes. Field reversals during which the geomagnetic field is much weaker than current values total about 10% of the past 4 million years. This suggests that a very large flare delivering a large dose worldwide at ground level cannot be ruled out. (author)

  18. The influence of active region information on the prediction of solar flares: an empirical model using data mining

    Directory of Open Access Journals (Sweden)

    M. Núñez

    2005-11-01

    Full Text Available Predicting the occurrence of solar flares is a challenge of great importance for many space weather scientists and users. We introduce a data mining approach, called Behavior Pattern Learning (BPL, for automatically discovering correlations between solar flares and active region data, in order to predict the former. The goal of BPL is to predict the interval of time to the next solar flare and provide a confidence value for the associated prediction. The discovered correlations are described in terms of easy-to-read rules. The results indicate that active region dynamics is essential for predicting solar flares.

  19. ELECTRON ACCELERATION IN CONTRACTING MAGNETIC ISLANDS DURING SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Borovikov, D.; Tenishev, V.; Gombosi, T. I. [University of Michigan, Department of Climate and Space Sciences and Engineering, 2455 Hayward Street, Ann Arbor, MI 48104-2143 (United States); Guidoni, S. E. [The Catholic University of America, 620 Michigan Avenue Northeast, Washington, DC 20064 (United States); DeVore, C. R.; Karpen, J. T.; Antiochos, S. K. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2017-01-20

    Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integration of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons’ energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.

  20. A Heuristic Approach to Remove the Background Intensity on White-light Solar Images. I. STEREO /HI-1 Heliospheric Images

    Energy Technology Data Exchange (ETDEWEB)

    Stenborg, Guillermo; Howard, Russell A. [Space Science Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

    2017-04-10

    White-light coronal and heliospheric imagers observe scattering of photospheric light from both dust particles (the F-Corona) and free electrons in the corona (the K-corona). The separation of the two coronae is thus vitally important to reveal the faint K-coronal structures (e.g., streamers, co-rotating interaction regions, coronal mass ejections, etc.). However, the separation of the two coronae is very difficult, so we are content in defining a background corona that contains the F- and as little K- as possible. For both the LASCO-C2 and LASCO-C3 coronagraphs aboard the Solar and Heliospheric Observatory ( SOHO ) and the white-light imagers of the SECCHI suite aboard the Solar Terrestrial Relationships Observatory ( STEREO ), a time-dependent model of the background corona is generated from about a month of similar images. The creation of such models is possible because the missions carrying these instruments are orbiting the Sun at about 1 au. However, the orbit profiles for the upcoming Solar Orbiter and Solar Probe Plus missions are very different. These missions will have elliptic orbits with a rapidly changing radial distance, hence invalidating the techniques in use for the SOHO /LASCO and STEREO /SECCHI instruments. We have been investigating techniques to generate background models out of just single images that could be used for the Solar Orbiter Heliospheric Imager and the Wide-field Imager for the Solar Probe Plus packages on board the respective spacecraft. In this paper, we introduce a state-of-the-art, heuristic technique to create the background intensity models of STEREO /HI-1 data based solely on individual images, report on new results derived from its application, and discuss its relevance to instrumental and operational issues.

  1. Theoretical studies on rapid fluctuations in solar flares

    International Nuclear Information System (INIS)

    Vlahos, L.

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins, e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed

  2. Theoretical studies on rapid fluctuations in solar flares

    Science.gov (United States)

    Vlahos, Loukas

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed.

  3. Observations of the 12.3 micron Mg I emission line during a major solar flare

    Science.gov (United States)

    Deming, Drake; Jennings, Donald E.; Osherovich, Vladimir; Wiedemann, Gunter; Hewagama, Tilak

    1990-01-01

    The extremely Zeeman-sensitive 12.32 micron Mg I solar emission line was observed during a 3B/X5.7 solar flare on October 24, 1989. When compared to postflare values, Mg I emission-line intensity in the penumbral flare ribbon was 20 percent greater at the peak of the flare in soft X-rays, and the 12 micron continuum intensity was 7 percent greater. The flare also excited the emission line in the umbra where it is normally absent. The umbral flare emission exhibits a Zeeman splitting 200 G less than the adjacent penumbra, suggesting that it is excited at higher altitude. The absolute penumbral magnetic field strength did not change by more than 100 G between the flare peak and postflare period. However, a change in the inclination of the field lines, probably related to the formation and development of the flare loop system, was seen.

  4. Acceleration of runaway electrons in solar flares

    Science.gov (United States)

    Moghaddam-Taaheri, E.; Goertz, C. K.

    1990-01-01

    The dc electric field acceleration of electrons out of a thermal plasma and the evolution of the runaway tail are studied numerically, using a relativistic quasi-linear code based on the Ritz-Galerkin method and finite elements. A small field-aligned electric field is turned on at a certain time. The resulting distribution function from the runaway process is used to calculate the synchrotron emission during the evolution of the runaway tail. It is found that, during the runaway tail formation, which lasts a few tens of seconds for typical solar flare conditions, the synchrotron emission level is low, almost ot the same order as the emission from the thermal plasma, at the high-frequency end of the spectrum. However, the emission is enhanced explosively in a few microseconds by several orders of magnitude at the time the runaway tail stops growing along the magnetic field and tends toward isotropy due to the pitch-angle scattering of the fast particles. Results indicate that, in order to account for the observed synchrotron emission spectrum of a typical solar flare, the electric field acceleration phase must be accompanied or preceded by a heating phase which yields an enhanced electron temperature of about 2-15 keV in the flare region if the electric field is 0.1-0.2 times the Dreicer field and cyclotron-to-plasma frequency ratios are of order 1-2.

  5. Observations of gamma-ray emission in solar flares

    International Nuclear Information System (INIS)

    Forrest, D.J.; Chupp, E.L.; Suri, A.N.; Reppin, C.

    1973-01-01

    This paper reviews the observations of gamma-ray emission made from the OSO-7 satellite in connection with two solar flares in early August 1972. The details of the measurements and a preliminary interpretation of some of the observed features are given. (U.S.)

  6. Deduction of solar neutron fluences from large gamma-ray flares

    International Nuclear Information System (INIS)

    Yoshimori, Masato; Watanabe, Hiroyuki; Takahashi, Kazuyoshi.

    1986-01-01

    Solar neutron fluences from large gamma-ray flares are deduced from accelerated proton spectra and numbers derived from the gamma-ray observations. The deduced solar neutron fluences range from 1 to 200 neutrons cm -2 . The present result indicates a possibility that high sensitivity ground-based neutron monitors can detect solar neutron events, just as detected by the Jungfraujoch and Rome neutron monitors. (author)

  7. SHORT-TERM SOLAR FLARE LEVEL PREDICTION USING A BAYESIAN NETWORK APPROACH

    International Nuclear Information System (INIS)

    Yu Daren; Huang Xin; Hu Qinghua; Zhou Rui; Wang Huaning; Cui Yanmei

    2010-01-01

    A Bayesian network approach for short-term solar flare level prediction has been proposed based on three sequences of photospheric magnetic field parameters extracted from Solar and Heliospheric Observatory/Michelson Doppler Imager longitudinal magnetograms. The magnetic measures, the maximum horizontal gradient, the length of neutral line, and the number of singular points do not have determinate relationships with solar flares, so the solar flare level prediction is considered as an uncertainty reasoning process modeled by the Bayesian network. The qualitative network structure which describes conditional independent relationships among magnetic field parameters and the quantitative conditional probability tables which determine the probabilistic values for each variable are learned from the data set. Seven sequential features-the maximum, the mean, the root mean square, the standard deviation, the shape factor, the crest factor, and the pulse factor-are extracted to reduce the dimensions of the raw sequences. Two Bayesian network models are built using raw sequential data (BN R ) and feature extracted data (BN F ), respectively. The explanations of these models are consistent with physical analyses of experts. The performances of the BN R and the BN F appear comparable with other methods. More importantly, the comprehensibility of the Bayesian network models is better than other methods.

  8. Investigation of solar flares in X-ray and optical spectral region

    International Nuclear Information System (INIS)

    Kurt, V.; Kurochka, L.N.; Zenchenko, V.M.

    1989-01-01

    Measurements of hard X h radiation of 180 solar flares carried out on board of the space probes Venera-13,-14, were compared with measurements of optical and thermal X t radiation. Values of total energy release during a flare in these regions are calculated, and correlation analysis is carried out. The bond correlations found have shown that total energy of fast electrons, caused X h -flare in the flare pulse phase, and thermal energy at the end of a pulse phase are practically connected with each othesr functionally. Quantitative connection between a flare ball in H α -line and the most probable energy values, being in different radiation regions calculated in the scope of generally accepted models, is established. The total energy of an optical (cold) part of the flare, radiation energy in X-ray region and the energy introduced to the flare volume by energy particles are shown to be compared between each other

  9. TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Kowalski, Adam F.; Hawley, Suzanne L.; Davenport, James R. A. [Astronomy Department, University of Washington, Box 351580, U.W. Seattle, WA 98195-1580 (United States); Wisniewski, John P. [HL Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks Street, Norman, OK 73019 (United States); Osten, Rachel A. [Space Telescope Science Institute, 3700 San Martin Drive Baltimore, MD 21218 (United States); Hilton, Eric J. [Universe Sandbox, Seattle, WA (United States); Holtzman, Jon A. [Department of Astronomy, New Mexico State University, Box 30001, Las Cruces, NM 88003 (United States); Schmidt, Sarah J., E-mail: adam.f.kowalski@nasa.gov [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

    2013-07-15

    We present a homogeneous analysis of line and continuum emission from simultaneous high-cadence spectra and photometry covering near-ultraviolet and optical wavelengths for 20 M dwarf flares. These data were obtained to study the white-light continuum components at bluer and redder wavelengths than the Balmer jump. Our goals were to break the degeneracy between emission mechanisms that have been fit to broadband colors of flares and to provide constraints for radiative-hydrodynamic (RHD) flare models that seek to reproduce the white-light flare emission. The main results from the analysis are the following: (1) the detection of Balmer continuum (in emission) that is present during all flares and with a wide range of relative contributions to the continuum flux at bluer wavelengths than the Balmer jump; (2) a blue continuum at flare maximum that is linearly decreasing with wavelength from {lambda} = 4000-4800 A, indicative of hot, blackbody emission with typical temperatures of T{sub BB} {approx} 9000-14, 000 K; (3) a redder continuum apparent at wavelengths longer than H{beta} ({lambda} {approx}> 4900 A) which becomes relatively more important to the energy budget during the late gradual phase. The hot blackbody component and redder continuum component have been detected in previous studies of flares. However, we have found that although the hot blackbody emission component is relatively well-represented by a featureless, single-temperature Planck function, this component includes absorption features and has a continuum shape strikingly similar to the spectrum of an A-type star as directly observed in our flare spectra. New model constraints are presented for the time evolution among the hydrogen Balmer lines and between Ca II K and the blackbody continuum emission. We calculate Balmer jump flux ratios and compare to the solar-type flare heating predictions from RHD models. The model ratios are too large and the blue-optical ({lambda} = 4000-4800 A) slopes are too

  10. TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

    International Nuclear Information System (INIS)

    Kowalski, Adam F.; Hawley, Suzanne L.; Davenport, James R. A.; Wisniewski, John P.; Osten, Rachel A.; Hilton, Eric J.; Holtzman, Jon A.; Schmidt, Sarah J.

    2013-01-01

    We present a homogeneous analysis of line and continuum emission from simultaneous high-cadence spectra and photometry covering near-ultraviolet and optical wavelengths for 20 M dwarf flares. These data were obtained to study the white-light continuum components at bluer and redder wavelengths than the Balmer jump. Our goals were to break the degeneracy between emission mechanisms that have been fit to broadband colors of flares and to provide constraints for radiative-hydrodynamic (RHD) flare models that seek to reproduce the white-light flare emission. The main results from the analysis are the following: (1) the detection of Balmer continuum (in emission) that is present during all flares and with a wide range of relative contributions to the continuum flux at bluer wavelengths than the Balmer jump; (2) a blue continuum at flare maximum that is linearly decreasing with wavelength from λ = 4000-4800 Å, indicative of hot, blackbody emission with typical temperatures of T BB ∼ 9000-14, 000 K; (3) a redder continuum apparent at wavelengths longer than Hβ (λ ∼> 4900 Å) which becomes relatively more important to the energy budget during the late gradual phase. The hot blackbody component and redder continuum component have been detected in previous studies of flares. However, we have found that although the hot blackbody emission component is relatively well-represented by a featureless, single-temperature Planck function, this component includes absorption features and has a continuum shape strikingly similar to the spectrum of an A-type star as directly observed in our flare spectra. New model constraints are presented for the time evolution among the hydrogen Balmer lines and between Ca II K and the blackbody continuum emission. We calculate Balmer jump flux ratios and compare to the solar-type flare heating predictions from RHD models. The model ratios are too large and the blue-optical (λ = 4000-4800 Å) slopes are too red in both the impulsive and

  11. Enhancement in electron and ion temperatures due to solar flares as measured by SROSS-C2 satellite

    Directory of Open Access Journals (Sweden)

    D. K. Sharma

    2004-06-01

    Full Text Available The observations on the ionospheric electron and ion temperatures (Te and Ti measured by the RPA payload aboard the SROSS-C2 satellite have been used to study the effect of solar flares on ionospheric heating. The data on solar flare has been obtained from the National Geophysical Data Center (NGDC Boulder, Colorado (USA. It has been found that the electron and ion temperatures have a consistent enhancement during the solar flares on the dayside Earth's ionosphere. The estimated enhancement for the average electron temperature is from 1.3 to 1.9 times whereas for ion temperature it is from 1.2 to 1.4 times to the normal days average temperature. The enhancement of ionospheric temperatures due to solar flares is correlated with the diurnal variation of normal days' ionospheric temperatures. The solar flare does not have any significant effect on the nightside ionosphere. A comparison with the temperature obtained from the IRI-95 model also shows a similar enhancement.

  12. Spectropolarimetric Inversions of the Ca II 8542 Å Line in an M-class Solar Flare

    Science.gov (United States)

    Kuridze, D.; Henriques, V. M. J.; Mathioudakis, M.; Rouppe van der Voort, L.; de la Cruz Rodríguez, J.; Carlsson, M.

    2018-06-01

    We study the M1.9-class solar flare SOL2015-09-27T10:40 UT using high-resolution full Stokes imaging spectropolarimetry of the Ca II 8542 Å line obtained with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope. Spectropolarimetric inversions using the non-LTE code NICOLE are used to construct semiempirical models of the flaring atmosphere to investigate the structure and evolution of the flare temperature and magnetic field. A comparison of the temperature stratification in flaring and nonflaring areas reveals strong heating of the flare ribbon during the flare peak. The polarization signals of the ribbon in the chromosphere during the flare maximum become stronger when compared to its surroundings and to pre- and post-flare profiles. Furthermore, a comparison of the response functions to perturbations in the line-of-sight magnetic field and temperature in flaring and nonflaring atmospheres shows that during the flare, the Ca II 8542 Å line is more sensitive to the lower atmosphere where the magnetic field is expected to be stronger. The chromospheric magnetic field was also determined with the weak-field approximation, which led to results similar to those obtained with the NICOLE inversions.

  13. Simulation of the charging process of the LISA test masses due to solar flares

    International Nuclear Information System (INIS)

    Vocca, H; Grimani, C; Amico, P; Bosi, L; Marchesoni, F; Punturo, M; Travasso, F; Barone, M; Stanga, R; Vetrano, F; Vicere, A

    2004-01-01

    Cosmic-ray and solar high energy particles penetrate the LISA experiment test masses. Consequently, an electric charge accumulates in the bodies of the masses, generating spurious Coulomb forces between the masses and the surrounding electrodes. This process increases the noise level of the experiment. We have estimated the amount of charge deposited per second on the LISA test masses by solar flares and primary cosmic-ray protons at solar minimum. The simulation has been carried out with the Fluka Monte Carlo program. A simplified geometry for the experiment has been considered. We have found a net charging rate of 37 ± 1 e + /s for primary protons at solar minimum between 0.1 and 1000 GeV/n. The amount of charge released by a medium-strong solar flare, like that of 16 February 1984, is 10 732 ± 30 e + /s in the energy range 0.1-10 GeV/n. This value increases or decreases by approximately one order of magnitude for strong (weak) solar flares

  14. Solar flare location effect on the spectral characteristics of the diurnal anisotropy of cosmic ray intensity

    Energy Technology Data Exchange (ETDEWEB)

    Yadava, R S; Kumar, S; Naqvi, T N [Aligarh Muslim Univ. (India)

    1977-01-01

    The spectral parameters of the diurnal anisotropy of cosmic ray intensity are studied separately for days where the solar flares have occurred on the western limb as well as on the eastern limb of the solar disc for both nucleonic as well as mesonic components of the cosmic rays. It is observed that the diurnal amplitude of the cosmic ray intensity in space is larger for days where solar flares have occurred on the western limb of the solar disc as compared to the days where solar flares have occurred on the eartern limb of the solar disc. This is true in both nucleonic as well as mesonic components of the cosmic ray intensity. The average value of the direction in space of diurnal anisotropy in local asymptotic time for various stations is almost same and is observed at around the same hours for flares which occur on the western as well as eastern limb of the solar disc. When these results are compared with the direction of the diurnal anisotropy in space on quiet days, it is found that the direction of the diurnal anisotropy on days where solar flares have occurred on the western limb as well as eastern limb of the solar disc is earlier in comparison to quiet days. This phase shift towards earlier hours is about three hours for nucleonic as well as mesonic components of the cosmic rays intensity. The variation of the rigidity exponent observed on different types of days for the nucleonic component has also been discussed.

  15. Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

    Science.gov (United States)

    Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J.

    2016-01-01

    The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

  16. Neutron-decay Protons from Solar Flares as Seed Particles for CME-shock Acceleration in the Inner Heliosphere

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Ronald J. [Code 7650, Naval Research Laboratory, Washington, DC 20375 (United States); Ko, Yuan-Kuen, E-mail: ronald.murphy@nrl.navy.mil, E-mail: yuan-kuen.ko@nrl.navy.mil [Code 7680, Naval Research Laboratory, Washington, DC 20375 (United States)

    2017-09-01

    The protons in large solar energetic particle events are accelerated in the inner heliosphere by fast shocks produced by coronal mass ejections. Unless there are other sources, the protons these shocks act upon would be those of the solar wind (SW). The efficiency of the acceleration depends on the kinetic energy of the protons. For a 2000 km s{sup −1} shock, the most effective proton energies would be 30–100 keV; i.e., within the suprathermal tail component of the SW. We investigate one possible additional source of such protons: those resulting from the decay of solar-flare-produced neutrons that escape from the Sun into the low corona. The neutrons are produced by interactions of flare-accelerated ions with the solar atmosphere. We discuss the production of low-energy neutrons in flares and their decay on a interplanetary magnetic field line near the Sun. We find that even when the flaring conditions are optimal, the 30–100 keV neutron-decay proton density produced by even a very large solar flare would be only about 10% of that of the 30–100 keV SW suprathermal tail. We discuss the implication of a seed-particle source of more frequent, small flares.

  17. FARIMA MODELING OF SOLAR FLARE ACTIVITY FROM EMPIRICAL TIME SERIES OF SOFT X-RAY SOLAR EMISSION

    International Nuclear Information System (INIS)

    Stanislavsky, A. A.; Burnecki, K.; Magdziarz, M.; Weron, A.; Weron, K.

    2009-01-01

    A time series of soft X-ray emission observed by the Geostationary Operational Environment Satellites from 1974 to 2007 is analyzed. We show that in the solar-maximum periods the energy distribution of soft X-ray solar flares for C, M, and X classes is well described by a fractional autoregressive integrated moving average model with Pareto noise. The model incorporates two effects detected in our empirical studies. One effect is a long-term dependence (long-term memory), and another corresponds to heavy-tailed distributions. The parameters of the model: self-similarity exponent H, tail index α, and memory parameter d are statistically stable enough during the periods 1977-1981, 1988-1992, 1999-2003. However, when the solar activity tends to minimum, the parameters vary. We discuss the possible causes of this evolution and suggest a statistically justified model for predicting the solar flare activity.

  18. Properties of an impulsive compact solar flare determined from Solar Maximum Mission X-ray measurements

    Science.gov (United States)

    Linford, G. A.; Wolfson, C. J.

    1988-01-01

    Soft X-ray, hard X-ray magnetogram, and H-alpha data have been analyzed for an impulsive compact solar flare which occurred on May 21, 1985. The derived flare loop dimensions are about 20,000 km length and about 150 km diameter. Measurements of line ratios from the Mg XI ion indicate that the plasma density varied from about 4 x 10 to the 12th/cu cm early in the flare to about 10 to the 12th/cu cm during the flare decay. The initial temperature of this plasma was about 8 x 10 to the 6th K and dropped to about 5 x 10 to the 6th K during the decay phase. The simplest interpretation of the event is one in which the source of the soft X-ray flare emission is confined to a thin loop of very high density.

  19. Properties of an impulsive compact solar flare determined from Solar Maximum Mission X-ray measurements

    International Nuclear Information System (INIS)

    Linford, G.A.; Wolfson, C.J.

    1988-01-01

    Soft X-ray, hard X-ray magnetogram, and H-alpha data have been analyzed for an impulsive compact solar flare which occurred on May 21, 1985. The derived flare loop dimensions are about 20,000 km length and about 150 km diameter. Measurements of line ratios from the Mg XI ion indicate that the plasma density varied from about 4 x 10 to the 12th/cu cm early in the flare to about 10 to the 12th/cu cm during the flare decay. The initial temperature of this plasma was about 8 x 10 to the 6th K and dropped to about 5 x 10 to the 6th K during the decay phase. The simplest interpretation of the event is one in which the source of the soft X-ray flare emission is confined to a thin loop of very high density. 44 references

  20. Properties of an impulsive compact solar flare determined from Solar Maximum Mission X-ray measurements

    Energy Technology Data Exchange (ETDEWEB)

    Linford, G.A.; Wolfson, C.J.

    1988-08-01

    Soft X-ray, hard X-ray magnetogram, and H-alpha data have been analyzed for an impulsive compact solar flare which occurred on May 21, 1985. The derived flare loop dimensions are about 20,000 km length and about 150 km diameter. Measurements of line ratios from the Mg XI ion indicate that the plasma density varied from about 4 x 10 to the 12th/cu cm early in the flare to about 10 to the 12th/cu cm during the flare decay. The initial temperature of this plasma was about 8 x 10 to the 6th K and dropped to about 5 x 10 to the 6th K during the decay phase. The simplest interpretation of the event is one in which the source of the soft X-ray flare emission is confined to a thin loop of very high density. 44 references.

  1. SIGN SINGULARITY AND FLARES IN SOLAR ACTIVE REGION NOAA 11158

    Energy Technology Data Exchange (ETDEWEB)

    Sorriso-Valvo, L.; De Vita, G. [IMIP-CNR, U.O.S. LICRYL di Cosenza, Ponte P. Bucci, Cubo 31C, I-87036 Rende (Italy); Kazachenko, M. D.; Krucker, S.; Welsch, B. T.; Fisher, G. H. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley 94720, California (United States); Primavera, L.; Servidio, S.; Lepreti, F.; Carbone, V. [Dipartimento di Fisica, Università della Calabria, Ponte P. Bucci, Cubo 31C, I-87036 Rende (Italy); Vecchio, A., E-mail: sorriso@fis.unical.it [INGV, Sede di Cosenza, Ponte P. Bucci, Cubo 30C, I-87036 Rende (Italy)

    2015-03-01

    Solar Active Region NOAA 11158 has hosted a number of strong flares, including one X2.2 event. The complexity of current density and current helicity are studied through cancellation analysis of their sign-singular measure, which features power-law scaling. Spectral analysis is also performed, revealing the presence of two separate scaling ranges with different spectral index. The time evolution of parameters is discussed. Sudden changes of the cancellation exponents at the time of large flares and the presence of correlation with Extreme-Ultra-Violet and X-ray flux suggest that eruption of large flares can be linked to the small-scale properties of the current structures.

  2. MULTI-VIEWPOINT OBSERVATIONS OF A WIDELY DISTRIBUTED SOLAR ENERGETIC PARTICLE EVENT: THE ROLE OF EUV WAVES AND WHITE-LIGHT SHOCK SIGNATURES

    Energy Technology Data Exchange (ETDEWEB)

    Kouloumvakos, A.; Patsourakos, S.; Nindos, A. [Section of Astrogeophysics, Department of Physics, University of Ioannina, 45110 Ioannina (Greece); Vourlidas, A. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States); Anastasiadis, A.; Sandberg, I. [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, 15236 Penteli (Greece); Hillaris, A. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, 15783 Athens (Greece)

    2016-04-10

    On 2012 March 7, two large eruptive events occurred in the same active region within 1 hr from each other. Each consisted of an X-class flare, a coronal mass ejection (CME), an extreme-ultraviolet (EUV) wave, and a shock wave. The eruptions gave rise to a major solar energetic particle (SEP) event observed at widely separated (∼120°) points in the heliosphere. From multi-viewpoint energetic proton recordings we determine the proton release times at STEREO B and A (STB, STA) and the first Lagrange point (L1) of the Sun–Earth system. Using EUV and white-light data, we determine the evolution of the EUV waves in the low corona and reconstruct the global structure and kinematics of the first CME’s shock, respectively. We compare the energetic proton release time at each spacecraft with the EUV waves’ arrival times at the magnetically connected regions and the timing and location of the CME shock. We find that the first flare/CME is responsible for the SEP event at all three locations. The proton release at STB is consistent with arrival of the EUV wave and CME shock at the STB footpoint. The proton release time at L1 was significantly delayed compared to STB. Three-dimensional modeling of the CME shock shows that the particle release at L1 is consistent with the timing and location of the shock’s western flank. This indicates that at L1 the proton release did not occur in low corona but farther away from the Sun. However, the extent of the CME shock fails to explain the SEP event observed at STA. A transport process or a significantly distorted interplanetary magnetic field may be responsible.

  3. RELATIONSHIP BETWEEN CHROMOSPHERIC EVAPORATION AND MAGNETIC FIELD TOPOLOGY IN AN M-CLASS SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Sadykov, Viacheslav M; Kosovichev, Alexander G [Department of Physics, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Sharykin, Ivan N; Zimovets, Ivan V [Space Research Institute (IKI) of Russian Academy of Sciences, Moscow 117997 (Russian Federation); Dominguez, Santiago Vargas [Universidad Nacional de Colombia, Sede Bogotá, Observatorio Astronómico, Carrera 45 # 26-85, Bogotá (Colombia)

    2016-09-01

    Chromospheric evaporation is observed as Doppler blueshift during solar flares. It plays a key role in the dynamics and energetics of solar flares; however, its mechanism is still unknown. In this paper, we present a detailed analysis of spatially resolved multi-wavelength observations of chromospheric evaporation during an M 1.0-class solar flare (SOL2014-06-12T21:12) using data from NASA’s Interface Region Imaging Spectrograph and HMI/ SDO (the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory), and high-resolution observations from VIS/NST (the Visible Imaging Spectrometer at the New Solar Telescope). The results show that the averaged over the flare region Fe xxi blueshift of the hot (10{sup 7} K) evaporating plasma is delayed relative to the C ii redshift of the relatively cold (10{sup 4} K) chromospheric plasma by about one minute. The spatial distribution of the delays is not uniform across the region and can be as long as two minutes in several zones. Using vector magnetograms from HMI, we reconstruct the magnetic field topology and the quasi-separatrix layer, and find that the blueshift delay regions as well as the H α flare ribbons are connected to the region of the magnetic polarity inversion line (PIL) and an expanding flux rope via a system of low-lying loop arcades with a height of ≲4.5 Mm. As a result, the chromospheric evaporation may be driven by the energy release in the vicinity of PIL, and has the observed properties due to a local magnetic field topology.

  4. HYDRO2GEN: Non-thermal hydrogen Balmer and Paschen emission in solar flares generated by electron beams

    Science.gov (United States)

    Druett, M. K.; Zharkova, V. V.

    2018-03-01

    Aim. Sharp rises of hard X-ray (HXR) emission accompanied by Hα line profiles with strong red-shifts up to 4 Å from the central wavelength, often observed at the onset of flares with the Specola Solare Ticinese Telescope (STT) and the Swedish Solar Telescope (SST), are not fully explained by existing radiative models. Moreover, observations of white light (WL) and Balmer continuum emission with the Interface Region Imaging Spectrograph (IRISH) reveal strong co-temporal enhancements and are often nearly co-spatial with HXR emission. These effects indicate a fast effective source of excitation and ionisation of hydrogen atoms in flaring atmospheres associated with HXR emission. In this paper, we investigate electron beams as the agents accounting for the observed hydrogen line and continuum emission. Methods: Flaring atmospheres are considered to be produced by a 1D hydrodynamic response to the injection of an electron beam defining their kinetic temperatures, densities, and macro velocities. We simulated a radiative response in these atmospheres using a fully non-local thermodynamic equilibrium (NLTE) approach for a 5-level plus continuum hydrogen atom model, considering its excitation and ionisation by spontaneous, external, and internal diffusive radiation and by inelastic collisions with thermal and beam electrons. Simultaneous steady-state and integral radiative transfer equations in all optically thick transitions (Lyman and Balmer series) were solved iteratively for all the transitions to define their source functions with the relative accuracy of 10-5. The solutions of the radiative transfer equations were found using the L2 approximation. Resulting intensities of hydrogen line and continuum emission were also calculated for Balmer and Paschen series. Results: We find that inelastic collisions with beam electrons strongly increase excitation and ionisation of hydrogen atoms from the chromosphere to photosphere. This leads to an increase in Lyman continuum

  5. Collisionless shock formation and the prompt acceleration of solar flare ions

    Science.gov (United States)

    Cargill, P. J.; Goodrich, C. C.; Vlahos, L.

    1988-01-01

    The formation mechanisms of collisionless shocks in solar flare plasmas are investigated. The priamry flare energy release is assumed to arise in the coronal portion of a flare loop as many small regions or 'hot spots' where the plasma beta locally exceeds unity. One dimensional hybrid numerical simulations show that the expansion of these 'hot spots' in a direction either perpendicular or oblique to the ambient magnetic field gives rise to collisionless shocks in a few Omega(i), where Omega(i) is the local ion cyclotron frequency. For solar parameters, this is less than 1 second. The local shocks are then subsequently able to accelerate particles to 10 MeV in less than 1 second by a combined drift-diffusive process. The formation mechanism may also give rise to energetic ions of 100 keV in the shock vicinity. The presence of these energetic ions is due either to ion heating or ion beam instabilities and they may act as a seed population for further acceleration. The prompt acceleration of ions inferred from the Gamma Ray Spectrometer on the Solar Maximum Mission can thus be explained by this mechanism.

  6. Method of separation of celestial gamma-ray bursts from solar flares

    International Nuclear Information System (INIS)

    Chuang, K.W.; White, R.S.; Klebesadel, R.W.; Laros, J.G.

    1991-01-01

    We recently discovered 217 ''new'' celestial gamma-ray burst candidates from the ''new'' burst search of the PVO real time data base. 1 The burst search covered the time period from September 1978 to July 1988. Sixty were confirmed by at lest on other spacecraft, e.g., ISEE-3, V-11, V-12, etc. None triggered the PVO high time resolution memory. In this paper we describe a new algorithm based ont eh relationship between time width T w and hardness ratio HR, to distinguish cosmic gamma-ray bursts from solar flares without knowing the directions of the events. The criteria for identification as a gamma-ray burst candidate are: If T ww ≤a then HR≥bT w , or T w >a then HR>c. Otherwise, the event is a solar flare candidate. Here, a, b, and c are parameter which differ for different gamma-ray burst detectors. For PVO, a=18.8 s, b=(1.38/18.8) s -1 , and c=1.38. This algorithm was tested with 83 triggered and 60 nontriggered confirmed gamma-ray burst and 30 confirmed solar flares from PVO

  7. ASASSN-16ae: A POWERFUL WHITE-LIGHT FLARE ON AN EARLY-L DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Sarah J. [Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482, Potsdam (Germany); Shappee, Benjamin J.; Seibert, Mark [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Gagné, Jonathan [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Stanek, K. Z.; Holoien, Thomas W.-S.; Kochanek, C. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Prieto, José L. [Núcleo de Astronomía de la Facultad de Ingenierá, Universidad Diego Portales, Av. Ejército 441, Santiago (Chile); Chomiuk, Laura; Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Dong, Subo, E-mail: sjschmidt@aip.de [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871 (China)

    2016-09-10

    We report the discovery and classification of SDSS J053341.43+001434.1 (SDSS0533), an early-L dwarf first discovered during a powerful Δ V< −11 magnitude flare observed as part of the ASAS-SN survey. Optical and infrared spectroscopy indicate a spectral type of L0 with strong H α emission and a blue NIR spectral slope. Combining the photometric distance, proper motion, and radial velocity of SDSS0533 yields three-dimensional velocities of ( U , V , W ) = (14 ± 13, −35 ± 14, −94 ± 22) km s{sup −1}, indicating that it is most likely part of the thick disk population and probably old. The three detections of SDSS0533 obtained during the flare are consistent with a total V -band flare energy of at least 4.9 × 10{sup 33} erg (corresponding to a total thermal energy of at least E {sub tot} > 3.7 × 10{sup 34} erg), placing it among the strongest detected M dwarf flares. The presence of this powerful flare on an old L0 dwarf may indicate that stellar-type magnetic activity persists down to the end of the main sequence and on older ML transition dwarfs.

  8. Internal and External Reconnection Series Homologous Solar Flares

    Science.gov (United States)

    Sterling, Alphonse C.; Moore, Ronald L.

    2001-01-01

    Using data from the extreme ultraviolet imaging telescope (EIT) on SOHO and the soft X-ray telescope (SXT) on Yohkoh, we examine a series of morphologically homologous solar flares occurring in National Oceanic and Atmospheric Administration (NOAA) active region 8210 over May 1-2, 1998. An emerging flux region (EFR) impacted against a sunspot to the west and next to a coronal hole to the east is the source of the repeated flaring. An SXT sigmoid parallels the EFR's neutral line at the site of the initial flaring in soft X rays. In EIT each flaring episode begins with the formation of a crinkle pattern external to the EFR. These EIT crinkles move out from, and then in toward, the EFR with velocities approx. 20 km/ s. A shrinking and expansion of the width of the coronal hole coincides with the crinkle activity, and generation and evolution of a postflare loop system begins near the time of crinkle formation. Using a schematic based on magnetograms of the region, we suggest that these observations are consistent with the standard reconnection-based model for solar eruptions but are modified by the presence of the additional magnetic fields of the sunspot and coronal hole. In the schematic, internal reconnection begins inside of the EFR-associated fields, unleashing a flare, postflare loops, and a coronal mass ejection (CME). External reconnection, first occurring between the escaping CME and the coronal hole field and second occurring between fields formed as a result of the first external reconnection, results in the EIT crinkles and changes in the coronal hole boundary. By the end of the second external reconnection, the initial setup is reinstated; thus the sequence can repeat, resulting in morphologically homologous eruptions. Our inferred magnetic topology is similar to that suggested in the "breakout model" of eruptions although we cannot determine if our eruptions are released primarily by the breakout mechanism (external reconnection) or, alternatively

  9. Two-phase Heating in Flaring Loops

    Science.gov (United States)

    Zhu, Chunming; Qiu, Jiong; Longcope, Dana W.

    2018-03-01

    We analyze and model a C5.7 two-ribbon solar flare observed by the Solar Dynamics Observatory, Hinode, and GOES on 2011 December 26. The flare is made of many loops formed and heated successively over one and half hours, and their footpoints are brightened in the UV 1600 Å before enhanced soft X-ray and EUV missions are observed in flare loops. Assuming that anchored at each brightened UV pixel is a half flaring loop, we identify more than 6700 half flaring loops, and infer the heating rate of each loop from the UV light curve at the footpoint. In each half loop, the heating rate consists of two phases: intense impulsive heating followed by a low-rate heating that is persistent for more than 20 minutes. Using these heating rates, we simulate the evolution of their coronal temperatures and densities with the model of the “enthalpy-based thermal evolution of loops.” In the model, suppression of thermal conduction is also considered. This model successfully reproduces total soft X-ray and EUV light curves observed in 15 passbands by four instruments GOES, AIA, XRT, and EVE. In this flare, a total energy of 4.9 × 1030 erg is required to heat the corona, around 40% of this energy is in the slow-heating phase. About two-fifths of the total energy used to heat the corona is radiated by the coronal plasmas, and the other three fifth transported to the lower atmosphere by thermal conduction.

  10. Pure white-light emitting ultrasmall organic-inorganic hybrid perovskite nanoclusters.

    Science.gov (United States)

    Teunis, Meghan B; Lawrence, Katie N; Dutta, Poulami; Siegel, Amanda P; Sardar, Rajesh

    2016-10-14

    Organic-inorganic hybrid perovskites, direct band-gap semiconductors, have shown tremendous promise for optoelectronic device fabrication. We report the first colloidal synthetic approach to prepare ultrasmall (∼1.5 nm diameter), white-light emitting, organic-inorganic hybrid perovskite nanoclusters. The nearly pure white-light emitting ultrasmall nanoclusters were obtained by selectively manipulating the surface chemistry (passivating ligands and surface trap-states) and controlled substitution of halide ions. The nanoclusters displayed a combination of band-edge and broadband photoluminescence properties, covering a major part of the visible region of the solar spectrum with unprecedentedly large quantum yields of ∼12% and photoluminescence lifetime of ∼20 ns. The intrinsic white-light emission of perovskite nanoclusters makes them ideal and low cost hybrid nanomaterials for solid-state lighting applications.

  11. Observations of Reconnection Flows in a Flare on the Solar Disk

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Juntao; Simões, P. J. A.; Jeffrey, N. L. S.; Fletcher, L.; Wright, P. J.; Hannah, I. G., E-mail: j.wang.4@research.gla.ac.uk [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2017-09-20

    Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (CSHKP model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. We report on a unique set of Solar Dynamics Observatory /Atmospheric Imaging Assembly imaging and Hinode /EUV Imaging Spectrometer spectroscopic observations of the disk flare SOL2016-03-23T03:54 in which all four flows are present simultaneously. This includes spectroscopic evidence for a plasma upflow in association with large-scale expanding closed inflow field. The reconnection inflows are symmetric, and consistent with fast reconnection, and the post-reconnection loops show a clear cooling and deceleration as they retract. Observations of coronal reconnection flows are still rare, and most events are observed at the solar limb, obscured by complex foregrounds, making their relationship to the flare ribbons, cusp field, and arcades formed in the lower atmosphere difficult to interpret. The disk location and favorable perspective of this event have removed these ambiguities giving a clear picture of the reconnection dynamics.

  12. Observations of Reconnection Flows in a Flare on the Solar Disk

    International Nuclear Information System (INIS)

    Wang, Juntao; Simões, P. J. A.; Jeffrey, N. L. S.; Fletcher, L.; Wright, P. J.; Hannah, I. G.

    2017-01-01

    Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (CSHKP model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. We report on a unique set of Solar Dynamics Observatory /Atmospheric Imaging Assembly imaging and Hinode /EUV Imaging Spectrometer spectroscopic observations of the disk flare SOL2016-03-23T03:54 in which all four flows are present simultaneously. This includes spectroscopic evidence for a plasma upflow in association with large-scale expanding closed inflow field. The reconnection inflows are symmetric, and consistent with fast reconnection, and the post-reconnection loops show a clear cooling and deceleration as they retract. Observations of coronal reconnection flows are still rare, and most events are observed at the solar limb, obscured by complex foregrounds, making their relationship to the flare ribbons, cusp field, and arcades formed in the lower atmosphere difficult to interpret. The disk location and favorable perspective of this event have removed these ambiguities giving a clear picture of the reconnection dynamics.

  13. High-energy solar flare observations at the Y2K maximum

    Science.gov (United States)

    Emslie, A. Gordon

    2000-04-01

    Solar flares afford an opportunity to observe processes associated with the acceleration and propagation of high-energy particles at a level of detail not accessible in any other astrophysical source. I will review some key results from previous high-energy solar flare observations, including those from the Compton Gamma-Ray Observatory, and the problems that they pose for our understanding of energy release and particle acceleration processes in the astrophysical environment. I will then discuss a program of high-energy observations to be carried out during the upcoming 2000-2001 solar maximum that is aimed at addressing and resolving these issues. A key element in this observational program is the High Energy Solar Spectroscopic Imager (HESSI) spacecraft, which will provide imaging spectroscopic observations with spatial, temporal, and energy resolutions commensurate with the physical processes believed to be operating, and will in addition provide the first true gamma-ray spectroscopy of an astrophysical source. .

  14. IMPLOSION OF CORONAL LOOPS DURING THE IMPULSIVE PHASE OF A SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Simões, P. J. A.; Fletcher, L.; Hudson, H. S.; Russell, A. J. B., E-mail: paulo.simoes@glasgow.ac.uk, E-mail: lyndsay.fletcher@glasgow.ac.uk, E-mail: arussell@maths.dundee.ac.uk, E-mail: hhudson@ssl.berkeley.edu [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2013-11-10

    We study the relationship between implosive motions in a solar flare, and the energy redistribution in the form of oscillatory structures and particle acceleration. The flare SOL2012-03-09T03:53 (M6.4) shows clear evidence for an irreversible (stepwise) coronal implosion. Extreme-ultraviolet (EUV) images show at least four groups of coronal loops at different heights overlying the flaring core undergoing fast contraction during the impulsive phase of the flare. These contractions start around a minute after the flare onset, and the rate of contraction is closely associated with the intensity of the hard X-ray and microwave emissions. They also seem to have a close relationship with the dimming associated with the formation of the coronal mass ejection and a global EUV wave. Several studies now have detected contracting motions in the corona during solar flares that can be interpreted as the implosion necessary to release energy. Our results confirm this, and tighten the association with the flare impulsive phase. We add to the phenomenology by noting the presence of oscillatory variations revealed by Geostationary Operational Environmental Satellite soft X-rays (SXR) and spatially integrated EUV emission at 94 and 335 Å. We identify pulsations of ≈60 s in SXR and EUV data, which we interpret as persistent, semi-regular compressions of the flaring core region which modulate the plasma temperature and emission measure. The loop oscillations, observed over a large region, also allow us to provide rough estimates of the energy temporarily stored in the eigenmodes of the active-region structure as it approaches its new equilibrium.

  15. Flaring red dwarf stars: news from Crimea

    International Nuclear Information System (INIS)

    Gershberg, Roald E

    1998-01-01

    Important phenomena are briefly described which have recently been discovered in the Crimean studies of flaring red dwarf stars believed to be the most common type of variable stars in the Galaxy. These phenomena include (i) long-lived radiation from a blueshifted component in the ionized-helium λ 4686 A emission line in the active state of one such star, (ii) a long-lived absorption component in the stellar flare light curves with a lifetime exceeding that of the conventional flare emission, and (iii) solarcycle-like activity periodicity of the star EV Lac, whose mass is only 0.3 solar masses. In theoretical terms, a red dwarf star spot model is constructed which, in contrast to the commonly accepted model, agrees well with the solar spot picture. (physics of our days)

  16. Flaring red dwarf stars: news from Crimea

    Energy Technology Data Exchange (ETDEWEB)

    Gershberg, Roald E [Crimean Astrophysical Observatory, Nauchnyi, Crimea (Ukraine)

    1998-08-31

    Important phenomena are briefly described which have recently been discovered in the Crimean studies of flaring red dwarf stars believed to be the most common type of variable stars in the Galaxy. These phenomena include (i) long-lived radiation from a blueshifted component in the ionized-helium {lambda} 4686 A emission line in the active state of one such star, (ii) a long-lived absorption component in the stellar flare light curves with a lifetime exceeding that of the conventional flare emission, and (iii) solarcycle-like activity periodicity of the star EV Lac, whose mass is only 0.3 solar masses. In theoretical terms, a red dwarf star spot model is constructed which, in contrast to the commonly accepted model, agrees well with the solar spot picture. (physics of our days)

  17. A very small and super strong zebra pattern burst at the beginning of a solar flare

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Baolin; Tan, Chengming; Zhang, Yin; Huang, Jing; Yan, Yihua [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China); Mészárosová, Hana; Karlický, Marian, E-mail: bltan@nao.cas.cn [Astronomical Institute of the Academy of Sciences of the Czech Republic, Ondřejov 15165 (Czech Republic)

    2014-08-01

    Microwave emission with spectral zebra pattern structures (ZPs) is frequently observed in solar flares and the Crab pulsar. The previous observations show that ZP is a structure only overlapped on the underlying broadband continuum with slight increments and decrements. This work reports an unusually strong ZP burst occurring at the beginning of a solar flare observed simultaneously by two radio telescopes located in China and the Czech Republic and by the EUV telescope on board NASA's satellite Solar Dynamics Observatory on 2013 April 11. It is a very short and super strong explosion whose intensity exceeds several times that of the underlying flaring broadband continuum emission, lasting for just 18 s. EUV images show that the flare starts from several small flare bursting points (FBPs). There is a sudden EUV flash with extra enhancement in one of these FBPs during the ZP burst. Analysis indicates that the ZP burst accompanying an EUV flash is an unusual explosion revealing a strong coherent process with rapid particle acceleration, violent energy release, and fast plasma heating simultaneously in a small region with a short duration just at the beginning of the flare.

  18. HOW DID A MAJOR CONFINED FLARE OCCUR IN SUPER SOLAR ACTIVE REGION 12192?

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Chaowei; Feng, Xueshang [SIGMA Weather Group, State Key Laboratory for Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China); Wu, S. T.; Hu, Qiang [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Yurchyshyn, Vasyl; Wang, Haiming, E-mail: cwjiang@spaceweather.ac.cn [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2016-09-01

    We study the physical mechanism of a major X-class solar flare that occurred in the super NOAA active region (AR) 12192 using data-driven numerical magnetohydrodynamic (MHD) modeling complemented with observations. With the evolving magnetic fields observed at the solar surface as bottom boundary input, we drive an MHD system to evolve self-consistently in correspondence with the realistic coronal evolution. During a two-day time interval, the modeled coronal field has been slowly stressed by the photospheric field evolution, which gradually created a large-scale coronal current sheet, i.e., a narrow layer with intense current, in the core of the AR. The current layer was successively enhanced until it became so thin that a tether-cutting reconnection between the sheared magnetic arcades was set in, which led to a flare. The modeled reconnecting field lines and their footpoints match well the observed hot flaring loops and the flare ribbons, respectively, suggesting that the model has successfully “reproduced” the macroscopic magnetic process of the flare. In particular, with simulation, we explained why this event is a confined eruption—the consequence of the reconnection is a shared arcade instead of a newly formed flux rope. We also found a much weaker magnetic implosion effect compared to many other X-class flares.

  19. Max '91: Flare research at the next solar maximum

    Science.gov (United States)

    Dennis, Brian; Canfield, Richard; Bruner, Marilyn; Emslie, Gordon; Hildner, Ernest; Hudson, Hugh; Hurford, Gordon; Lin, Robert; Novick, Robert; Tarbell, Ted

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided.

  20. Max '91: flare research at the next solar maximum

    International Nuclear Information System (INIS)

    Dennis, B.; Canfield, R.; Bruner, M.

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided

  1. Solar storms; Tormentas solares

    Energy Technology Data Exchange (ETDEWEB)

    Collaboration: Pereira Cuesta, S.; Pereira Pagan, B.

    2016-08-01

    Solar storms begin with an explosion, or solar flare, on the surface of the sun. The X-rays and extreme ultraviolet radiation from the flare reach the Earths orbit minutes later-travelling at light speed. The ionization of upper layers of our atmosphere could cause radio blackouts and satellite navigation errors (GPS). Soon after, a wave of energetic particles, electrons and protons accelerated by the explosion crosses the orbit of the Earth, and can cause real and significant damage. (Author)

  2. SOLAR FLARE PREDICTION USING SDO/HMI VECTOR MAGNETIC FIELD DATA WITH A MACHINE-LEARNING ALGORITHM

    International Nuclear Information System (INIS)

    Bobra, M. G.; Couvidat, S.

    2015-01-01

    We attempt to forecast M- and X-class solar flares using a machine-learning algorithm, called support vector machine (SVM), and four years of data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager, the first instrument to continuously map the full-disk photospheric vector magnetic field from space. Most flare forecasting efforts described in the literature use either line-of-sight magnetograms or a relatively small number of ground-based vector magnetograms. This is the first time a large data set of vector magnetograms has been used to forecast solar flares. We build a catalog of flaring and non-flaring active regions sampled from a database of 2071 active regions, comprised of 1.5 million active region patches of vector magnetic field data, and characterize each active region by 25 parameters. We then train and test the machine-learning algorithm and we estimate its performances using forecast verification metrics with an emphasis on the true skill statistic (TSS). We obtain relatively high TSS scores and overall predictive abilities. We surmise that this is partly due to fine-tuning the SVM for this purpose and also to an advantageous set of features that can only be calculated from vector magnetic field data. We also apply a feature selection algorithm to determine which of our 25 features are useful for discriminating between flaring and non-flaring active regions and conclude that only a handful are needed for good predictive abilities

  3. NuSTAR Hard X-Ray Observation of a Sub-A Class Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Glesener, Lindsay [School of Physics and Astronomy, University of Minnesota, Minneapolis (United States); Krucker, Säm; Hudson, Hugh [Space Sciences Laboratory, University of California at Berkeley, Berkeley (United States); Hannah, Iain G. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom); Grefenstette, Brian W. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena (United States); White, Stephen M. [Air Force Research Laboratory, Albuquerque (United States); Smith, David M.; Marsh, Andrew J. [Santa Cruz Institute of Particle Physics and Department of Physics, University of California at Santa Cruz, Santa Cruz (United States)

    2017-08-20

    We report a Nuclear Spectroscopic Telescope Array ( NuSTAR ) observation of a solar microflare, SOL2015-09-01T04. Although it was too faint to be observed by the GOES X-ray Sensor, we estimate the event to be an A0.1 class flare in brightness. This microflare, with only ∼5 counts s{sup −1} detector{sup −1} observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager ( RHESSI ), is fainter than any hard X-ray (HXR) flare in the existing literature. The microflare occurred during a solar pointing by the highly sensitive NuSTAR astrophysical observatory, which used its direct focusing optics to produce detailed HXR microflare spectra and images. The microflare exhibits HXR properties commonly observed in larger flares, including a fast rise and more gradual decay, earlier peak time with higher energy, spatial dimensions similar to the RHESSI microflares, and a high-energy excess beyond an isothermal spectral component during the impulsive phase. The microflare is small in emission measure, temperature, and energy, though not in physical size; observations are consistent with an origin via the interaction of at least two magnetic loops. We estimate the increase in thermal energy at the time of the microflare to be 2.4 × 10{sup 27} erg. The observation suggests that flares do indeed scale down to extremely small energies and retain what we customarily think of as “flare-like” properties.

  4. Fluctuation analysis of solar radio bursts associated with geoeffective X-class flares

    Czech Academy of Sciences Publication Activity Database

    Veronese, T.B.; Rosa, R. R.; Bolzan, M.J.A.; Fernandes, F. C. R.; Sawant, H. S.; Karlický, Marian

    2011-01-01

    Roč. 73, 11-12 (2011), s. 1311-1316 ISSN 1364-6826 Institutional research plan: CEZ:AV0Z10030501 Keywords : decimetric solar radio bursts * solar flares * detrended fluctuation analysis Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.596, year: 2011

  5. Effect of solar flare on the equatorial electrojet in eastern Brazil region

    Indian Academy of Sciences (India)

    R G Rastogi

    2017-06-07

    Jun 7, 2017 ... The effect of solar flare, sudden commencement of magnetic storm and of the disturbances ring current on the ... and measured east of geographic north. The ΔH .... Figure 2 shows the intensity of solar x-ray radiations in the ...

  6. Gamma-ray Burst X-ray Flares Light Curve Fitting

    Science.gov (United States)

    Aubain, Jonisha

    2018-01-01

    Gamma Ray Bursts (GRBs) are the most luminous explosions in the Universe. These electromagnetic explosions produce jets demonstrated by a short burst of prompt gamma-ray emission followed by a broadband afterglow. There are sharp increases of flux in the X-ray light curves known as flares that occurs in about 50% of the afterglows. In this study, we characterized all of the X-ray afterglows that were detected by the Swift X-ray Telescope (XRT), whether with flares or without. We fit flares to the Norris function (Norris et al. 2005) and power laws with breaks where necessary (Racusin et al. 2009). After fitting the Norris function and power laws, we search for the residual pattern detected in prompt GRB pulses (Hakkila et al. 2014, 2015, 2017), that may indicate a common signature of shock physics. If we find the same signature in flares and prompt pulses, it provides insight into what causes them, as well as, how these flares are produced.

  7. Concept of white light in stage lighting

    Science.gov (United States)

    Rinaldi, Mauricio R.

    2002-06-01

    In perceiving objects, generally we see them in a white light situation. But, actually, there is not an absolute white, in such a manner that the different light sources have a determined kind of white, what it is known as color temperature. Even the white light may be of different kinds (different color temperature), the individual mind tends to perceive it as the same kind of white, that is to say, there is in our mind a psychological function by which we operate an integration in the perception in order to do the object perceptually invariable. On the other hand, it is a common practice in stage lighting to use color light sources. It is a well known phenomenon that a color of light produces a change in the object color perception. However, when we go to theater, we see the objects as having their real color, even if the lighting is not white. In this paper the concept of white light in stage lighting is presented, showing its possibilities of aesthetical expression.

  8. EOSCOR: a light weight, microprocessor controlled solar neutron detector

    International Nuclear Information System (INIS)

    Koga, R.; Albats, P.; Frye, G.M. Jr.; Schindler, S.M.; Denehy, B.V.; Hopper, V.D.; Mace, O.B.

    1979-01-01

    A light weight high energy neutron detector with vertical detection efficiency of 0.005 at 40 MeV and 1.4 m 2 sensitive area has been developed for long duration super-pressure balloon flight observations of solar neutrons and gamma rays. It consists of two sets of four plastic scintillator hodoscopes separated by a 1 m time-of-flight path to observe n-p, C(n,p), and C(n,d) interactions. The neutron interactions are separated from gamma ray events through TOF measurements. For a large flare, the signal from solar neutrons is expected to be an order of magnitude greater than that of the atmospheric background. The microprocessor controls the data acquisition, accumulation of histograms, and the encoding of data for the telemetry systems. A test flight of the detector was made with a zero-pressure balloon. The expected many-week duration of a super-pressure balloon flight would significantly increase the probability of observing 20-150 MeV neutrons from a medium or large flare. (Auth.)

  9. Diagnostics of solar flare reconnection

    Directory of Open Access Journals (Sweden)

    M. Karlický

    2004-01-01

    Full Text Available We present new diagnostics of the solar flare reconnection, mainly based on the plasma radio emission. We propose that the high-frequency (600-2000 MHz slowly drifting pulsating structures map the flare magnetic field reconnection. These structures correspond to the radio emission from plasmoids which are formed in the extended current sheet due to tearing and coalescence processes. An increase of the frequency drift of the drifting structures is interpreted as an increase of the reconnection rate. Using this model, time scales of slowly drifting pulsating structure observed during the 12 April 2001 flare by the Trieste radiopolarimeter with high time resolution (1 ms are interpreted as a radio manifestation of electron beams accelerated in the multi-scale reconnection process. For short periods Fourier spectra of the observed structure have a power-law form with power-law indices in the 1.3-1.6 range. For comparison the 2-D MHD numerical modeling of the multi-scale reconnection is made and it is shown that Fourier spectrum of the reconnection dissipation power has also a power-law form, but with power-law index 2. Furthermore, we compute a time evolution of plasma parameters (density, magnetic field etc in the 2-D MHD model of the reconnection. Then assuming a plasma radio emission from locations, where the 'double-resonance' instability generates the upper-hybrid waves due to unstable distribution function of suprathermal electrons, we model radio spectra. Effects of the MHD turbulence are included. The resulting spectra are compared with those observed. It is found, that depending on model parameters the lace bursts and the decimetric spikes can be reproduced. Thus, it is shown that the model can be used for diagnostics of the flare reconnection process. We also point out possible radio signatures of reconnection outflow termination shocks. They are detected as type II-like herringbone structures in the 200-700 MHz frequency range. Finally

  10. Solar Flares, Type III Radio Bursts, Coronal Mass Ejections, and Energetic Particles

    Science.gov (United States)

    Cane, Hilary V.; Erickson, W. C.; Prestage, N. P.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    In this correlative study between greater than 20 MeV solar proton events, coronal mass ejections (CMEs), flares, and radio bursts it is found that essentially all of the proton events are preceded by groups of type III bursts and all are preceded by CMEs. These type III bursts (that are a flare phenomenon) usually are long-lasting, intense bursts seen in the low-frequency observations made from space. They are caused by streams of electrons traveling from close to the solar surface out to 1 AU. In most events the type III emissions extend into, or originate at, the time when type II and type IV bursts are reported (some 5 to 10 minutes after the start of the associated soft X-ray flare) and have starting frequencies in the 500 to approximately 100 MHz range that often get lower as a function of time. These later type III emissions are often not reported by ground-based observers, probably because of undue attention to type II bursts. It is suggested to call them type III-1. Type III-1 bursts have previously been called shock accelerated (SA) events, but an examination of radio dynamic spectra over an extended frequency range shows that the type III-1 bursts usually start at frequencies above any type II burst that may be present. The bursts sometimes continue beyond the time when type II emission is seen and, furthermore, sometimes occur in the absence of any type II emission. Thus the causative electrons are unlikely to be shock accelerated and probably originate in the reconnection regions below fast CMEs. A search did not find any type III-1 bursts that were not associated with CMEs. The existence of low-frequency type III bursts proves that open field lines extend from within 0.5 radius of the Sun into the interplanetary medium (the bursts start above 100 MHz, and such emission originates within 0.5 solar radius of the solar surface). Thus it is not valid to assume that only closed field lines exist in the flaring regions associated with CMEs and some

  11. Concentration of solar radiation by white painted transparent plates.

    Science.gov (United States)

    Smestad, G; Hamill, P

    1982-04-01

    A simple flat-plate solar concentrator is described in this paper. The device is composed of a white painted transparent plate with a photovoltaic cell fixed to an unpainted area on the bottom of the plate. Light scattering off the white material is either lost or directed to the solar cell. Experimental concentrations of up to 1.9 times the incident solar flux have been achieved using white clays. These values are close to those predicted by theory for the experimental parameters investigated. A theory of the device operation is developed. Using this theory suggestions are made for optimizing the concentrator system. For reasonable choices of cell and plate size and reflectivities of 80% concentrations of over 2x are possible. The concentrator has the advantage over other systems in that the concentration is independent of incidence angle and the concentrator is easy to produce. The device needs no tracking system and will concentrate on a cloudy day.

  12. DATA-DRIVEN RADIATIVE HYDRODYNAMIC MODELING OF THE 2014 MARCH 29 X1.0 SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Fatima Rubio da; Petrosian, Vahé [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kleint, Lucia [University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch (Switzerland); Liu, Wei [Bay Area Environmental Research Institute, 625 2nd Street, Suite 209, Petaluma, CA 94952-5159 (United States); Allred, Joel C., E-mail: frubio@stanford.edu [NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2016-08-10

    Spectroscopic observations of solar flares provide critical diagnostics of the physical conditions in the flaring atmosphere. Some key features in observed spectra have not yet been accounted for in existing flare models. Here we report a data-driven simulation of the well-observed X1.0 flare on 2014 March 29 that can reconcile some well-known spectral discrepancies. We analyzed spectra of the flaring region from the Interface Region Imaging Spectrograph ( IRIS ) in Mg ii h and k, the Interferometric BIdimensional Spectropolarimeter at the Dunn Solar Telescope (DST/IBIS) in H α 6563 Å and Ca ii 8542 Å, and the Reuven Ramaty High Energy Solar Spectroscope Imager ( RHESSI ) in hard X-rays. We constructed a multithreaded flare loop model and used the electron flux inferred from RHESSI data as the input to the radiative hydrodynamic code RADYN to simulate the atmospheric response. We then synthesized various chromospheric emission lines and compared them with the IRIS and IBIS observations. In general, the synthetic intensities agree with the observed ones, especially near the northern footpoint of the flare. The simulated Mg ii line profile has narrower wings than the observed one. This discrepancy can be reduced by using a higher microturbulent velocity (27 km s{sup −1}) in a narrow chromospheric layer. In addition, we found that an increase of electron density in the upper chromosphere within a narrow height range of ≈800 km below the transition region can turn the simulated Mg ii line core into emission and thus reproduce the single peaked profile, which is a common feature in all IRIS flares.

  13. Block-induced Complex Structures Building the Flare-productive Solar Active Region 12673

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuhong; Zhang, Jun [CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Zhu, Xiaoshuai [Max-Planck Institute for Solar System Research, D-37077 Göttingen (Germany); Song, Qiao, E-mail: shuhongyang@nao.cas.cn [Key Laboratory of Space Weather, National Center for Space Weather, China Meteorological Administration, Beijing 100081 (China)

    2017-11-10

    Solar active region (AR) 12673 produced 4 X-class, 27 M-class, and numerous lower-class flares during its passage across the visible solar disk in 2017 September. Our study is to answer the questions why this AR was so flare-productive and how the X9.3 flare, the largest one of the past decade, took place. We find that there was a sunspot in the initial several days, and then two bipolar regions emerged nearby it successively. Due to the standing of the pre-existing sunspot, the movement of the bipoles was blocked, while the pre-existing sunspot maintained its quasi-circular shaped umbra only with the disappearance of a part of penumbra. Thus, the bipolar patches were significantly distorted, and the opposite polarities formed two semi-circular shaped structures. After that, two sequences of new bipolar regions emerged within the narrow semi-circular zone, and the bipolar patches separated along the curved channel. The new bipoles sheared and interacted with the previous ones, forming a complex topological system, during which numerous flares occurred. At the highly sheared region, a great deal of free energy was accumulated. On September 6, one negative patch near the polarity inversion line began to rapidly rotate and shear with the surrounding positive fields, and consequently the X9.3 flare erupted. Our results reveal that the block-induced complex structures built the flare-productive AR and the X9.3 flare was triggered by an erupting filament due to the kink instability. To better illustrate this process, a block-induced eruption model is proposed for the first time.

  14. Wavelength Dependence of Solar Irradiance Enhancement During X-Class Flares and Its Influence on the Upper Atmosphere

    Science.gov (United States)

    Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Chamberlin, Phillip C.; Qian, Liying; Solomon, Stanley C.; Roble, Raymond G.; Xiao, Zuo

    2013-01-01

    The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61 X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-14 nm irradiance increases much more (approx. 680% on average) than that in the 14-25 nm waveband (approx. 65% on average), except at 24 nm (approx. 220%). The average percentage increases for the 25-105 nm and 122-190 nm wavebands are approx. 120% and approx. 35%, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105- 120 nm, 121.56 nm, and 122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the 0-14 nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and approx. 7.4% of the total approx. 11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

  15. Morphology and velocity field of the large flare on the solar disc on July 14, 1980

    International Nuclear Information System (INIS)

    Xuan, J.; Li, Z.

    1982-01-01

    The active region morphology and the features of solar radio bursts and the sight-line velocity distribution of a flare of importance 3B on the solar disk (AR 2562) on July 14, 1980, are discussed. The preliminary analysis made here suggests that measurement of the velocity fields of active regions is important in treating flare mechanisms. It is noted that a few hours before the eruption of the flare, the penumbral fibers of the sunspots on the corresponding photospheric part under the flare rapidly attenuated. It is thought that the instability of the flare may derive from the rapid changes occurring in the magnetic boundary conditions of the photosphere. These in turn denote the rapid emergence, subsidence, or dissipation of the magnetic flux. The spectra of the active filament in the later period of the flare are seen as indicating that most of the ejection matter was rolling, in addition to ascending or descending

  16. The Next Level in Automated Solar Flare Forecasting: the EU FLARECAST Project

    Science.gov (United States)

    Georgoulis, M. K.; Bloomfield, D.; Piana, M.; Massone, A. M.; Gallagher, P.; Vilmer, N.; Pariat, E.; Buchlin, E.; Baudin, F.; Csillaghy, A.; Soldati, M.; Sathiapal, H.; Jackson, D.; Alingery, P.; Argoudelis, V.; Benvenuto, F.; Campi, C.; Florios, K.; Gontikakis, C.; Guennou, C.; Guerra, J. A.; Kontogiannis, I.; Latorre, V.; Murray, S.; Park, S. H.; Perasso, A.; Sciacchitano, F.; von Stachelski, S.; Torbica, A.; Vischi, D.

    2017-12-01

    We attempt an informative description of the Flare Likelihood And Region Eruption Forecasting (FLARECAST) project, European Commission's first large-scale investment to explore the limits of reliability and accuracy achieved for the forecasting of major solar flares. We outline the consortium, top-level objectives and first results of the project, highlighting the diversity and fusion of expertise needed to deliver what was promised. The project's final product, featuring an openly accessible, fully modular and free to download flare forecasting facility will be delivered in early 2018. The project's three objectives, namely, science, research-to-operations and dissemination / communication, are also discussed: in terms of science, we encapsulate our close-to-final assessment on how close (or far) are we from a practically exploitable solar flare forecasting. In terms of R2O, we briefly describe the architecture of the FLARECAST infrastructure that includes rigorous validation for each forecasting step. From the three different communication levers of the project we finally focus on lessons learned from the two-way interaction with the community of stakeholders and governmental organizations. The FLARECAST project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216.

  17. Relation between gamma-ray emission, radio bursts, and proton fluxes from solar flares

    International Nuclear Information System (INIS)

    Fomichev, V.V.; Chertok, I.M.

    1985-01-01

    Data on solar gamma-ray flares, including 24 flares with gamma-ray lines, recorded up to June 1982, are analyzed. It is shown that from the point of view of radio emission the differences between flares with and without gamma-ray lines has a purely quantitative character: the former are accompanied by the most intense microwave bursts. Meter type II bursts are not a distinctive feature of flares with gamma-ray lines. Pulsed flares, regardless of the presence or absence of gamma-ray lines, are not accompanied by significant proton fluxes at the earth. On the whole, contrary to the popular opinion in the literature, flares with gamma-ray lines do not display a deficit of proton flux in interplanetary space in comparison with similar flares without gamma-ray lines. The results of quantitative diagnostics of proton flares based on radio bursts are not at variance with the presence of flares without detectable gamma-ray emission in lines but with a pronounced increase in the proton flux at the earth. 23 references

  18. VizieR Online Data Catalog: Quasi-periodic pulsations in solar flares (Inglis+, 2016)

    Science.gov (United States)

    Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L.; Gallagher, P.

    2018-04-01

    We have used data from the Geostationary Operational Environmental Satellite (GOES) instrument series, and from Fermi/Gamma-ray Burst Monitor (GBM). For this reason, we choose the interval 2011 February 1 - 2015 December 31, as it not only coincides with the availability of GOES-15 satellite data, but also includes regular solar observations by GBM. GOES satellites are equipped with solar X-ray detectors that record the incident flux in the 0.5-4Å and 1-8Å wavelength ranges. Solar X-ray data from the most recent satellite, GOES-15, has been available since 2010 at a nominal 2s cadence. To access the GOES catalog, we use the Heliophysics Event Knowledgebase (HEK). Fermi/GBM operates in the 8keV-40MeV range and regularly observes emission from solar flares, with a solar duty cycle of ~60%, similar to the solar-dedicated Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). To accumulate the database of Fermi/GBM events, we use the GBM trigger catalog produced by the instrument team, selecting all events marked as flares. (2 data files).

  19. Search for neutrino events in the Kamiokande-II detector in correlation with the solar-flare activity in March 1989

    International Nuclear Information System (INIS)

    Hirata, K.S.; Kajita, T.; Kifune, T.

    1989-12-01

    A search has been made for neutrino events (E v > or approx. 50 MeV) in the Kamiokande-II water Cherenkov detector in correlation with the great solar-flare activity observed in March 1989. No evidence was obtained for such a correlation. Upper limits are separately given for the optical importance 4, 3, and 2 flares for both time-integrated and time-averaged solar-flare ν e fluxes at E v = 50 MeV and 100 MeV. At E v = 100 MeV, the 90% confidence-level upper limit for the time-integrated ν e flux per importance 4 (3) flare is 3.5 x 10 7 (1.4x10 7 ) cm -2 . Even the upper limit for the importance 4 flare is considerably lower than the ν e flux at the corresponding energy needed to explain the excess neutrino captures reported in some of the 37 Cl experimental runs when large solar flares occurred. A search has also been made for low-energy events (recoil e +- energy > or approx. 10 MeV) in correlation with importance ≥ 2 flares and with the solar proton flux ≥ 10 MeV). Again, no significant signal has been observed. (author)

  20. White Light Solar Corona: An Atlas of 1988 K-Coronameter Synoptic Charts, December 1987-January 1989. Technical note

    International Nuclear Information System (INIS)

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.

    1990-03-01

    The synoptic observing project of the High Altitude Observatory's Coronal Dynamics Program began on 30 July 1980. The data obtained for it are gathered by the Mark-III K-coronameter located at the Mauna Loa Solar Observatory, Hawaii, and are published yearly in volumes of The White Light Solar Corona: An Atlas of K-Coronameter Synoptic Charts (Table 1). The data, in the form of synoptic charts, are extended at both the beginning and the end of each year to provide some overlap with the preceding and succeeding volumes. This is also necessary to provide a complete set of the data organized into Carrington rotations covering a specific time period, since the rotations do not coincide with the yearly calendar. Further observations are made at the limb, and west limb passage occurs 14 days after east limb passage. Thus, an entire rotation's data requires more than 28 days to collect. Together with the synoptic maps and polar synoptic maps, two additional sections designed to aid the user are included in the volume. As in previous Atlases, the Activity Report Summary for the year is given and the Mauna Loa Solar Observatory Calendar for 1988 (Table III) is also included. This is a list of days on which no coronal observations were achieved. These synoptic data should be regarded as a preliminary presentation in which corrections have not fully been made for the day-to-day variations and scattering of polarized light by the earth's atmosphere. Data from the east and west limbs are presented separately in the synoptic charts, as transient and evolutionary changes in the white light corona can substantially modify the distribution of coronal material over the 14 days between sequential limb passages

  1. Seismic probing of solar flows using high-degree oscillations

    International Nuclear Information System (INIS)

    Haber, D.A.

    1987-01-01

    Employing solar-oscillation modes of degree 50 ≤ l ≤ 850, the author estimated the equatorial rotation rate with depth, searched for possible anisotropies in power for modes travelling in different directions, and examined the influence of a major flare on the oscillations. Motivated by the need in studying solar rotation for accurate frequency splittings between individual modes, different spatial-filtering methods were evaluated to determine which yield the most-accurate frequencies. A filtering method based on spherical-harmonic projection of the data is found to be superior in this regard. The various filtering techniques are applied to three days of concatenated Doppler-velocity data taken on a long, narrow grid centered on the solar disk. An inversion procedure is then performed to determine the equatorial solar rotation in the upper convection zone. The rotation rate is found to increase to a depth of about 2 Mm before decreasing over the next 14 Mm. Power in sectoral modes traveling along the equator (equatorial modes) is compared to that in poleward-traveling sectoral modes (polar modes). Full-disk Doppler velocities observed before and after a major white-light flare are compared to detect any influence of the flare on the 5-minute oscillations

  2. Automatic detection of white-light flare kernels in SDO/HMI intensitygrams

    Czech Academy of Sciences Publication Activity Database

    Mravcová, L.; Švanda, Michal

    2017-01-01

    Roč. 57, November (2017), s. 14-21 ISSN 1384-1076 Institutional support: RVO:67985815 Keywords : Sun * activity * flares Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 0.938, year: 2016

  3. Solar flare X-radiation and energetic particles by the observation data from the Venera-13,14 space probes

    International Nuclear Information System (INIS)

    Belyakov, S.A.; Dajbog, E.I.; D'yachkov, A.P.

    1984-01-01

    The relationship between bursts of solar hard X-radiation quanta (Esub(x) > 0.055 MeV) and flares of solar cosmic rays (SCR) was considered on the basis of the data from the Venera-13, 14 space probes. The data on solar flares in Hsub(α) and thermal X-radiation range as well as radio-frequency radiation of the 3d type were used for analysis. It was established that the intensity amplitude of flare electrons (Esub(e) > 0.025 and > 0.07 MeV) and protons (Esub(p) > 1.0 MeV) correlates best with the flare importance in the thermal X-radiation range (r approximately 0.8+-0.03). The use of flare importance in thermal X-radiation range was independent measure of flare power in which SCR particles were generated enabled to construct heliolongitudinal dependences of the flare electron fluxes and to obtain the idea of the heliolongitudinal flare interval in which the effects of coronal propagation could be ignored. It is shown that the flux of the flare nonrelativistic electrons is related with the total energy release in the burst of hard X-radiation better than with the amplitude of this burst. Distributions of the solar events were studied with respect to the amplitudes of the intensity of electrons of SCR, thermal and hard X-radiation. It is shown that in the most part of the varying amplitude ranqe the distribution functions are approximated according to the power law. It is shown that the distribution function factor depends both on the parameter used for its construction and the type of events being used for analysis

  4. A Compressed Sensing-based Image Reconstruction Algorithm for Solar Flare X-Ray Observations

    Energy Technology Data Exchange (ETDEWEB)

    Felix, Simon; Bolzern, Roman; Battaglia, Marina, E-mail: simon.felix@fhnw.ch, E-mail: roman.bolzern@fhnw.ch, E-mail: marina.battaglia@fhnw.ch [University of Applied Sciences and Arts Northwestern Switzerland FHNW, 5210 Windisch (Switzerland)

    2017-11-01

    One way of imaging X-ray emission from solar flares is to measure Fourier components of the spatial X-ray source distribution. We present a new compressed sensing-based algorithm named VIS-CS, which reconstructs the spatial distribution from such Fourier components. We demonstrate the application of the algorithm on synthetic and observed solar flare X-ray data from the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite and compare its performance with existing algorithms. VIS-CS produces competitive results with accurate photometry and morphology, without requiring any algorithm- and X-ray-source-specific parameter tuning. Its robustness and performance make this algorithm ideally suited for the generation of quicklook images or large image cubes without user intervention, such as for imaging spectroscopy analysis.

  5. A Compressed Sensing-based Image Reconstruction Algorithm for Solar Flare X-Ray Observations

    Science.gov (United States)

    Felix, Simon; Bolzern, Roman; Battaglia, Marina

    2017-11-01

    One way of imaging X-ray emission from solar flares is to measure Fourier components of the spatial X-ray source distribution. We present a new compressed sensing-based algorithm named VIS_CS, which reconstructs the spatial distribution from such Fourier components. We demonstrate the application of the algorithm on synthetic and observed solar flare X-ray data from the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite and compare its performance with existing algorithms. VIS_CS produces competitive results with accurate photometry and morphology, without requiring any algorithm- and X-ray-source-specific parameter tuning. Its robustness and performance make this algorithm ideally suited for the generation of quicklook images or large image cubes without user intervention, such as for imaging spectroscopy analysis.

  6. Prompt acceleration of ions by oblique turbulent shocks in solar flares

    Science.gov (United States)

    Decker, R. B.; Vlahos, L.

    1985-01-01

    Solar flares often accelerate ions and electrons to relativistic energies. The details of the acceleration process are not well understood, but until recently the main trend was to divide the acceleration process into two phases. During the first phase elctrons and ions are heated and accelerated up to several hundreds of keV simultaneously with the energy release. These mildly relativistic electrons interact with the ambient plasma and magnetic fields and generate hard X-ray and radio radiation. The second phase, usually delayed from the first by several minutes, is responsible for accelerating ions and electrons to relativistic energies. Relativistic electrons and ions interact with the solar atmosphere or escape from the Sun and generate gamma ray continuum, gamma ray line emission, neutron emission or are detected in space by spacecraft. In several flares the second phase is coincident with the start of a type 2 radio burst that is believed to be the signature of a shock wave. Observations from the Solar Maximum Mission spacecraft have shown, for the first time, that several flares accelerate particles to all energies nearly simultaneously. These results posed a new theoretical problem: How fast are shocks and magnetohydrodynamic turbulence formed and how quickly can they accelerate ions to 50 MeV in the lower corona? This problem is discussed.

  7. Prompt acceleration of ions by oblique turbulent shocks in solar flares

    International Nuclear Information System (INIS)

    Decker, R.B.; Vlahos, L.

    1985-01-01

    Solar flares often accelerate ions and electrons to relativistic energies. The details of the acceleration process are not well understood, but until recently the main trend was to divide the acceleration process into two phases. During the first phase elctrons and ions are heated and accelerated up to several hundreds of keV simultaneously with the energy release. These mildly relativistic electrons interact with the ambient plasma and magnetic fields and generate hard x-ray and radio radiation. The second phase, usually delayed from the first by several minutes, is responsible for accelerating ions and electrons to relativistic energies. Relativistic electrons and ions interact with the solar atmosphere or escape from the Sun and generate gamma ray continuum, gamma ray line emission, neutron emission or are detected in space by spacecraft. In several flares the second phase is coincident with the start of a type 2 radio burst that is believed to be the signature of a shock wave. Observations from the Solar Maximum Mission spacecraft have shown, for the first time, that several flares accelerate particles to all energies nearly simultaneously. These results posed a new theoretical problem: How fast are shocks and magnetohydrodynamic turbulence formed and how quickly can they accelerate ions to 50 MeV in the lower corona. This problem is discussed

  8. “Dandelion” Filament Eruption and Coronal Waves Associated with a Solar Flare on 2011 February 16

    International Nuclear Information System (INIS)

    Cabezas, Denis P.; Ishitsuka, Mutsumi; Ishitsuka, José K.; Martínez, Lurdes M.; Buleje, Yovanny J.; Morita, Satoshi; Asai, Ayumi; UeNo, Satoru; Ishii, Takako T.; Kitai, Reizaburo; Takasao, Shinsuke; Yoshinaga, Yusuke; Otsuji, Kenichi; Shibata, Kazunari

    2017-01-01

    Coronal disturbances associated with solar flares, such as H α Moreton waves, X-ray waves, and extreme ultraviolet (EUV) coronal waves, are discussed herein in relation to magnetohydrodynamic fast-mode waves or shocks in the corona. To understand the mechanism of coronal disturbances, full-disk solar observations with high spatial and temporal resolution over multiple wavelengths are of crucial importance. We observed a filament eruption, whose shape is like a “dandelion,” associated with the M1.6 flare that occurred on 2011 February 16 in H α images taken by the Flare Monitoring Telescope at Ica University, Peru. We derive the three-dimensional velocity field of the erupting filament. We also identify winking filaments that are located far from the flare site in the H α images, whereas no Moreton wave is observed. By comparing the temporal evolution of the winking filaments with those of the coronal wave seen in the EUV images data taken by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and by the Extreme Ultraviolet Imager on board the Solar Terrestrial Relations Observatory-Ahead , we confirm that the winking filaments were activated by the EUV coronal wave.

  9. “Dandelion” Filament Eruption and Coronal Waves Associated with a Solar Flare on 2011 February 16

    Energy Technology Data Exchange (ETDEWEB)

    Cabezas, Denis P.; Ishitsuka, Mutsumi; Ishitsuka, José K. [Geophysical Institute of Peru, Calle Badajoz 169, Mayorazgo IV Etapa, Ate Vitarte, Lima (Peru); Martínez, Lurdes M.; Buleje, Yovanny J. [Centro de Investigación del Estudio de la Actividad Solar y sus Efectos Sobre la Tierra, Facultad de Ciencias, Universidad Nacional San Luis Gonzaga de Ica, Av. Los Maestros S/N, Ica (Peru); Morita, Satoshi [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588 (Japan); Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Sakyo, Kyoto, 606-8502 (Japan); UeNo, Satoru; Ishii, Takako T.; Kitai, Reizaburo; Takasao, Shinsuke; Yoshinaga, Yusuke; Otsuji, Kenichi; Shibata, Kazunari, E-mail: denis@kwasan.kyoto-u.ac.jp [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto, 607-8471 (Japan)

    2017-02-10

    Coronal disturbances associated with solar flares, such as H α Moreton waves, X-ray waves, and extreme ultraviolet (EUV) coronal waves, are discussed herein in relation to magnetohydrodynamic fast-mode waves or shocks in the corona. To understand the mechanism of coronal disturbances, full-disk solar observations with high spatial and temporal resolution over multiple wavelengths are of crucial importance. We observed a filament eruption, whose shape is like a “dandelion,” associated with the M1.6 flare that occurred on 2011 February 16 in H α images taken by the Flare Monitoring Telescope at Ica University, Peru. We derive the three-dimensional velocity field of the erupting filament. We also identify winking filaments that are located far from the flare site in the H α images, whereas no Moreton wave is observed. By comparing the temporal evolution of the winking filaments with those of the coronal wave seen in the EUV images data taken by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and by the Extreme Ultraviolet Imager on board the Solar Terrestrial Relations Observatory-Ahead , we confirm that the winking filaments were activated by the EUV coronal wave.

  10. PRODUCTIVITY OF SOLAR FLARES AND MAGNETIC HELICITY INJECTION IN ACTIVE REGIONS

    International Nuclear Information System (INIS)

    Park, Sung-hong; Wang Haimin; Chae, Jongchul

    2010-01-01

    The main objective of this study is to better understand how magnetic helicity injection in an active region (AR) is related to the occurrence and intensity of solar flares. We therefore investigate the magnetic helicity injection rate and unsigned magnetic flux, as a reference. In total, 378 ARs are analyzed using SOHO/MDI magnetograms. The 24 hr averaged helicity injection rate and unsigned magnetic flux are compared with the flare index and the flare-productive probability in the next 24 hr following a measurement. In addition, we study the variation of helicity over a span of several days around the times of the 19 flares above M5.0 which occurred in selected strong flare-productive ARs. The major findings of this study are as follows: (1) for a sub-sample of 91 large ARs with unsigned magnetic fluxes in the range from (3-5) x 10 22 Mx, there is a difference in the magnetic helicity injection rate between flaring ARs and non-flaring ARs by a factor of 2; (2) the GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones; (3) the history of helicity injection before all the 19 major flares displayed a common characteristic: a significant helicity accumulation of (3-45) x 10 42 Mx 2 during a phase of monotonically increasing helicity over 0.5-2 days. Our results support the notion that helicity injection is important in flares, but it is not effective to use it alone for the purpose of flare forecast. It is necessary to find a way to better characterize the time history of helicity injection as well as its spatial distribution inside ARs.

  11. A Study of Sympathetic Flaring Using a Full-Sun Event Catalog

    Science.gov (United States)

    Higgins, P. A.; Schrijver, C. J.; Title, A. M.; Bloomfield, D.; Gallagher, P.

    2013-12-01

    There has been a trove of papers published on the statistics of flare occurrence. These studies are trying to answer the question of whether or not subsequent solar flares are related. The majority of these works have not included both flare location information and the physical properties of the regions responsible for the eruptions, and none have taken advantage of full-Sun event coverage. Now that SDO/AIA is available and the STEREO spacecraft have progressed past 90 degrees from Earth's heliographic longitude, this new information is available to us. This work aims to quantify how common sympathetic events are, and how important they are in the forecasting of solar flares. A 3D plot of detected and clustered flare events for a full solar rotation, including the Valentine's Day Event of 2011. A full-Sun image in the EUV (304A) including both STEREO view points and AIA. The GOES X-ray light curves during the February period of 2011 are shown in the bottom panel. Detected flare events are indicated by the green dashed lines and the time stamp of this image is denoted by the red line.

  12. Impulsive and gradual phases of a solar limb flare as observed from the solar maximum mission satellite

    Energy Technology Data Exchange (ETDEWEB)

    Poland, A.I.; Frost, K.J.; Woodgate, B.E.; Shine, R.A.; Kenny, P.J. (National Aeronautics and Space Administration, Greenbelt, MD (USA). Lab. for Astronomy and Solar Physics); Machado, M.E. (Observatorio Nacional de Fisica Cosmica, San Miguel (Argentina)); Wolfson, C.J.; Bruner, E.C. (Lockheed Palo Alto Research Labs., CA (USA)); Cheng, C.C. (Naval Research Lab., Washington, DC (USA)); Tandberg-Hanssen, E.A. (National Aeronautics and Space Administration, Huntsville, AL (USA). George C. Marshall Space Flight Center)

    1982-06-01

    Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10'' spatial resolution in the lines of O v (Tsub(e) approx. equal to 2.5 x 10/sup 5/ K) and Fe XXI (Tsub(e) approx. equal to 1.1 x 10/sup 7/ K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30,000 km above the solar surface at specific points in the flare loop. The Fe XXI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient.

  13. The impulsive and gradual phases of a solar limb flare as observed from the solar maximum mission satellite

    International Nuclear Information System (INIS)

    Poland, A.I.; Frost, K.J.; Woodgate, B.E.; Shine, R.A.; Kenny, P.J.; Wolfson, C.J.; Bruner, E.C.; Cheng, C.C.; Tandberg-Hanssen, E.A.

    1982-01-01

    Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10'' spatial resolution in the lines of O v (Tsub(e) approx. equal to 2.5 x 10 5 K) and Fe XXI (Tsub(e) approx. equal to 1.1 x 10 7 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30,000 km above the solar surface at specific points in the flare loop. The Fe XXI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient. (orig.)

  14. Current Fragmentation and Particle Acceleration in Solar Flares

    Science.gov (United States)

    Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.; Nordlund, Å.

    2012-11-01

    Particle acceleration in solar flares remains an outstanding problem in plasma physics and space science. While the observed particle energies and timescales can perhaps be understood in terms of acceleration at a simple current sheet or turbulence site, the vast number of accelerated particles, and the fraction of flare energy in them, defies any simple explanation. The nature of energy storage and dissipation in the global coronal magnetic field is essential for understanding flare acceleration. Scenarios where the coronal field is stressed by complex photospheric motions lead to the formation of multiple current sheets, rather than the single monolithic current sheet proposed by some. The currents sheets in turn can fragment into multiple, smaller dissipation sites. MHD, kinetic and cellular automata models are used to demonstrate this feature. Particle acceleration in this environment thus involves interaction with many distributed accelerators. A series of examples demonstrate how acceleration works in such an environment. As required, acceleration is fast, and relativistic energies are readily attained. It is also shown that accelerated particles do indeed interact with multiple acceleration sites. Test particle models also demonstrate that a large number of particles can be accelerated, with a significant fraction of the flare energy associated with them. However, in the absence of feedback, and with limited numerical resolution, these results need to be viewed with caution. Particle in cell models can incorporate feedback and in one scenario suggest that acceleration can be limited by the energetic particles reaching the condition for firehose marginal stability. Contemporary issues such as footpoint particle acceleration are also discussed. It is also noted that the idea of a "standard flare model" is ill-conceived when the entire distribution of flare energies is considered.

  15. RADIOEMISSÕES SOLARES TIPO II ASSOCIADAS A FLARES E CMES

    Directory of Open Access Journals (Sweden)

    Rafael Douglas Cunha-Silva

    2013-12-01

    Full Text Available Atribuídas a ondas de choque e a ejeções de plasmoide, as emissões solares tipo II são ondaseletromagnéticas geradas a partir de oscilações do plasma coronal. A origem dos choques associados a essasemissões é ainda uma questão em aberto da física solar. Enquanto alguns trabalhos sugerem os flares solarescomo seus acionadores, outros fornecem indícios de serem as ejeções de massa coronal (CMEs sua origemmais provável. Este trabalho apresenta os resultados da análise de duas emissões tipo II, registradas por doisespectrômetros da rede e-CALLISTO (extended-Compound Astronomical Low-cost Low-frequency Instrument forSpectroscopy and Transportable Observatory, os quais operam na faixa de frequências de 45-870 MHz. Oprimeiro evento, observado em 13 de junho de 2010, às 05:38 UT, apresentou uma taxa de deriva em frequênciade -0,2 MHz s-1, correspondente a uma velocidade de choque de 528 km s-1, estando, temporalmente, associadoa uma CME lenta (~320 km s-1 e a um flare solar em raios-X, classe M1.0. O segundo evento, observado em 09de Agosto de 2011, às 08:02 UT, apresentou uma taxa de deriva em frequência de -1,4 MHz s-1, correspondentea uma velocidade de choque de 1375 km s-1, estando, temporalmente, associado a uma CME tipo halo (~1610km s-1 e a um flare solar em raios-X, classe X6.9. Os resultados obtidos, para os parâmetros observacionais dasemissões tipo II e para os parâmetros físicos de suas fontes, são discutidos no contexto de sua relação com seuflares e CMEs associados.

  16. Recent big flare

    International Nuclear Information System (INIS)

    Moriyama, Fumio; Miyazawa, Masahide; Yamaguchi, Yoshisuke

    1978-01-01

    The features of three big solar flares observed at Tokyo Observatory are described in this paper. The active region, McMath 14943, caused a big flare on September 16, 1977. The flare appeared on both sides of a long dark line which runs along the boundary of the magnetic field. Two-ribbon structure was seen. The electron density of the flare observed at Norikura Corona Observatory was 3 x 10 12 /cc. Several arc lines which connect both bright regions of different magnetic polarity were seen in H-α monochrome image. The active region, McMath 15056, caused a big flare on December 10, 1977. At the beginning, several bright spots were observed in the region between two main solar spots. Then, the area and the brightness increased, and the bright spots became two ribbon-shaped bands. A solar flare was observed on April 8, 1978. At first, several bright spots were seen around the solar spot in the active region, McMath 15221. Then, these bright spots developed to a large bright region. On both sides of a dark line along the magnetic neutral line, bright regions were generated. These developed to a two-ribbon flare. The time required for growth was more than one hour. A bright arc which connects two ribbons was seen, and this arc may be a loop prominence system. (Kato, T.)

  17. KIC 9451096: Magnetic Activity, Flares and Differential Rotation

    Science.gov (United States)

    Özdarcan, O.; Yoldaş, E.; Dal, H. A.

    2018-04-01

    We present a spectroscopic and photometric analysis of KIC 9451096. The combined spectroscopic and photometric modelling shows that the system is a detached eclipsing binary in a circular orbit and composed of F5V + K2V components. Subtracting the best-fitting light curve model from the whole long cadence data reveals additional low (mmag) amplitude light variations in time and occasional flares, suggesting a low, but still remarkable level of magnetic spot activity on the K2V component. Analyzing the rotational modulation of the light curve residuals enables us to estimate the differential rotation coefficient of the K2V component as k = 0.069 ± 0.008, which is 3 times weaker compared with the solar value of k = 0.19, assuming a solar type differential rotation. We find the stellar flare activity frequency for the K2V component as 0.000368411 h-1 indicating a low magnetic activity level.

  18. Time Variations of Observed H α Line Profiles and Precipitation Depths of Nonthermal Electrons in a Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Falewicz, Robert; Radziszewski, Krzysztof; Rudawy, Paweł; Berlicki, Arkadiusz, E-mail: falewicz@astro.uni.wroc.pl, E-mail: radziszewski@astro.uni.wroc.pl, E-mail: rudawy@astro.uni.wroc.pl, E-mail: berlicki@astro.uni.wroc.pl [Astronomical Institute, University of Wrocław, 51-622 Wrocław, ul. Kopernika 11 (Poland)

    2017-10-01

    We compare time variations of the H α and X-ray emissions observed during the pre-impulsive and impulsive phases of the C1.1-class solar flare on 2013 June 21 with those of plasma parameters and synthesized X-ray emission from a 1D hydrodynamic numerical model of the flare. The numerical model was calculated assuming that the external energy is delivered to the flaring loop by nonthermal electrons (NTEs). The H α spectra and images were obtained using the Multi-channel Subtractive Double Pass spectrograph with a time resolution of 50 ms. The X-ray fluxes and spectra were recorded by RHESSI . Pre-flare geometric and thermodynamic parameters of the model and the delivered energy were estimated using RHESSI data. The time variations of the X-ray light curves in various energy bands and those of the H α intensities and line profiles were well correlated. The timescales of the observed variations agree with the calculated variations of the plasma parameters in the flaring loop footpoints, reflecting the time variations of the vertical extent of the energy deposition layer. Our result shows that the fast time variations of the H α emission of the flaring kernels can be explained by momentary changes of the deposited energy flux and the variations of the penetration depths of the NTEs.

  19. Predicting Solar Flares Using SDO /HMI Vector Magnetic Data Products and the Random Forest Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang; Deng, Na; Wang, Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Wang, Jason T. L., E-mail: chang.liu@njit.edu, E-mail: na.deng@njit.edu, E-mail: haimin.wang@njit.edu, E-mail: jason.t.wang@njit.edu [Department of Computer Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States)

    2017-07-10

    Adverse space-weather effects can often be traced to solar flares, the prediction of which has drawn significant research interests. The Helioseismic and Magnetic Imager (HMI) produces full-disk vector magnetograms with continuous high cadence, while flare prediction efforts utilizing this unprecedented data source are still limited. Here we report results of flare prediction using physical parameters provided by the Space-weather HMI Active Region Patches (SHARP) and related data products. We survey X-ray flares that occurred from 2010 May to 2016 December and categorize their source regions into four classes (B, C, M, and X) according to the maximum GOES magnitude of flares they generated. We then retrieve SHARP-related parameters for each selected region at the beginning of its flare date to build a database. Finally, we train a machine-learning algorithm, called random forest (RF), to predict the occurrence of a certain class of flares in a given active region within 24 hr, evaluate the classifier performance using the 10-fold cross-validation scheme, and characterize the results using standard performance metrics. Compared to previous works, our experiments indicate that using the HMI parameters and RF is a valid method for flare forecasting with fairly reasonable prediction performance. To our knowledge, this is the first time that RF has been used to make multiclass predictions of solar flares. We also find that the total unsigned quantities of vertical current, current helicity, and flux near the polarity inversion line are among the most important parameters for classifying flaring regions into different classes.

  20. ASASSN-16ae: A POWERFUL WHITE-LIGHT FLARE ON AN EARLY-L DWARF

    International Nuclear Information System (INIS)

    Schmidt, Sarah J.; Shappee, Benjamin J.; Seibert, Mark; Gagné, Jonathan; Stanek, K. Z.; Holoien, Thomas W.-S.; Kochanek, C. S.; Prieto, José L.; Chomiuk, Laura; Strader, Jay; Dong, Subo

    2016-01-01

    We report the discovery and classification of SDSS J053341.43+001434.1 (SDSS0533), an early-L dwarf first discovered during a powerful Δ V 3.7 × 10"3"4 erg), placing it among the strongest detected M dwarf flares. The presence of this powerful flare on an old L0 dwarf may indicate that stellar-type magnetic activity persists down to the end of the main sequence and on older ML transition dwarfs.

  1. Chromosphere flare models

    International Nuclear Information System (INIS)

    Avrett, E.H.; Kurucz, R.L.; Machado, M.E.; NASA, Marshall Space Flight Center, Huntsville, AL)

    1985-01-01

    Further calculated results based on the F1 and F2 chromospheric models of Machado et al. (1980) are presented in addition to results from a model with enhanced temperatures relative to the weak-flare model F1 in the upper photosphere and low chromosphere, and from a model with enhanced temperatures relative to the strong flare model F2 in the upper chromosphere. The coupled equations of statistical equilibrium and radiative transfer for H, H(-), He I-II, C I-IV, Si I-II, Mg I-II, Fe, Al, O I-II, Na, and Ca II are solved, and the overall absorption and emission of radiation by lines throughout the spectrum are determined by means of a reduced set of opacities taken from a compilation of over 10 million lines. Semiempirical models show that the white light flare continuum may arise by extreme chromospheric overheating, as well as by an enhancement of the minimum temperature region. 34 references

  2. Planetary Protection: X-ray Super-Flares Aid Formation of "Solar Systems"

    Science.gov (United States)

    2005-05-01

    New results from NASA's Chandra X-ray Observatory imply that X-ray super-flares torched the young Solar System. Such flares likely affected the planet-forming disk around the early Sun, and may have enhanced the survival chances of Earth. By focusing on the Orion Nebula almost continuously for 13 days, a team of scientists used Chandra to obtain the deepest X-ray observation ever taken of this or any star cluster. The Orion Nebula is the nearest rich stellar nursery, located just 1,500 light years away. These data provide an unparalleled view of 1400 young stars, 30 of which are prototypes of the early Sun. The scientists discovered that these young suns erupt in enormous flares that dwarf - in energy, size, and frequency -- anything seen from the Sun today. Illustration of Large Flares Illustration of Large Flares "We don't have a time machine to see how the young Sun behaved, but the next best thing is to observe Sun-like stars in Orion," said Scott Wolk of Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "We are getting a unique look at stars between one and 10 million years old - a time when planets form." A key result is that the more violent stars produce flares that are a hundred times as energetic as the more docile ones. This difference may specifically affect the fate of planets that are relatively small and rocky, like the Earth. "Big X-ray flares could lead to planetary systems like ours where Earth is a safe distance from the Sun," said Eric Feigelson of Penn State University in University Park, and principal investigator for the international Chandra Orion Ultradeep Project. "Stars with smaller flares, on the other hand, might end up with Earth-like planets plummeting into the star." Animation of X-ray Flares from a Young Sun Animation of X-ray Flares from a "Young Sun" According to recent theoretical work, X-ray flares can create turbulence when they strike planet-forming disks, and this affects the position of rocky planets as they

  3. The Solar Flare of the 14th of July 2000 (L3+C detector results)

    CERN Document Server

    Achard, P; Aguilar-Benítez, M; Van den Akker, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Bähr, J; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, G J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, M; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chiarusi, T; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, L; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; Dela Cruz, B; Cucciarelli, S; De Asmundis, R; Dglon, P; Debreczeni, J; Degré, A; Dehmelt, K; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Ding, L K; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Durán, I; Echenard, B; Eline, A; El-Hage, A; El-Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Faber, G; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, F; Fisher, W; Forconi, G; Freudenreich, K; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grabosch, H J; Grimm, O; Groenstege, H; Grünewald, M W; Guida, M; Guo, Y N; Gupta, S K; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Haller, C; Hatzifotiadou, D; Hayashi, Y; He, Z X; Hebbeker, T; Herv, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, A; Hou, S R; Huo, A X; Ito, N; Jin, B N; Jindal, P; Jing, C L; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kantserov, V A; Kaur, M; Kawakami, S; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, W; Klimentov, A; König, A C; Kok, E; Korn, A; Kopal, M; Koutsenko, V F; Kraber, M; Kuang, H H; Krämer, R W; Krüger, A; Kuijpers, J; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Lei, Y; Leich, H; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Li, L; Li, Z C; Likhoded, S; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Luci, C; Luminari, L; Lustermann, W; Ma, W G; Ma, X H; Ma, Y Q; Malgeri, L; Malinin, A; Maña, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Meng, X W; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Van Mil, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Monteleoni, B; Muanza, G S; Muijs, A J M; Musy, M; Nagy, S; Nahnhauer, R; Naumov, V A; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Novák, T; Nowak, H; Ofierzynski, R A; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Parriaud, J F; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, F; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pieri, M; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofev, D; Prokofiev, D O; Qing, C R; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Ravindran, K C; Razis, P; Rembeczki, S; Ren, D; Rescigno, M; Reucroft, S; Rewiersma, P A M; Riemann, S; Rojkov, A; Romero, L; Rosca, A; Rosemann, C; Rosenbleck, C; Rosier-Lees, S; Roth, S; Rubio, J A; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Schäfer, C; Shchegelskii, V; Schöneich, B; Schotanus, D J; Sciacca, C; Servoli, L; Shen, C Q; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, L; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Trowitzsch, G; Tully, C; Tung, K L; Ulbricht, J; Unger, M; Valente, E; Verkooijen, H; Van de Walle, R T; Vásquez, R; Vesztergombi, G; Vetlitskii, I; Viertel, G; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, G; Wang, Q; Wang, X L; Wang, X W; Wang, Z M; Weber, M; Van Wijk, R; Wijnen, T A M; Wilkens, H; Wynhoff, S; Xia, L; Xu, Y P; Xu, Z Z; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yang, X F; Yao, Z G; Yeh, S C; Yu, Z Q; Zalite, A; Zalite, Yu; Zhang, C; Zhang, F; Zhang, J; Zhang, S; Zhang, Z P; Zhao, J; Zhou, S J; Zhu, G Y; Zhu, R Y; Zhu, Q Q; Zhuang, H L; Zichichi, A; Zimmermann, B; Zöller, M; Zwart, A N M

    2006-01-01

    Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV. The solar flare of the 14 July 2000 offers a unique opportunity for the L3+C experiment to search for a correlated enhancement in the flux of muons using the L3 precision muon spectrometer. Its capabilities for observing a directional excess in the flux of muons above 15 GeV (corresponding to primary proton energies above 40 GeV) are presented along with observations made on the 14th of July 2000. We report an excess which appeared at a time coincident with the peak increase of solar protons observed at lower energies. The probability that the excess is a background fluctuation is estimated to be 1%. No similar excess of the muon flux was observed up to 1.5 hours after the solar flare ...

  4. Latitude-dependent delay in the responses of the equatorial electrojet and Sq currents to X-class solar flares

    Science.gov (United States)

    Nogueira, Paulo A. B.; Abdu, Mangalathayil A.; Souza, Jonas R.; Denardini, Clezio M.; Barbosa Neto, Paulo F.; Serra de Souza da Costa, João P.; Silva, Ana P. M.

    2018-01-01

    We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field.

  5. DUAL-STAGE RECONNECTION DURING SOLAR FLARES OBSERVED IN HARD X-RAY

    International Nuclear Information System (INIS)

    Xu Yan; Jing Ju; Wang Haimin; Cao Wenda

    2010-01-01

    In this Letter, we present hard X-ray (HXR) observation by the Reuven Ramaty High Energy Solar Spectroscopic Imager of the 2003 October 29 X10 flare. Two pairs of HXR conjugate footpoints have been identified during the early impulsive phase. This geometric configuration is very much in the manner predicted by the 'tether-cutting' scenario first proposed by Moore and Roumeliotis. The HXR light curves show that the outer pair of footpoints disappeared much faster than the other pair. This temporal behavior further confirms that this event is a good example of the 'tether-cutting' model. In addition, we reconstructed a three-dimensional magnetic field based on the nonlinear force-free extrapolation and found that each pair of HXR footpoints were indeed linked by corresponding magnetic field lines.

  6. A Parameter Study for Modeling Mg ii h and k Emission during Solar Flares

    Energy Technology Data Exchange (ETDEWEB)

    Rubio da Costa, Fatima [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kleint, Lucia, E-mail: frubio@stanford.edu [University of Applied Sciences and Arts Northwestern Switzerland, 5210, Windisch (Switzerland)

    2017-06-20

    Solar flares show highly unusual spectra in which the thermodynamic conditions of the solar atmosphere are encoded. Current models are unable to fully reproduce the spectroscopic flare observations, especially the single-peaked spectral profiles of the Mg ii h and k lines. We aim to understand the formation of the chromospheric and optically thick Mg ii h and k lines in flares through radiative transfer calculations. We take a flare atmosphere obtained from a simulation with the radiative hydrodynamic code RADYN as input for a radiative transfer modeling with the RH code. By iteratively changing this model atmosphere and varying thermodynamic parameters such as temperature, electron density, and velocity, we study their effects on the emergent intensity spectra. We reproduce the typical single-peaked Mg ii h and k flare spectral shape and approximate the intensity ratios to the subordinate Mg ii lines by increasing either densities, temperatures, or velocities at the line core formation height range. Additionally, by combining unresolved upflows and downflows up to ∼250 km s{sup −1} within one resolution element, we reproduce the widely broadened line wings. While we cannot unambiguously determine which mechanism dominates in flares, future modeling efforts should investigate unresolved components, additional heat dissipation, larger velocities, and higher densities and combine the analysis of multiple spectral lines.

  7. Localization of the solar flare SF900610 in X-rays with the WATCH instrument of the GRANAT observatory

    DEFF Research Database (Denmark)

    Terekhov, O.V.; Kuzmin, A.G.; Shevchenko, A.V.

    2002-01-01

    -ray source do not coincide with the coordinates of the Ha-line flare. The X-ray source moved over the solar disk during the flare. This probably implies that, as the X-ray emission was generated, different parts of one loop or a system of magnetic loops dominated at different flare times.......During the solar flare of June 10, 1990, the WATCH instrument of the GRANAT space observatory obtained 110 localizations of the X-ray source in the X-ray range 8-20 keV. Its coordinates were measured with an accuracy of similar to2 arcmin at a 3sigma confidence level. The coordinates of the X...

  8. Solar flare effects and storm sudden commencement even in ...

    African Journals Online (AJOL)

    1998-05-08

    Variations in the three components of geomagnetic field were observed at the twenty-two geomagnetic Euro-African Observatories during the solar flare that occurred on the 6 May, 1998 at 0080UT and storm sudden commencement that took place on May 8, 1998 at 15.00 UT. The geomagnetic field on 6 May, 1998 was ...

  9. Far-IR and Radio Thermal Continua in Solar Flares

    Czech Academy of Sciences Publication Activity Database

    Kašparová, Jana; Heinzel, Petr; Karlický, Marian; Moravec, Z.; Varady, M.

    2009-01-01

    Roč. 33, - (2009), s. 309-315 ISSN 1845-8319 R&D Projects: GA ČR GA205/04/0358; GA ČR GP205/06/P135; GA ČR GA205/07/1100 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flares * radiative hydrodynamics * continuum emission Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  10. Signatures of moderate (M-class) and low (C and B class) intensity solar flares on the equatorial electrojet current: Case studies

    Science.gov (United States)

    Chakrabarty, D.; Bagiya, Mala S.; Thampi, Smitha V.; Pathan, B. M.; Sekar, R.

    2013-12-01

    The present investigation brings out, in contrast to the earlier works, the changes in the equatorial electrojet (EEJ) current in response to a few moderate (M-class) and low (C and B class) intensity solar flares during 2005-2010. Special care is taken to pick these flare events in the absence of prompt electric field perturbations associated with geomagnetic storms and substorms that also affect the electrojet current. Interestingly, only the normalized (with respect to the pre-flare level) deviations of daytime EEJ (and not the deviations alone) change linearly with the increases in the EUV and X-ray fluxes. These linear relationships break down during local morning hours when the E-region electric field approaches zero before reversal of polarity. This elicits that the response of EEJ strength corresponding to less-intense flares can be appropriately gauged only when the local time variation of the quiet time E-region zonal electric field is taken into account. The flare events enhanced the EEJ strength irrespective of normal or counter electrojet (CEJ) conditions that shows that solar flares change the E-region ionization density and not the electric field. In addition, the enhancements in the X-ray and EUV fluxes, for these flares occurring during this solar minimum period, are found to be significantly correlated as opposed to the solar maximum period, indicating the differences in the solar processes in different solar epochs.

  11. Global energetics of solar flares. I. Magnetic energies

    Energy Technology Data Exchange (ETDEWEB)

    Aschwanden, Markus J. [Lockheed Martin, Solar and Astrophysics Laboratory, Org. A021S, Bldg. 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States); Xu, Yan; Jing, Ju, E-mail: aschwanden@lmsal.com, E-mail: yan.xu@njit.edu, E-mail: ju.jing@njit.edu [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102-1982 (United States)

    2014-12-10

    We present the first part of a project on the global energetics of solar flares and coronal mass ejections that includes about 400 M- and X-class flares observed with Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). We calculate the potential (E{sub p} ), the nonpotential (E {sub np}) or free energies (E {sub free} = E {sub np} – E{sub p} ), and the flare-dissipated magnetic energies (E {sub diss}). We calculate these magnetic parameters using two different NLFFF codes: the COR-NLFFF code uses the line-of-sight magnetic field component B{sub z} from HMI to define the potential field, and the two-dimensional (2D) coordinates of automatically detected coronal loops in six coronal wavelengths from AIA to measure the helical twist of coronal loops caused by vertical currents, while the PHOT-NLFFF code extrapolates the photospheric three-dimensional (3D) vector fields. We find agreement between the two codes in the measurement of free energies and dissipated energies within a factor of ≲ 3. The size distributions of magnetic parameters exhibit powerlaw slopes that are approximately consistent with the fractal-diffusive self-organized criticality model. The magnetic parameters exhibit scaling laws for the nonpotential energy, E{sub np}∝E{sub p}{sup 1.02}, for the free energy, E{sub free}∝E{sub p}{sup 1.7} and E{sub free}∝B{sub φ}{sup 1.0}L{sup 1.5}, for the dissipated energy, E{sub diss}∝E{sub p}{sup 1.6} and E{sub diss}∝E{sub free}{sup 0.9}, and the energy dissipation volume, V∝E{sub diss}{sup 1.2}. The potential energies vary in the range of E{sub p} = 1 × 10{sup 31}-4 × 10{sup 33} erg, while the free energy has a ratio of E {sub free}/E{sub p} ≈ 1%-25%. The Poynting flux amounts to F {sub flare} ≈ 5 × 10{sup 8}-10{sup 10} erg cm{sup –2} s{sup –1} during flares, which averages to F {sub AR} ≈ 6 × 10{sup 6} erg cm{sup –2} s{sup –1} during the entire observation

  12. Detection of the Acceleration Site in a Solar Flare

    Science.gov (United States)

    Fleishman, Gregory D.; Kontar, E. P.; Nita, G. M.; Gary, D. E.

    2011-05-01

    We report the observation of an unusual cold, tenuous solar flare (ApJL, v. 731, p. L19, 2011), which reveals itself via numerous and prominent non-thermal manifestations, while lacking any noticeable thermal emission signature. RHESSI hard X-rays and 0.1-18 GHz radio data from OVSA and Phoenix-2 show copious electron acceleration (1035 electrons per second above 10 keV) typical for GOES M-class flares with electrons energies up to 100 keV, but GOES temperatures not exceeding 6.1 MK. The HXR footpoints and coronal radio sources belong, supposedly, to a single magnetic loop, which departs strongly from the corresponding potential loop (obtained from a photospheric extrapolation) in agreement with the apparent need of a non-potential magnetic field structure to produce a flare. The imaging, temporal, and spectral characteristics of the flare have led us to a firm conclusion that the bulk of the microwave continuum emission from this flare was produced directly in the acceleration region. We found that the electron acceleration efficiency is very high in the flare, so almost all available thermal electrons are eventually accelerated. However, given a relatively small flaring volume and rather low thermal density at the flaring loop, the total energy release turned out to be insufficient for a significant heating of the coronal plasma or for a prominent chromospheric response giving rise to chromospheric evaporation. Some sort of stochastic acceleration process is needed to account for an approximately energy-independent lifetime of about 3 s for the electrons in the acceleration region. This work was supported in part by NSF grants AGS-0961867, AST-0908344, and NASA grants NNX10AF27G and NNX11AB49G to New Jersey Institute of Technology. This work was supported by a UK STFC rolling grant, STFC/PPARC Advanced Fellowship, and the Leverhulme Trust, UK. Financial support by the European Commission through the SOLAIRE and HESPE Networks is gratefully acknowledged.

  13. Determining the solar-flare photospheric scale height from SMM gamma-ray measurements

    Science.gov (United States)

    Lingenfelter, Richard E.

    1991-01-01

    A connected series of Monte Carlo programs was developed to make systematic calculations of the energy, temporal and angular dependences of the gamma-ray line and neutron emission resulting from such accelerated ion interactions. Comparing the results of these calculations with the Solar Maximum Mission/Gamma Ray Spectrometer (SMM/GRS) measurements of gamma-ray line and neutron fluxes, the total number and energy spectrum of the flare-accelerated ions trapped on magnetic loops at the Sun were determined and the angular distribution, pitch angle scattering, and mirroring of the ions on loop fields were constrained. Comparing the calculations with measurements of the time dependence of the neutron capture line emission, a determination of the He-3/H ratio in the photosphere was also made. The diagnostic capabilities of the SMM/GRS measurements were extended by developing a new technique to directly determine the effective photospheric scale height in solar flares from the neutron capture gamma-ray line measurements, and critically test current atmospheric models in the flare region.

  14. Dynamic radio bursts associated with important flare activity in Hale region 16923 and the problem of the relative locations of type II 'slow drift' bursts and coronal transients

    Energy Technology Data Exchange (ETDEWEB)

    Mckenna-Lawlor, S.M.P.

    1983-03-01

    Seven type-II radio bursts associated with solar flares in the Hale region 16923 on June 27-29, 1980, are characterized on the basis of data from dynamic radio spectra, white-light observations, radioheliograms, SMM-C/P observations, and Helios I magnetic-field and solar-wind measurements. The data are summarized in tables and graphs and discussed in terms of transient events occurring in the same region. The magnetic shock waves recorded during the period by Helios are described, and channeling effects which may have prevented the detection of type-II burst shocks are examined.

  15. MAGNETIC AND DYNAMICAL PHOTOSPHERIC DISTURBANCES OBSERVED DURING AN M3.2 SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Kuckein, C. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482, Potsdam (Germany); Collados, M.; Sainz, R. Manso, E-mail: ckuckein@aip.de [Instituto de Astrofísica de Canarias (IAC), Vía Láctea s/n, E-38205, La Laguna, Tenerife (Spain)

    2015-02-01

    This Letter reports on a set of full-Stokes spectropolarimetric observations in the near-infrared He i 10830 Å spectral region covering the pre-flare, flare, and post-flare phases of an M3.2 class solar flare. The flare originated on 2013 May 17 and belonged to active region NOAA 11748. We detected strong He i 10830 Å emission in the flare. The red component of the He i triplet peaks at an intensity ratio to the continuum of about 1.86. During the flare, He i Stokes V is substantially larger and appears reversed compared to the usually larger Si i Stokes V profile. The photospheric Si i inversions of the four Stokes profiles reveal the following: (1) the magnetic field strength in the photosphere decreases or is even absent during the flare phase, as compared to the pre-flare phase. However, this decrease is not permanent. After the flare, the magnetic field recovers its pre-flare configuration in a short time (i.e., 30 minutes after the flare). (2) In the photosphere, the line of sight velocities show a regular granular up- and downflow pattern before the flare erupts. During the flare, upflows (blueshifts) dominate the area where the flare is produced. Evaporation rates of ∼10{sup −3} and ∼10{sup −4} g cm{sup −2} s{sup −1} have been derived in the deep and high photosphere, respectively, capable of increasing the chromospheric density by a factor of two in about 400 s.

  16. Transition Region Emission and the Energy Input to Thermal Plasma in Solar Flares

    Science.gov (United States)

    Holman, Gordon D.; Holman, Gordon D.; Dennis, Brian R.; Haga, Leah; Raymond, John C.; Panasyuk, Alexander

    2005-01-01

    Understanding the energetics of solar flares depends on obtaining reliable determinations of the energy input to flare plasma. X-ray observations of the thermal bremsstrahlung from hot flare plasma provide temperatures and emission measures which, along with estimates of the plasma volume, allow the energy content of this hot plasma to be computed. However, if thermal energy losses are significant or if significant energy goes directly into cooler plasma, this is only a lower limit on the total energy injected into thermal plasma during the flare. We use SOHO UVCS observations of O VI flare emission scattered by coronal O VI ions to deduce the flare emission at transition region temperatures between 100,000 K and 1 MK for the 2002 July 23 and other flares. We find that the radiated energy at these temperatures significantly increases the deduced energy input to the thermal plasma, but by an amount that is less than the uncertainty in the computed energies. Comparisons of computed thermal and nonthermal electron energies deduced from RHESSI, GOES, and UVCS are shown.

  17. Energetic Particle Estimates for Stellar Flares

    Science.gov (United States)

    Youngblood, Allison; Chamberlin, Phil; Woods, Tom

    2018-01-01

    In the heliosphere, energetic particles are accelerated away from the Sun during solar flares and/or coronal mass ejections where they frequently impact the Earth and other solar system bodies. Solar (or stellar) energetic particles (SEPs) not only affect technological assets, but also influence mass loss and chemistry in planetary atmospheres (e.g., depletion of ozone). SEPs are increasingly recognized as an important factor in assessing exoplanet habitability, but we do not yet have constraints on SEP emission from any stars other than the Sun. Until indirect measurements are available, we must assume solar-like particle production and apply correlations between solar flares and SEPs detected near Earth to stellar flares. We present improved scaling relations between solar far-UV flare flux and >10 MeV proton flux near Earth. We apply these solar scaling relations to far-UV flares from exoplanet host stars and discuss the implications for modeling chemistry and mass loss in exoplanet atmospheres.

  18. M-number dependence of rotation period of the solar magnetic field and its effect on coronal hole and solar flare

    International Nuclear Information System (INIS)

    Saito, Takao; Oki, Tosio

    1989-01-01

    The photospheric magnetic field is revealed to rotate with different solar rotation periods depending on its m-number, or its longitudinal range. The m-dependent rotation reveals the unexplained solar cycle variation of the 28-day period of the IMF 2-sector structure in inclining/minimum years and of the 27-day period in the declining/minimum years. The m-dependent rotation reveals also the unexplained 155-day periodicity in the occurrence of solar flare clusters, suggesting a motion of the sunspot field relative to the large-scale field. The IMF sector structure is closely related to recurrent geomagnetic storms, while the flare occurrence is related to sporadic SC storms. Hence, the m-dependent rotation is quite important in the study of the STE forecast. (author)

  19. Statistical properties of correlated solar flares and coronal mass ejections in cycles 23 and 24

    Science.gov (United States)

    Aarnio, Alicia

    2018-01-01

    Outstanding problems in understanding early stellar systems include mass loss, angular momentum evolution, and the effects of energetic events on the surrounding environs. The latter of these drives much research into our own system's space weather and the development of predictive algorithms for geomagnetic storms. So dually motivated, we have leveraged a big-data approach to combine two decades of GOES and LASCO data to identify a large sample of spatially and temporally correlated solar flares and CMEs. In this presentation, we revisit the analysis of Aarnio et al. (2011), adding 10 years of data and further exploring the relationships between correlated flare and CME properties. We compare the updated data set results to those previously obtained, and discuss the effects of selecting smaller time windows within solar cycles 23 and 24 on the empirically defined relationships between correlated flare and CME properties. Finally, we discuss a newly identified large sample of potentially interesting correlated flares and CMEs perhaps erroneously excluded from previous searches.

  20. On the Nature of Off-limb Flare Continuum Sources Detected by SDO /HMI

    Energy Technology Data Exchange (ETDEWEB)

    Heinzel, P.; Kašparová, J. [Astronomical Institute, Czech Academy of Sciences, 25165 Ondřejov (Czech Republic); Kleint, L.; Krucker, S., E-mail: pheinzel@asu.cas.cz [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland)

    2017-09-20

    The Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory has provided unique observations of off-limb flare emission. White-light continuum enhancements were detected in the “continuum” channel of the Fe 6173 Å line during the impulsive phase of the observed flares. In this paper we aim to determine which radiation mechanism is responsible for such enhancement being seen above the limb, at chromospheric heights around or below 1000 km. Using a simple analytical approach, we compare two candidate mechanisms, the hydrogen recombination continuum (Paschen) and the Thomson continuum due to scattering of disk radiation on flare electrons. Both mechanisms depend on the electron density, which is typically enhanced during the impulsive phase of a flare as the result of collisional ionization (both thermal and also non-thermal due to electron beams). We conclude that for electron densities higher than 10{sup 12} cm{sup −3}, the Paschen recombination continuum significantly dominates the Thomson scattering continuum and there is some contribution from the hydrogen free–free emission. This is further supported by detailed radiation-hydrodynamical (RHD) simulations of the flare chromosphere heated by the electron beams. We use the RHD code FLARIX to compute the temporal evolution of the flare-heating in a semi-circular loop. The synthesized continuum structure above the limb resembles the off-limb flare structures detected by HMI, namely their height above the limb, as well as the radiation intensity. These results are consistent with recent findings related to hydrogen Balmer continuum enhancements, which were clearly detected in disk flares by the IRIS near-ultraviolet spectrometer.

  1. Biotic extinctions by solar flares; and reply

    International Nuclear Information System (INIS)

    Beland, P.; Russell, D.A.; Crutzen, P.J.; Reid, G.C.

    1976-01-01

    Some comments are offered on the paper by Reid and others (nature 259:177 (1976)) in which a mechanism was suggested by which solar protons might catastrophically deplete atmospheric D 3 during a reversal of the Earth's geomagnetic field. Organisms would thereby be exposed to a more intense UV environment, leading to species extinctions. These authors assumed that during a reversal the geomagnetic field effectively disappears for about 1000 years, and also that solar flares sufficiently intense to cause extinctions occur at intervals of 1000 years or more. The validity of these assumptions is here examined using data on geomagnetic reversals identified over the past 75 M years, together with extinction data, and some anomalies are pointed out. A reply by Reid and others is appended. (U.K.)

  2. Acceleration of runaway electrons and Joule heating in solar flares

    Science.gov (United States)

    Holman, G. D.

    1985-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  3. Continuum emission in the 1980 July 1 solar flare

    International Nuclear Information System (INIS)

    Zirin, H.; Neidig, D.F.

    1981-01-01

    Comparison of continuum measurements of the 1980 July 1 flare at Big Bear Solar Observatory and Sacramento Peak Observatory show strong blue emission kernels with the ratio of Balmer continuum (Bac):lambda3862 continuum:continuum above 4275 A to be about 10:5:1. The blue continuum at 3862 A is too strong to be explained by unresolved lines. The Bac intensity was 2.5 times the photosphere and the strongest lambda3862 continuum was 2 times the photosphere. The brightest continuum kernel occurred late in the flare, after the hard X-ray peak and related in time to an isolated peak in the 2.2 MeV line, suggesting that the continuum was excited by protons above 20 MeV

  4. CHARGE-EXCHANGE LIMITS ON LOW-ENERGY {alpha}-PARTICLE FLUXES IN SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, H. S. [SSL, UC Berkeley, CA 94720 (United States); Fletcher, L.; MacKinnon, A. L. [School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Woods, T. N., E-mail: hhudson@ssl.berkeley.edu [Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Dr., Boulder, CO 80303 (United States)

    2012-06-20

    This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Ly{alpha} line of He II at 304 A, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary {alpha} particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He II bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment on board the Solar Dynamics Observatory gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV nucleon{sup -1}. We study 10 events in total, including the {gamma}-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic particles. The absence of charge-exchange line wings may point to a need for more complete theoretical work. Some of the events do have broadband signatures, which could correspond to continua from other origins, but these do not have the spectral signatures expected from the Orrall-Zirker mechanism.

  5. Solar Flare Physics Enlivened by TRACE and RHESSI Markus J ...

    Indian Academy of Sciences (India)

    the highest EUV spatial resolution and the Ramaty High Energy Solar Spec- trometric Imager ... Displaced Electron and Ion Acceleration Sources. Key words. ... 2002) and the solid-state detectors of the Soft ... new diagnostic of the flare plasma temperature and iron abundance. 3. .... from the thick-target model (Fig. 3, right ...

  6. EVIDENCE OF SIGNIFICANT ENERGY INPUT IN THE LATE PHASE OF A SOLAR FLARE FROM NuSTAR X-RAY OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kuhar, Matej; Krucker, Säm [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland); Hannah, Iain G.; Wright, Paul J. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Glesener, Lindsay [School of Physics and Astronomy, University of Minnesota—Twin Cities, Minneapolis, MN 55455 (United States); Saint-Hilaire, Pascal; Hudson, Hugh S.; Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States); Grefenstette, Brian W.; Harrison, Fiona A. [Cahill Center for Astrophysics, 1216 E. California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); White, Stephen M. [Air Force Research Laboratory, Albuquerque, NM (United States); Smith, David M.; Marsh, Andrew J. [Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Christensen, Finn E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, Charles J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Zhang, William W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2017-01-20

    We present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray ( NuSTAR ) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory ( SDO )/AIA and FOXSI-2 sounding rocket observations. The active region produced a medium-size solar flare 1 day before the observations, at ∼18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/ AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8–4.6 MK, emission measure (0.3–1.8) × 10{sup 46} cm{sup −3}, and density estimated at (2.5–6.0) × 10{sup 8} cm{sup −3}. The observed AIA fluxes are consistent with the derived NuSTAR temperature range, favoring temperature values in the range of 4.0–4.3 MK. By examining the post-flare loops’ cooling times and energy content, we estimate that at least 12 sets of post-flare loops were formed and subsequently cooled between the onset of the flare and NuSTAR observations, with their total thermal energy content an order of magnitude larger than the energy content at flare peak time. This indicates that the standard approach of using only the flare peak time to derive the total thermal energy content of a flare can lead to a large underestimation of its value.

  7. Electron-cyclotron maser emission during solar and stellar flares

    International Nuclear Information System (INIS)

    Winglee, R.M.

    1985-01-01

    Radio bursts, with high brightness temperature 10 to the 10th power K and high degree of polarization, and the heating of the solar and stellar coronae during flares have been attributed to emission from the semirelativistic maser instability. In plasmas where the electron-plasma frequency, p, omega sub p, and the electron-cyclotron frequency, Omega sub e, are such that omega sup 2 sub p/Omega sup 2 sub e 1, x-mode growth dominates while z-mode growth dominates if omega sup 2 sub p/Omega sup 2 sub e is of order unity. The actual value of omega sup 2 sub p/Omega sup 2 sub e at which x-mode growth dominates is shown to be dependent on the plasma temperature with x-mode growth dominating at higher omega sub p/Omega sub e as the plasma temperature increases. Observations from a set of 20 impulsive flares indicate that the derived conditions for the dominance of x-mode growth are satisfied in about 75 percent of the flares

  8. MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

    International Nuclear Information System (INIS)

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay

    2010-01-01

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  9. Minor impact of solar flare events accompanied with SRBT III to the ...

    African Journals Online (AJOL)

    The dynamical behavior of the Sun exhibits a variety of physical phenomena, some of which are still not at all or only barely understood due to the complexity of the structure of the Sun. The aim of this study is to investigate the correlation of solar flare event and solar radio bursts type III that happen on 23rd July 2017.

  10. The size of coronal hard X-ray sources in solar flares: How big are they?

    Science.gov (United States)

    Effenberger, F.; Krucker, S.; Rubio da Costa, F.

    2017-12-01

    Coronal hard X-ray sources are considered to be one of the key signatures of non-thermal particle acceleration and heating during the energy release in solar flares. In some cases, X-ray observations reveal multiple components spatially located near and above the loop top and even further up in the corona. Here, we combine a detailed RHESSI imaging analysis of near-limb solar flares with occulted footpoints and a multi-wavelength study of the flare loop evolution in SDO/AIA. We connect our findings to different current sheet formation and magnetic break-out scenarios and relate it to particle acceleration theory. We find that the upper and usually fainter emission regions can be underestimated in their size due to the majority of flux originating from the lower loops.

  11. Principle of Minimum Energy in Magnetic Reconnection in a Self-organized Critical Model for Solar Flares

    Science.gov (United States)

    Farhang, Nastaran; Safari, Hossein; Wheatland, Michael S.

    2018-05-01

    Solar flares are an abrupt release of magnetic energy in the Sun’s atmosphere due to reconnection of the coronal magnetic field. This occurs in response to turbulent flows at the photosphere that twist the coronal field. Similar to earthquakes, solar flares represent the behavior of a complex system, and expectedly their energy distribution follows a power law. We present a statistical model based on the principle of minimum energy in a coronal loop undergoing magnetic reconnection, which is described as an avalanche process. We show that the distribution of peaks for the flaring events in this self-organized critical system is scale-free. The obtained power-law index of 1.84 ± 0.02 for the peaks is in good agreement with satellite observations of soft X-ray flares. The principle of minimum energy can be applied for general avalanche models to describe many other phenomena.

  12. Energetic-particle abundances in impulsive solar flares

    Science.gov (United States)

    Reames, D. V.; Cane, H. V.; Von Rosenvinge, T. T.

    1990-01-01

    The abundances of elements and of He-3 in 90 solar electron events have been examined. It is found that the events fall into two distinct groups based upon their F/C ratio. Events in the F-rich group frequently have high He-3/He-4 ratios and are associated with type III and type V radio bursts in the parent flare. The F-poor events are associated with type IV bursts. These results on individual events support the conclusions of earlier work done with daily-averaged abundances.

  13. HARD X-RAY AND MICROWAVE EMISSIONS FROM SOLAR FLARES WITH HARD SPECTRAL INDICES

    Energy Technology Data Exchange (ETDEWEB)

    Kawate, T. [Kwasan and Hida Observatory, Kitashirakawa-oiwakecho, Sakyo, Kyoto 606-8502 (Japan); Nishizuka, N. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Oi, A. [College of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Ohyama, M. [Faculty of Education, Shiga University, 2-5-1 Hiratsu, Otsu, Shiga 1-1, Baba Hikone city, Siga 522-8522 (Japan); Nakajima, H., E-mail: kawate@kusastro.kyoto-u.ac.jp [Nobeyama Solar Radio Observatory, NAOJ, Nobeyama, Minamisaku, Nagano 384-1305 (Japan)

    2012-03-10

    We analyze 10 flare events that radiate intense hard X-ray (HXR) emission with significant photons over 300 keV to verify that the electrons that have a common origin of acceleration mechanism and energy power-law distribution with solar flares emit HXRs and microwaves. Most of these events have the following characteristics. HXRs emanate from the footpoints of flare loops, while microwaves emanate from the tops of flare loops. The time profiles of the microwave emission show delays of peak with respect to those of the corresponding HXR emission. The spectral indices of microwave emissions show gradual hardening in all events, while the spectral indices of the corresponding HXR emissions are roughly constant in most of the events, though rather rapid hardening is simultaneously observed in some for both indices during the onset time and the peak time. These characteristics suggest that the microwave emission emanates from the trapped electrons. Then, taking into account the role of the trapping of electrons for the microwave emission, we compare the observed microwave spectra with the model spectra calculated by a gyrosynchrotron code. As a result, we successfully reproduce the eight microwave spectra. From this result, we conclude that the electrons that have a common acceleration and a common energy distribution with solar flares emit both HXR and microwave emissions in the eight events, though microwave emission is contributed to by electrons with much higher energy than HXR emission.

  14. Solar-flare-induced Forbush decreases - Dependence on shock wave geometry

    Science.gov (United States)

    Thomas, B. T.; Gall, R.

    1984-01-01

    It is argued that the principal mechanism for the association of Forbush decreases with the passage of a solar flare shock wave is prolonged containment of cosmic ray particles behind the flare compression region, which acts as a semipermeable obstacle to particle motion along the field lines, leading to additional adiabatic cooling of the particles. Liouville's theorem is used to calculate the instantaneous distribution function at 1 AU for each particle arriving at the earth. By averaging over a large number of individual estimates, a representative estimate of the omnidirectional phase space density and the corresponding particle intensity is obtained. The energy change of individual particles at the shocks is found to be small in comparison to the energy lost by adiabatic cooling of the cosmic rays between the shock wave and the sun. The effects of particle rigidity, diffusion coefficient, and flare longitude on the magnitude of the Forbush decrease are quantitatively investigated.

  15. HARD X-RAY ASYMMETRY LIMITS IN SOLAR FLARE CONJUGATE FOOTPOINTS

    Energy Technology Data Exchange (ETDEWEB)

    Daou, Antoun G.; Alexander, David, E-mail: agdaou@rice.edu, E-mail: dalex@rice.edu [Department of Physics and Astronomy, Rice University, 6100 Main Street, MS 108, Houston, TX, 77005 (United States)

    2016-11-20

    The transport of energetic electrons in a solar flare is modeled using a time-dependent one-dimensional Fokker–Planck code that incorporates asymmetric magnetic convergence. We derive the temporal and spectral evolution of the resulting hard X-ray (HXR) emission in the conjugate chromospheric footpoints, assuming thick target photon production, and characterize the time evolution of the numerically simulated footpoint asymmetry and its relationship to the photospheric magnetic configuration. The thick target HXR asymmetry in the conjugate footpoints is found to increase with magnetic field ratio as expected. However, we find that the footpoint HXR asymmetry saturates for conjugate footpoint magnetic field ratios ≥4. This result is borne out in a direct comparison with observations of 44 double-footpoint flares. The presence of such a limit has not been reported before, and may serve as both a theoretical and observational benchmark for testing a range of particle transport and flare morphology constraints, particularly as a means to differentiate between isotropic and anisotropic particle injection.

  16. OBSERVATIONS OF LINEAR POLARIZATION IN A SOLAR CORONAL LOOP PROMINENCE SYSTEM OBSERVED NEAR 6173 Å

    Energy Technology Data Exchange (ETDEWEB)

    Saint-Hilaire, Pascal; Martínez Oliveros, Juan-Carlos; Hudson, Hugh S.; Krucker, Säm; Bain, Hazel [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Schou, Jesper [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Couvidat, Sébastien, E-mail: shilaire@ssl.berkeley.edu [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-05-10

    White-light observations by the Solar Dynamics Observatory's Helioseismic and Magnetic Imager of a loop-prominence system occurring in the aftermath of an X-class flare on 2013 May 13 near the eastern solar limb show a linearly polarized component, reaching up to ∼20% at an altitude of ∼33 Mm, about the maximum amount expected if the emission were due solely to Thomson scattering of photospheric light by the coronal material. The mass associated with the polarized component was 8.2 × 10{sup 14} g. At 15 Mm altitude, the brightest part of the loop was 3(±0.5)% linearly polarized, only about 20% of that expected from pure Thomson scattering, indicating the presence of an additional unpolarized component at wavelengths near Fe I (617.33 nm). We estimate the free electron density of the white-light loop system to possibly be as high as 1.8 × 10{sup 12} cm{sup –3}.

  17. Conversion of piston-driven shocks from powerful solar flares to blast wave shocks in the solar wind

    International Nuclear Information System (INIS)

    Pinter, S.

    1990-01-01

    It was suggested by Smart and Shea (1985) that the time of arrival of solar-flare-generated shock waves at any point in space may be predicted by assuming that they are first driven from the Sun after which they decay into blast shocks. Their study was extended by using the duration of the Type IV radio emission as a phenomenological symptom of the piston-driven phase of these shocks. Using a sample of 39 cases of combined Type II/Type IV observations from 1972 to 1982 solar flares, it was found that the average predicted times-of-arrival of these shocks to Earth (and elsewhere) deviate from the actual times by 1.40 hr with a standard deviation of 1.25 hr. On the average, a representative shock from this sample is emitted from a powerful flare with a velocity of 1,560 km sec -1 ; moves at a constant inertial velocity to a distance of 0.12 AU after which it begins to decelerate as a classical (Sedov-type) blast shock that is convected by the ambient solar wind as suggested by Smart and Shea; and arrives to Earth 45.8 hr after its initiation in the Sun. Shocks that appear to deviate from this phenomenological scenario by virtue of lack of detection on Earth are assumed to decay into fast mode MHD waves. (author). 7 figs., 1 tab., 53 refs

  18. Solar flare activity in 2006 - 2016 according to PAMELA and ARINA spectrometers

    Science.gov (United States)

    Rodenko, S. A.; Borkut, I. K.; Mayorov, A. G.; Malakhov, V. V.; PAMELA Collaboration

    2018-01-01

    From 2006 to 2016 years on the board of RESURS-DK1 satellite PAMELA and ARINA cosmic rays experiments was carried out. The main goal of experiments is measurement of galactic component of cosmic rays; it also registers solar particles accelerated in powerful explosive processes on the sun (solar flares) in wide energy range. The article includes the list of solar events when PAMELA or ARINA spectrometers have registered increasing of proton flux intensities for energies more than 4 MeV.

  19. Proceedings of the second workshop on thermal-non-thermal interactions in solar flares [TNT-II

    International Nuclear Information System (INIS)

    Phillips, K.J.H.

    1989-09-01

    The Second Workshop on the theme of Thermal-Non-thermal Interactions in Solar Flares (TNT-II) was held at Somerville College, University of Oxford, England, during the week of April 10-14, 1989. The keynote address, gave a view of the problems still outstanding with regard to soft and hard X-ray observations of flares. The gathering broke up into four subgroups. The subjects under discussion were: large-scale magnetic field phenomena, flare dynamics, energy release and deposition, and global energy balance. (author)

  20. Solar activity and heliosphere-wide cosmic ray modulation in mid-1982

    International Nuclear Information System (INIS)

    Cliver, E.W.; Mihalov, J.D.; Sheeley, N.R. Jr.; Howard, R.A.; Koomen, M.J.; Schwenn, R.

    1987-01-01

    A major episode of flare activity in June and July 1982 was accompaniedby a pair of heliosphere-wide cosmic ray modulation events. In each case, a large Forbush decrease (FD) at earth was followed in turn by apparently related decreases at Pioneer 11 (P11) and Pioneer 10 (P10). The Pioneer spacecraft were separated by --155 0 in ecliptic longitude. We reviewed white light coronagraph and near-sun (≤1 AU) satellite data to identify plausible solar origins of these modulation events. The first widespread intensity decrease (FD 1) can be attributed to the combined effects of a backside flare on June 3 from solar active region 18382/18383, located 23 0 in ecliptic longitude from Pioneer 10, and a visible disk flare from 18405 on June 6, when this region was 9 0 from Pioneer 11. The second widespread modulation event during this period (FD 2) may be linked to flares from active region 18474 on July 12 and 22. The July 12 flare was located 34 0 in azimuth from Pioneer 11, and the July 22 flare was 24 0 from Pioneer 10. Since even fast shocks would take --1 month to propagate to Pioneer 11 (12 AU) and --2 months to reach Pioneer 10 (28 AU) in mid-1982, these ''one-to-one'' associations must be regarded with caution. The processes of entrainment and coalescence can cause a given traveling interplanetary disturbance to lose its identify enroute to the outer heliosphere. The fact that we were able to identify plausible solar flare candidates for each of the four Forbushlike decreases observed at the Pioneer satellites (two each at P10 and P11), however, removes the need to invoke a chock from a single flare as the sole cause of either FD 1 (at both P10 and P11) or FD 2

  1. A Double Candle-Flame-Shaped Solar Flare Observed by SDO and STEREO

    Science.gov (United States)

    Gou, T.; Liu, R.; Wang, Y.; Liu, K.; Zhuang, B.; Zhang, Q.; Liu, J.

    2015-12-01

    We investigate an M1.4 flare occurring on 2011 January 28 near the northwest solar limb. The flare loop system exhibits a double candle-flame configuration in SDO/AIA's hot passbands, sharing a much larger cusp-shaped structure. The results of DEM analysis show that each candle flame has a similar temperature distribution as the famous Tsuneta flare. STEREO-A provides us a view from directly above the flare, and in SECCHI/EUVI 195 Å the post-flare loops are observed to propagate eastward. We performed a 3D reconstruction of the pos-flare loops with AIA and EUVI data. With the aid of the squashing factor Q based on a potential extrapolation of the photospheric field, we recognized that the footpoints of the post-flare loops were slipping along high-Q lines on the photosphere, and the reconstructed loops share similarity with the filed lines that are traced starting from the high-Q lines. The heights of the loops increase as they slip horizontally eastward, giving the loop-top a velocity of about 10 km/s. An extremely large EUV late phase in Fe XVI 33.5 nm observed by SDO/EVE is suggested to be related to the slipping magnetic reconnection occurring in the quasi-separatrix layers (QSLs) whose photosheric footprints are featured by the high-Q lines.

  2. Solar flare effect in equatorial magnetic field during morning counter electrojet

    International Nuclear Information System (INIS)

    Rangarajan, G.K.; Rastogi, R.G.

    1981-01-01

    Surface geomagnetic signatures of intense solar radio noise bursts are studied from the magnetograms of several equatorial and low latitude observatories. It is shown that for the even on 21 June 1980, the solar flare effect recorded was during a period of counter electrojet currents in the morning hours in the Indian region, and hence it reverses direction between Alibag and Trivandrum. The longitudinal extent of this event has been estimated to be less than three hours (45). (author)

  3. A BRIGHT IMPULSIVE SOLAR BURST DETECTED AT 30 THz

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, P.; Fernandes, L. O. T.; Kudaka, A. S.; De Souza, R. V.; Valio, A.; Raulin, J.-P. [Center of Radio Astronomy and Astrophysics, Engineering School, Mackenzie Presbyterian University, Sao Paulo, SP (Brazil); White, S. M. [Air Force Research Laboratories, Space Vehicles Directorate, Albuquerque, NM 87117 (United States); Freeland, S. L. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Marcon, R. [' ' Gleb Wataghin' ' Physics Institute, State University of Campinas, Campinas, SP (Brazil); Aballay, J. L.; Fernandez, G.; Godoy, R.; Marun, A.; Gimenez de Castro, C. G. [El Leoncito Astronomical Complex, CONICET, San Juan (Argentina)

    2013-05-10

    Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV, and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies.

  4. Ionospheric response to X-class solar flares in the ascending half of ...

    Indian Academy of Sciences (India)

    during solar flare events can significantly change the density, temperature .... responding changes in TEC for all visible GPS ... figures, the green lines represent the TEC for differ- ..... Webster A R and Chin P 1974 Behavior of the ionospheric.

  5. Transient rotation of photospheric vector magnetic fields associated with a solar flare.

    Science.gov (United States)

    Xu, Yan; Cao, Wenda; Ahn, Kwangsu; Jing, Ju; Liu, Chang; Chae, Jongchul; Huang, Nengyi; Deng, Na; Gary, Dale E; Wang, Haimin

    2018-01-03

    As one of the most violent eruptions on the Sun, flares are believed to be powered by magnetic reconnection. The fundamental physics involving the release, transfer, and deposition of energy have been studied extensively. Taking advantage of the unprecedented resolution provided by the 1.6 m Goode Solar Telescope, here, we show a sudden rotation of vector magnetic fields, about 12-20° counterclockwise, associated with a flare. Unlike the permanent changes reported previously, the azimuth-angle change is transient and cospatial/temporal with Hα emission. The measured azimuth angle becomes closer to that in potential fields suggesting untwist of flare loops. The magnetograms were obtained in the near infrared at 1.56 μm, which is minimally affected by flare emission and no intensity profile change was detected. We believe that these transient changes are real and discuss the possible explanations in which the high-energy electron beams or Alfve'n waves play a crucial role.

  6. Solar Flare Track Exposure Ages in Regolith Particles: A Calibration for Transmission Electron Microscope Measurements

    Science.gov (United States)

    Berger, Eve L.; Keller, Lindsay P.

    2015-01-01

    Mineral grains in lunar and asteroidal regolith samples provide a unique record of their interaction with the space environment. Space weathering effects result from multiple processes including: exposure to the solar wind, which results in ion damage and implantation effects that are preserved in the rims of grains (typically the outermost 100 nm); cosmic ray and solar flare activity, which result in track formation; and impact processes that result in the accumulation of vapor-deposited elements, impact melts and adhering grains on particle surfaces. Determining the rate at which these effects accumulate in the grains during their space exposure is critical to studies of the surface evolution of airless bodies. Solar flare energetic particles (mainly Fe-group nuclei) have a penetration depth of a few millimeters and leave a trail of ionization damage in insulating materials that is readily observable by transmission electron microscope (TEM) imaging. The density of solar flare particle tracks is used to infer the length of time an object was at or near the regolith surface (i.e., its exposure age). Track measurements by TEM methods are routine, yet track production rate calibrations have only been determined using chemical etching techniques [e.g., 1, and references therein]. We used focused ion beam-scanning electron microscope (FIB-SEM) sample preparation techniques combined with TEM imaging to determine the track density/exposure age relations for lunar rock 64455. The 64455 sample was used earlier by [2] to determine a track production rate by chemical etching of tracks in anorthite. Here, we show that combined FIB/TEM techniques provide a more accurate determination of a track production rate and also allow us to extend the calibration to solar flare tracks in olivine.

  7. Slipping magnetic reconnection during an X-class solar flare observed by SDO/AIA

    Energy Technology Data Exchange (ETDEWEB)

    Dudík, J.; Del Zanna, G.; Mason, H. E. [DAMTP, CMS, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Janvier, M. [Department of Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom); Aulanier, G.; Schmieder, B. [LESIA, Observatoire de Paris, UMR 8109 (CNRS), F-92195 Meudon Principal Cedex (France); Karlický, M., E-mail: J.Dudik@damtp.cam.ac.uk, E-mail: mjanvier@maths.dundee.ac.uk [Astronomical Institute of the Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov (Czech Republic)

    2014-04-01

    We present SDO/AIA observations of an eruptive X-class flare of 2012 July 12, and compare its evolution with the predictions of a three-dimensional (3D) numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s{sup –1} along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A differential emission measure analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a coronal mass ejection observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the 'standard solar flare model in 3D.' This model matches the observations well, reproducing the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of the reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour.

  8. Solar weather monitoring

    Directory of Open Access Journals (Sweden)

    J.-F. Hochedez

    2005-11-01

    Full Text Available Space Weather nowcasting and forecasting require solar observations because geoeffective disturbances can arise from three types of solar phenomena: coronal mass ejections (CMEs, flares and coronal holes. For each, we discuss their definition and review their precursors in terms of remote sensing and in-situ observations. The objectives of Space Weather require some specific instrumental features, which we list using the experience gained from the daily operations of the Solar Influences Data analysis Centre (SIDC at the Royal Observatory of Belgium. Nowcasting requires real-time monitoring to assess quickly and reliably the severity of any potentially geoeffective solar event. Both research and forecasting could incorporate more observations in order to feed case studies and data assimilation respectively. Numerical models will result in better predictions of geomagnetic storms and solar energetic particle (SEP events. We review the data types available to monitor solar activity and interplanetary conditions. They come from space missions and ground observatories and range from sequences of dopplergrams, magnetograms, white-light, chromospheric, coronal, coronagraphic and radio images, to irradiance and in-situ time-series. Their role is summarized together with indications about current and future solar monitoring instruments.

  9. ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yan; Liu, Chang; Jing, Ju; Wang, Haimin [Space Weather Research Lab, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd, Newark, NJ 07102-1982 (United States); Cao, Wenda; Gary, Dale [Big Bear Solar Observatory, New Jersey Institute of Technology 323 Martin Luther King Blvd, Newark, NJ 07102-1982 (United States); Ding, Mingde [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Kleint, Lucia [Fachhochschule Nordwestschweiz (FHNW), Institute of 4D technologies Bahnhofstr. 6, CH-5210 Windisch (Switzerland); Su, Jiangtao [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Ji, Haisheng [Purple Mountain Observatory, 2 Beijing Xi Lu, Nanjing, 210008 (China); Chae, Jongchul; Cho, Kyuhyoun [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Cho, Kyungsuk [Korea Astronomy and Space Science Institute, Daedeokdae-ro 776, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)

    2016-03-10

    Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6 m New Solar Telescope at Big Bear Solar Observatory, we show a striking “negative” flare with a narrow but unambiguous “dark” moving front observed in He i 10830 Å, which is as narrow as 340 km and is associated with distinct spectral characteristics in Hα and Mg ii lines. Theoretically, such negative contrast in He i 10830 Å can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects.

  10. ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE

    International Nuclear Information System (INIS)

    Xu, Yan; Liu, Chang; Jing, Ju; Wang, Haimin; Cao, Wenda; Gary, Dale; Ding, Mingde; Kleint, Lucia; Su, Jiangtao; Ji, Haisheng; Chae, Jongchul; Cho, Kyuhyoun; Cho, Kyungsuk

    2016-01-01

    Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6 m New Solar Telescope at Big Bear Solar Observatory, we show a striking “negative” flare with a narrow but unambiguous “dark” moving front observed in He i 10830 Å, which is as narrow as 340 km and is associated with distinct spectral characteristics in Hα and Mg ii lines. Theoretically, such negative contrast in He i 10830 Å can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects

  11. A Comparative Study of the Eruptive and Non-eruptive Flares Produced by the Largest Active Region of Solar Cycle 24

    Science.gov (United States)

    Sarkar, Ranadeep; Srivastava, Nandita

    2018-02-01

    We investigate the morphological and magnetic characteristics of solar active region (AR) NOAA 12192. AR 12192 was the largest region of Solar Cycle 24; it underwent noticeable growth and produced 6 X-class flares, 22 M-class flares, and 53 C-class flares in the course of its disc passage. However, the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we carry out a comparative study between the eruptive and non-eruptive flares produced by AR 12192. We find that the magnitude of abrupt and permanent changes in the horizontal magnetic field and Lorentz force are significantly smaller in the case of the confined flares compared to the eruptive one. We present the areal evolution of AR 12192 during its disc passage. We find the flare-related morphological changes to be weaker during the confined flares, whereas the eruptive flare exhibits a rapid and permanent disappearance of penumbral area away from the magnetic neutral line after the flare. Furthermore, from the extrapolated non-linear force-free magnetic field, we examine the overlying coronal magnetic environment over the eruptive and non-eruptive zones of the AR. We find that the critical decay index for the onset of torus instability was achieved at a lower height over the eruptive flaring region, than for the non-eruptive core area. These results suggest that the decay rate of the gradient of overlying magnetic-field strength may play a decisive role to determine the CME productivity of the AR. In addition, the magnitude of changes in the flare-related magnetic characteristics are found to be well correlated with the nature of solar eruptions.

  12. Solar origins of coronal mass ejections

    Science.gov (United States)

    Kahler, Stephen

    1987-01-01

    The large scale properties of coronal mass ejections (CMEs), such as morphology, leading edge speed, and angular width and position, have been cataloged for many events observed with coronagraphs on the Skylab, P-78, and SMM spacecraft. While considerable study has been devoted to the characteristics of the SMEs, their solar origins are still only poorly understood. Recent observational work has involved statistical associations of CMEs with flares and filament eruptions, and some evidence exists that the flare and eruptive-filament associated CMEs define two classes of events, with the former being generally more energetic. Nevertheless, it is found that eruptive-filament CMEs can at times be very energetic, giving rise to interplanetary shocks and energetic particle events. The size of the impulsive phase in a flare-associated CME seems to play no significant role in the size or speed of the CME, but the angular sizes of CMEs may correlate with the scale sizes of the 1-8 angstrom x-ray flares. At the present time, He 10830 angstrom observations should be useful in studying the late development of double-ribbon flares and transient coronal holes to yield insights into the CME aftermath. The recently available white-light synoptic maps may also prove fruitful in defining the coronal conditions giving rise to CMEs.

  13. Quantitative Examination of a Large Sample of Supra-Arcade Downflows in Eruptive Solar Flares

    Science.gov (United States)

    Savage, Sabrina L.; McKenzie, David E.

    2011-01-01

    Sunward-flowing voids above post-coronal mass ejection flare arcades were first discovered using the soft X-ray telescope aboard Yohkoh and have since been observed with TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays). Supra-arcade downflow (SAD) observations suggest that they are the cross-sections of thin flux tubes retracting from a reconnection site high in the corona. Supra-arcade downflowing loops (SADLs) have also been observed under similar circumstances and are theorized to be SADs viewed from a perpendicular angle. Although previous studies have focused on dark flows because they are easier to detect and complementary spectral data analysis reveals their magnetic nature, the signal intensity of the flows actually ranges from dark to bright. This implies that newly reconnected coronal loops can contain a range of hot plasma density. Previous studies have presented detailed SAD observations for a small number of flares. In this paper, we present a substantial SADs and SADLs flare catalog. We have applied semiautomatic detection software to several of these events to detect and track individual downflows thereby providing statistically significant samples of parameters such as velocity, acceleration, area, magnetic flux, shrinkage energy, and reconnection rate. We discuss these measurements (particularly the unexpected result of the speeds being an order of magnitude slower than the assumed Alfven speed), how they were obtained, and potential impact on reconnection models.

  14. Super enrichment of Fe-group nuclei in solar flares and their association with large 3He enrichments

    International Nuclear Information System (INIS)

    Anglin, J.D.; Dietrich, W.F.; Simpson, J.A.

    1977-01-01

    ''Fe''/He ratios at approximately 2 MeV/n have been measured in 60 solar flares and periods of enhanced fluxes during the interval 1972-1976. The observed ditribution of ratios is extremely wide with values ranging from approximately 1 to more than 1000 times the solar abundance ratio. In constrast, most of the CHO/He ratios for the same flares lie within a factor 2 of the observed mean value of 2 x 10 -2 . While experimental limitations prevent a complete correlation study of Fe-group and 3 He abundances, comparison of flares with large Fe enrichments with flares with large 3 He enrichments for the period 1969-1976 shows that a 3 He-rich flare is also likely to be rich in iron. We feel that the association of 3 He and Fe enrichments may be explained by a two-stage process in which a preliminary enrichment of heavy nuclei precedes the preferential acceleration of ambient 3 He. Nuclear interactions are ruled out as the principal source of the enriched 3 He. (author)

  15. DETERMINING HEATING RATES IN RECONNECTION FORMED FLARE LOOPS OF THE M8.0 FLARE ON 2005 MAY 13

    Energy Technology Data Exchange (ETDEWEB)

    Liu Wenjuan; Qiu Jiong; Longcope, Dana W. [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States); Caspi, Amir [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States)

    2013-06-20

    We analyze and model an M8.0 flare on 2005 May 13 observed by the Transition Region and Coronal Explorer and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to determine the energy release rate from magnetic reconnection that forms and heats numerous flare loops. The flare exhibits two ribbons in UV 1600 A emission. Analysis shows that the UV light curve at each flaring pixel rises impulsively within a few minutes, and decays slowly with a timescale longer than 10 minutes. Since the lower atmosphere (the transition region and chromosphere) responds to energy deposit nearly instantaneously, the rapid UV brightening is thought to reflect the energy release process in the newly formed flare loop rooted at the footpoint. In this paper, we utilize the spatially resolved (down to 1'') UV light curves and the thick-target hard X-ray emission to construct heating functions of a few thousand flare loops anchored at the UV footpoints, and compute plasma evolution in these loops using the enthalpy-based thermal evolution of loops model. The modeled coronal temperatures and densities of these flare loops are then used to calculate coronal radiation. The computed soft X-ray spectra and light curves compare favorably with those observed by RHESSI and by the Geostationary Operational Environmental Satellite X-ray Sensor. The time-dependent transition region differential emission measure for each loop during its decay phase is also computed with a simplified model and used to calculate the optically thin C IV line emission, which dominates the UV 1600 A bandpass during the flare. The computed C IV line emission decays at the same rate as observed. This study presents a method to constrain heating of reconnection-formed flare loops using all available observables independently, and provides insight into the physics of energy release and plasma heating during the flare. With this method, the lower limit of the total energy used to heat the flare loops in

  16. On Flare-CME Characteristics from Sun to Earth Combining Remote-Sensing Image Data with In Situ Measurements Supported by Modeling

    Science.gov (United States)

    Temmer, Manuela; Thalmann, Julia K.; Dissauer, Karin; Veronig, Astrid M.; Tschernitz, Johannes; Hinterreiter, Jürgen; Rodriguez, Luciano

    2017-07-01

    We analyze the well-observed flare and coronal mass ejection (CME) from 1 October 2011 (SOL2011-10-01T09:18) covering the complete chain of effects - from Sun to Earth - to better understand the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere associated with the flare and CME using the Solar Dynamics Observatory (SDO) and ground-based instruments. We also track the CME signature off-limb with combined extreme ultraviolet (EUV) and white-light data from the Solar Terrestrial Relations Observatory (STEREO). By applying the graduated cylindrical shell (GCS) reconstruction method and total mass to stereoscopic STEREO-SOHO ( Solar and Heliospheric Observatory) coronagraph data, we track the temporal and spatial evolution of the CME in the interplanetary space and derive its geometry and 3D mass. We combine the GCS and Lundquist model results to derive the axial flux and helicity of the magnetic cloud (MC) from in situ measurements from Wind. This is compared to nonlinear force-free (NLFF) model results, as well as to the reconnected magnetic flux derived from the flare ribbons (flare reconnection flux) and the magnetic flux encompassed by the associated dimming (dimming flux). We find that magnetic reconnection processes were already ongoing before the start of the impulsive flare phase, adding magnetic flux to the flux rope before its final eruption. The dimming flux increases by more than 25% after the end of the flare, indicating that magnetic flux is still added to the flux rope after eruption. Hence, the derived flare reconnection flux is most probably a lower limit for estimating the magnetic flux within the flux rope. We find that the magnetic helicity and axial magnetic flux are lower in the interplanetary space by ˜ 50% and 75%, respectively, possibly indicating an erosion process. A CME mass increase of 10% is observed over a range of {˜} 4 - 20 R_{⊙}. The temporal evolution of the CME

  17. Solar flare and galactic cosmic ray tracks in lunar samples and meteorites - What they tell us about the ancient sun

    International Nuclear Information System (INIS)

    Crozaz, G.

    1980-01-01

    Evidence regarding the past activity of the sun in the form of nuclear particle tracks in lunar samples and meteorites produced by heavy ions in galactic cosmic rays and solar flares is reviewed. Observations of track-rich grains found in deep lunar cores and meteorite interiors are discussed which demonstrate the presence of solar flare activity for at least the past 4 billion years, and the similarity of track density profiles from various lunar and meteoritic samples with those in a glass filter from Surveyor 3 exposed at the lunar surface for almost three years is presented as evidence of the relative constancy of the solar flare energy spectrum over the same period. Indications of a heavy ion enrichment in solar flares are considered which are confirmed by recent satellite measurements, although difficult to quantify in lunar soil grains. Finally, it is argued that, despite previous claims, there exists as yet no conclusive evidence for either a higher solar activity during the early history of the moon or a change in galactic cosmic ray intensity, average composition or spectrum over the last 50 million years

  18. Studies of soft x-ray emission during solar flares

    International Nuclear Information System (INIS)

    Anandaram, M.N.

    1973-01-01

    Solar flare soft x-ray emission from 0.5 A to 8.5 A was observed during 1967-68 by Bragg crystal (LiF and EDDT) spectrometers aboard the OSO-4 satellite and also by NRL broad-band ionization detectors aboard the OGO-4 satellite. In this work, instrumental parameters for the LiF crystal spectrometer based on experimental values have been determined and used in the data analysis. The total continuum emission in the 0.5 to 3 A and the 1 to 8 A broad band segments has been determined from OGO-4 data for 21 flares. In doing this, a simple and approximate method of converting the total emission based on the gray body approximation (in which the OGO-4 data are reported) to one based on the thermal continuum spectrum has been developed. (author)

  19. Internal and External reconnection in a Series of Homologous Solar Flares

    Science.gov (United States)

    Sterling, Alphonse C.; Moore, Ronald L.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Using data from the Extreme Ultraviolet Telescope (EIT) on SOHO and the Soft X-ray Telescope (SXT) on Yohkoh, we examine a series of morphologically homologous solar flares occurring in NOAA AR 8210 over May 1-2, 1998. An emerging flux region (EFR) impacted against a sunspot to the west and next to a coronal hole to the east is the source of the repeated flaring. An SXT sigmoid parallels the EFR's neutral line at the site of the initial flaring in soft X-rays. In EIT, each flaring episode begins with the formation of a crinkle pattern external to the EFR. These EIT crinkles move out from, and then in toward, the EFR with velocities approximately 20 km/s. A shrinking and expansion of the width of the coronal hole coincides with the crinkle activity, and generation and evolution of a postflare loop system begins near the. time of crinkle formation. Using a schematic based on magnetograms of the region, we suggest that these observations are consistent with the standard reconnection-based model for solar eruptions, but modified by the presence of the additional magnetic fields of the sunspot and coronal hole. In the schematic, internal reconnection begins inside of the EFR-associated fields, unleashing a flare, postflare loops, and a CME. External reconnection, first occurring between the escaping CME and the coronal hole field, and second occurring between fields formed as a result of the first external reconnection, results in the EIT crinkles and changes in the coronal hole boundary. By the end of the second external reconnection, the initial setup is reinstated; thus the sequence can repeat, resulting in morphologically homologous eruptions. Our inferred magnetic topology is similar to that suggested in the "breakout model" of eruptions [Antiochos, 1998], although we cannot determine if our eruptions are released primarily by the breakout mechanism (external reconnection) or, alternatively, are released primarily by the internal reconnection.

  20. The thermal phase of solar flares

    International Nuclear Information System (INIS)

    Hirayama, Tadashi

    1979-01-01

    This paper is described on the observation of the flares, and then the numerical simulation on the structural change in the corona and the chromosphere during the flare is briefly discussed. Most of the flares occur on the active region where the density and the electron temperature are higher than those in the quiet region. The temperature and density increase after the flare started. The temperature of the pre-flare chromosphere is about 6000 K, and it rises during the flare. The temperature of the transition region is about 10 5 K, and the gas pressure increases more than one order of magnitude during the flare. Sometimes, the flaring in the photosphere is observed. Large amount of mass ejected at the time of the flare is observed. Most probable energy source of the flare is the magnetic energy contained in the form of electric current. Liberation of this energy into the corona is discussed in this paper. It is assumed that a column of unit area is standing vertically in the corona, the top being closed. A hydrostatic model of the corona-chromosphere is constructed, in which the heat source is assumed to be in the corona. As the results of calculation, it can be said that the temperature of the flaring corona does not depend upon the liberated energy, the density in the corona increases proportionally to the energy, and particles are supplied from the chromosphere with the upward velocity of about 100 km/s. The gas pressure of the transition region can become up to three orders of magnitude larger. All these are consistent with the observation. Extension of this calculation is also performed. (Kato, T.)

  1. A Proton Flare Triggered the Mw 8.1 Chiapos Mexican Earthquake

    Science.gov (United States)

    Elfaki, H.; Yousef, S.

    2017-12-01

    In a 2015 Cairo University M.Sc. thesis by Sarah Khodairy, very strong earthquakes were found to be highly correlated with proton flares. Strange blue and green bright flashes of light across Mexico accompanied the 8th of September 2017 Mw 1.8 Chiapas earthquake. Those lights were contemporary with a solar proton flare. Those green and blue lights are indicative of the arrival of proton streams over Mexico and their interaction with atmospheric Oxygen and Nitrogen atoms respectively in analogy with aurora lights. The proton streams attacked the weak spots of tectonic plates where the Coscos plate is being subducted below the North American plate. It is suggested that they induced telluric electric currents in the ground and in the magma thus caused motion and more subduction in the tectonic plates. Such motion immediately trigged the Chiapas earthquake in the near vicinity. The Bz component of the interplanetary magnetic field was highly negative, a door was opened in the magnetosphere and the proton stream easily leaked inside and targeted Mexico. This proton flare was accompanied by coronal mass ejection and extremely strong X.9.3- class X-ray flare as well as magnetic storms. On the other hand, the 19th of September Mw 7.1 Puebla central Mexico earthquake was initiated by fast solar wind coronal hole stream. Such stream if they hit ground they cause earthquakes, if they hit narrow seas like the Red Sea they cause flash floods. However if they target Oceans they initiate hurricanes.

  2. Solar-energy production and energy-efficient lighting: photovoltaic devices and white-light-emitting diodes using poly(2,7-fluorene), poly(2,7-carbazole), and poly(2,7-dibenzosilole) derivatives.

    Science.gov (United States)

    Beaupré, Serge; Boudreault, Pierre-Luc T; Leclerc, Mario

    2010-02-23

    World energy needs grow each year. To address global warming and climate changes the search for renewable energy sources with limited greenhouse gas emissions and the development of energy-efficient lighting devices are underway. This Review reports recent progress made in the synthesis and characterization of conjugated polymers based on bridged phenylenes, namely, poly(2,7-fluorene)s, poly(2,7-carbazole)s, and poly(2,7-dibenzosilole)s, for applications in solar cells and white-light-emitting diodes. The main strategies and remaining challenges in the development of reliable and low-cost renewable sources of energy and energy-saving lighting devices are discussed.

  3. Flare Seismology from SDO Observations

    Science.gov (United States)

    Lindsey, Charles; Martinez Oliveros, Juan Carlos; Hudson, Hugh

    2011-10-01

    Some flares release intense seismic transients into the solar interior. These transients are the sole instance we know of in which the Sun's corona exerts a conspicuous influence on the solar interior through flares. The desire to understand this phenomenon has led to ambitious efforts to model the mechanisms by which energy stored in coronal magnetic fields drives acoustic waves that penetrate deep into the Sun's interior. These mechanisms potentially involve the hydrodynamic response of the chromosphere to thick-target heating by high-energy particles, radiative exchange in the chromosphere and photosphere, and Lorentz-force transients to account for acoustic energies estimated up to at 5X10^27 erg and momenta of order 6X10^19 dyne sec. An understanding of these components of flare mechanics promises more than a powerful diagnostic for local helioseismology. It could give us fundamental new insight into flare mechanics themselves. The key is appropriate observations to match the models. Helioseismic observations have identified the compact sources of transient seismic emission at the foot points of flares. The Solar Dynamics Observatory is now giving us high quality continuum-brightness and Doppler observations of acoustically active flares from HMI concurrent with high-resolution EUV observations from AIA. Supported by HXR observations from RHESSI and a broad variety of other observational resources, the SDO promises a leading role in flare research in solar cycle 24.

  4. Hα and Hβ emission in a C3.3 solar flare: comparison between observations and simulations

    Science.gov (United States)

    Zuccarello, F.; Simoes, P. J. D. A.; Capparelli, V.; Fletcher, L.; Romano, P.; Mathioudakis, M.; Cauzzi, G.; Carlsson, M.; Kuridze, D.; Keys, P.

    2017-12-01

    This work is based on the analysis of an extremely rare set of simultaneous observations of a C3.3 solar flare in the Hα and Hβ lines at high spatial and temporal resolution, which were acquired at the Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22) made at various wavelengths along the Hα line profile by the Interferometric Bidimensional Spectrometer (IBIS) and in the Hβ with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband imager are analyzed to obtain the intensity evolution. The analysis shows that Hα and Hβ intensity excesses in three identified flare footpoints are well correlated in time. In the stronger footpoints, the typical value of the the Hα/Hβ intensity ratio observed is ˜ 0.4 - 0.5, in broad agreement with values obtained from a RADYN non-LTE simulation driven by an electron beam with parameters constrained by observations. The weaker footpoint has a larger Hα/Hβ ratio, again consistent with a RADYN simulation but with a smaller energy flux.

  5. Solar Flare Five-Day Predictions from Quantum Detectors of Dynamical Space Fractal Flow Turbulence: Gravitational Wave Diminution and Earth Climate Cooling

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2014-10-01

    Full Text Available Space speed fluctuations, which have a 1 / f spectrum, are shown to be the cause of solar flares. The direction and magnitude of the space flow has been detected from numer- ous different experimental techniques, and is close to the normal to the plane of the ecliptic. Zener diode data shows that the fluctuations in the space speed closely match the Sun Solar Cycle 23 flare count, and reveal that major solar flares follow major space speed fluctuations by some 6 days. This implies that a warning period of some 5 days in predicting major solar flares is possible using such detectors. This has significant conse- quences in being able to protect various spacecraft and Earth located electrical systems from the subsequent arrival of ejected plasma from a solar flare. These space speed fluctuations are the actual gravitational waves, and have a significant magnitude. This discovery is a significant application of the dynamical space phenomenon and theory. We also show that space flow turbulence impacts on the Earth’s climate, as such tur- bulence can input energy into systems, which is the basis of the Zener Diode Quantum Detector. Large scale space fluctuations impact on both the sun and the Earth, and as well explain temperature correlations with solar activity, but that the Earth temperatures are not caused by such solar activity. This implies that the Earth climate debate has been missing a key physical process. Observed diminishing gravitational waves imply a cooling epoch for the Earth for the next 30 years.

  6. Long Duration Gamma-Ray Flares & Solar Energetic Particles — Is there a Connection?

    Science.gov (United States)

    de Nolfo, G. A.; Boezio, M.; Bruno, A.; Christian, E. R.; Martucci, M.; Mergè, M.; Munini, R.; Ricci, M.; Ryan, J. M.; Share, G.; Stochaj, S.

    2017-12-01

    Little is known still about the origin of the high-energy and sustained emission from Long Duration Gamma-Ray Flares (LDGRFs), identified with Compton Gamma-Ray Observatory (CGRO), the Solar Maximum Mission (SMM), and now Fermi. Though Fermi/LAT has identified dozens of flares with LDGRF emission, the nature of this emission has been a challenge to explain both due to the extreme energies and long durations. The highest energy emission has generally been attributed to pion production from the interaction of high-energy protons with the ambient matter, suggesting that particle acceleration occurs over large volumes extending high in the corona, either from stochastic acceleration within large coronal loops or from back precipitation from CME-driven shocks. It is possible to test these models by making direct comparisons between the accelerated ion population at the flare derived from the observations of Fermi/LAT with PAMELA measurements of solar energetic particles in the energy range corresponding to the pion-related emission observed with Fermi. For nearly a dozen SEP events, we compare the two populations (SEPs in space and the interacting population at the Sun) and discuss the implications in terms of particle acceleration and transport models.

  7. Evidence for explosive chromospheric evaporation in a solar flare observed with SMM

    Science.gov (United States)

    Zarro, D. M.; Saba, J. L. R.; Strong, K. T.; Canfield, R. C.; Metcalf, T.

    1986-01-01

    SMM soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflow motions, was observed in the coronal Ca XIX line during the soft X-ray rise phase. H-alpha redshifts, indicative of downward motions, were observed simultaneously in bright flare kernels during the period of hard X-ray emission. It is shown that, to within observational errors, the impulsive phase momentum transported by the upflowing soft X-ray plasma is equivalent to that of the downward moving chromospheric material.

  8. Multi-wavelength imaging of solar plasma. High-beta disruption model of solar flares

    International Nuclear Information System (INIS)

    Shibasaki, Kiyoto

    2007-01-01

    Solar atmosphere is filled with plasma and magnetic field. Activities in the atmosphere are due to plasma instabilities in the magnetic field. To understand the physical mechanisms of activities / instabilities, it is necessary to know the physical conditions of magnetized plasma, such as temperature, density, magnetic field, and their spatial structures and temporal developments. Multi-wavelength imaging is essential for this purpose. Imaging observations of the Sun at microwave, X-ray, EUV and optical ranges are routinely going on. Due to free exchange of original data among solar physics and related field communities, we can easily combine images covering wide range of spectrum. Even under such circumstances, we still do not understand the cause of activities in the solar atmosphere well. The current standard model of solar activities is based on magnetic reconnection: release of stored magnetic energy by reconnection is the cause of solar activities on the Sun such as solar flares. However, recent X-ray, EUV and microwave observations with high spatial and temporal resolution show that dense plasma is involved in activities from the beginning. Based on these observations, I propose a high-beta model of solar activities, which is very similar to high-beta disruptions in magnetically confined fusion experiments. (author)

  9. Transient behavior of flare-associated solar wind. II - Gas dynamics in a nonradial open field region

    Science.gov (United States)

    Nagai, F.

    1984-01-01

    Transient behavior of flare-associated solar wind in the nonradial open field region is numerically investigated, taking into account the thermal and dynamical coupling between the chromosphere and the corona. A realistic steady solar wind is constructed which passes through the inner X-type critical point in the rapidly diverging region. The wind speed shows a local maximum at the middle, O-type, critical point. The wind's density and pressure distributions decrease abruptly in the rapidly diverging region of the flow tube. The transient behavior of the wind following flare energy deposition includes ascending and descending conduction fronts. Thermal instability occurs in the lower corona, and ascending material flows out through the throat after the flare energy input ceases. A local density distribution peak is generated at the shock front due to the pressure deficit just behind the shock front.

  10. Flare Prediction Using Photospheric and Coronal Image Data

    Science.gov (United States)

    Jonas, E.; Shankar, V.; Bobra, M.; Recht, B.

    2016-12-01

    We attempt to forecast M-and X-class solar flares using a machine-learning algorithm and five years of image data from both the Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) instruments aboard the Solar Dynamics Observatory. HMI is the first instrument to continuously map the full-disk photospheric vector magnetic field from space (Schou et al., 2012). The AIA instrument maps the transition region and corona using various ultraviolet wavelengths (Lemen et al., 2012). HMI and AIA data are taken nearly simultaneously, providing an opportunity to study the entire solar atmosphere at a rapid cadence. Most flare forecasting efforts described in the literature use some parameterization of solar data - typically of the photospheric magnetic field within active regions. These numbers are considered to capture the information in any given image relevant to predicting solar flares. In our approach, we use HMI and AIA images of solar active regions and a deep convolutional kernel network to predict solar flares. This is effectively a series of shallow-but-wide random convolutional neural networks stacked and then trained with a large-scale block-weighted least squares solver. This algorithm automatically determines which patterns in the image data are most correlated with flaring activity and then uses these patterns to predict solar flares. Using the recently-developed KeystoneML machine learning framework, we construct a pipeline to process millions of images in a few hours on commodity cloud computing infrastructure. This is the first time vector magnetic field images have been combined with coronal imagery to forecast solar flares. This is also the first time such a large dataset of solar images, some 8.5 terabytes of images that together capture over 3000 active regions, has been used to forecast solar flares. We evaluate our method using various flare prediction windows defined in the literature (e.g. Ahmed et al., 2013) and a novel per

  11. Meridional Motions and Reynolds Stress Determined by Using Kanzelhöhe Drawings and White Light Solar Images from 1964 to 2016

    Science.gov (United States)

    Ruždjak, Domagoj; Sudar, Davor; Brajša, Roman; Skokić, Ivica; Poljančić Beljan, Ivana; Jurdana-Šepić, Rajka; Hanslmeier, Arnold; Veronig, Astrid; Pötzi, Werner

    2018-04-01

    Sunspot position data obtained from Kanzelhöhe Observatory for Solar and Environmental Research (KSO) sunspot drawings and white light images in the period 1964 to 2016 were used to calculate the rotational and meridional velocities of the solar plasma. Velocities were calculated from daily shifts of sunspot groups and an iterative process of calculation of the differential rotation profiles was used to discard outliers. We found a differential rotation profile and meridional motions in agreement with previous studies using sunspots as tracers and conclude that the quality of the KSO data is appropriate for analysis of solar velocity patterns. By analyzing the correlation and covariance of meridional velocities and rotation rate residuals we found that the angular momentum is transported towards the solar equator. The magnitude and latitudinal dependence of the horizontal component of the Reynolds stress tensor calculated is sufficient to maintain the observed solar differential rotation profile. Therefore, our results confirm that the Reynolds stress is the dominant mechanism responsible for transport of angular momentum towards the solar equator.

  12. What can He II 304 Å tell us about transient seismic emission from solar flares?

    Science.gov (United States)

    Lindsey, C.; Donea, A. C.

    2017-10-01

    After neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations-under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients-similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

  13. Evidence of significant energy input in the late phase of a solar flare from NuSTAR x-ray observations

    DEFF Research Database (Denmark)

    Kuhar, Matej; Krucker, Säm; Hannah, Iain G.

    2017-01-01

    -size solar flare 1 day before the observations, at ∼18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused......We present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory (SDO)/AIA and FOXSI-2 sounding rocket observations. The active region produced a medium...... by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8–4.6 MK, emission measure (0.3–1.8) × 1046 cm−3, and density estimated at (2.5–6.0) × 108 cm−3. The observed AIA fluxes...

  14. ENHANCEMENT OF A SUNSPOT LIGHT WALL WITH EXTERNAL DISTURBANCES

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuhong; Zhang, Jun [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Erdélyi, Robert, E-mail: shuhongyang@nao.cas.cn [Solar Physics and Space Plasma Research Centre, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2016-12-20

    Based on the Interface Region Imaging Spectrograph observations, we study the response of a solar sunspot light wall to external disturbances. A flare occurrence near the light wall caused material to erupt from the lower solar atmosphere into the corona. Some material falls back to the solar surface and hits the light bridge (i.e., the base of the light wall), then sudden brightenings appear at the wall base followed by the rise of wall top, leading to an increase of the wall height. Once the brightness of the wall base fades, the height of the light wall begins to decrease. Five hours later, another nearby flare takes place, and a bright channel is formed that extends from the flare toward the light bridge. Although no obvious material flow along the bright channel is found, some ejected material is conjectured to reach the light bridge. Subsequently, the wall base brightens and the wall height begins to increase again. Once more, when the brightness of the wall base decays, the wall top fluctuates to lower heights. We suggest, based on the observed cases, that the interaction of falling material and ejected flare material with the light wall results in the brightenings of wall base and causes the height of the light wall to increase. Our results reveal that the light wall can be not only powered by the linkage of p -mode from below the photosphere, but may also be enhanced by external disturbances, such as falling material.

  15. Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014

    Science.gov (United States)

    Sharykin, I. N.; Kuznetsov, A. A.; Myshyakov, I. I.

    2018-02-01

    This work demonstrates the possibility of magnetic-field topology investigations using microwave polarimetric observations. We study a solar flare of GOES M1.7 class that occurred on 11 February, 2014. This flare revealed a clear signature of spatial inversion of the radio-emission polarization sign. We show that the observed polarization pattern can be explained by nonthermal gyrosynchrotron emission from the twisted magnetic structure. Using observations of the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Observatory, Radio Solar Telescope Network, and Solar Dynamics Observatory, we have determined the parameters of nonthermal electrons and thermal plasma and identified the magnetic structure where the flare energy release occurred. To reconstruct the coronal magnetic field, we use nonlinear force-free field (NLFFF) and potential magnetic-field approaches. Radio emission of nonthermal electrons is simulated by the GX Simulator code using the extrapolated magnetic field and the parameters of nonthermal electrons and thermal plasma inferred from the observations; the model radio maps and spectra are compared with observations. We have found that the potential-magnetic-field approach fails to explain the observed circular polarization pattern; on the other hand, the Stokes-V map is successfully explained by assuming nonthermal electrons to be distributed along the twisted magnetic structure determined by the NLFFF extrapolation approach. Thus, we show that the radio-polarization maps can be used for diagnosing the topology of the flare magnetic structures where nonthermal electrons are injected.

  16. Study of coronal and interplanetary propagation of solar particles following the E450 solar flare on July 29, 1973

    International Nuclear Information System (INIS)

    Gombosi, T.; Somogyi, A.J.; Kolesov, G.Ya.; Kurt, V.G.; Kuzhevskii, B.M.; Logachev, Yu.I.; Savenko, I.A.; Shestopalov, I.P.

    1977-01-01

    Intensity profiles of protons and electrons of various energies measured onboard the high-apogee Prognos-3 satellite are analysed as well as the energy balance between the various flare produced phenomena. The general behaviour of the solar particle event following the 3B flare at E45 0 can be well described in terms of a simple model which takes into account coronal diffusion with a leakage time and a Krimigis' type interplanetary diffusion. The results suggest an inverse dependence of coronal diffusion coefficient on rigidity. (author)

  17. Can we explain atypical solar flares?

    Science.gov (United States)

    Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G.

    2015-02-01

    Context. We used multiwavelength high-resolution data from ARIES, THEMIS, and SDO instruments to analyze a non-standard, C3.3 class flare produced within the active region NOAA 11589 on 2012 October 16. Magnetic flux emergence and cancellation were continuously detected within the active region, the latter leading to the formation of two filaments. Aims: Our aim is to identify the origins of the flare taking the complex dynamics of its close surroundings into account. Methods: We analyzed the magnetic topology of the active region using a linear force-free field extrapolation to derive its 3D magnetic configuration and the location of quasi-separatrix layers (QSLs), which are preferred sites for flaring activity. Because the active region's magnetic field was nonlinear force-free, we completed a parametric study using different linear force-free field extrapolations to demonstrate the robustness of the derived QSLs. Results: The topological analysis shows that the active region presented a complex magnetic configuration comprising several QSLs. The considered data set suggests that an emerging flux episode played a key role in triggering the flare. The emerging flux probably activated the complex system of QSLs, leading to multiple coronal magnetic reconnections within the QSLs. This scenario accounts for the observed signatures: the two extended flare ribbons developed at locations matched by the photospheric footprints of the QSLs and were accompanied with flare loops that formed above the two filaments, which played no important role in the flare dynamics. Conclusions: This is a typical example of a complex flare that can a priori show standard flare signatures that are nevertheless impossible to interpret with any standard model of eruptive or confined flare. We find that a topological analysis, however, permitted us to unveil the development of such complex sets of flare signatures. Movies associated to Figs. 1, 3, and 9 are only available at the CDS via

  18. Electron density diagnostics in the 10-100 A interval for a solar flare

    Science.gov (United States)

    Brown, W. A.; Bruner, M. E.; Acton, L. W.; Mason, H. E.

    1986-01-01

    Electron density measurements from spectral-line diagnostics are reported for a solar flare on July 13, 1982, 1627 UT. The spectrogram, covering the 10-95 A interval, contained usable lines of helium-like ions C V, N VI, O VII, and Ne IX which are formed over the temperature interval 0.7-3.5 x 10 to the 6th K. In addition, spectral-line ratios of Si IX, Fe XIV, and Ca XV were compared with new theoretical estimates of their electron density sensitivity to obtain additional electron density diagnostics. An electron density of 3 x 10 to the 10th/cu cm was obtained. The comparison of these results from helium-like and other ions gives confidence in the utility of these tools for solar coronal analysis and will lead to a fuller understanding of the phenomena observed in this flare.

  19. Multiwavelength analysis of a well observed flare from SMM. [Solar Maximum Mission

    Science.gov (United States)

    Macneice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Dennis, B. R.

    1985-01-01

    Observations of an M 1.4 flare which began at 17:00 UT on November 12, 1980, are presented and analyzed. Ground based H-alpha and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission satellite. The preflare phase was marked by a gradual brightening of the flare site in O v and the disappearance of an H-alpha filament. Filament ejecta were seen in O v moving southward at a speed of about 60 km/s, before the impulsive phase. The flare loop footpoints brightened in H-alpha and the Ca XIX resonance line broadened dramatically 2 min before the impulsive phase. Nonthermal hard X-ray emission was detected from the loop footpoints during the impulsive phase, while during the same period blue-shifts corresponding to upflows of 200-250 km/s were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. Two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona are considered, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.

  20. Transient behavior of a flare-associated solar wind. I - Gas dynamics in a radial open field region

    Science.gov (United States)

    Nagai, F.

    1984-01-01

    A numerical investigation is conducted into the way in which a solar wind model initially satisfying both steady state and energy balance conditions is disturbed and deformed, under the assumption of heating that correspoonds to the energy release of solar flares of an importance value of approximately 1 which occur in radial open field regions. Flare-associated solar wind transient behavior is modeled for 1-8 solar radii. The coronal temperature around the heat source region rises, and a large thermal conductive flux flows inward to the chromosphere and outward to interplanetary space along field lines. The speed of the front of expanding chromospheric material generated by the impingement of the conduction front on the upper chromosphere exceeds the local sound velocity in a few minutes and eventually exceeds 100 million cm/sec.

  1. Radio observations of the fine structure inside a post-CME current sheet

    International Nuclear Information System (INIS)

    Gao Guan-Nan; Wang Min; Lin Jun; Kliem Berhard; Wu Ning; Tan Cheng-Ming; Su Yang

    2014-01-01

    A solar radio burst was observed in a coronal mass ejection/flare event by the Solar Broadband Radio Spectrometer at the Huairou Solar Observing Station on 2004 December 1. The data exhibited various patterns of plasma motions, suggestive of the interaction between sunward moving plasmoids and the flare loop system during the impulsive phase of the event. In addition to the radio data, the associated white-light, Hα, extreme ultraviolet light, and soft and hard X-rays were also studied. (mini-volume: solar radiophysics — recent results on observations and theories)

  2. Kepler Data on KIC 7341653: A Nearby M Dwarf with Monster Flares and a Phase-coherent Variability

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, Valeri V. [US Naval Observatory, 3450 Massachusetts Ave. NW, Washington DC 20392-5420 (United States); Goldin, Alexey, E-mail: valeri.makarov@navy.mil, E-mail: alexey.goldin@gmail.com [Teza Technology, 150 N Michigan Ave., Chicago IL 60601 (United States)

    2017-08-20

    KIC 7341653 is one of several late-type M dwarfs observed by the main mission of Kepler with peculiar infrared colors placing them in the domain of suspected young stellar objects (YSO). It is likely associated with a powerful X-ray emitter with X-ray flares. Kepler light curves reveal two distinct types of activity: frequent flares lasting from less than 30 minutes to a few hours, and a periodic variability with a period of 0.5463441(7) days. The largest detected flare increased the flux in the Kepler passband by a factor of 2.8 and released an estimated 4 × 10{sup 34} erg of energy in the Kepler band. Segmented periodogram analysis reveals that the amplitude of the periodic variation was subject to secular changes, dropping from peak values around 20 ppt to below 5 ppt toward the end of the mission, while the phase varied periodically with an amplitude of 0.15 rad and period 362(3) days. Two possible interpretations of the phase periodicity are discussed: a migrating long-lived photospheric spot, and a Doppler frequency shift generated by a solar-mass faint companion, such as a white dwarf.

  3. Reconstruction of a Large-scale Pre-flare Coronal Current Sheet Associated with a Homologous X-shaped Flare

    Science.gov (United States)

    Jiang, Chaowei; Yan, Xiaoli; Feng, Xueshang; Duan, Aiying; Hu, Qiang; Zuo, Pingbing; Wang, Yi

    2017-11-01

    As a fundamental magnetic structure in the solar corona, electric current sheets (CSs) can form either prior to or during a solar flare, and they are essential for magnetic energy dissipation in the solar corona because they enable magnetic reconnection. However, the static reconstruction of a CS is rare, possibly due to limitations that are inherent in the available coronal field extrapolation codes. Here we present the reconstruction of a large-scale pre-flare CS in solar active region 11967 using an MHD-relaxation model constrained by the SDO/HMI vector magnetogram. The CS is associated with a set of peculiar homologous flares that exhibit unique X-shaped ribbons and loops occurring in a quadrupolar magnetic configuration.This is evidenced by an ’X’ shape, formed from the field lines traced from the CS to the photosphere. This nearly reproduces the shape of the observed flare ribbons, suggesting that the flare is a product of the dissipation of the CS via reconnection. The CS forms in a hyperbolic flux tube, which is an intersection of two quasi-separatrix layers. The recurrence of the X-shaped flares might be attributed to the repetitive formation and dissipation of the CS, as driven by the photospheric footpoint motions. These results demonstrate the power of a data-constrained MHD model in reproducing a CS in the corona as well as providing insight into the magnetic mechanism of solar flares.

  4. Aperture synthesis observations of solar and stellar radio emission

    International Nuclear Information System (INIS)

    Bastian, T.S.

    1987-01-01

    The work presented in this thesis relied upon the radio astronomical instrument, The Very Large Array. The thesis is divided into three major sections. In the first the author applied maximum entropy-type image reconstruction techniques, using both single dish and iterferometer data, to generate full disk images of the Sun at a wavelength λ ∼ 21 cm. Using a set of six such images obtained during the Sun's decline from sunspot maximum to minimum, he has noted a number of previously unreported phenomena. Among these: (1) a systematic decrease in quiet Sun's brightness temperature as it declined to minimum; (2) a systematic decrease in the Sun's radius at 21 cm; (3) evidence for the evolution of polar coronal holes during the course of the solar cycle. The observed variation, though not noted previously at radio wavelengths, is entirely consistent with white light K coronagraph data. The results reported here explain the conflicting nature of a number of past observations. In the second section of the thesis, he presents the results of a long term survey of magnetic cataclysmic variables (CVs). Cataclysmic variables are close binary systems which contain a white dwarf accreting mass from a late-type secondary, typically a dwarf of spectral type, G, K, or M. The survey resulted in the detection of two out of the eighteen systems observed. In the third section of the thesis, he presents new results on flare stars in the solar neighborhood and in the Pleiades. He has successfully employed the technique of dynamic spectroscopy to constrain the mechanisms(s) for radio flaring on other stars. The second part of section three is devoted to a search for radio emission from flare stars in the Pleiades which was motivated by the evolutionary questions raised by flare stars and the Pleiades lower main sequence

  5. Effect of solar flare ans sunspot numbers on the intensity of 5577A line in the night airglow

    International Nuclear Information System (INIS)

    Kundu, N.; Ghosh, S.N.

    1981-01-01

    The effects of solar flare and sunspot number on the intensity of 5577 A line emission are presented. The time lag between the occurrence of a flare and the enhancement of 5577 A line intensity is determined by observing the intensity of the line on three successive nights- the night preceding the flare and the two nights following it. The velocity of the solar corpuscles is then calculated. The value obtained at Allahabad (2400 Km/sec) is in agreement with the De Jager's prediction for explosive flare. Day-to-day analyses of the observations taken at Allahabad exhibit high correlation of the intensity of 5577 A line emission with sunspot number. Also, correlation is found for the intensity of 5577 A with the change in sunspot number (DELTA R) from the day preceding the night of observation to the day following it. The intensity appears to vary with the magnetic field produced by the sunspot and not with the spot area. (author)

  6. Solar Flare Prediction Science-to-Operations: the ESA/SSA SWE A-EFFort Service

    Science.gov (United States)

    Georgoulis, Manolis K.; Tziotziou, Konstantinos; Themelis, Konstantinos; Magiati, Margarita; Angelopoulou, Georgia

    2016-07-01

    We attempt a synoptical overview of the scientific origins of the Athens Effective Solar Flare Forecasting (A-EFFort) utility and the actions taken toward transitioning it into a pre-operational service of ESA's Space Situational Awareness (SSA) Programme. The preferred method for solar flare prediction, as well as key efforts to make it function in a fully automated environment by coupling calculations with near-realtime data-downloading protocols (from the Solar Dynamics Observatory [SDO] mission), pattern recognition (solar active-region identification) and optimization (magnetic connectivity by simulated annealing) will be highlighted. In addition, the entire validation process of the service will be described, with its results presented. We will conclude by stressing the need for across-the-board efforts and synergistic work in order to bring science of potentially limited/restricted interest into realizing a much broader impact and serving the best public interests. The above presentation was partially supported by the ESA/SSA SWE A-EFFort project, ESA Contract No. 4000111994/14/D/MRP. Special thanks go to the ESA Project Officers R. Keil, A. Glover, and J.-P. Luntama (ESOC), M. Bobra and C. Balmer of the SDO/HMI team at Stanford University, and M. Zoulias at the RCAAM of the Academy of Athens for valuable technical help.

  7. Lower Ionosphere Sensitivity to Solar X-ray Flares Over a Complete Solar Cycle Evaluated From VLF Signal Measurements

    Science.gov (United States)

    Macotela, Edith L.; Raulin, Jean-Pierre; Manninen, Jyrki; Correia, Emília; Turunen, Tauno; Magalhães, Antonio

    2017-12-01

    The daytime lower ionosphere behaves as a solar X-ray flare detector, which can be monitored using very low frequency (VLF) radio waves that propagate inside the Earth-ionosphere waveguide. In this paper, we infer the lower ionosphere sensitivity variation over a complete solar cycle by using the minimum X-ray fluence (FXmin) necessary to produce a disturbance of the quiescent ionospheric conductivity. FXmin is the photon energy flux integrated over the time interval from the start of a solar X-ray flare to the beginning of the ionospheric disturbance recorded as amplitude deviation of the VLF signal. FXmin is computed for ionospheric disturbances that occurred in the time interval of December-January from 2007 to 2016 (solar cycle 24). The computation of FXmin uses the X-ray flux in the wavelength band below 0.2 nm and the amplitude of VLF signals transmitted from France (HWU), Turkey (TBB), and U.S. (NAA), which were recorded in Brazil, Finland, and Peru. The main result of this study is that the long-term variation of FXmin is correlated with the level of solar activity, having FXmin values in the range (1 - 12) × 10-7 J/m2. Our result suggests that FXmin is anticorrelated with the lower ionosphere sensitivity, confirming that the long-term variation of the ionospheric sensitivity is anticorrelated with the level of solar activity. This result is important to identify the minimum X-ray fluence that an external source of ionization must overcome in order to produce a measurable ionospheric disturbance during daytime.

  8. Diagnostics of electron-heated solar flare models. III - Effects of tapered loop geometry and preheating

    Science.gov (United States)

    Emslie, A. G.; Li, Peng; Mariska, John T.

    1992-01-01

    A series of hydrodynamic numerical simulations of nonthermal electron-heated solar flare atmospheres and their corresponding soft X-ray Ca XIX emission-line profiles, under the conditions of tapered flare loop geometry and/or a preheated atmosphere, is presented. The degree of tapering is parameterized by the magnetic mirror ratio, while the preheated atmosphere is parameterized by the initial upper chromospheric pressure. In a tapered flare loop, it is found that the upward motion of evaporated material is faster compared with the case where the flare loop is uniform. This is due to the diverging nozzle seen by the upflowing material. In the case where the flare atmosphere is preheated and the flare geometry is uniform, the response of the atmosphere to the electron collisional heating is slow. The upward velocity of the hydrodynamic gas is reduced due not only to the large coronal column depth, but also to the increased inertia of the overlying material. It is concluded that the only possible electron-heated scenario in which the predicted Ca XIX line profiles agree with the BCS observations is when the impulsive flare starts in a preheated dense corona.

  9. Effect of solar flare on the equatorial electrojet in eastern Brazil region

    Indian Academy of Sciences (India)

    The effect of solar flare, sudden commencement of magnetic storm and of the disturbances ring current on the equatorial electrojet in the Eastern Brazil region, where the ground magnetic declination is as large as 20∘W is studied based on geomagnetic data with one minute resolution from Bacabal during ...

  10. Spatial and temporal structures of impulsive bursts from solar flares observed in UV and hard X-rays

    Science.gov (United States)

    Cheng, C.-C.; Tandberg-Hanssen, E.; Bruner, E. C.; Orwig, L.; Frost, K. J.; Kenny, P. J.; Woodgate, B. E.; Shine, R. A.

    1981-01-01

    New observations are presented of impulsive UV and hard X-rays bursts in two solar flares obtained with instruments on Solar Maximum Mission. The UV bursts were observed in the Si IV and O IV emission lines, whose intensity ratio is density-sensitive. By comparing the spatially resolved Si IV/O IV observations with the corresponding hard X-ray observations, it is possible to study their spatial and temporal relationships. For one flare, the individual component spikes in the multiply peaked hard X-ray burst can be identified with different discrete Si IV/O IV flaring kernels of size 4 arcsec x 4 arcsec or smaller, which brighten up sequentially in time. For the other, many Si IV/O kernels, widely distributed over a large area, show impulsive bursts at the same time, which correlate with the main peak of the impulsive hard X-ray burst. The density of the flaring Si IV/O IV kernels is in the range from 5 x 10 to the 12th-13th/cu cm.

  11. STEREO Observations of Energetic Neutral Hydrogen Atoms during the 5 December 2006 Solar Flare

    Science.gov (United States)

    Mewaldt, R. A.; Leske, R. A.; Stone, E. C.; Barghouty, A. F.; Labrador, A. W.; Cohen, C. M. S.; Cummings, A. C.; Davis, A. J.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2009-01-01

    We report the discovery of energetic neutral hydrogen atoms emitted during the X9 solar event of December 5, 2006. Beginning 1 hour following the onset of this E79 flare, the Low Energy Telescopes (LETs) on both the STEREO A and B spacecraft observed a sudden burst of 1.6 to 15 MeV protons beginning hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within 10 of the Sun, consistent with the measurement resolution. The derived emission profile at the Sun had onset and peak times remarkably similar to the GOES soft X-ray profile and continued for more than an hour. The observed arrival directions and energy spectrum argue strongly that the particle events less than 5 MeV were due to energetic neutral hydrogen atoms (ENAs). To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. Possible origins for the production of ENAs in a large solar event are considered. We conclude that the observed ENAs were most likely produced in the high corona and that charge-transfer reactions between accelerated protons and partially-stripped coronal ions are an important source of ENAs in solar events.

  12. Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients

    Science.gov (United States)

    Maxwell, A.; Dryer, M.

    1981-01-01

    An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.

  13. Characteristics of hard X-ray double sources in impulsive solar flares

    Science.gov (United States)

    Sakao, T.; Kosugi, T.; Masuda, S.; Yaji, K.; Inda-Koide, M.; Makishima, K.

    1996-01-01

    Imaging observations of solar flare hard X-ray sources with the Hard X-ray Telescope (HXT) aboard the Yohkoh satellite have revealed that hard X-ray emissions (greater than 30 ke V) originate most frequently from double sources. The double sources are located on both sides of the magnetic neutral line, suggesting that the bulk of hard X-rays is emitted from footpoints of flaring magnetic loops. We also found that hard X-rays from the double sources are emitted simultaneously within a fraction of second and that the weaker source tends to be located in the stronger magnetic field region, showing a softer spectrum. Physcial implications on the observed characteristics of the hard X-ray double sources are discussed.

  14. Plasma dynamics above solar flare soft x-ray loop tops

    Energy Technology Data Exchange (ETDEWEB)

    Doschek, G. A.; Warren, H. P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); McKenzie, D. E. [Montana State University, Bozeman, MT 59717 (United States)

    2014-06-10

    We measure non-thermal motions in flare loop tops and above the loop tops using profiles of highly ionized spectral lines of Fe XXIV and Fe XXIII formed at multimillion-degree temperatures. Non-thermal motions that may be due to turbulence or multiple flow regions along the line of sight are extracted from the line profiles. The non-thermal motions are measured for four flares seen at or close to the solar limb. The profile data are obtained using the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. The multimillion-degree non-thermal motions are between 20 and 60 km s{sup –1} and appear to increase with height above the loop tops. Motions determined from coronal lines (i.e., lines formed at about 1.5 MK) tend to be smaller. The multimillion-degree temperatures in the loop tops and above range from about 11 MK to 15 MK and also tend to increase with height above the bright X-ray-emitting loop tops. The non-thermal motions measured along the line of sight, as well as their apparent increase with height, are supported by Solar Dynamics Observatory Atmospheric Imaging Assembly measurements of turbulent velocities in the plane of the sky.

  15. Studies of Solar Flare and Interplanetary Particle Acceleration and Coordination of Ground-Based Solar Observations in Support of US and International Space Missions

    Science.gov (United States)

    Kiplinger, Alan L.

    1998-01-01

    A primary focus has been to conduct studies of particular types of hard X-ray evolution in solar flares and their associations with high energy interplanetary protons observed near Earth. Previously, two large investigations were conducted that revealed strong associations between episodes of progressive spectral hardening seen in solar events and interplanetary proton events (Kiplinger, 1995). An algorithm was developed for predicting interplanetary protons that is more accurate than those currently in use when hard X-ray spectra are available. The basic research on a third study of the remaining independent subset of Hard X-ray Burst Spectrometer (HXRBS) events randomly not selected by the original studies was completed. This third study involves independent analyses of the data by two analysts. The results echo the success of the earlier studies. Of 405 flares analyzed, 12 events were predicted to have associated interplanetary protons at the Space Environment Service Center (SESC) level. Of these, five events appear to be directly associated with SESC proton events, six other events had lower level associated proton events, and there was only one false alarm with no protons. Another study by Garcia and Kiplinger (1995) established that progressively hardening hard X-ray flares associated with interplanetary proton events are intrinsically cooler and not extremely intense in soft X-rays unless a "contaminating" large impulsive flare accompanies the hardening flare.

  16. A study of solar flare energy transport based on coordinated H-alpha and X-ray observations

    International Nuclear Information System (INIS)

    Canfield, R.C.; Wulser, J.; Zarro, D.M.; Dennis, B.R.

    1991-01-01

    The temporal evolution of the ratio between H-alpha to nonthermal hard X-ray emission was investigated using coordinated H-alpha and hard- and soft-X-ray observations of five solar flares (on May 7, June 23, June 24, and June 25, 1980 and on April 30, 1985). These observations were used to estimate the emitted flare energy flux F(H-alpha) in H-alpha, the flux of F(2O) energy deposited by nonthermal electrons with energies above 20 keV, and the pressure p(c) of soft X-ray-emitting plasma as functions of time during the impulsive phase of each flare. It was found that the F(H-alpha)/F(2O) ratio shows a power-law dependence on F(2O), with a slope that differs slightly from that predicted by the static thick-target model of solar transport. Results also indicate that the power-law dependence is modified by hydrostatic pressure effects. 25 refs

  17. A unique UV flare in the optical light curve of the quasar J004457.9+412344

    Directory of Open Access Journals (Sweden)

    Hatzidimitriou D.

    2012-12-01

    Full Text Available We found that the nova candidate J004457.9+412344 is a radio-quiet quasar at z ∼ 2. Its optical long-term light curve, covering more than half a century, shows quasar typical flux variations superimposed by a spectacular single flare lasting more than one year (observer frame. We could not find comparable light curves among the several thousand catalogued radio-quiet quasars in the stripe 82 of the Sloan Digital Sky Survey. The decreasing part of the flare light curve roughly follows a power law t−5/3. The quasar spectrum, the total energy of the flare, and the decline of the light curve are consistent with the tidal disruption of a ∼10 Mʘ giant star by a supermassive black hole of a few 108 Mʘ. We argue that the alternative explanation by gravitational microlensing is less likely, though it cannot be definitely excluded.

  18. White Light Photorefractive Phase Zone Plates

    International Nuclear Information System (INIS)

    Yuan-Mei, Gao; Si-Min, Liu

    2008-01-01

    Incoherent white light from an incandescent source is employed to fabricate volume phase zone plates in LiNbO 3 : Fe, for the first time to our knowledge, which can guide and modulate the input white light or laser light. The diffractive efficiency of the white light volume phase zone plates fabricated can reach as high as 12%. In addition, we test the volume phase zone plates by a probe beam and find that the volume phase zone plate is present in the direction perpendicular to the c-axis and absent in the direction parallel to the c-axis. This directly proves the existence of photovoltaic photorefractive anisotropy of white light

  19. COMPTEL gamma-ray observations of the C4 solar flare on 20 January 2000

    International Nuclear Information System (INIS)

    Young, C.A.; Arndt, M.B.; Bennett, K.; Winkler, C.; Connors, A.; Debrunner, H.; Diehl, R.; Rank, G.; Schoenfelder, V.; McConnell, M.; Miller, R.S.; Ryan, J.M.

    2001-01-01

    The 'Pre-SMM' (Vestrand and Miller 1998) picture of gamma-ray line (GRL) flares was that they are relatively rare events. This picture was quickly put in question with the launch of the Solar Maximum Mission (SMM). Over 100 GRL flares were seen with sizes ranging from very large GOES class events (X12) down to moderately small events (M2). It was argued by some (Bai 1986) that this was still consistent with the idea that GRL events are rare. Others, however, argued the opposite (Vestrand 1988; Cliver, Crosby and Dennis 1994), stating that the lower end of this distribution was just a function of SMM's sensitivity. They stated that the launch of the Compton Gamma-ray Observatory (CGRO) would in fact continue this distribution to show even smaller GRL flares. In response to a BACODINE cosmic gamma-ray burst alert, COMPtonTELescope on the CGRO recorded gamma rays above 1 MeV from the C4 flare at 0221 UT 20 January 2000. This event, though at the limits of COMPTEL's sensitivity, clearly shows a nuclear line excess above the continuum. Using new spectroscopy techniques we were able to resolve individual lines. This has allowed us to make a basic comparison of this event with the GRL flare distribution from SMM and also compare this flare with a well-observed large GRL flare seen by OSSE

  20. MASC: Magnetic Activity of the Solar Corona

    Science.gov (United States)

    Auchere, Frederic; Fineschi, Silvano; Gan, Weiqun; Peter, Hardi; Vial, Jean-Claude; Zhukov, Andrei; Parenti, Susanna; Li, Hui; Romoli, Marco

    orientation is primarily based on extrapolations from photospheric observations, not from direct measurements. These extrapolations require strong assumptions on critical but unobserved quantities and thus fail to accurately reproduce the complex topologies inferred from remote-sensing observations of coronal structures in white light, EUV, and X-rays. Direct measurements of the coronal magnetic field are also clearly identified by the international heliophysics community as a key element susceptible to lead to major breakthroughs in the understanding of our star. MASC is thus designed to answer the following top-level scientific questions: 1. What is the global magnetic field configuration in the corona? 2. What is the role of the magnetic field in the triggering of flares and CMEs? 3. What is the role of the magnetic field in the acceleration mechanisms of the solar winds? 4. What is the energy spectrum and in particular what are the highest energies to which charged particles can be accelerated in the solar corona? MASC will address these fundamental questions with a suite of instruments composed of an X-ray spectrometer, a UV / EUV imager, and a coronagraph working in the visible and at Lyman alpha. The spectrometer will provide information on the energetics of solar flares, in particular at very high energies of accelerated particles. The UV / EUV imager will provide constraints on the temperature of the flaring and non-flaring corona. The coronagraph will provide the number density of free electrons in the corona, maps of the outflow velocity of neutral hydrogen, and measurements of the coronal magnetic field, via the Hanle effect. These measurements will be performed at all steps of the flare-CME processes, thus providing a detailed picture of the solar coronal dynamics in the quiet and eruptive periods.

  1. Flare energetics

    Science.gov (United States)

    Wu, S. T.; Dejager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.

    1986-01-01

    In this investigation of flare energetics, researchers sought to establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. To achieve this goal, they chose five flares in 1980 that were well observed with instruments on the Solar Maximum Mission, and with other space-borne and ground-based instruments. The events were chosen to represent various types of flares. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energics of these flares. The role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model is discussed. Finally, a critique of the current understanding of flare energetics and the methods used to determine various energetics terms is outlined, and possible future directions of research in this area are suggested.

  2. On the Generation of Hydrodynamic Shocks by Mixed Beams and Occurrence of Sunquakes in Flares

    Science.gov (United States)

    Zharkova, Valentina; Zharkov, Sergei

    2015-11-01

    Observations of solar flares with sunquakes by space- and ground-based instruments reveal essentially different dynamics of seismic events in different flares. Some sunquakes are found to be closely associated with the locations of hard X-ray (HXR) and white-light (WL) emission, while others are located outside either of them. In this article we investigate possible sources causing a seismic response in a form of hydrodynamic shocks produced by the injection of mixed (electron plus proton) beams, discuss the velocities of these shocks, and the depths where they deposit the bulk of their energy and momentum. The simulation of hydrodynamic shocks in flaring atmospheres induced by electron-rich and proton-rich beams reveals that the linear depth of the shock termination is shifted beneath the level of the quiet solar photosphere on a distance from 200 to 5000 km. The parameters of these atmospheric hydrodynamic shocks are used as initial condition for another hydrodynamic model developed for acoustic-wave propagation in the solar interior (Zharkov, Mon. Not. Roy. Astron. Soc. 431, 3414, 2013). The model reveals that the depth of energy and momentum deposition by the atmospheric shocks strongly affects the propagation velocity of the acoustic-wave packet in the interior. The locations of the first bounces from the photosphere of acoustic waves generated in the vicinity of a flare are seen as ripples on the solar surface, or sunquakes. Mixed proton-dominated beams are found to produce a strong supersonic shock at depths 200 - 300 km under the level of the quiet-Sun photosphere and in this way produce well-observable acoustic waves, while electron-dominated beams create a slightly supersonic shock propagating down to 5000 km under the photosphere. This shock can only generate acoustic waves at the top layers beneath the photosphere since the shock velocity very quickly drops below the local sound speed. The distance Δ of the first bounce of the generated acoustic waves

  3. Solar Flare Prediction Model with Three Machine-learning Algorithms using Ultraviolet Brightening and Vector Magnetograms

    Science.gov (United States)

    Nishizuka, N.; Sugiura, K.; Kubo, Y.; Den, M.; Watari, S.; Ishii, M.

    2017-02-01

    We developed a flare prediction model using machine learning, which is optimized to predict the maximum class of flares occurring in the following 24 hr. Machine learning is used to devise algorithms that can learn from and make decisions on a huge amount of data. We used solar observation data during the period 2010-2015, such as vector magnetograms, ultraviolet (UV) emission, and soft X-ray emission taken by the Solar Dynamics Observatory and the Geostationary Operational Environmental Satellite. We detected active regions (ARs) from the full-disk magnetogram, from which ˜60 features were extracted with their time differentials, including magnetic neutral lines, the current helicity, the UV brightening, and the flare history. After standardizing the feature database, we fully shuffled and randomly separated it into two for training and testing. To investigate which algorithm is best for flare prediction, we compared three machine-learning algorithms: the support vector machine, k-nearest neighbors (k-NN), and extremely randomized trees. The prediction score, the true skill statistic, was higher than 0.9 with a fully shuffled data set, which is higher than that for human forecasts. It was found that k-NN has the highest performance among the three algorithms. The ranking of the feature importance showed that previous flare activity is most effective, followed by the length of magnetic neutral lines, the unsigned magnetic flux, the area of UV brightening, and the time differentials of features over 24 hr, all of which are strongly correlated with the flux emergence dynamics in an AR.

  4. Solar Flare Prediction Model with Three Machine-learning Algorithms using Ultraviolet Brightening and Vector Magnetograms

    International Nuclear Information System (INIS)

    Nishizuka, N.; Kubo, Y.; Den, M.; Watari, S.; Ishii, M.; Sugiura, K.

    2017-01-01

    We developed a flare prediction model using machine learning, which is optimized to predict the maximum class of flares occurring in the following 24 hr. Machine learning is used to devise algorithms that can learn from and make decisions on a huge amount of data. We used solar observation data during the period 2010–2015, such as vector magnetograms, ultraviolet (UV) emission, and soft X-ray emission taken by the Solar Dynamics Observatory and the Geostationary Operational Environmental Satellite . We detected active regions (ARs) from the full-disk magnetogram, from which ∼60 features were extracted with their time differentials, including magnetic neutral lines, the current helicity, the UV brightening, and the flare history. After standardizing the feature database, we fully shuffled and randomly separated it into two for training and testing. To investigate which algorithm is best for flare prediction, we compared three machine-learning algorithms: the support vector machine, k-nearest neighbors (k-NN), and extremely randomized trees. The prediction score, the true skill statistic, was higher than 0.9 with a fully shuffled data set, which is higher than that for human forecasts. It was found that k-NN has the highest performance among the three algorithms. The ranking of the feature importance showed that previous flare activity is most effective, followed by the length of magnetic neutral lines, the unsigned magnetic flux, the area of UV brightening, and the time differentials of features over 24 hr, all of which are strongly correlated with the flux emergence dynamics in an AR.

  5. Solar Flare Prediction Model with Three Machine-learning Algorithms using Ultraviolet Brightening and Vector Magnetograms

    Energy Technology Data Exchange (ETDEWEB)

    Nishizuka, N.; Kubo, Y.; Den, M.; Watari, S.; Ishii, M. [Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology, 4-2-1, Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan); Sugiura, K., E-mail: nishizuka.naoto@nict.go.jp [Advanced Speech Translation Research and Development Promotion Center, National Institute of Information and Communications Technology (Japan)

    2017-02-01

    We developed a flare prediction model using machine learning, which is optimized to predict the maximum class of flares occurring in the following 24 hr. Machine learning is used to devise algorithms that can learn from and make decisions on a huge amount of data. We used solar observation data during the period 2010–2015, such as vector magnetograms, ultraviolet (UV) emission, and soft X-ray emission taken by the Solar Dynamics Observatory and the Geostationary Operational Environmental Satellite . We detected active regions (ARs) from the full-disk magnetogram, from which ∼60 features were extracted with their time differentials, including magnetic neutral lines, the current helicity, the UV brightening, and the flare history. After standardizing the feature database, we fully shuffled and randomly separated it into two for training and testing. To investigate which algorithm is best for flare prediction, we compared three machine-learning algorithms: the support vector machine, k-nearest neighbors (k-NN), and extremely randomized trees. The prediction score, the true skill statistic, was higher than 0.9 with a fully shuffled data set, which is higher than that for human forecasts. It was found that k-NN has the highest performance among the three algorithms. The ranking of the feature importance showed that previous flare activity is most effective, followed by the length of magnetic neutral lines, the unsigned magnetic flux, the area of UV brightening, and the time differentials of features over 24 hr, all of which are strongly correlated with the flux emergence dynamics in an AR.

  6. Initiation and early evolution of a Coronal Mass Ejection on May 13, 2009 from EUV and white-light observations

    Science.gov (United States)

    Reva, Anton; Kuzin, Sergey; Bogachev, Sergey; Ulyanov, Artyom

    In this talk we present results of the observations of a CME, which occurred on May 13, 2009. The most important feature of these observations is that the CME was observed from the very beginning stage (the solar surface) up to the distance of 15 solar radii (R_⊙). Below 2 R_⊙ we used the data from the TESIS EUV telescopes obtained in the Fe 171 Å and He 304 Å lines, and above 2 R_⊙ we used the observations of the LASCO C2 and C3 coronagraphs. Using data of these three instruments, we have studied the evolution of the CME in details. The CME had a curved trajectory -- its helio-latitude decreased with time. The mass ejection originated at a latitudes of about 50(°) and reached the ecliptic plane at a distance of 2.5 R_⊙ from the Sun’s center. The CME velocity and acceleration increased as the CME went away from the Sun. At the distance of 15 R_⊙ from the Sun’s center the CME had a velocity of 250 km/s and an acceleration of 5 m/s(2) . The CME was not associated with a flare, and didn’t have an impulsive acceleration phase. The mass ejection had U-shaped structure which was observed both in the 171 Å images and in white-light. The CME was formed at a distance of about 0.2 -- 0.5 R_⊙ from the Sun’s surface. Observations in the line 304 Å showed that the CME was associated with the erupting prominence, which was located in the lowest part of the U-shaped structure close to the X-point of the magnetic reconnection. The prominence disappeared at the height of 0.4 R_⊙ above the solar limb. Some aspects of these observations can’t be explained in the standard CME model, which predicts that the prominence should be located inside the U-shaped structure, and the CME should be associated with a flare and have an impulsive acceleration phase.

  7. Electron Acceleration In Impulsive Solar Flares : extract of a thesis

    CERN Document Server

    Lenters, G T

    1999-01-01

    Impulsive solar flares generate a wide range of photon and particle emissions and hence provide an excellent backyard laboratory for studying particle acceleration processes in astrophysical plasmas. The source of the acceleration remains unidentified, but the basic observations are clear: (1) Hard X-ray and gamma-ray line emission occur simultaneously, indicating that electron and ion acceleration must occur simultaneously; (2) the electron and ion precipitation rates at the foot-points of the flare must be extremely large to account for the photon emission (∼1037 electrons s −1 and ∼1035 protons s−1, respectively), which means that replenishment of the acceleration region (which contains ≈1037 fully ionized hydrogen atoms) is a crucial issue; and (3) there are enhancements of the heavy ion abundances relative to normal coronal values. The basic model proposed assumes the generation of extremely low levels of magnetohydrodynamic (MHD) turb...

  8. The Flare Irradiance Spectral Model (FISM) and its Contributions to Space Weather Research, the Flare Energy Budget, and Instrument Design

    Science.gov (United States)

    Chamberlin, Phillip

    2008-01-01

    The Flare Irradiance Spectral Model (FISM) is an empirical model of the solar irradiance spectrum from 0.1 to 190 nm at 1 nm spectral resolution and on a 1-minute time cadence. The goal of FISM is to provide accurate solar spectral irradiances over the vacuum ultraviolet (VUV: 0-200 nm) range as input for ionospheric and thermospheric models. The seminar will begin with a brief overview of the FISM model, and also how the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) will contribute to improving FISM. Some current studies will then be presented that use FISM estimations of the solar VUV irradiance to quantify the contributions of the increased irradiance from flares to Earth's increased thermospheric and ionospheric densites. Initial results will also be presented from a study looking at the electron density increases in the Martian atmosphere during a solar flare. Results will also be shown quantifying the VUV contributions to the total flare energy budget for both the impulsive and gradual phases of solar flares. Lastly, an example of how FISM can be used to simplify the design of future solar VUV irradiance instruments will be discussed, using the future NOAA GOES-R Extreme Ultraviolet and X-Ray Sensors (EXIS) space weather instrument.

  9. Coherent-phase or random-phase acceleration of electron beams in solar flares

    Science.gov (United States)

    Aschwanden, Markus J.; Benz, Arnold O.; Montello, Maria L.

    1994-01-01

    Time structures of electron beam signatures at radio wavelengths are investigated to probe correlated versus random behavior in solar flares. In particular we address the issue whether acceleration and injection of electron beams is coherently modulated by a single source, or whether the injection is driven by a stochastic (possibly spatially fragmented) process. We analyze a total of approximately = 6000 type III bursts observed by Ikarus (Zurich) in the frequency range of 100-500 MHz, during 359 solar flares with simultaneous greater than or = 25 keV hard X-ray emission, in the years 1890-1983. In 155 flares we find a total of 260 continuous type III groups, with an average number of 13 +/- 9 bursts per group, a mean duration of D = 12 +/- 14 s, a mean period of P = 2.0 +/- 1.2 s, with the highest burst rate at a frequency of nu = 310 +/- 120 MHz. Pulse periods have been measured between 0.5 and 10 s, and can be described by an exponential distribution, i.e., N(P) varies as e (exp -P/1.0s). The period shows a frequency dependence of P(nu)=46(exp-0.6)(sub MHz)s for different flares, but is invariant during a particular flare. We measure the mean period P and its standard deviation sigma (sub p) in each type III group, and quantify the degree of periodicity (or phase-coherence) by the dimensionless parameter sigma (sub p)P. The representative sample of 260 type III burst groups shows a mean periodicity of sigma (sub p/P) = 0.37 +/- 0.12, while Monte Carlo simulations of an equivalent set of truly random time series show a distinctly different value of sigma (sub p)P = 0.93 +/- 0.26. This result indicates that the injection of electron beams is coherently modulated by a particle acceleration source which is either compact or has a global organization on a timescale of seconds, in contrast to an incoherent acceleration source, which is stochastic either in time or space. We discuss the constraints on the size of the acceleration region resulting from electron beam

  10. The reason for magnetospheric substorms and solar flares

    International Nuclear Information System (INIS)

    Heikkila, W.J.

    1983-01-01

    It has been proposed that magnetospheric substorms and solar flares are a result of the same mechanism. In our view this mechanism is connected with the escape, or attempted escape, of energized plasma from a region of closed magnetic field lines bounded by a magnetic bottle. In the case of the Earth, it must be plasma that is a able to maintain a discrete auroral arc, and we propose that the cross-tail current connected to the arc is filamentary in nature to provide the field-aligned current sheet above the arc. A localized meander of such an intense current filament could be caused by a tearing instability in the neutral sheet. Such a meander will cause an inductive electric field opposing the current change everywhere. In trying to reduce the component of the induction electric field parallel to the magnetic field lines, the plasma must enhance the transverse or cross-tail component; this action leads to eruptive behavior, in agreement with tearing theories. This enhanced induction electric field will cause a discharge along the magnetic neutral line at the apex of the magnetic arches, constituting an impulsive acceleration of all charged particles originally near the neutral line. The products of this phase then undergo betatron acceleration for a second phase. This discharge eventually reduces the electric field along the neutral line, and thereafter the enclosed magnetic flux through the neutral line remains nearly constant. The result is a plasmoid that has definite identity; its buoyancy leads to its escape. The auroral breakup (and solar flare) is the complex plasma response to the changing electromagnetic field. (orig.)

  11. Models for stellar flares

    International Nuclear Information System (INIS)

    Cram, L.E.; Woods, D.T.

    1982-01-01

    We study the response of certain spectral signatures of stellar flares (such as Balmer line profiles and the broad-band continuum) to changes in atmospheric structure which might result from physical processes akin to those thought to occur in solar flares. While each physical process does not have a unique signature, we can show that some of the observed properties of stellar flares can be explained by a model which involves increased pressures and temperatures in the flaring stellar chromosphere. We suggest that changes in stellar flare area, both with time and with depth in the atmosphere, may play an important role in producing the observed flare spectrum

  12. Electron precipitation in solar flares - Collisionless effects

    Science.gov (United States)

    Vlahos, L.; Rowland, H. L.

    1984-01-01

    A large fraction of the electrons which are accelerated during the impulsive phase of solar flares stream towards the chromosphere and are unstable to the growth of plasma waves. The linear and nonlinear evolution of plasma waves as a function of time is analyzed with a set of rate equations that follows, in time, the nonlinearly coupled system of plasma waves-ion fluctuations. As an outcome of the fast transfer of wave energy from the beam to the ambient plasma, nonthermal electron tails are formed which can stabilize the anomalous Doppler resonance instability responsible for the pitch angle scattering of the beam electrons. The non-collisional losses of the precipitating electrons are estimated, and the observational implication of these results are discussed.

  13. Prospective Out-of-ecliptic White-light Imaging of Interplanetary Corotating Interaction Regions at Solar Maximum

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Ming; Yang, Liping; Liu, Ying D.; Keiji, Hayashi; Li, Huichao [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing (China); Davies, Jackie A.; Harrison, Richard A. [RAL Space, STFC-Rutherford Appleton Laboratory, Harwell Campus, Didcot (United Kingdom); Li, Bo; Xia, Lidong, E-mail: mxiong@spacweather.ac.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai (China)

    2017-07-20

    Interplanetary corotating interaction regions (CIRs) can be remotely imaged in white light (WL), as demonstrated by the Solar Mass Ejection Imager (SMEI) on board the Coriolis spacecraft and Heliospheric Imagers (HIs) on board the twin Solar TErrestrial RElations Observatory ( STEREO ) spacecraft. The interplanetary WL intensity, due to Thomson scattering of incident sunlight by free electrons, is jointly determined by the 3D distribution of electron number density and line-of-sight (LOS) weighting factors of the Thomson-scattering geometry. The 2D radiance patterns of CIRs in WL sky maps look very different from different 3D viewpoints. Because of the in-ecliptic locations of both the STEREO and Coriolis spacecraft, the longitudinal dimension of interplanetary CIRs has, up to now, always been integrated in WL imagery. To synthesize the WL radiance patterns of CIRs from an out-of-ecliptic (OOE) vantage point, we perform forward magnetohydrodynamic modeling of the 3D inner heliosphere during Carrington Rotation CR1967 at solar maximum. The mixing effects associated with viewing 3D CIRs are significantly minimized from an OOE viewpoint. Our forward modeling results demonstrate that OOE WL imaging from a latitude greater than 60° can (1) enable the garden-hose spiral morphology of CIRs to be readily resolved, (2) enable multiple coexisting CIRs to be differentiated, and (3) enable the continuous tracing of any interplanetary CIR back toward its coronal source. In particular, an OOE view in WL can reveal where nascent CIRs are formed in the extended corona and how these CIRs develop in interplanetary space. Therefore, a panoramic view from a suite of wide-field WL imagers in a solar polar orbit would be invaluable in unambiguously resolving the large-scale longitudinal structure of CIRs in the 3D inner heliosphere.

  14. A New Paradigm for Flare Particle Acceleration

    Science.gov (United States)

    Guidoni, Silvina E.; Karpen, Judith T.; DeVore, C. Richard

    2017-08-01

    The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission and its spectra in solar flares is not well understood. Here, we propose a first-principle-based model of particle acceleration that produces energy spectra that closely resemble those derived from hard X-ray observations. Our mechanism uses contracting magnetic islands formed during fast reconnection in solar flares to accelerate electrons, as first proposed by Drake et al. (2006) for kinetic-scale plasmoids. We apply these ideas to MHD-scale islands formed during fast reconnection in a simulated eruptive flare. A simple analytic model based on the particles’ adiabatic invariants is used to calculate the energy gain of particles orbiting field lines in our ultrahigh-resolution, 2.5D, MHD numerical simulation of a solar eruption (flare + coronal mass ejection). Then, we analytically model electrons visiting multiple contracting islands to account for the observed high-energy flare emission. Our acceleration mechanism inherently produces sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each macroscopic island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare current sheet is a promising candidate for electron acceleration in solar eruptions. This work was supported in part by the NASA LWS and H-SR programs..

  15. DESTABILIZATION OF A SOLAR PROMINENCE/FILAMENT FIELD SYSTEM BY A SERIES OF EIGHT HOMOLOGOUS ERUPTIVE FLARES LEADING TO A CME

    Energy Technology Data Exchange (ETDEWEB)

    Panesar, Navdeep K.; Moore, Ronald L. [Center for Space Plasma and Aeronomic Research (CSPAR), UAH, Huntsville, AL 35805 (United States); Sterling, Alphonse C. [Heliophysics and Planetary Science Office, ZP13, Marshall Space Flight Center, Huntsville, AL 35812 (United States); Innes, Davina E., E-mail: navdeep.k.panesar@nasa.gov [Max Planck Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2015-09-20

    Homologous flares are flares that occur repetitively in the same active region, with similar structure and morphology. A series of at least eight homologous flares occurred in active region NOAA 11237 over 2011 June 16–17. A nearby prominence/filament was rooted in the active region, and situated near the bottom of a coronal cavity. The active region was on the southeast solar limb as seen from the Solar Dynamics Observatory/Atmospheric Imaging Assembly, and on the disk as viewed from the Solar TErrestrial RElations Observatory/EUVI-B. The dual perspective allows us to study in detail behavior of the prominence/filament material entrained in the magnetic field of the repeatedly erupting system. Each of the eruptions were mainly confined, but expelled hot material into the prominence/filament cavity system (PFCS). The field carrying and containing the ejected hot material interacted with the PFCS and caused it to inflate, resulting in a step-wise rise of the PFCS approximately in step with the homologous eruptions. The eighth eruption triggered the PFCS to move outward slowly, accompanied by a weak coronal dimming. As this slow PFCS eruption was underway, a final “ejective” flare occurred in the core of the active region, resulting in strong dimming in the EUVI-B images and expulsion of a coronal mass ejection (CME). A plausible scenario is that the repeated homologous flares could have gradually destabilized the PFCS, and its subsequent eruption removed field above the acitive region and in turn led to the ejective flare, strong dimming, and CME.

  16. Self-similar Lagrangian hydrodynamics of beam-heated solar flare atmospheres

    International Nuclear Information System (INIS)

    Brown, J.C.; Emslie, A.G.

    1989-01-01

    The one-dimensional hydrodynamic problem in Lagrangian coordinates (Y, t) is considered for which the specific energy input Q has a power-law dependence on both Y and t, and the initial density distribution is rho(0) which is directly proportional to Y exp gamma. In regimes where the contributions of radiation, conduction, quiescent heating, and gravitational terms in the energy equation are negligible compared to those arising from Q, the problem has a self-similar solution, with the hydrodynamic variables depending only on a single independent variable which is a combination of Y, t, and the dimensional constants of the problem. It is then shown that the problem of solar flare chromospheric heating due to collisional interaction of a beam of electrons (or protons) with a power-law energy spectrum can be approximated by such forms of Q(Y, t) and rho(0)(Y), and that other terms are negligible compared to Q over a restricted regime early in the flare. 29 refs

  17. The inner-relationship of hard X-ray and EUV bursts during solar flares

    International Nuclear Information System (INIS)

    Emslie, A.G.; Brown, J.C.; Donnelly, R.F.

    1978-01-01

    A comparison is made between the flux-versus-time profile in the EUV band and the thick target electron flux profile as inferred from hard X-rays for a number of moderately large solar flares. This complements Kane and Donnelly's (1971) study of small flares. The hard X-ray data are from ESRO TD-1A and the EUV inferred from SFD observations. Use of a chi 2 minimising method shows that the best overall fit between the profile fine structures obtains for synchronism to < approximately 5 s which is within the timing accuracy. This suggests that neither conduction nor convection is fast enough as the primary mechanism of energy transport into the EUV flare and rather favours heating by the electrons themselves or by some MHD wave process much faster than acoustic waves. The electron power deposited, for a thick target model, is however far greater than the EUV luminosity for any reasonable assumptions about the area and depth over which EUV is emitted. This means that either most of the power deposited is conducted away to the optical flare or that only a fraction < approximately 1-10% of the X-ray emitting electrons are injected downwards. Recent work on Hα flare heating strongly favours the latter alternative - i.e. that electrons are mostly confined in the corona. (Auth.)

  18. Study of the effect of solar flares on VLF signals during D-layer preparation or disappearance time

    Science.gov (United States)

    Ray, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav

    2016-07-01

    "Very Low Frequency" (VLF) is one of the bands of the Radio waves having frequency 3-30 KHz, which propagates through the Earth-ionosphere wave-guide. In relation to propagation of radio waves through ionosphere, low mass and high mobility cause electrons to play a vital role. Electrons are not distributed uniformly in the ionosphere and depending on this factor, ionosphere has different layers namely D, E and F. Different ionospheric layers generally exist during day and night time. During day-time when the main source of the ionization of the ionosphere is Sun, the lower most layer of ionosphere is D-layer. But during the night-time when Sun is absent and cosmic ray is the main source of the ionization of the ionosphere, this D-layer disappears and E-layer becomes the lower most region of the ionosphere. Normally, patterns of VLF signal depend on regular solar flux variations. However, during solar flares extra energetic particles are released from Sun, which makes the changes in the ionization of the ionosphere and these changes can perturb VLF signal amplitude. Usually if a solar flare occurs during any time of day, it only affects the amplitude and phase of the VLF signals. But in the present work, we found the if the flare occurs during D-layer preparation / disappearance time, then it will not only affect to amplitude and phase of the VLF signals but also to terminator times of VLF signals. We have observed that the sun set terminator time of the VLF signals shifted towards night time due to the effect of a M-class solar flare which occurred during the D-layer disappearance time. The shift is so high that it crossed 5σ level. We are now trying to a make model using the ion-chemistry and LWPC code to explain this observed effect.

  19. Detection of Three-minute Oscillations in Full-disk Ly α Emission during a Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Milligan, Ryan O.; Fletcher, Lyndsay [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom); Fleck, Bernhard [ESA Directorate of Science, Operations Department, c/o NASA/GSFC Code 671, Greenbelt, MD 20071 (United States); Ireland, Jack; Dennis, Brian R. [Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2017-10-10

    In this Letter we report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Ly α (from GOES /EUVS) and Lyman continuum (from Solar Dynamics Observatory ( SDO )/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed a ∼3 minute period present during the flare’s main phase. The formation temperature of this emission locates this radiation at the flare’s chromospheric footpoints, and similar behavior is found in the SDO /Atmospheric Imaging Assembly 1600 and 1700 Å channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray (HXR) energies (50–100 keV) in Reuven Ramaty High Energy Solar Spectroscopic Imager data we can state that this 3-minute oscillation does not depend on the rate of energization of non-thermal electrons. However, a second period of 120 s found in both HXR and chromospheric lightcurves is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Ly α line may influence the composition and dynamics of planetary atmospheres during periods of high activity.

  20. Solar Imagery - White Light - ISOON

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Improved Solar Observing Optical Network (ISOON) project is a collaboration between the Air Force Research Laboratory Space Vehicles Directorate and the National...

  1. Statistics of “Cold” Early Impulsive Solar Flares in X-Ray and Microwave Domains

    Science.gov (United States)

    Lysenko, Alexandra L.; Altyntsev, Alexander T.; Meshalkina, Natalia S.; Zhdanov, Dmitriy; Fleishman, Gregory D.

    2018-04-01

    Solar flares often happen after a preflare/preheating phase, which is almost or entirely thermal. In contrast, there are the so-called early impulsive flares that do not show a (significant) preflare heating, but instead often show the Neupert effect—a relationship where the impulsive phase is followed by a gradual, cumulative-like, thermal response. This has been interpreted as a dominance of nonthermal energy release at the impulsive phase, even though a similar phenomenology is expected if the thermal and nonthermal energies are released in comparable amounts at the impulsive phase. Nevertheless, some flares do show a good quantitative correspondence between the nonthermal electron energy input and plasma heating; in such cases, the thermal response was weak, which results in them being called “cold” flares. We undertook a systematic search for such events among early impulsive flares registered by the Konus-Wind instrument in the triggered mode from 11/1994 to 4/2017, and selected 27 cold flares based on relationships between hard X-ray (HXR) (Konus-Wind) and soft X-ray (Geostationary Operational Environmental Satellite) emission. For these events, we put together all available microwave data from different instruments. We obtained temporal and spectral parameters of HXR and microwave emissions of the events and examined correlations between them. We found that, compared to a “mean” flare, the cold flares: (i) are weaker, shorter, and harder in the X-ray domain; (ii) are harder and shorter, but not weaker in the microwaves; (iii) have a significantly higher spectral peak frequencies in the microwaves. We discuss the possible physical reasons for these distinctions and implication of the finding.

  2. RE-EVALUATION OF THE NEUTRON EMISSION FROM THE SOLAR FLARE OF 2005 SEPTEMBER 7, DETECTED BY THE SOLAR NEUTRON TELESCOPE AT SIERRA NEGRA

    Energy Technology Data Exchange (ETDEWEB)

    González, L. X. [SCiESMEX, Instituto de Geofísica Unidad Michoacán, Universidad Nacional Autónoma de México, 58190, Morelia, Michoacán (Mexico); Valdés-Galicia, J. F.; Musalem, O.; Hurtado, A. [Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510, D. F. Mexico (Mexico); Sánchez, F. [Instituto de Tecnologías en Detección de Astropartículas, Comisión Nacional de Energía Atómica, 1429, Buenos Aires (Argentina); Muraki, Y.; Sako, T.; Matsubara, Y.; Nagai, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Watanabe, K. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai, chuo-ku, Sagamihara 252-5210 (Japan); Shibata, S. [College of Engineering, Chubu University, Kasugai, Aichi 487-8501 (Japan); Sakai, T. [College of Industrial Technologies, Nihon University, Narashino 275-0005 (Japan)

    2015-12-01

    The X17.0 solar flare of 2005 September 7 released high-energy neutrons that were detected by the Solar Neutron Telescope (SNT) at Sierra Negra, Mexico. In three separate and independent studies of this solar neutron event, several of its unique characteristics were studied; in particular, a power-law energy spectra was estimated. In this paper, we present an alternative analysis, based on improved numerical simulations of the detector using GEANT4, and a different technique for processing the SNT data. The results indicate that the spectral index that best fits the neutron flux is around 3, in agreement with previous works. Based on the numerically calculated neutron energy deposition on the SNT, we confirm that the detected neutrons might have reached an energy of 1 GeV, which implies that 10 GeV protons were probably produced; these could not be observed at Earth, as their parent flare was an east limb event.

  3. Return currents in solar flares - Collisionless effects

    Science.gov (United States)

    Rowland, H. L.; Vlahos, L.

    1985-01-01

    If the primary, precipitating electrons in a solar flare are unstable to beam plasma interactions, it is shown that strong Langmuir turbulence can seriously modify the way in which a return current is carried by the background plasma. In particular, the return (or reverse) current will not be carried by the bulk of the electrons, but by a small number of high velocity electrons. For beam/plasma densities greater than 0.01, this can reduce the effects of collisions on the return current. For higher density beams where the return current could be unstable to current driven instabilities, the effects of strong turbulence anomalous resistivity is shown to prevent the appearance of such instabilities. Again in this regime, how the return current is carried is determined by the beam generated strong turbulence.

  4. XUV spectrum of C I observed from Skylab during a solar flare

    International Nuclear Information System (INIS)

    Feldman, U.; Brown, C.M.; Doschek, G.A.; Moore, C.E.; Rosenberg, F.D.

    1976-01-01

    An intense spectrum of C I in the wavelength region from 1100 to 2000 A has been recorded by the Naval Research Laboratory normal incidence spectrograph flown on Skylab. The source of the spectrum was a large solar flare. The spectral resolution was about 20 000 at 1200 A. We have identified 69 new lines of C I, and determined 63 new energy levels. The new lines arise from transitions from upper levels of high principal quantum number n where n approximately-greater-than 6. A list of 193 C I lines observed in the spectrum between 1140 and 1931 A is presented, as well as calculated wavelengths for an additional 109 transitions between the new levels and the 2s 2 2p 2 3 P 0 , 1 , 2 levels. The calculated lines fall between 1102 and 1140 A and were not observed in the solar flare spectrum due to low instrumental efficiency at these wavelengths. The relative wavelength accuracy of most of the observed and calculated lines is about +- 0.004 A. The intensities of the C I lines are qualitatively compared with corresponding intensities in the laboratory spectrum

  5. White-light-emitting supramolecular gels.

    Science.gov (United States)

    Praveen, Vakayil K; Ranjith, Choorikkat; Armaroli, Nicola

    2014-01-07

    Let there be light, let it be white: Recent developments in the use of chromophore-based gels as scaffolds for the assembly of white-light-emitting soft materials have been significant. The main advantage of this approach lies in the facile accommodation of selected luminescent components within the gel. Excitation-energy-transfer processes between these components ultimately generate the desired light output. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Dynamic Spectral Imaging of Decimetric Fiber Bursts in an Eruptive Solar Flare

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhitao; Chen, Bin; Gary, Dale E., E-mail: zw56@njit.edu [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102 (United States)

    2017-10-20

    Fiber bursts are a type of fine structure that is often superposed on type IV radio continuum emission during solar flares. Although studied for many decades, its physical exciter, emission mechanism, and association with the flare energy release remain unclear, partly due to the lack of simultaneous imaging observations. We report the first dynamic spectroscopic imaging observations of decimetric fiber bursts, which occurred during the rise phase of a long-duration eruptive flare on 2012 March 3, as obtained by the Karl G. Jansky Very Large Array in 1–2 GHz. Our results show that the fiber sources are located near and above one footpoint of the flare loops. The fiber source and the background continuum source are found to be co-spatial and share the same morphology. It is likely that they are associated with nonthermal electrons trapped in the converging magnetic fields near the footpoint, as supported by a persistent coronal hard X-ray source present during the flare rise phase. We analyze three groups of fiber bursts in detail with dynamic imaging spectroscopy and obtain their mean frequency-dependent centroid trajectories in projection. By using a barometric density model and magnetic field based on a potential field extrapolation, we further reconstruct the 3D source trajectories of fiber bursts, for comparison with expectations from the whistler wave model and two MHD-based models. We conclude that the observed fiber burst properties are consistent with an exciter moving at the propagation velocity expected for whistler waves, or models that posit similar exciter velocities.

  7. Feature Selection, Flaring Size and Time-to-Flare Prediction Using Support Vector Regression, and Automated Prediction of Flaring Behavior Based on Spatio-Temporal Measures Using Hidden Markov Models

    Science.gov (United States)

    Al-Ghraibah, Amani

    Solar flares release stored magnetic energy in the form of radiation and can have significant detrimental effects on earth including damage to technological infrastructure. Recent work has considered methods to predict future flare activity on the basis of quantitative measures of the solar magnetic field. Accurate advanced warning of solar flare occurrence is an area of increasing concern and much research is ongoing in this area. Our previous work 111] utilized standard pattern recognition and classification techniques to determine (classify) whether a region is expected to flare within a predictive time window, using a Relevance Vector Machine (RVM) classification method. We extracted 38 features which describing the complexity of the photospheric magnetic field, the result classification metrics will provide the baseline against which we compare our new work. We find a true positive rate (TPR) of 0.8, true negative rate (TNR) of 0.7, and true skill score (TSS) of 0.49. This dissertation proposes three basic topics; the first topic is an extension to our previous work [111, where we consider a feature selection method to determine an appropriate feature subset with cross validation classification based on a histogram analysis of selected features. Classification using the top five features resulting from this analysis yield better classification accuracies across a large unbalanced dataset. In particular, the feature subsets provide better discrimination of the many regions that flare where we find a TPR of 0.85, a TNR of 0.65 sightly lower than our previous work, and a TSS of 0.5 which has an improvement comparing with our previous work. In the second topic, we study the prediction of solar flare size and time-to-flare using support vector regression (SVR). When we consider flaring regions only, we find an average error in estimating flare size of approximately half a GOES class. When we additionally consider non-flaring regions, we find an increased average

  8. Particle acceleration in solar flares: observations versus numerical simulations

    International Nuclear Information System (INIS)

    Benz, A O; Grigis, P C; Battaglia, M

    2006-01-01

    Solar flares are generally agreed to be impulsive releases of magnetic energy. Reconnection in dilute plasma is the suggested trigger for the coronal phenomenon. It releases up to 10 26 J, accelerates up to 10 38 electrons and ions and must involve a volume that greatly exceeds the current sheet dimension. The Ramaty High-Energy Solar Spectroscopic Imager satellite can image a source in the corona that appears to contain the acceleration region and can separate it from other x-ray emissions. The new observations constrain the acceleration process by a quantitative relation between spectral index and flux. We present recent observational results and compare them with theoretical modelling by a stochastic process assuming transit-time damping of fast-mode waves, escape and replenishment. The observations can only be fitted if additional assumptions on trapping by an electric potential and possibly other processes such as isotropization and magnetic trapping are made

  9. M DWARFS IN SLOAN DIGITAL SKY SURVEY STRIPE 82: PHOTOMETRIC LIGHT CURVES AND FLARE RATE ANALYSIS

    International Nuclear Information System (INIS)

    Kowalski, Adam F.; Hawley, Suzanne L.; Hilton, Eric J.; Becker, Andrew C.; Sesar, Branimir; West, Andrew A.; Bochanski, John J.

    2009-01-01

    We present a flare rate analysis of 50,130 M dwarf light curves in Sloan Digital Sky Survey Stripe 82. We identified 271 flares using a customized variability index to search ∼2.5 million photometric observations for flux increases in the u and g bands. Every image of a flaring observation was examined by eye and with a point-spread function-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of Hα in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify eight as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type m dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with Δu ≥ 0.7 mag on stars with u -1 deg -2 but can vary significantly with the line of sight.

  10. Stochastic three-wave interaction in flaring solar loops

    Science.gov (United States)

    Vlahos, L.; Sharma, R. R.; Papadopoulos, K.

    1983-01-01

    A model is proposed for the dynamic structure of high-frequency microwave bursts. The dynamic component is attributed to beams of precipitating electrons which generate electrostatic waves in the upper hybrid branch. Coherent upconversion of the electrostatic waves to electromagnetic waves produces an intrinsically stochastic emission component which is superposed on the gyrosynchrotron continuum generated by stably trapped electron fluxes. The role of the density and temperature of the ambient plasma in the wave growth and the transition of the three wave upconversion to stochastic, despite the stationarity of the energy source, are discussed in detail. The model appears to reproduce the observational features for reasonable parameters of the solar flare plasma.

  11. Stochastic three-wave interaction in flaring solar loops

    International Nuclear Information System (INIS)

    Vlahos, L.; Sharma, R.R.; Papadopoulos, K.

    1983-01-01

    We propose a model for the dynamic structure of high-frequency microwave bursts. The dynamic component is attributed to beams of precipitating electrons which generate electrostatic waves in the upper hybrid branch. Coherent upconversion of the electrostatic waves to electromagnetic waves produces an intrinsically stochastic emission component which is superposed on the gyrosynchrotron continuum generated by stably trapped electron fluxes. The role of the density and temperature of the ambient plasma in the wave growth and the transition of the three wave upconversion to stochastic, despite the stationarity of the energy source are discussed in detail. The model appears to reproduce the observational features for reasonable parameters of the solar flare plasma

  12. Nano-particle based scattering layers for optical efficiency enhancement of organic light-emitting diodes and organic solar cells

    Science.gov (United States)

    Chang, Hong-Wei; Lee, Jonghee; Hofmann, Simone; Hyun Kim, Yong; Müller-Meskamp, Lars; Lüssem, Björn; Wu, Chung-Chih; Leo, Karl; Gather, Malte C.

    2013-05-01

    The performance of both organic light-emitting diodes (OLEDs) and organic solar cells (OSC) depends on efficient coupling between optical far field modes and the emitting/absorbing region of the device. Current approaches towards OLEDs with efficient light-extraction often are limited to single-color emission or require expensive, non-standard substrates or top-down structuring, which reduces compatibility with large-area light sources. Here, we report on integrating solution-processed nano-particle based light-scattering films close to the active region of organic semiconductor devices. In OLEDs, these films efficiently extract light that would otherwise remain trapped in the device. Without additional external outcoupling structures, translucent white OLEDs containing these scattering films achieve luminous efficacies of 46 lm W-1 and external quantum efficiencies of 33% (both at 1000 cd m-2). These are by far the highest numbers ever reported for translucent white OLEDs and the best values in the open literature for any white device on a conventional substrate. By applying additional light-extraction structures, 62 lm W-1 and 46% EQE are reached. Besides universally enhancing light-extraction in various OLED configurations, including flexible, translucent, single-color, and white OLEDs, the nano-particle scattering film boosts the short-circuit current density in translucent organic solar cells by up to 70%.

  13. Solar charge controller in solar street light

    OpenAIRE

    Dong, Haibo

    2014-01-01

    Recently, with the rapid development of scientific technology, the conventional energy cannot meet the requirement of human beings. People are looking for the utilization of renew energy. Solar en-ergy as a new clean energy has attract the eyes of people. The applications of solar energy are popular to human society. Solar street light is a good example. This thesis will focus on a deeper research of the popular and ubiquitous solar street light in China. However, solar charge controll...

  14. Long-term hemispheric variation of the flare index

    International Nuclear Information System (INIS)

    Feng Song; Deng Lin-Hua; Xu Shi-Chun

    2013-01-01

    The long-term hemispheric variation of the flare index is investigated. It is found that, (1) the phase difference of the flare index between the northern and southern hemispheres is about 6–7 months, which is near the time delay between flare activity and sunspot activity; (2) both the dominant and phase-leading hemisphere of the flare index is the northern hemisphere in the considered time interval, implying that the hemispheric asynchrony of solar activity has a close connection with the N-S asymmetry of solar activity. (research papers)

  15. Very fast optical flaring from a possible new Galactic magnetar.

    Science.gov (United States)

    Stefanescu, A; Kanbach, G; Słowikowska, A; Greiner, J; McBreen, S; Sala, G

    2008-09-25

    Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars and black holes. In the high-energy regime of X-rays and gamma-rays, outbursts with variabilities on timescales of seconds or less are routinely observed, for example in gamma-ray bursts or soft gamma-ray repeaters. At optical wavelengths, flaring activity on such timescales has not been observed, other than from the prompt phase of one exceptional gamma-ray burst. This is mostly due to the fact that outbursts with strong, fast flaring are usually discovered in the high-energy regime; most optical follow-up observations of such transients use instruments with integration times exceeding tens of seconds, which are therefore unable to resolve fast variability. Here we show the observation of extremely bright and rapid optical flaring in the Galactic transient SWIFT J195509.6+261406. Our optical light curves are phenomenologically similar to high-energy light curves of soft gamma-ray repeaters and anomalous X-ray pulsars, which are thought to be neutron stars with extremely high magnetic fields (magnetars). This suggests that similar processes are in operation, but with strong emission in the optical, unlike in the case of other known magnetars.

  16. Non-Local Diffusion of Energetic Electrons during Solar Flares

    Science.gov (United States)

    Bian, N. H.; Emslie, G.; Kontar, E.

    2017-12-01

    The transport of the energy contained in suprathermal electrons in solar flares plays a key role in our understanding of many aspects of flare physics, from the spatial distributions of hard X-ray emission and energy deposition in the ambient atmosphere to global energetics. Historically the transport of these particles has been largely treated through a deterministic approach, in which first-order secular energy loss to electrons in the ambient target is treated as the dominant effect, with second-order diffusive terms (in both energy and angle) generally being either treated as a small correction or even neglected. Here, we critically analyze this approach, and we show that spatial diffusion through pitch-angle scattering necessarily plays a very significant role in the transport of electrons. We further show that a satisfactory treatment of the diffusion process requires consideration of non-local effects, so that the electron flux depends not just on the local gradient of the electron distribution function but on the value of this gradient within an extended region encompassing a significant fraction of a mean free path. Our analysis applies generally to pitch-angle scattering by a variety of mechanisms, from Coulomb collisions to turbulent scattering. We further show that the spatial transport of electrons along the magnetic field of a flaring loop can be modeled as a Continuous Time Random Walk with velocity-dependent probability distribution functions of jump sizes and occurrences, both of which can be expressed in terms of the scattering mean free path.

  17. New Results from the Flare Genesis Experiment

    Science.gov (United States)

    Rust, D. M.; Bernasconi, P. N.; Eaton, H. A.; Keller, C.; Murphy, G. A.; Schmieder, B.

    2000-05-01

    From January 10 to 27, 2000, the Flare Genesis solar telescope observed the Sun while suspended from a balloon in the stratosphere above Antarctica. The goal of the mission was to acquire long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. Images were obtained in the magnetically sensitive Ca I line at 6122 Angstroms and at H-alpha (6563 Angstroms). The FGE data were obtained in the context of Max Millennium Observing Campaign #004, the objective of which was to study the ``Genesis of Solar Flares and Active Filaments/Sigmoids." Flare Genesis obtained about 26,000 usable images on the 8 targeted active regions. A preliminary examination reveals a good sequence on an emerging flux region and data on the M1 flare on January 22, as well as a number of sequences on active filaments. We will present the results of our first analysis efforts. Flare Genesis was supported by NASA grants NAG5-4955, NAG5-5139, and NAG5-8331 and by NSF grant OPP-9615073. The Air Force Office of Scientific Research and the Ballistic Missile Defense Organization supported early development of the Flare Genesis Experiment.

  18. Recurrent pulse trains in the solar hard X-ray flare of 1980 June 7

    International Nuclear Information System (INIS)

    Kiplinger, A.L.; Dennis, B.R.; Frost, K.J.; Orwig, L.E.

    1983-01-01

    This study presents a detailed examination of the solar hard X-ray and γ-ray flare of 1980 June 7 as seen by the Hard X-Ray Burst Spectrometer on SMM. The hard X-ray profile is most unusual in that it is characterized by an initial pulse train of seven intense hard X-ray spikes. However, the event is unique among the 6300 events observed by HXRBS in that the temporal signature of this pulse train recurs twice during the flare. Such signatures of temporal stability in impulsive solar flares have not been observed before. Examinations of the hard X-ray data in conjunction with radio and γ-ray observations show that the 28--480 keV X-ray emission is simultaneous with the 17 GHz microwave fluxes within 128 ms and that the 3.5--6.5 MeV prompt γ-ray line emission is coincident with secondary maxima of the microwave and X-ray fluxes. Studies of the temporal and spectral properties of the pulses indicate that the pulses are not produced by purely reversible processes, and that if the source is oscillatory, it is not a high quality oscillator. Although the absence of spatially resolved hard X-ray observations leaves other possibilities open, a parameterization of the event as a set of seven sequentially firing loops is presented that offers many satisfying explanations of the observations

  19. THE NATURE OF CME-FLARE-ASSOCIATED CORONAL DIMMING

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, J. X. [Key Laboratory of Planetary Sciences, Shanghai Astronomical Observatory, Shanghai 200030 (China); Qiu, J., E-mail: chengjx@shao.ac.cn [Department of Physics, Montana State University, Bozeman MT 59717-3840 (United States)

    2016-07-01

    Coronal mass ejections (CMEs) are often accompanied by coronal dimming that is evident in extreme ultraviolet (EUV) and soft X-ray observations. The locations of dimming are sometimes considered to map footpoints of the erupting flux rope. As the emitting material expands in the corona, the decreased plasma density leads to reduced emission observed in spectral and irradiance measurements. Therefore, signatures of dimming may reflect the properties of CMEs in the early phase of their eruption. In this study, we analyze the event of flare, CME, and coronal dimming on 2011 December 26. We use the data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory for disk observations of the dimming, and analyze images taken by EUVI, COR1, and COR2 on board the Solar Terrestrial Relations Observatory to obtain the height and velocity of the associated CMEs observed at the limb. We also measure the magnetic reconnection rate from flare observations. Dimming occurs in a few locations next to the flare ribbons, and it is observed in multiple EUV passbands. Rapid dimming starts after the onset of fast reconnection and CME acceleration, and its evolution tracks the CME height and flare reconnection. The spatial distribution of dimming exhibits cores of deep dimming with a rapid growth, and their light curves are approximately linearly scaled with the CME height profile. From the dimming analysis we infer the process of the CME expansion, and estimate properties of the CME.

  20. THE NATURE OF CME-FLARE-ASSOCIATED CORONAL DIMMING

    International Nuclear Information System (INIS)

    Cheng, J. X.; Qiu, J.

    2016-01-01

    Coronal mass ejections (CMEs) are often accompanied by coronal dimming that is evident in extreme ultraviolet (EUV) and soft X-ray observations. The locations of dimming are sometimes considered to map footpoints of the erupting flux rope. As the emitting material expands in the corona, the decreased plasma density leads to reduced emission observed in spectral and irradiance measurements. Therefore, signatures of dimming may reflect the properties of CMEs in the early phase of their eruption. In this study, we analyze the event of flare, CME, and coronal dimming on 2011 December 26. We use the data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory for disk observations of the dimming, and analyze images taken by EUVI, COR1, and COR2 on board the Solar Terrestrial Relations Observatory to obtain the height and velocity of the associated CMEs observed at the limb. We also measure the magnetic reconnection rate from flare observations. Dimming occurs in a few locations next to the flare ribbons, and it is observed in multiple EUV passbands. Rapid dimming starts after the onset of fast reconnection and CME acceleration, and its evolution tracks the CME height and flare reconnection. The spatial distribution of dimming exhibits cores of deep dimming with a rapid growth, and their light curves are approximately linearly scaled with the CME height profile. From the dimming analysis we infer the process of the CME expansion, and estimate properties of the CME.

  1. A VERY BRIGHT, VERY HOT, AND VERY LONG FLARING EVENT FROM THE M DWARF BINARY SYSTEM DG CVn

    Energy Technology Data Exchange (ETDEWEB)

    Osten, Rachel A. [Space Telescope Science Institute (United States); Kowalski, Adam [U. Md/GSFC (United States); Drake, Stephen A. [USRA/CRESST and NASA/GSFC (United States); Krimm, Hans [USRA/CRESST (United States); Page, Kim [X-ray and Observational Astronomy Group, Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Gazeas, Kosmas [Department of Astrophysics, Astronomy and Mechanics, University of Athens, GR-15784 Zografos, Athens (Greece); Kennea, Jamie [Penn State (United States); Oates, Samantha [Instituto de Astrofsica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, E-18008, Granada (Spain); Page, Mathew [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom); De Miguel, Enrique [Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, E-21071 Huelva (Spain); Novák, Rudolf [Research Centre for Toxic Compounds in the Environment, Faculty of Science, Masaryk University, Kamenice 3, 625 00 Brno (Czech Republic); Apeltauer, Tomas [Brno University of Technology, Faculty of Civil Engineering, Veveri 331/95, 602 00 Brno (Czech Republic); Gehrels, Neil, E-mail: osten@stsci.edu [NASA/GSFC (United States)

    2016-12-01

    On 2014 April 23, the Swift satellite responded to a hard X-ray transient detected by its Burst Alert Telescope, which turned out to be a stellar flare from a nearby, young M dwarf binary DG CVn. We utilize observations at X-ray, UV, optical, and radio wavelengths to infer the properties of two large flares. The X-ray spectrum of the primary outburst can be described over the 0.3–100 keV bandpass by either a single very high-temperature plasma or a nonthermal thick-target bremsstrahlung model, and we rule out the nonthermal model based on energetic grounds. The temperatures were the highest seen spectroscopically in a stellar flare, at T{sub X} of 290 MK. The first event was followed by a comparably energetic event almost a day later. We constrain the photospheric area involved in each of the two flares to be >10{sup 20} cm{sup 2}, and find evidence from flux ratios in the second event of contributions to the white light flare emission in addition to the usual hot, T  ∼ 10{sup 4} K blackbody emission seen in the impulsive phase of flares. The radiated energy in X-rays and white light reveal these events to be the two most energetic X-ray flares observed from an M dwarf, with X-ray radiated energies in the 0.3–10 keV bandpass of 4 × 10{sup 35} and 9 × 10{sup 35} erg, and optical flare energies at E{sub V} of 2.8 × 10{sup 34} and 5.2 × 10{sup 34} erg, respectively. The results presented here should be integrated into updated modeling of the astrophysical impact of large stellar flares on close-in exoplanetary atmospheres.

  2. A Very Bright, Very Hot, and Very Long Flaring Event from the M Dwarf Binary System DG CVn

    Science.gov (United States)

    Osten, Rachel A.; Kowalski, Adam; Drake, Stephen; Krimm, Hans; Page, Kim; Gazeas, Kosmas; Page, Mathew; Miguel, Enrique De; Novak, Rudolf; Gehrels, Cornelis

    2016-01-01

    On 2014 April 23, the Swift satellite responded to a hard X-ray transient detected by its Burst Alert Telescope, which turned out to be a stellar flare from a nearby, young M dwarf binary DG CVn. We utilize observations at X-ray, UV, optical, and radio wavelengths to infer the properties of two large flares. The X-ray spectrum of the primary outburst can be described over the 0.3100 kiloelectron volts bandpass by either a single very high-temperature plasma or a nonthermal thick-target bremsstrahlung model, and we rule out the nonthermal model based on energetic grounds. The temperatures were the highest seen spectroscopically in a stellar flare, at T(sub x) of 290 megakelvin. The first event was followed by a comparably energetic event almost a day later. We constrain the photospheric area involved in each of the two flares to be greater than 10(exp 20) sq cm, and find evidence from flux ratios in the second event of contributions to the white light flare emission in addition to the usual hot, T approximately 10(exp 4) K blackbody emission seen in the impulsive phase of flares. The radiated energy in X-rays and white light reveal these events to be the two most energetic X-ray flares observed from an M dwarf, with X-ray radiated energies in the 0.3-10 kiloelectron volts bandpass of 4 x 10(exp 35) and 9 x 10(exp 35) erg, and optical flare energies at E(sub V) of 2.8 x 10(exp 34) and 5.2 x 10(exp 34) erg, respectively. The results presented here should be integrated into updated modeling of the astrophysical impact of large stellar flares on close-in exoplanetary atmospheres.

  3. CAN A NANOFLARE MODEL OF EXTREME-ULTRAVIOLET IRRADIANCES DESCRIBE THE HEATING OF THE SOLAR CORONA?

    Energy Technology Data Exchange (ETDEWEB)

    Tajfirouze, E.; Safari, H. [Department of Physics, University of Zanjan, P.O. Box 45195-313, Zanjan (Iran, Islamic Republic of)

    2012-01-10

    Nanoflares, the basic units of impulsive energy release, may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies, can give an estimation of the importance of nanoflares for heating the solar corona. If the power-law index is greater than 2, then the nanoflare contribution is dominant. We model a time series of extreme-ultraviolet emission radiance as random flares with a power-law exponent of the flare event distribution. The model is based on three key parameters: the flare rate, the flare duration, and the power-law exponent of the flare intensity frequency distribution. We use this model to simulate emission line radiance detected in 171 A, observed by Solar Terrestrial Relation Observatory/Extreme-Ultraviolet Imager and Solar Dynamics Observatory/Atmospheric Imaging Assembly. The observed light curves are matched with simulated light curves using an Artificial Neural Network, and the parameter values are determined across the active region, quiet Sun, and coronal hole. The damping rate of nanoflares is compared with the radiative losses cooling time. The effect of background emission, data cadence, and network sensitivity on the key parameters of the model is studied. Most of the observed light curves have a power-law exponent, {alpha}, greater than the critical value 2. At these sites, nanoflare heating could be significant.

  4. CONNECTING FLARES AND TRANSIENT MASS-LOSS EVENTS IN MAGNETICALLY ACTIVE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Osten, Rachel A. [Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218 (United States); Wolk, Scott J., E-mail: osten@stsci.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)

    2015-08-10

    We explore the ramification of associating the energetics of extreme magnetic reconnection events with transient mass-loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass-loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin. If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass-loss in the form of coronal mass ejections, then the cumulative effect of this mass-loss could be large. We find that for young solar-like stars and active M dwarfs, the total mass lost due to transient magnetic eruptions could have significant impacts on disk evolution, and thus planet formation, and also exoplanet habitability.

  5. White butterflies as solar photovoltaic concentrators

    Science.gov (United States)

    Shanks, Katie; Senthilarasu, S.; Ffrench-Constant, Richard H.; Mallick, Tapas K.

    2015-07-01

    Man’s harvesting of photovoltaic energy requires the deployment of extensive arrays of solar panels. To improve both the gathering of thermal and photovoltaic energy from the sun we have examined the concept of biomimicry in white butterflies of the family Pieridae. We tested the hypothesis that the V-shaped posture of basking white butterflies mimics the V-trough concentrator which is designed to increase solar input to photovoltaic cells. These solar concentrators improve harvesting efficiency but are both heavy and bulky, severely limiting their deployment. Here, we show that the attachment of butterfly wings to a solar cell increases its output power by 42.3%, proving that the wings are indeed highly reflective. Importantly, and relative to current concentrators, the wings improve the power to weight ratio of the overall structure 17-fold, vastly expanding their potential application. Moreover, a single mono-layer of scale cells removed from the butterflies’ wings maintained this high reflectivity showing that a single layer of scale cell-like structures can also form a useful coating. As predicted, the wings increased the temperature of the butterflies’ thorax dramatically, showing that the V-shaped basking posture of white butterflies has indeed evolved to increase the temperature of their flight muscles prior to take-off.

  6. White butterflies as solar photovoltaic concentrators.

    Science.gov (United States)

    Shanks, Katie; Senthilarasu, S; Ffrench-Constant, Richard H; Mallick, Tapas K

    2015-07-31

    Man's harvesting of photovoltaic energy requires the deployment of extensive arrays of solar panels. To improve both the gathering of thermal and photovoltaic energy from the sun we have examined the concept of biomimicry in white butterflies of the family Pieridae. We tested the hypothesis that the V-shaped posture of basking white butterflies mimics the V-trough concentrator which is designed to increase solar input to photovoltaic cells. These solar concentrators improve harvesting efficiency but are both heavy and bulky, severely limiting their deployment. Here, we show that the attachment of butterfly wings to a solar cell increases its output power by 42.3%, proving that the wings are indeed highly reflective. Importantly, and relative to current concentrators, the wings improve the power to weight ratio of the overall structure 17-fold, vastly expanding their potential application. Moreover, a single mono-layer of scale cells removed from the butterflies' wings maintained this high reflectivity showing that a single layer of scale cell-like structures can also form a useful coating. As predicted, the wings increased the temperature of the butterflies' thorax dramatically, showing that the V-shaped basking posture of white butterflies has indeed evolved to increase the temperature of their flight muscles prior to take-off.

  7. Solar flares associated coronal mass ejection accompanied with DH type II radio burst in relation with interplanetary magnetic field, geomagnetic storms and cosmic ray intensity

    Science.gov (United States)

    Chandra, Harish; Bhatt, Beena

    2018-04-01

    In this paper, we have selected 114 flare-CME events accompanied with Deca-hectometric (DH) type II radio burst chosen from 1996 to 2008 (i.e., solar cycle 23). Statistical analyses are performed to examine the relationship of flare-CME events accompanied with DH type II radio burst with Interplanetary Magnetic field (IMF), Geomagnetic storms (GSs) and Cosmic Ray Intensity (CRI). The collected sample events are divided into two groups. In the first group, we considered 43 events which lie under the CME span and the second group consists of 71 events which are outside the CME span. Our analysis indicates that flare-CME accompanied with DH type II radio burst is inconsistent with CSHKP flare-CME model. We apply the Chree analysis by the superposed epoch method to both set of data to find the geo-effectiveness. We observed different fluctuations in IMF for arising and decay phase of solar cycle in both the cases. Maximum decrease in Dst during arising and decay phase of solar cycle is different for both the cases. It is noted that when flare lie outside the CME span CRI shows comparatively more variation than the flare lie under the CME span. Furthermore, we found that flare lying under the CME span is more geo effective than the flare outside of CME span. We noticed that the time leg between IMF Peak value and GSs, IMF and CRI is on average one day for both the cases. Also, the time leg between CRI and GSs is on average 0 to 1 day for both the cases. In case flare lie under the CME span we observed high correlation (0.64) between CRI and Dst whereas when flare lie outside the CME span a weak correlation (0.47) exists. Thus, flare position with respect to CME span play a key role for geo-effectiveness of CME.

  8. Plasma heating in solar flares and their soft and hard X-ray emissions

    International Nuclear Information System (INIS)

    Falewicz, R.

    2014-01-01

    In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is

  9. Plasma Heating in Solar Flares and their Soft and Hard X-Ray Emissions

    Science.gov (United States)

    Falewicz, R.

    2014-07-01

    In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is

  10. Solar maximum mission

    International Nuclear Information System (INIS)

    Ryan, J.

    1981-01-01

    By understanding the sun, astrophysicists hope to expand this knowledge to understanding other stars. To study the sun, NASA launched a satellite on February 14, 1980. The project is named the Solar Maximum Mission (SMM). The satellite conducted detailed observations of the sun in collaboration with other satellites and ground-based optical and radio observations until its failure 10 months into the mission. The main objective of the SMM was to investigate one aspect of solar activity: solar flares. A brief description of the flare mechanism is given. The SMM satellite was valuable in providing information on where and how a solar flare occurs. A sequence of photographs of a solar flare taken from SMM satellite shows how a solar flare develops in a particular layer of the solar atmosphere. Two flares especially suitable for detailed observations by a joint effort occurred on April 30 and May 21 of 1980. These flares and observations of the flares are discussed. Also discussed are significant discoveries made by individual experiments

  11. Studying Light Color using White LED Lighting

    Science.gov (United States)

    Yamagishi, Misako; Yamaba, Kazuo; Nagata, Manori; Kubo, Chiho; Nokura, Kunihiro

    Recently, white Light Emitting Diodes (LEDs) are receiving attention worldwide as new lighting devices. This study examined effects of a lighting application on performance using white LEDs. The light color—the correlated color temperature (CCT) —was assessed. It affected to psychological states and physiological conditions. Three CCT conditions were respectively set for the experiment: 2500 K, 5000 K, and 8200 K. In all, 20 younger subjects (20-30 years old), 15 middle-aged to elderly subjects (45-60 years old) and 12 elderly subjects (over 65 years-old) participated. They were presented a Numerical Verification (NV) task for performance measurement. The psychological states on performance were evaluated using the lighting assessment questionnaire. The physiological conditions were recorded using an electrocardiograph. Results show that the effects of CCT differ among age groups. Especially, the performance of younger subjects might differ from CCT conditions; elderly subjects are affected by CCT condition because of their visual acuity or response to contrast of objects.

  12. 3D Reconnection and SEP Considerations in the CME-Flare Problem

    Science.gov (United States)

    Moschou, S. P.; Cohen, O.; Drake, J. J.; Sokolov, I.; Borovikov, D.; Alvarado Gomez, J. D.; Garraffo, C.

    2017-12-01

    Reconnection is known to play a major role in particle acceleration in both solar and astrophysical regimes, yet little is known about its connection with the global scales and its comparative contribution in the generation of SEPs with respect to other acceleration mechanisms, such as the shock at a fast CME front, in the presence of a global structure such as a CME. Coupling efforts, combining both particle and global scales, are necessary to answer questions about the fundamentals of the energetic processes evolved. We present such a coupling modeling effort that looks into particle acceleration through reconnection in a self-consistent CME-flare model in both particle and fluid regimes. Of special interest is the supra-thermal component of the acceleration due to the reconnection that will at a later time interact colliding with the solar atmospheric material of the more dense chromospheric layer and radiate in hard X- and γ-rays for super-thermal electrons and protons respectively. Two cutting edge computational codes are used to capture the global CME and flare dynamics, specifically a two fluid MHD code and a 3D PIC code for the flare scales. Finally, we are connecting the simulations with current observations in different wavelengths in an effort to shed light to the unified CME-flare picture.

  13. Principal component analysis of solar flares in the soft X-ray flux

    International Nuclear Information System (INIS)

    Teuber, D.L.; Reichmann, E.J.; Wilson, R.M.; National Aeronautics and Space Administration, Huntsville, AL

    1979-01-01

    Principal component analysis is a technique for extracting the salient features from a mass of data. It applies, in particular, to the analysis of nonstationary ensembles. Computational schemes for this task require the evaluation of eigenvalues of matrices. We have used EISPACK Matrix Eigen System Routines on an IBM 360-75 to analyze full-disk proportional-counter data from the X-ray event analyzer (X-REA) which was part of the Skylab ATM/S-056 experiment. Empirical orthogonal functions have been derived for events in the soft X-ray spectrum between 2.5 and 20 A during different time frames between June 1973 and January 1974. Results indicate that approximately 90% of the cumulative power of each analyzed flare is contained in the largest eigenvector. The first two largest eigenvectors are sufficient for an empirical curve-fit through the raw data and a characterization of solar flares in the soft X-ray flux. Power spectra of the two largest eigenvectors reveal a previously reported periodicity of approximately 5 min. Similar signatures were also obtained from flares that are synchronized on maximum pulse-height when subjected to a principal component analysis. (orig.)

  14. The evolution of flaring and non-flaring active regions

    Science.gov (United States)

    Kilcik, A.; Yurchyshyn, V.; Sahin, S.; Sarp, V.; Obridko, V.; Ozguc, A.; Rozelot, J. P.

    2018-06-01

    According to the modified Zurich classification, sunspot groups are classified into seven different classes (A, B, C, D, E, F and H) based on their morphology and evolution. In this classification, classes A and B, which are small groups, describe the beginning of sunspot evolution, while classes D, E and F describe the large and evolved groups. Class C describes the middle phase of sunspot evolution and the class H describes the end of sunspot evolution. Here, we compare the lifetime and temporal evolution of flaring and non-flaring active regions (ARs), and the flaring effect on ARs in these groups in detail for the last two solar cycles (1996 through 2016). Our main findings are as follows: (i) Flaring sunspot groups have longer lifetimes than non-flaring ones. (ii) Most of the class A, B and C flaring ARs rapidly evolve to higher classes, while this is not applicable for non-flaring ARs. More than 50 per cent of the flaring A, B and C groups changed morphologically, while the remaining D, E, F and H groups did not change remarkably after the flare activity. (iii) 75 per cent of all flaring sunspot groups are large and complex. (iv) There is a significant increase in the sunspot group area in classes A, B, C, D and H after flaring activity. In contrast, the sunspot group area of classes E and F decreased. The sunspot counts of classes D, E and F decreased as well, while classes A, B, C and H showed an increase.

  15. Flare Prediction Using Photospheric and Coronal Image Data

    Science.gov (United States)

    Jonas, Eric; Bobra, Monica; Shankar, Vaishaal; Todd Hoeksema, J.; Recht, Benjamin

    2018-03-01

    The precise physical process that triggers solar flares is not currently understood. Here we attempt to capture the signature of this mechanism in solar-image data of various wavelengths and use these signatures to predict flaring activity. We do this by developing an algorithm that i) automatically generates features in 5.5 TB of image data taken by the Solar Dynamics Observatory of the solar photosphere, chromosphere, transition region, and corona during the time period between May 2010 and May 2014, ii) combines these features with other features based on flaring history and a physical understanding of putative flaring processes, and iii) classifies these features to predict whether a solar active region will flare within a time period of T hours, where T = 2 and 24. Such an approach may be useful since, at the present time, there are no physical models of flares available for real-time prediction. We find that when optimizing for the True Skill Score (TSS), photospheric vector-magnetic-field data combined with flaring history yields the best performance, and when optimizing for the area under the precision-recall curve, all of the data are helpful. Our model performance yields a TSS of 0.84 ±0.03 and 0.81 ±0.03 in the T = 2- and 24-hour cases, respectively, and a value of 0.13 ±0.07 and 0.43 ±0.08 for the area under the precision-recall curve in the T=2- and 24-hour cases, respectively. These relatively high scores are competitive with previous attempts at solar prediction, but our different methodology and extreme care in task design and experimental setup provide an independent confirmation of these results. Given the similar values of algorithm performance across various types of models reported in the literature, we conclude that we can expect a certain baseline predictive capacity using these data. We believe that this is the first attempt to predict solar flares using photospheric vector-magnetic field data as well as multiple wavelengths of image

  16. The solar flare of 18 August 1979: Incoherent scatter radar data and photochemical model comparisons

    International Nuclear Information System (INIS)

    Zinn, J.; Sutherland, C.D.; Fenimore, E.E.; Ganguly, S.

    1988-04-01

    Measurements of electron density at seven D-region altidues were made with the Arecibo radar during a Class-X solar flare on 18 August 1979. Measurements of solar x-ray fluxes during the same period were available from the GOES-2 satellite (0.5 to 4 /angstrom/ and 1 to 8 /angstrom/) and from ISEE-3 (in four bands between 26 and 400 keV). From the x-ray flux data we computed ionization rates in the D-region and the associated chemical changes, using a coupled atmospheric chemistry and diffusion model (with 836 chemical reactions and 19 vertical levels). The computed electron densities matched the data fairly well after we had adjusted the rate coefficients of two reactions. We discuss the hierarchies among the many flare-induced chemical reactions in two altitude ranges within the D-region and the effects of adjusting several other rate coefficients. 51 refs., 6 figs., 3 tabs

  17. THE EFFECTS OF WAVE ESCAPE ON FAST MAGNETOSONIC WAVE TURBULENCE IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Pongkitiwanichakul, Peera; Chandran, Benjamin D. G.; Karpen, Judith T.; DeVore, C. Richard

    2012-01-01

    One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ( f ast waves ) . In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term. We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region. We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

  18. Light Sterile Neutrinos: A White Paper

    DEFF Research Database (Denmark)

    Abazajian, K. N.; Acero, M. A.; Agarwalla, S. K.

    2012-01-01

    This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data.......This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data....

  19. ON THE CAUSE OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Cassak, P. A.; Shepherd, L. S.; Drake, J. F.; Gosling, J. T.; Phan, T.-D.; Shay, M. A.

    2013-01-01

    A model of supra-arcade downflows (SADs), dark low density regions also known as tadpoles that propagate sunward during solar flares, is presented. It is argued that the regions of low density are flow channels carved by sunward-directed outflow jets from reconnection. The solar corona is stratified, so the flare site is populated by a lower density plasma than that in the underlying arcade. As the jets penetrate the arcade, they carve out regions of depleted plasma density which appear as SADs. The present interpretation differs from previous models in that reconnection is localized in space but not in time. Reconnection is continuous in time to explain why SADs are not filled in from behind as they would if they were caused by isolated descending flux tubes or the wakes behind them due to temporally bursty reconnection. Reconnection is localized in space because outflow jets in standard two-dimensional reconnection models expand in the normal (inflow) direction with distance from the reconnection site, which would not produce thin SADs as seen in observations. On the contrary, outflow jets in spatially localized three-dimensional reconnection with an out-of-plane (guide) magnetic field expand primarily in the out-of-plane direction and remain collimated in the normal direction, which is consistent with observed SADs being thin. Two-dimensional proof-of-principle simulations of reconnection with an out-of-plane (guide) magnetic field confirm the creation of SAD-like depletion regions and the necessity of density stratification. Three-dimensional simulations confirm that localized reconnection remains collimated

  20. OBSERVATIONS AND SIMULATIONS OF THE Na i D{sub 1} LINE PROFILES IN AN M-CLASS SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Kuridze, D.; Mathioudakis, M.; Jess, D. B.; Grant, S. D. T.; Kawate, T.; Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom); Christian, D. J. [Department of Physics and Astronomy, California State University, Northridge, CA 91330 (United States); Kowalski, A. F.; Allred, J. C. [NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Simões, P. J. A. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2016-12-01

    We study the temporal evolution of the Na i D{sub 1} line profiles in the M3.9 flare SOL2014-06-11T21:03 UT, using observations at high spectral resolution obtained with the Interferometric Bidimensional Spectrometer instrument on the Dunn Solar Telescope combined with radiative hydrodynamic simulations. Our results show a significant increase in the intensities of the line core and wings during the flare. The analysis of the line profiles from the flare ribbons reveals that the Na i D{sub 1} line has a central reversal with excess emission in the blue wing (blue asymmetry). We combine RADYN and RH simulations to synthesize Na i D{sub 1} line profiles of the flaring atmosphere and find good agreement with the observations. Heating with a beam of electrons modifies the radiation field in the flaring atmosphere and excites electrons from the ground state 3s {sup 2}S to the first excited state 3p {sup 2}P, which in turn modifies the relative population of the two states. The change in temperature and the population density of the energy states make the sodium line profile revert from absorption into emission. Furthermore, the rapid changes in temperature break the pressure balance between the different layers of the lower atmosphere, generating upflow/downflow patterns. Analysis of the simulated spectra reveals that the asymmetries of the Na i D{sub 1} flare profile are produced by the velocity gradients in the lower solar atmosphere.

  1. The EVE plus RHESSI DEM for Solar Flares, and Implications for Residual Non-Thermal X-Ray Emission

    Science.gov (United States)

    McTiernan, James; Caspi, Amir; Warren, Harry

    2016-05-01

    Solar flare spectra are typically dominated by thermal emission in the soft X-ray energy range. The low energy extent of non-thermal emission can only be loosely quantified using currently available X-ray data. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) to calculate the Differential Emission Measure (DEM) for solar flares. This improvement over the isothermal approximation helps to resolve the ambiguity in the range where the thermal and non-thermal components may have similar photon fluxes. This "crossover" range can extend up to 30 keV.Previous work (Caspi et.al. 2014ApJ...788L..31C) concentrated on obtaining DEM models that fit both instruments' observations well. For this current project we are interested in breaks and cutoffs in the "residual" non-thermal spectrum; i.e., the RHESSI spectrum that is left over after the DEM has accounted for the bulk of the soft X-ray emission. As in our earlier work, thermal emission is modeled using a DEM that is parametrized as multiple gaussians in temperature. Non-thermal emission is modeled as a photon spectrum obtained using a thin-target emission model ('thin2' from the SolarSoft Xray IDL package). Spectra for both instruments are fit simultaneously in a self-consistent manner.For this study, we have examined the DEM and non-thermal resuidual emission for a sample of relatively large (GOES M class and above) solar flares observed from 2011 to 2014. The results for the DEM and non-thermal parameters found using the combined EVE-RHESSI data are compared with those found using only RHESSI data.

  2. SUPPRESSION OF PARALLEL TRANSPORT IN TURBULENT MAGNETIZED PLASMAS AND ITS IMPACT ON THE NON-THERMAL AND THERMAL ASPECTS OF SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Bian, Nicolas H.; Kontar, Eduard P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Emslie, A. Gordon, E-mail: n.bian@physics.gla.ac.uk, E-mail: emslieg@wku.edu [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2016-06-20

    The transport of the energy contained in electrons, both thermal and suprathermal, in solar flares plays a key role in our understanding of many aspects of the flare phenomenon, from the spatial distribution of hard X-ray emission to global energetics. Motivated by recent RHESSI observations that point to the existence of a mechanism that confines electrons to the coronal parts of flare loops more effectively than Coulomb collisions, we here consider the impact of pitch-angle scattering off turbulent magnetic fluctuations on the parallel transport of electrons in flaring coronal loops. It is shown that the presence of such a scattering mechanism in addition to Coulomb collisional scattering can significantly reduce the parallel thermal and electrical conductivities relative to their collisional values. We provide illustrative expressions for the resulting thermoelectric coefficients that relate the thermal flux and electrical current density to the temperature gradient and the applied electric field. We then evaluate the effect of these modified transport coefficients on the flare coronal temperature that can be attained, on the post-impulsive-phase cooling of heated coronal plasma, and on the importance of the beam-neutralizing return current on both ambient heating and the energy loss rate of accelerated electrons. We also discuss the possible ways in which anomalous transport processes have an impact on the required overall energy associated with accelerated electrons in solar flares.

  3. On a Flat-shape Emission in the Solar Flare on 7th June 2012

    Czech Academy of Sciences Publication Activity Database

    Kotrč, Pavel; Kupryakov, Yu. A.; Kashapova, L. K.; Bárta, Miroslav

    2013-01-01

    Roč. 37, č. 2 (2013), s. 555-562 ISSN 1845-8319. [Hvar Astrophysical Colloquium /12./. Hvar, 03.09.2012-07.09.2012] R&D Projects: GA ČR GAP209/12/1652; GA ČR GA13-24782S Institutional support: RVO:67985815 Keywords : solar flare * energy relase * energy transport Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  4. Theoretical light curve for the recurrent nova RS Ophiuchi - Determination of the white dwarf mass, composition, and distance

    International Nuclear Information System (INIS)

    Kato, M.

    1991-01-01

    Sequences of steady mass-loss solutions are constructed for the envelopes on a white dwarf with mass 1.33, 1.35, 1.36, 1.37, and 1.377 solar mass as models of the decay phase of novae. The envelopes are assumed to have a uniform chemical composition with X = 0.73, 0.6, 0.52, 0.44, 0.33, and 0.11 for hydrogen and Z = 0.02 for heavy elements by weight. An excellent agreement with the observed light curves of UV and optical is obtained in the models with a white dwarf mass of 1.36 solar mass with hydrogen content X = 0.52, and 1.37 solar mass with X = 0.6. The distance of RS Oph is obtained to be 1.6 kpc from the comparison between the theoretical and observed light curves. The success of this wind model is a strong indication from the theoretical point of view that RS Oph is a thermonuclear runaway event. 31 refs

  5. Recent developments in white light emitting diodes

    Science.gov (United States)

    Lohe, P. P.; Nandanwar, D. V.; Belsare, P. D.; Moharil, S. V.

    2018-05-01

    In the recent years solid state lighting based on LEDs has revolutionized lighting technology. LEDs have many advantages over the conventional lighting based on fluorescent and incandescent lamps such as mercury free, high conversion efficiency of electrical energy into light, long lifetime reliability and ability to use with many types of devices. LEDs have emerged as a new potentially revolutionary technology that could save up to half of energy used for lighting applications. White LEDs would be the most important light source in the future, so much so that this aspect had been highlighted by the Nobel committee during the award of 2014 Nobel Prize for Physics. Recent advancement in the fabrication of GaN chip capable of emitting in blue and near UV region paved way for fabrication of white LED lamps. Mainly there are two approaches used for preparing white emitting solid state lamp. In the first approach blue light (λ=450 nm) emitted from the InGaN LED chip is partially absorbed by the YAG:Ce3+ phosphor coated on it and re-emitted as yellow fluorescence. A white light can be generated by the combination of blue + yellow emission bands. These lamps are already available. But they are suffering from major drawback that their Colour Rendering Index (CRI) is low. In the second approach, white LEDs are made by coating near ultraviolet emitting (360 to 410nm) LED with a mixture of high efficiency red, green and blue emitting phosphors, analogous to the fluorescent lamp. This method yields lamps with better color rendition. Addition of a yellow emitting phosphor improves CRI further. However conversion efficiency is compromised to some extent. Further the cost of near UV emitting chip is very high compared to blue emitting chips. Thus cost and light output wise, near UV chips are much inferior to blue chips. Recently some rare earth activated oxynitrides, silicates, fluorides have emerged as an important family of luminescent materials for white LED application

  6. Radio imaging of solar flares using the very large array - New insights into flare process

    Science.gov (United States)

    Kundu, M. R.; Schmahl, E. J.; Vlahos, L.; Velusamy, T.

    1982-01-01

    An interpretation of VLA observations of microwave bursts is presented in an attempt to distinguish between certain models of flares. The VLA observations provide information about the pre-flare magnetic field topology and the existence of mildly relativistic electrons accelerated during flares. Examples are shown of changes in magnetic field topology in the hour before flares. In one case, new bipolar loops appear to emerge, which is an essential component of the model developed by Heyvaerts et al. (1977). In another case, a quadrupole structure, suggestive of two juxtaposed bipolar loops, appears to trigger the flare. Because of the observed diversity of magnetic field topologies in microwave bursts, it is believed that the magnetic energy must be dissipated in more than one way. The VLA observations are clearly providing means for sorting out the diverse flare models.

  7. Estimating the contribution from different ionospheric regions to the TEC response to the solar flares using data from the international GPS network

    Directory of Open Access Journals (Sweden)

    L. A. Leonovich

    Full Text Available This paper proposes a new method for estimating the contribution from different ionospheric regions to the response of total electron content variations to the solar flare, based on data from the international network of two-frequency multichannel receivers of the navigation GPS system. The method uses the effect of partial "shadowing" of the atmosphere by the terrestrial globe. The study of the solar flare influence on the atmosphere uses GPS stations located near the boundary of the shadow on the ground in the nightside hemisphere. The beams between the satellite-borne transmitter and the receiver on the ground for these stations pass partially through the atmosphere lying in the region of total shadow, and partially through the illuminated atmosphere. The analysis of the ionospheric effect of a powerful solar flare of class X5.7/3B that was recorded on 14 July 2000 (10:24 UT, N22 W07 in quiet geomagnetic conditions (Dst = -10 nT has shown that about 75% of the TEC increase corresponds to the ionospheric region lying below 300 km and about 25% to regions lying above 300 km.

    Key words. Ionosphere (solar radiation and cosmic ray effects; instruments and techniques – Solar physics, astrophysics and astronomy (ultraviolet emissions

  8. Efficient and stable laser-driven white lighting

    Directory of Open Access Journals (Sweden)

    Kristin A. Denault

    2013-07-01

    Full Text Available Laser-based white lighting offers a viable option as an efficient and color-stable high-power solid-state white light source. We show that white light generation is possible using blue or near-UV laser diodes in combination with yellow-emitting cerium-substituted yttrium aluminum garnet (YAG:Ce or a mixture of red-, green-, and blue-emitting phosphors. A variety of correlated color temperatures (CCT are achieved, ranging from cool white light with a CCT of 4400 K using a blue laser diode to a warm white light with a CCT of 2700 K using a near-UV laser diode, with respective color rendering indices of 57 and 95. The luminous flux of these devices are measured to be 252 lm and 53 lm with luminous efficacies of 76 lm/W and 19 lm/W, respectively. An estimation of the maximum efficacy of a device comprising a blue laser diode in combination with YAG:Ce is calculated and the results are used to optimize the device.

  9. System of an analysis of a fine time structure of X-ray solar flares in the RGS-1M spectrometer

    International Nuclear Information System (INIS)

    Lazutkov, V.P.

    1980-01-01

    The possibilities of RGS-1M spectral equipment intended for determination of more detailed data on the solar flare structure are discussed. Spectrometer modernization permits to record the fine time structure of solar events in the hard X-ray range (50-90 keV). The main requirement for fine time analysis of nonstationary processes is determination of the maximum possible resolution at the maximum available length of the signal under investigation. The scheme of the time analyzer of splash events with the time resolution Δt=62.5 ms and the length of the range processed T=27.6 s is given and described. Operation of the spectrometer telemetric apparatus is considered in detail. The fine solar flare structure occurred on 14.04.79 with visually chosen periodic structure is shown as an example [ru

  10. Nanopatterned yttrium aluminum garnet phosphor incorporated film for high-brightness GaN-based white light emitting diodes

    International Nuclear Information System (INIS)

    Cho, Joong-yeon; Park, Sang-Jun; Ahn, Jinho; Lee, Heon

    2014-01-01

    In this study, we fabricated high-brightness white light emitting diodes (LEDs) by developing a nanopatterned yttrium aluminum garnet (YAG) phosphor-incorporated film. White light can be obtained by mixing blue light from a GaN-based LED and yellow light of the YAG phosphor-incorporated film. If white light sources can be fabricated by exciting proper yellow phosphor using blue light, then these sources can be used instead of the conventional fluorescent lamps with a UV source, for backlighting of displays. In this work, a moth-eye structure was formed on the YAG phosphor-incorporated film by direct spin-on glass (SOG) printing. The moth-eye structures have been investigated to improve light transmittance in various optoelectronic devices, including photovoltaic solar cells, light emitting diodes, and displays, because of their anti-reflection property. Direct SOG printing, which is a simple, easy, and relatively inexpensive process, can be used to fabricate nanoscale structures. After direct SOG printing, the moth-eye structure with a diameter of 220 nm was formed uniformly on the YAG phosphor-incorporated film. As a result of moth-eye patterning on the YAG phosphor-incorporated film, the light output power of a white LED with a patterned YAG phosphor-incorporated film increased to up to 13% higher than that of a white LED with a non-patterned film. - Highlights: • GaN-based high-brightness white LED was prepared using patterned YAG phosphor-incorporated films. • Direct hydrogen silsesquioxane printing was used to form moth-eye patterns on the YAG films. • The electroluminescence intensity of the white LED was enhanced by up to 14.9%

  11. Nanopatterned yttrium aluminum garnet phosphor incorporated film for high-brightness GaN-based white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Joong-yeon; Park, Sang-Jun [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Ahn, Jinho, E-mail: jhahn@hanyang.ac.kr [Department of Material Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Lee, Heon, E-mail: heonlee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of)

    2014-11-03

    In this study, we fabricated high-brightness white light emitting diodes (LEDs) by developing a nanopatterned yttrium aluminum garnet (YAG) phosphor-incorporated film. White light can be obtained by mixing blue light from a GaN-based LED and yellow light of the YAG phosphor-incorporated film. If white light sources can be fabricated by exciting proper yellow phosphor using blue light, then these sources can be used instead of the conventional fluorescent lamps with a UV source, for backlighting of displays. In this work, a moth-eye structure was formed on the YAG phosphor-incorporated film by direct spin-on glass (SOG) printing. The moth-eye structures have been investigated to improve light transmittance in various optoelectronic devices, including photovoltaic solar cells, light emitting diodes, and displays, because of their anti-reflection property. Direct SOG printing, which is a simple, easy, and relatively inexpensive process, can be used to fabricate nanoscale structures. After direct SOG printing, the moth-eye structure with a diameter of 220 nm was formed uniformly on the YAG phosphor-incorporated film. As a result of moth-eye patterning on the YAG phosphor-incorporated film, the light output power of a white LED with a patterned YAG phosphor-incorporated film increased to up to 13% higher than that of a white LED with a non-patterned film. - Highlights: • GaN-based high-brightness white LED was prepared using patterned YAG phosphor-incorporated films. • Direct hydrogen silsesquioxane printing was used to form moth-eye patterns on the YAG films. • The electroluminescence intensity of the white LED was enhanced by up to 14.9%.

  12. Rocket spectrogram of a solar flare in the 10-100 A region

    International Nuclear Information System (INIS)

    Acton, L.W.; Bruner, M.E.; Brown, W.A.; Fawcett, B.C.; Schweizer, W.; Speer, R.J.; Science and Engineering Research Council, Oxon, England; Fraunhofer Institut fuer physikalische Messtechnik, Freiburg-im-Breisgau, West Germany; Imperial College of Science and Technology, London, England)

    1985-01-01

    The soft (10-100 A) X-ray spectrum of an M-class solar flare was observed with a high-resolution (0.02 A) rocket-borne spectrograph on 1982 July 13. The spectrum samples an area of 600/sq arcsec on the sun, centered on or near the brightest X-ray feature of the flare. Several hundred emission lines characteristic of temperatures from about 0.5 to 7 x 10 to the 6th K have been photographically recorded. All but three of the stronger lines have been identified. It is argued that previous identification of the line at 17.62 A as iron Ly-alpha is incorrect. Spectral lines from nickel, iron, chromium, calcium, sulphur, silicon, aluminium, magnesium, neon, oxygen, nitrogen, and carbon are tabulated and discussed with extensive reference to earlier work. Absolute line intensities are given and the calibration of the telescope-spectrograph is discussed. 42 references

  13. Rocket spectrogram of a solar flare in the 10-100 A region

    Science.gov (United States)

    Acton, L. W.; Bruner, M. E.; Brown, W. A.; Fawcett, B. C.; Schweizer, W.; Speer, R. J.

    1985-01-01

    The soft (10-100 A) X-ray spectrum of an M-class solar flare was observed with a high-resolution (0.02 A) rocket-borne spectrograph on 1982 July 13. The spectrum samples an area of 600/sq arcsec on the sun, centered on or near the brightest X-ray feature of the flare. Several hundred emission lines characteristic of temperatures from about 0.5 to 7 x 10 to the 6th K have been photographically recorded. All but three of the stronger lines have been identified. It is argued that previous identification of the line at 17.62 A as iron Ly-alpha is incorrect. Spectral lines from nickel, iron, chromium, calcium, sulphur, silicon, aluminium, magnesium, neon, oxygen, nitrogen, and carbon are tabulated and discussed with extensive reference to earlier work. Absolute line intensities are given and the calibration of the telescope-spectrograph is discussed.

  14. The Effects of Flare Definitions on the Statistics of Derived Flare Distrubtions

    Science.gov (United States)

    Ryan, Daniel; Dominique, Marie; Seaton, Daniel B.; Stegen, Koen; White, Arthur

    2016-05-01

    The statistical examination of solar flares is crucial to revealing their global characteristics and behaviour. However, statistical flare studies are often performed using standard but basic flare detection algorithms relying on arbitrary thresholds which may affect the derived flare distributions. We explore the effect of the arbitrary thresholds used in the GOES event list and LYRA Flare Finder algorithms. We find that there is a small but significant relationship between the power law exponent of the GOES flare peak flux frequency distribution and the algorithms’ flare start thresholds. We also find that the power law exponents of these distributions are not stable but appear to steepen with increasing peak flux. This implies that the observed flare size distribution may not be a power law at all. We show that depending on the true value of the exponent of the flare size distribution, this deviation from a power law may be due to flares missed by the flare detection algorithms. However, it is not possible determine the true exponent from GOES/XRS observations. Additionally we find that the PROBA2/LYRA flare size distributions are clearly non-power law. We show that this is consistent with an insufficient degradation correction which causes LYRA absolute irradiance values to be unreliable. This means that they should not be used for flare statistics or energetics unless degradation is adequately accounted for. However they can be used to study time variations over shorter timescales and for space weather monitoring.

  15. Concentration of solar radiation by white backed photovoltaic panels.

    Science.gov (United States)

    Smestad, G; Hamill, P

    1984-12-01

    In this paper, we present an analysis of the concentration achieved by white backed photovoltaic panels. Concentration is due to the trapping by light scattered in the refractive plate to which the solar cell is bonded. Using the reciprocity relation and assuming the ideal case of a Lambertian distribution, a detailed model is formulated that includes the effects of the thickness and walls of the concentrator. This model converges to the thermodynamic limit and is found to be consistent with experimental results for a wide range of cell sizes. Finally, the model is generalized to multiple-cell photovoltaic panels.

  16. Unambiguous Evidence of Coronal Implosions during Solar Eruptions and Flares

    Science.gov (United States)

    Wang, Juntao; Simões, P. J. A.; Fletcher, L.

    2018-05-01

    In the implosion conjecture, coronal loops contract as the result of magnetic energy release in solar eruptions and flares. However, after almost two decades, observations of this phenomenon are still rare and most previous reports are plagued by projection effects so that loop contraction could be either true implosion or just a change in loop inclination. In this paper, to demonstrate the reality of loop contractions in the global coronal dynamics, we present four events with the continuously contracting loops in an almost edge-on geometry from the perspective of SDO/AIA, which are free from the ambiguity caused by the projection effects, also supplemented by contemporary observations from STEREO for examination. In the wider context of observations, simulations and theories, we argue that the implosion conjecture is valid in interpreting these events. Furthermore, distinct properties of the events allow us to identify two physical categories of implosion. One type demonstrates a rapid contraction at the beginning of the flare impulsive phase, as magnetic free energy is removed rapidly by a filament eruption. The other type, which has no visible eruption, shows a continuous loop shrinkage during the entire flare impulsive phase, which we suggest shows the ongoing conversion of magnetic free energy in a coronal volume. Corresponding scenarios are described that can provide reasonable explanations for the observations. We also point out that implosions may be suppressed in cases when a heavily mass-loaded filament is involved, possibly serving as an alternative account for their observational rarity.

  17. Detection of 3-Minute Oscillations in Full-Disk Lyman-alpha Emission During A Solar Flare

    Science.gov (United States)

    Milligan, R. O.; Ireland, J.; Fleck, B.; Hudson, H. S.; Fletcher, L.; Dennis, B. R.

    2017-12-01

    We report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyman-alpha (from GOES/EUVS) and Lyman continuum (from SDO/EVE) emission from the 2011 February 15 X-class flare revealed a 3-minute period present during the flare's main phase. The formation temperature of this emission locates this radiation to the flare's chromospheric footpoints, and similar behaviour is found in the SDO/AIA 1600A and 1700A channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray energies (50-100 keV) in RHESSI data we can state that this 3-minute oscillation does not depend on the rate of energization of, or energy deposition by, non-thermal electrons. However, a second period of 120 s found in both hard X-ray and chromospheric emission is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Lyman-alpha line may influence the composition and dynamics of planetary atmospheres during periods of high activity.

  18. White-Light Emission from Layered Halide Perovskites.

    Science.gov (United States)

    Smith, Matthew D; Karunadasa, Hemamala I

    2018-03-20

    With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the

  19. Towards developing a tandem of organic solar cell and light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [School of Engineering and IT, B-purple-12, Faculty of EHS, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-01-15

    It is proposed here to design a tandem of organic solar cell (OSC) and white organic light emitting diode (WOLED) which can generate power in the day time from the sun and provide lighting at night. With the advancement of chemical technology, such device is expected to be very-cost effective and reasonably efficient. A device thus fabricated has the potential of meeting the world's sustainable domestic and commercial power and lighting needs (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow...

  1. Relationship between Hard X-Ray Footpoint Sources and Photospheric Electric Currents in Solar Flares: a Statistical Study

    Science.gov (United States)

    Zimovets, I. V.; Sharykin, I. N.; Wang, R.; Liu, Y. D.; Kosovichev, A. G.

    2017-12-01

    It is believed that solar flares are a result of release of free magnetic energy contained in electric currents (ECs) flowing in active regions (ARs). However, there are still debates whether the primary energy release and acceleration of electrons take place in coronal current sheets or in chromospheric footpoints of current-carrying magnetic flux tubes (loops). We present results of an observational statistical study of spatial relationship between hard X-ray (HXR; EHXR≥50keV) footpoint sources detected by RHESSI and vertical photospheric ECs calculated using vector magnetograms obtained from the SDO/HMI data. We found that for a sample of 47 flares (from C3.0 to X3.1 class) observed on the solar disk by both instruments in 2010-2016, at least one HXR source was in a region of strong (within 20% of the maximum EC density in the corresponding ARs) vertical ECs having the form of a ribbon (79%) or an island (21%). The total vertical ECs in such HXR sources are in the range of 1010-1013 A. The EC density is in the range of 0.01-1.0 A/m2. We found no correlation between intensity of the HXR sources and the EC density. By comparing pre-flare and post-flare EC maps we did not find evidences of significant dissipation of vertical ECs in the regions corresponding to the HXR sources. In some cases, we found amplification of ECs during flares. We discuss effects of sensitivity and angular resolution of RHESSI and SDO/HMI. In general, the results indicate that there is a link between the flare HXR footpoint sources and enhanced vertical ECs in the photosphere. However, the results do not support a concept of electron acceleration by the electric field excited in footpoints of current-carrying loops due to some (e.g. Rayleigh-Taylor) instabilities (Zaitsev et al., 2016), since strong correlation between the HXR intensity and the EC density is expected in such concept.

  2. The analysis and the three-dimensional, forward-fit modeling of the X-ray and the microwave emissions of major solar flares

    Science.gov (United States)

    Kuroda, Natsuha; Wang, Haimin; Gary, Dale E.

    2017-08-01

    It is well known that the time profiles of the hard X-ray (HXR) emission and the microwave (MW) emission during the impulsive phase of the solar flare are well correlated, and that their analysis can lead to the understandings of the flare-accelerated electrons. In this work, we first studied the source locations of seven distinct temporal peaks observed in HXR and MW lightcurves of the 2011-02-15 X2.2 flare using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Nobeyama Radioheliograph. We found that the seven emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW, which is consistent with the tether-cutting model of solar flares. Next, we closely examine the widely-used notion of a "common population" of the accelerated electrons producing the HXR and the MW, which has been challenged by some studies suggesting the differences in the inferred energy spectral index and emitting energies of the HXR- and MW- producing electrons. We use the Non-linear Force Free Field model extrapolated from the observed photospheric magnetogram in the three-dimensional, multi-wavelength modeling platform GX Simulator, and attempt to create a unified electron population model that can simultaneously reproduce the observed X-ray and MW observations of the 2015-06-22 M6.5 flare. We constrain the model parameters by the observations made by the highest-resolving instruments currently available in two wavelengths, the RHESSI for X-ray and the Expanded Owens Valley Solar Array for MW. The results suggest that the X-ray emitting electron population model fits to the standard flare model with the broken, hardening power-law spectrum at ~300 keV that simultaneously produces the HXR footpoint emission and the MW high frequency emission, and also reveals that there could be a

  3. A trigger mechanism for the emerging flux model of solar flares

    International Nuclear Information System (INIS)

    Tur, T.J.; Priest, E.R.

    1978-01-01

    The energetics of a current sheet that forms between newly emerging flux and an ambient field are considered. As more and more flux emerges, so the sheet rises in the solar atmosphere. The various contributions to the thermal energy balance in the sheet approximated and the resulting equation solved for the internal temperature of the sheet. It is found that, for certain choices of the ambient magnetic field strength and velocity, the internal temperature increases until, when the sheet reaches some critical height, no neighbouring equilibrium state exists. The temperature than increases rapidly, seeking a hotter branch of the solution curve. During this dynamic heating the threshold temperature for the onset of plasma microinstabilities may be attained. It is suggested that this may be a suitable trigger mechanism for the recently proposed 'emerging flux' model of a solar flare. (Auth.)

  4. Investigation of Relationship between High-energy X-Ray Sources and Photospheric and Helioseismic Impacts of X1.8 Solar Flare of 2012 October 23

    Energy Technology Data Exchange (ETDEWEB)

    Sharykin, I. N.; Zimovets, I. V. [Space Research Institute (IKI) of the Russian Academy of Sciences, Moscow (Russian Federation); Kosovichev, A. G.; Sadykov, V. M. [New Jersey Institute of Technology, Newark, NJ (United States); Myshyakov, I. I., E-mail: ivan.sharykin@phystech.edu [Institute of Solar-Terrestrial Research (ISTP) of the Russian Academy of Sciences, Siberian Branch, Irkutsk (Russian Federation)

    2017-07-01

    The X-class solar flare of 2012 October 23 generated continuum photospheric emission and a strong helioseismic wave (“sunquake”) that points to an intensive energy release in the dense part of the solar atmosphere. We study properties of the energy release with high temporal and spatial resolutions, using photospheric data from the Helioseismic Magnetic Imager (HMI) on board Solar Dynamics Observatory , and hard X-ray observations made by RHESSI . For this analysis we use level-1 HMI data (filtergrams), obtained by scanning the Fe i line (6731 Å) with the time cadence of ∼3.6 s and spatial resolution of ∼0.″5 per pixel. It is found that the photospheric disturbances caused by the flare spatially coincide with the region of hard X-ray emission but are delayed by ≲4 s. This delay is consistent with predictions of the flare hydrodynamics RADYN models. However, the models fail to explain the magnitude of variations observed by the HMI. The data indicate that the photospheric impact and helioseismic wave might be caused by the electron energy flux, which is substantially higher than that in the current flare radiative hydrodynamic models.

  5. Using Supra-Arcade Downflows as Probes of Particle Acceleration in Solar Flares

    Science.gov (United States)

    Savage, Sabrina

    2012-01-01

    Extracting information from coronal features above flares has become more reliable with the availability of increasingly higher spatial- and temporal-resolution data in recent decades. We are now able to sufficiently probe the region high above long-duration flaring active regions where reconnection is expected to be continually occurring. Flows in the supra-arcade region, first observed with Yohkoh/SXT, have been theorized to be associated with newly-reconnected outflowing loops. High resolution data appears to confirm these assertions. Assuming that these flows are indeed reconnection outflows, then the detection of those directed toward the solar surface (i.e. downflowing) should be associated with particle acceleration between the current sheet and the loop footpoints rooted in the chromosphere. RHESSI observations of highly energetic particles with respect to downflow detections could potentially constrain electron acceleration models. We provide measurements of these supra-arcade downflows (SADs) in relation to reconnection model parameters and present preliminary findings comparing the downflow timings with high-energy RHESSI lightcurves.

  6. Using Supra-Arcade Downflows as Probes of Electron Acceleration During Solar Flares

    Science.gov (United States)

    Savage, Sabrina L.

    2011-01-01

    Extracting information from coronal features above flares has become more reliable with the availability of increasingly higher spatial and temporal-resolution data in recent decades. We are now able to sufficiently probe the region high above long-duration flaring active regions where reconnection is expected to be continually occurring. Flows in the supra-arcade region, first observed with Yohkoh/SXT, have been theorized to be associated with newly-reconnected outflowing loops. High resolution data appears to confirm these assertions. Assuming that these flows are indeed reconnection outflows, then the detection of those directed toward the solar surface (i.e. downflowing) should be associated with particle acceleration between the current sheet and the loop footpoints rooted in the chromosphere. RHESSI observations of highly energetic particles with respect to downflow detections could potentially constrain electron acceleration models. I will discuss measurements of these supra-arcade downflows (SADs) in relation to reconnection model parameters and present preliminary findings comparing the downflow timings with high-energy RHESSI lightcurves.

  7. Multiple-wavelength analysis of energy release during a solar flare - Thermal and nonthermal electron populations

    Science.gov (United States)

    Willson, Robert F.; Lang, Kenneth R.; Klein, Karl-Ludwig; Kerdraon, Alain; Trottet, Gerard

    1990-01-01

    Collaborative solar investigations by Tufts University and the Observatoire de Paris have resulted in simultaneous radio observations with the Very Large Array (VLA) and the Nancay Radioheliograph (NR), comparisons of this radio data with X-ray observations, and theoretical interpretations of the dominant radiation mechanisms during a weak impulsive solar flare observed on May 28, 1988. The VLA has mapped the flaring structures at time intervals of 3.3 s, showing that the preflash and flash-phase components of the impulsive emission originate in spatially separated sources. The 20.7 cm preflash source is ascribed to thermal gyroresonance emission from coronal loops with typical magnetic field strengths of up to 270 G; this emission is associated with heating and exhibits no detectable hard X-ray radiation above 30 keV. The flash-phase 20.7 cm source and the hard X-ray emission are attributed to nonthermal electrons in the coronal and chromospheric portions of a magnetic loop. The combination of imaging observations at 20.7 and 91.6 cm excludes emission from a confined hot plasma during the flash phase.

  8. Background Conditions for the October 29, 2003 Solar Flare by the AVS-F Apparatus Data

    Science.gov (United States)

    Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Lyapin, A. R.; Troitskaya, E. V.

    The background model for AVS-F apparatus onboard CORONAS-F satellite for the October 29, 2003 X10-class solar flare is discussed in the presented work. This background model developed for AVS-F counts rate in the low- and high-energy spectral ranges in both individual channels and summarized. Count rate were approximated by polynomials of high order taking into account the mean count rate in the geomagnetic equatorial region at the different orbits parts and Kp-index averaged on 5 bins in time interval from -24 to -12 hours before the time of geomagnetic equator passing. The observed averaged counts rate on equator in the region of geomagnetic latitude ±5o and estimated minimum count rate values are in coincidence within statistical errors for all selected orbits parts used for background modeling. This model will used to refine the estimated energy of registered during the solar flare spectral features and detailed analysis of their temporal profiles behavior both in corresponding energy bands and in summarized energy range.

  9. FLARES AND THEIR UNDERLYING MAGNETIC COMPLEXITY

    International Nuclear Information System (INIS)

    Engell, Alexander J.; Golub, Leon; Korreck, Kelly; Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara; Cirtain, Jonathan

    2011-01-01

    SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 x 10 33 T 1.9±0.1 .

  10. Recent advances in light outcoupling from white organic light-emitting diodes

    Science.gov (United States)

    Gather, Malte C.; Reineke, Sebastian

    2015-01-01

    Organic light-emitting diodes (OLEDs) have been successfully introduced to the smartphone display market and have geared up to become contenders for applications in general illumination where they promise to combine efficient generation of white light with excellent color quality, glare-free illumination, and highly attractive designs. Device efficiency is the key requirement for such white OLEDs, not only from a sustainability perspective, but also because at the high brightness required for general illumination, losses lead to heating and may, thus, cause rapid device degradation. The efficiency of white OLEDs increased tremendously over the past two decades, and internal charge-to-photon conversion can now be achieved at ˜100% yield. However, the extraction of photons remains rather inefficient (typically physics of outcoupling in white OLEDs and review recent progress toward making light extraction more efficient. We describe how structures that scatter, refract, or diffract light can be attached to the outside of white OLEDs (external outcoupling) or can be integrated close to the active layers of the device (internal outcoupling). Moreover, the prospects of using top-emitting metal-metal microcavity designs for white OLEDs and of tuning the average orientation of the emissive molecules within the OLED are discussed.

  11. PLASMA SLOSHING IN PULSE-HEATED SOLAR AND STELLAR CORONAL LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Reale, F., E-mail: fabio.reale@unipa.it [Dipartimento di Fisica and Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)

    2016-08-01

    There is evidence that coronal heating is highly intermittent, and flares are the high energy extreme. The properties of the heat pulses are difficult to constrain. Here, hydrodynamic loop modeling shows that several large amplitude oscillations (∼20% in density) are triggered in flare light curves if the duration of the heat pulse is shorter than the sound crossing time of the flaring loop. The reason for this is that the plasma does not have enough time to reach pressure equilibrium during heating, and traveling pressure fronts develop. The period is a few minutes for typical solar coronal loops, dictated by the sound crossing time in the decay phase. The long period and large amplitude make these oscillations different from typical magnetohydrodynamic (MHD) waves. This diagnostic can be applied both to observations of solar and stellar flares and to future observations of non-flaring loops at high resolution.

  12. Observations of solar flare transition zone plasmas from the Solar Maximum Mission

    Science.gov (United States)

    Cheng, C.-C.; Bruner, E. C.; Tandberg-Hanssen, E.; Woodgate, B. E.; Shine, R. A.; Kenny, P. J.; Henze, W.; Poletto, G.

    1982-01-01

    The spatial and temporal evolution of the Si IV and O IV intensity, density and mass motions in preflare and flare transition zone plasmas are studied for the case of the April 8, 1980 flare. It is found that: (1) the UV flare observed in the Si IV and O IV lines is unambiguously identified as occurring in a low-lying, preexisting transition zone loop which spanned the magnetic neutral line separating a larger leader spot and a newly emerged, isolated spot of opposite polarity; (2) at the onset of the flare, the easternmost footpoint, which was anchored in an isolated spot region of high longitudinal magnetic field gradient, showed sudden, impulsive brightening with large intensity increases; and (3) the release flare energy was transported by way of large-scale connecting field lines to other parts of the active region, producing the hot plasma and H-alpha kernels observed near the trailing spot.

  13. The Effect of Magnetic Topology on the Escape of Flare Particles

    Science.gov (United States)

    Antiochos, S. K.; Masson, S.; DeVore, C. R.

    2012-01-01

    Magnetic reconnection in the solar atmosphere is believed to be the driver of most solar explosive phenomena. Therefore, the topology of the coronal magnetic field is central to understanding the solar drivers of space weather. Of particular importance to space weather are the impulsive Solar Energetic particles that are associated with some CME/eruptive flare events. Observationally, the magnetic configuration of active regions where solar eruptions originate appears to agree with the standard eruptive flare model. According to this model, particles accelerated at the flare reconnection site should remain trapped in the corona and the ejected plasmoid. However, flare-accelerated particles frequently reach the Earth long before the CME does. We present a model that may account for the injection of energetic particles onto open magnetic flux tubes connecting to the Earth. Our model is based on the well-known 2.5D breakout topology, which has a coronal null point (null line) and a four-flux system. A key new addition, however, is that we include an isothermal solar wind with open-flux regions. Depending on the location of the open flux with respect to the null point, we find that the flare reconnection can consist of two distinct phases. At first, the flare reconnection involves only closed field, but if the eruption occurs close to the open field, we find a second phase involving interchange reconnection between open and closed. We argue that this second reconnection episode is responsible for the injection of flare-accelerated particles into the interplanetary medium. We will report on our recent work toward understanding how flare particles escape to the heliosphere. This work uses high-resolution 2.5D MHD numerical simulations performed with the Adaptively Refined MHD Solver (ARMS).

  14. Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Muhamad, J.; Kusano, K.; Inoue, S.; Shiota, D. [Institute for Space-Earth Environmental Research, Nagoya University, Furocho, Chikusa-ku, Nagoya, Aichi, 464-8601 (Japan)

    2017-06-20

    In order to understand the flare trigger mechanism, we conduct three-dimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles are imposed into the photospheric boundary of the Nonlinear Force-free Field model of Active Region (AR) NOAA 10930 on 2006 December 13, to investigate what kind of magnetic disturbance may trigger the flare. As a result, we confirm that certain small bipole fields, which emerge into the highly sheared global magnetic field of an AR, can effectively trigger a flare. These bipole fields can be classified into two groups based on their orientation relative to the polarity inversion line: the so-called opposite polarity, and reversed shear structures, as suggested by Kusano et al. We also investigate the structure of the footpoints of reconnected field lines. By comparing the distribution of reconstructed field lines and observed flare ribbons, the trigger structure of the flare can be inferred. Our simulation suggests that the data-constrained simulation, taking into account both the large-scale magnetic structure and small-scale magnetic disturbance (such as emerging fluxes), is a good way to discover a flare-producing AR, which can be applied to space weather prediction.

  15. Non-Gaussian Velocity Distributions in Solar Flares from Extreme Ultraviolet Lines: A Possible Diagnostic of Ion Acceleration

    International Nuclear Information System (INIS)

    Jeffrey, Natasha L. S.; Fletcher, Lyndsay; Labrosse, Nicolas

    2017-01-01

    In a solar flare, a large fraction of the magnetic energy released is converted rapidly to the kinetic energy of non-thermal particles and bulk plasma motion. This will likely result in non-equilibrium particle distributions and turbulent plasma conditions. We investigate this by analyzing the profiles of high temperature extreme ultraviolet emission lines from a major flare (SOL2014-03-29T17:44) observed by the EUV Imaging Spectrometer (EIS) on Hinode . We find that in many locations the line profiles are non-Gaussian, consistent with a kappa distribution of emitting ions with properties that vary in space and time. At the flare footpoints, close to sites of hard X-ray emission from non-thermal electrons, the κ index for the Fe xvi 262.976 Å line at 3 MK takes values of 3–5. In the corona, close to a low-energy HXR source, the Fe xxiii 263.760 Å line at 15 MK shows κ values of typically 4–7. The observed trends in the κ parameter show that we are most likely detecting the properties of the ion population rather than any instrumental effects. We calculate that a non-thermal ion population could exist if locally accelerated on timescales ≤0.1 s. However, observations of net redshifts in the lines also imply the presence of plasma downflows, which could lead to bulk turbulence, with increased non-Gaussianity in cooler regions. Both interpretations have important implications for theories of solar flare particle acceleration.

  16. June-July 1974 proton-flare region. III

    International Nuclear Information System (INIS)

    Bumba, V.

    1982-01-01

    In this third part of a series of papers describing the regularities in the magnetic field as well as solar activity development in a large portion of the solar atmosphere in which the processes related to the June-July 1974 proton-flare region formation take place, we study some characteristics of the solar wind which emanates from this portion of the solar atmosphere. It is shown that during the time when fast disintegration and disappearance of the large-scale characteristic magnetic field patterns occur and a sudden cease of sunspot, flare and coronal activity is observed, daily geomagnetic character figures C9 reach their maximum. This solar wind enhancement is taken as one of the last observable manifestations of the whole complex process. (author)

  17. STELLAR CORONAE, SOLAR FLARES: A DETAILED COMPARISON OF {sigma} GEM, HR 1099, AND THE SUN IN HIGH-RESOLUTION X-RAYS

    Energy Technology Data Exchange (ETDEWEB)

    Huenemoerder, David P. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139 (United States); Phillips, Kenneth J. H. [Visiting Scientist, Space Research Center, Polish Academy of Sciences, 51-622, Kopernika 11, Wroclaw (Poland); Sylwester, Janusz; Sylwester, Barbara, E-mail: dph@space.mit.edu, E-mail: kennethjhphillips@yahoo.com, E-mail: js@cbk.pan.wroc.pl, E-mail: bs@cbk.pan.wroc.pl [Space Research Center, Polish Academy of Sciences, 51-622, Kopernika 11, Wroclaw (Poland)

    2013-05-10

    The Chandra High Energy Transmission Grating Spectrometer (HETG) spectra of the coronally active binary stars {sigma} Gem and HR 1099 are among the highest fluence observations for such systems taken at high spectral resolution in X-rays with this instrument. This allows us to compare their properties in detail to solar flare spectra obtained with the Russian CORONAS-F spacecraft's RESIK instrument at similar resolution in an overlapping bandpass. Here we emphasize the detailed comparisons of the 3.3-6.1 A region (including emission from highly ionized S, Si, Ar, and K) from solar flare spectra to the corresponding {sigma} Gem and HR 1099 spectra. We also model the larger wavelength range of the HETG, from 1.7 to 25 A - having emission lines from Fe, Ca, Ar, Si, Al, Mg, Ne, O, and N-to determine coronal temperatures and abundances. {sigma} Gem is a single-lined coronally active long-period binary which has a very hot corona. HR 1099 is a similar, but shorter period, double-lined system. With very deep HETG exposures we can even study emission from some of the weaker species, such as K, Na, and Al, which are important since they have the lowest first ionization potentials, a parameter well known to be correlated with elemental fractionation in the solar corona. The solar flare temperatures reach Almost-Equal-To 20 MK, comparable to the {sigma} Gem and HR 1099 coronae. During the Chandra exposures, {sigma} Gem was slowly decaying from a flare and its spectrum is well characterized by a collisional ionization equilibrium plasma with a broad temperature distribution ranging from 2 to 60 MK, peaking near 25 MK, but with substantial emission from 50 MK plasma. We have detected K XVIII and Na XI emission which allow us to set limits on their abundances. HR 1099 was also quite variable in X-rays, also in a flare state, but had no detectable K XVIII. These measurements provide new comparisons of solar and stellar coronal abundances, especially at the lowest first

  18. X-ray Emission Characteristics of Flares Associated with CMEs ...

    Indian Academy of Sciences (India)

    tics of solar flares and their relationship with the dynamics of CMEs have ... lation between X-ray peak intensity of the flares with linear speed as well ... shear angle (θ1, measured at the flare onset), the final shear angle (θ2, measured at the.

  19. Polymer OLED White Light Development Program

    Energy Technology Data Exchange (ETDEWEB)

    Homer Antoniadis; Vi-En Choong; Stelios Choulis; Brian Cumpston; Rahul Gupta; Mathew Mathai; Michael Moyer; Franky So

    2005-12-19

    OSRAM Opto Semiconductors (OSRAM) successfully completed development, fabrication and characterization of the large area, polymer based white light OLED prototype at their OLED Research and Development (R&D) facility in San Jose, CA. The program, funded by the Department of Energy (DOE), consisted of three key objectives: (1) Develop new polymer materials and device architectures--in order to improve the performance of organic light emitters. (2) Develop processing techniques--in order to demonstrate and enable the manufacturing of large area, white light and color tunable, solid state light sources. (3) Develop new electronics and driving schemes for organic light sources, including color-tunable light sources. The key performance goals are listed. A world record efficiency of 25 lm/W was established for the solution processed white organic device from the significant improvements made during the project. However, the challenges to transfer this technology from an R&D level to a large tile format such as, the robustness of the device and the coating uniformity of large area panels, remain. In this regard, the purity and the blend nature of the materials are two factors that need to be addressed in future work. During the first year, OSRAM's Materials and Device group (M&D) worked closely with the major polymer material suppliers to develop the polymer emissive technology. M&D was successful in demonstrating a 7-8 lm/W white light source which was based on fluorescent materials. However, it became apparent that the major gains in efficiency could only be made if phosphorescent materials were utilized. Thus, in order to improve the performance of the resulting devices, the focus of the project shifted towards development of solution-processable phosphorescent light emitting diodes (PHOLEDs) and device architectures. The result is a higher efficiency than the outlined project milestone.

  20. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    OpenAIRE

    Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

    2010-01-01

    White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incand...

  1. Collective plasma effects associated with the continuous injection model of solar flare particle streams

    International Nuclear Information System (INIS)

    Vlahos, L.; Paradopoulos, K.

    1979-01-01

    A modified continous injection model for impulsive solar flares that includes self-consistently plasma nonlinearities based on the concept of marginal stability is presented. A quasi-stationary state is established, composed of a hot truncated electron Maxwellian distribution confined by acoustic turbulence on the top of the loop and energetic electron beams precipitating in the chromosphere. It is shown that the radiation properties of the models are in accordance with observations

  2. Collective plasma effects associated with the continuous injection model of solar flare particle streams

    Science.gov (United States)

    Vlahos, L.; Papadopoulos, K.

    1979-01-01

    A modified continuous injection model for impulsive solar flares that includes self-consistent plasma nonlinearities based on the concept of marginal stability is presented. A quasi-stationary state is established, composed of a hot truncated electron Maxwellian distribution confined by acoustic turbulence on the top of the loop and energetic electron beams precipitating in the chromosphere. It is shown that the radiation properties of the model are in accordance with observations.

  3. The Duration of Energy Deposition on Unresolved Flaring Loops in the Solar Corona

    Science.gov (United States)

    Reep, Jeffrey W.; Polito, Vanessa; Warren, Harry P.; Crump, Nicholas A.

    2018-04-01

    Solar flares form and release energy across a large number of magnetic loops. The global parameters of flares, such as the total energy released, duration, physical size, etc., are routinely measured, and the hydrodynamics of a coronal loop subjected to intense heating have been extensively studied. It is not clear, however, how many loops comprise a flare, nor how the total energy is partitioned between them. In this work, we employ a hydrodynamic model to better understand the energy partition by synthesizing Si IV and Fe XXI line emission and comparing to observations of these lines with the Interface Region Imaging Spectrograph (IRIS). We find that the observed temporal evolution of the Doppler shifts holds important information on the heating duration. To demonstrate this, we first examine a single loop model, and find that the properties of chromospheric evaporation seen in Fe XXI can be reproduced by loops heated for long durations, while persistent redshifts seen in Si IV cannot be reproduced by any single loop model. We then examine a multithreaded model, assuming both a fixed heating duration on all loops and a distribution of heating durations. For a fixed heating duration, we find that durations of 100–200 s do a fair job of reproducing both the red- and blueshifts, while a distribution of durations, with a median of about 50–100 s, does a better job. Finally, we compare our simulations directly to observations of an M-class flare seen by IRIS, and find good agreement between the modeled and observed values given these constraints.

  4. Solar flares, coronal mass ejections and solar energetic particle event characteristics

    Science.gov (United States)

    Papaioannou, Athanasios; Sandberg, Ingmar; Anastasiadis, Anastasios; Kouloumvakos, Athanasios; Georgoulis, Manolis K.; Tziotziou, Kostas; Tsiropoula, Georgia; Jiggens, Piers; Hilgers, Alain

    2016-12-01

    A new catalogue of 314 solar energetic particle (SEP) events extending over a large time span from 1984 to 2013 has been compiled. The properties as well as the associations of these SEP events with their parent solar sources have been thoroughly examined. The properties of the events include the proton peak integral flux and the fluence for energies above 10, 30, 60 and 100 MeV. The associated solar events were parametrized by solar flare (SF) and coronal mass ejection (CME) characteristics, as well as related radio emissions. In particular, for SFs: the soft X-ray (SXR) peak flux, the SXR fluence, the heliographic location, the rise time and the duration were exploited; for CMEs the plane-of-sky velocity as well as the angular width were utilized. For radio emissions, type III, II and IV radio bursts were identified. Furthermore, we utilized element abundances of Fe and O. We found evidence that most of the SEP events in our catalogue do not conform to a simple two-class paradigm, with the 73% of them exhibiting both type III and type II radio bursts, and that a continuum of event properties is present. Although, the so-called hybrid or mixed events are found to be present in our catalogue, it was not possible to attribute each SEP event to a mixed/hybrid sub-category. Moreover, it appears that the start of the type III burst most often precedes the maximum of the SF and thus falls within the impulsive phase of the associated SF. At the same time, type III bursts take place within ≈5.22 min, on average, in advance from the time of maximum of the derivative of the SXR flux (Neupert effect). We further performed a statistical analysis and a mapping of the logarithm of the proton peak flux at E > 10 MeV, on different pairs of the parent solar source characteristics. This revealed correlations in 3-D space and demonstrated that the gradual SEP events that stem from the central part of the visible solar disk constitute a significant radiation risk. The velocity of

  5. Solar Indices - Solar Flares

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This...

  6. A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

    Energy Technology Data Exchange (ETDEWEB)

    Longcope, D. W. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2014-11-01

    Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux F. These relations are explored and refined using a series of numerical investigations in which the transition region (TR) is represented by a simplified density jump. The maximum evaporation velocity, for example, is well approximated by v{sub e} ≅ 0.38(F/ρ{sub co,} {sub 0}){sup 1/3}, where ρ{sub co,} {sub 0} is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the TR both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.

  7. USING CLOSE WHITE DWARF + M DWARF STELLAR PAIRS TO CONSTRAIN THE FLARE RATES IN CLOSE STELLAR BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Dylan P.; West, Andrew A. [Astronomy Department, Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States); Becker, Andrew C., E-mail: dpmorg@bu.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2016-05-01

    We present a study of the statistical flare rates of M dwarfs (dMs) with close white dwarf (WD) companions (WD+dM; typical separations <1 au). Our previous analysis demonstrated that dMs with close WD companions are more magnetically active than their field counterparts. One likely implication of having a close binary companion is increased stellar rotation through disk-disruption, tidal effects, and/or angular momentum exchange; increased stellar rotation has long been associated with an increase in stellar activity. Previous studies show a strong correlation between dMs that are magnetically active (showing H α in emission) and the frequency of stellar flare rates. We examine the difference between the flare rates observed in close WD+dM binary systems and field dMs. Our sample consists of a subset of 181 close WD+dM pairs from Morgan et al. observed in the Sloan Digital Sky Survey Stripe 82, where we obtain multi-epoch observations in the Sloan ugriz -bands. We find an increase in the overall flaring fraction in the close WD+dM pairs (0.09 ± 0.03%) compared to the field dMs (0.0108 ± 0.0007%) and a lower flaring fraction for active WD+dMs (0.05 ± 0.03%) compared to active dMs (0.28 ± 0.05%). We discuss how our results constrain both the single and binary dM flare rates. Our results also constrain dM multiplicity, our knowledge of the Galactic transient background, and may be important for the habitability of attending planets around dMs with close companions.

  8. Forecasting Flare Activity Using Deep Convolutional Neural Networks

    Science.gov (United States)

    Hernandez, T.

    2017-12-01

    Current operational flare forecasting relies on human morphological analysis of active regions and the persistence of solar flare activity through time (i.e. that the Sun will continue to do what it is doing right now: flaring or remaining calm). In this talk we present the results of applying deep Convolutional Neural Networks (CNNs) to the problem of solar flare forecasting. CNNs operate by training a set of tunable spatial filters that, in combination with neural layer interconnectivity, allow CNNs to automatically identify significant spatial structures predictive for classification and regression problems. We will start by discussing the applicability and success rate of the approach, the advantages it has over non-automated forecasts, and how mining our trained neural network provides a fresh look into the mechanisms behind magnetic energy storage and release.

  9. Great microwave bursts and hard X-rays from solar flares

    International Nuclear Information System (INIS)

    Wiehl, H.J.; Batchelor, D.A.; Crannell, C.J.; Dennis, B.R.; Price, P.N.

    1983-06-01

    The microwave and hard X-ray charateristics of 13 solar flares that produced microwave fluxes greater than 500 Solar Flux Units were analyzed. These Great Microwave Bursts were observed in the frequency range from 3 to 35 GHz at Berne, and simultaneous hard X-ray observations were made in the energy range from 30 to 500 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission spacecraft. The principal aim of this analysis is to determine whether or not the same distribution of energetic electrons can explain both emissions. Correlations were found between respective temporal characteristics and, for the first time, between microwave and hard X-ray spectral characteristics. A single-temperature and a multi-temperature model from the literature were tested for consistency with the coincident X-ray and microwave spectra at microwave burst maximum. Four events are inconsistent with both of the models tested, and neither of the models attempts to explain the high-frequency part of the microwave spectrum. A model in which the emissions above and below the peak frequency originate in two different parts of a diverging magnetic loop is proposed. With this model the entire microwave spectrum of all but one of the events is explained

  10. Statistical analysis of tiny SXR flares observed by SphinX

    Science.gov (United States)

    Gryciuk, Magdalena; Siarkowski, Marek; Sylwester, Janusz; Kepa, Anna; Gburek, Szymon; Mrozek, Tomasz; Podgórski, Piotr

    2015-08-01

    The Solar Photometer in X-rays (SphinX) was designed to observe soft X-ray solar emission in the energy range between ~1 keV and 15 keV with the resolution better than 0.5 keV. The instrument operated from February until November 2009 aboard CORONAS-Photon satellite, during the phase of exceptionally low minimum of solar activity. Here we use SphinX data for analysis of micro-flares and brightenings. Despite a very low activity more than a thousand small X-ray events have been recognized by semi-automatic inspection of SphinX light curves. A catalogue of temporal and physical characteristics of these events is shown and discussed and results of the statistical analysis of the catalogue data are presented.

  11. Determination of solar flare accelerated ion angular distributions from SMM gamma ray and neutron measurements and determination of the He-3/H ratio in the solar photosphere from SMM gamma ray measurements

    Science.gov (United States)

    Lingenfelter, Richard E.

    1989-01-01

    Comparisons of Solar Maximum Mission (SMM) observations of gamma-ray line and neutron emission with theoretical calculation of their expected production by flare accelerated ion interactions in the solar atmosphere have led to significant advances in the understanding of solar flare particle acceleration and interaction, as well as the flare process itself. These comparisons have enabled the determination of, not only the total number and energy spectrum of accelerated ions trapped at the sun, but also the ion angular distribution as they interact in the solar atmosphere. The Monte Carlo program was modified to include in the calculations of ion trajectories the effects of both mirroring in converging magnetic fields and of pitch angle scattering. Comparing the results of these calculations with the SMM observations, not only the angular distribution of the interacting ions can be determined, but also the initial angular distribution of the ions at acceleration. The reliable determination of the solar photospheric He-3 abundance is of great importance for understanding nucleosynthesis in the early universe and its implications for cosmology, as well as for the study of the evolution of the sun. It is also essential for the determinations of the spectrum and total number of flare accelerated ions from the SMM/GRS gamma-ray line measurements. Systematic Monte Carlo calculations of the time dependence were made as a function of the He-3 abundance and other variables. A new series of calculations were compared for the time-dependent flux of 2.223 MeV neutron capture line emission and the ratio of the time-integrated flux in the 2.223 MeV line to that in the 4.1 to 6.4 MeV nuclear deexcitation band.

  12. Solar flares at submillimeter wavelengths

    Czech Academy of Sciences Publication Activity Database

    Krucker, S.; Gimenez de Castro, C.G.; Hudson, H. S.; Trottet, G.; Bastian, T.S.; Hales, A.S.; Kašparová, Jana; Klein, K. L.; Kretzschmar, M.; Luethi, T.; Mackinnon, A.; Pohjolainen, S.; White, S.M.

    2013-01-01

    Roč. 21, č. 1 (2013), 58/1-58/45 ISSN 0935-4956 Institutional support: RVO:67985815 Keywords : Sun * flares * radio observations Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 13.312, year: 2013

  13. Reconnection Fluxes in Eruptive and Confined Flares and Implications for Superflares on the Sun

    Science.gov (United States)

    Tschernitz, Johannes; Veronig, Astrid M.; Thalmann, Julia K.; Hinterreiter, Jürgen; Pötzi, Werner

    2018-01-01

    We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use Hα filtergrams from Kanzelhöhe Observatory together with Solar Dynamics Observatory HMI and Solar and Heliospheric Observatory MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux is strongly correlated with the peak of the GOES 1–8 Å soft X-ray flux (c = 0.92, in log–log space) for both confined and eruptive flares. Confined flares of a certain GOES class exhibit smaller ribbon areas but larger magnetic flux densities in the flare ribbons (by a factor of 2). In the largest events, up to ≈50% of the magnetic flux of the active region (AR) causing the flare is involved in the flare magnetic reconnection. These findings allow us to extrapolate toward the largest solar flares possible. A complex solar AR hosting a magnetic flux of 2 × 1023 Mx, which is in line with the largest AR fluxes directly measured, is capable of producing an X80 flare, which corresponds to a bolometric energy of about 7 × 1032 erg. Using a magnetic flux estimate of 6 × 1023 Mx for the largest solar AR observed, we find that flares of GOES class ≈X500 could be produced (E bol ≈ 3 × 1033 erg). These estimates suggest that the present day’s Sun is capable of producing flares and related space weather events that may be more than an order of magnitude stronger than have been observed to date.

  14. Calibration of Solar Radio Spectrometer of the Purple Mountain Observatory

    Science.gov (United States)

    Lei, LU; Si-ming, LIU; Qi-wu, SONG; Zong-jun, NING

    2015-10-01

    Calibration is a basic and important job in solar radio spectral observations. It not only deduces the solar radio flux as an important physical quantity for solar observations, but also deducts the flat field of the radio spectrometer to display the radio spectrogram clearly. In this paper, we first introduce the basic method of calibration based on the data of the solar radio spectrometer of Purple Mountain Observatory. We then analyze the variation of the calibration coefficients, and give the calibrated results for a few flares. These results are compared with those of the Nobeyama solar radio polarimeter and the hard X-ray observations of the RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) satellite, it is shown that these results are consistent with the characteristics of typical solar flare light curves. In particular, the analysis on the correlation between the variation of radio flux and the variation of hard X-ray flux in the pulsing phase of a flare indicates that these observations can be used to study the relevant radiation mechanism, as well as the related energy release and particle acceleration processes.

  15. Flare Ribbon Expansion and Energy Release Ayumi Asai , Takaaki ...

    Indian Academy of Sciences (India)

    2001-04-10

    1Nobeyama Solar Radio Observatory, Minamisaku, Nagano, 384-1305, Japan. ... X2.3 solar flare which occurred on April 10, 2001. .... In the right panel of. Fig. 3, we show the temporal variation of the physical parameters, such as Bp, vf , ˙ , and S along a slit line. Here, we defined vf as the speed of the flare-ribbon ...

  16. White light Sagnac interferometer—a common (path) tale of light

    International Nuclear Information System (INIS)

    Schwartz, Eyal

    2017-01-01

    White or polychromatic light sources are vastly abundant in nature and lie in our most basic understanding of the theory of light, beginning from stars like our Sun and extending to every common household light bulb or street lamp. In this paper, I present concepts of white light interferometery using a common-path Sagnac interferometer, manifested in a straightforward laboratory experiment. I further show the use of this as a Fourier transform spectrometer while presenting a basic overview of the theoretical concepts and spectrum of different light sources obtained experimentally. This work, both experimentally and analytically, is suitable for upper-level undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment and theory presents important deep concepts and aspects in modern optics and physics that every science student should acquire. (paper)

  17. White light Sagnac interferometer—a common (path) tale of light

    Science.gov (United States)

    Schwartz, Eyal

    2017-11-01

    White or polychromatic light sources are vastly abundant in nature and lie in our most basic understanding of the theory of light, beginning from stars like our Sun and extending to every common household light bulb or street lamp. In this paper, I present concepts of white light interferometery using a common-path Sagnac interferometer, manifested in a straightforward laboratory experiment. I further show the use of this as a Fourier transform spectrometer while presenting a basic overview of the theoretical concepts and spectrum of different light sources obtained experimentally. This work, both experimentally and analytically, is suitable for upper-level undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment and theory presents important deep concepts and aspects in modern optics and physics that every science student should acquire.

  18. Steering and filtering white light with resonant waveguide gratings

    Science.gov (United States)

    Quaranta, Giorgio; Basset, Guillaume; Martin, Olivier J. F.; Gallinet, Benjamin

    2017-08-01

    A novel thin-film single-layer structure based on resonant waveguide gratings (RWGs) allows to engineer selective color filtering and steering of white light. The unit cell of the structure consists of two adjacent finite-length and cross-talking RWGs, where the former acts as in-coupler and the latter acts as out-coupler. The structure is made by only one nano-imprint lithography replication and one thin film layer deposition, making it fully compatible with up-scalable fabrication processes. We characterize a fabricated optical security element designed to work with the flash and the camera of a smartphone in off-axis light steering configuration, where the pattern is revealed only by placing the smartphone in the proper position. Widespread applications are foreseen in a variety of fields, such as multifocal or monochromatic lenses, solar cells, biosensors, security devices and seethrough optical combiners for near-eye displays.

  19. Three-dimensional configuration and damping effect of flare coronal transients

    International Nuclear Information System (INIS)

    Ivanov, K.G.; Kharshiladze, A.F.

    1989-01-01

    Inverse problem of searching for three - dimensional configuration of coronal mass outburst (CMO) in the class of flattened spheroids was solved on the basis of solving primal problem of projecting CMO of the given configuration on celestial plane, using experimental data of white light coronograph. It was obtained that CMO, as interplanetary shock waves, were oblate with ∼ 1.25 ratio of axes to the plane of great circle, passing through the flare, parallel to magnetic axis of the nearest bipolar group

  20. SLIPPING MAGNETIC RECONNECTION, CHROMOSPHERIC EVAPORATION, IMPLOSION, AND PRECURSORS IN THE 2014 SEPTEMBER 10 X1.6-CLASS SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Dudík, Jaroslav; Karlický, Marian; Dzifčáková, Elena [Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65 Ondřejov (Czech Republic); Polito, Vanessa; Mulay, Sargam M.; Zanna, Giulio Del; Mason, Helen E. [Department of Applied Mathematics and Theoretical Physics, CMS, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Janvier, Miho [Institut d’Astrophysique Spatiale, Centre Universitaire d’Orsay, Bt 120121, F-91405 Orsay Cedex (France); Aulanier, Guillaume; Schmieder, Brigitte, E-mail: dudik@asu.cas.cz [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, Univ. Paris-Diderot, Sorbonne Paris Cit, 5 place Jules Janssen, F-92195 Meudon (France)

    2016-05-20

    We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. Slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions toward both ends of the ribbons. Velocities of 20–40 km s{sup −1} are found within time windows where the slipping is well resolved. The warm coronal loops exhibit expanding and contracting motions that are interpreted as displacements due to the growing flux rope that subsequently erupts. This flux rope existed and erupted before the onset of apparent coronal implosion. This indicates that the energy release proceeds by slipping reconnection and not via coronal implosion. The slipping reconnection leads to changes in the geometry of the observed structures at the Interface Region Imaging Spectrograph slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromospheric evaporation in the early flare phase. Finally, it is found that the precursor signatures, including localized EUV brightenings as well as nonthermal X-ray emission, are signatures of the flare itself, progressing from the early phase toward the impulsive phase, with the tether-cutting being provided by the slipping reconnection. The dynamics of both the flare and outlying coronal loops is found to be consistent with the predictions of the standard solar flare model in three dimensions.