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Sample records for chromosphere

  1. A chromospheric conundrum?

    CERN Document Server

    Judge, Philip; Schmidt, Wolgang; Steiner, Oskar

    2010-01-01

    We examine spectra of the Ca II H line, obtained under good seeing conditions with the VTT Echelle Spectrograph in June of 2007, and higher resolution data of the Ca II 8542 Angstrom line from Fabry-Perot instruments. The VTT targets were areas near disk center which included quiet Sun and some dispersed plage. The infrared data included quiet Sun and plage associated with small pores. Bright chromospheric network emission patches expand little with wavelength from line wing to line center, i.e. with increasing line opacity and height. We argue that this simple observation has implications for the force and energy balance of the chromosphere, since bright chromospheric network emission is traditionally associated with enhanced local mechanical heating which increases temperatures and pressures. Simple physical considerations then suggest that the network chromosphere may not be able to reach horizontal force balance with its surroundings, yet the network is a long-lived structure. We speculate on possible rea...

  2. Stellar Chromospheric Activity

    Directory of Open Access Journals (Sweden)

    Hall Jeffrey C.

    2008-03-01

    Full Text Available The Sun, stars similar to it, and many rather dissimilar to it, have chromospheres, regions classically viewed as lying above the brilliant photosphere and characterized by a positive temperature gradient and a marked departure from radiative equilibrium. Stellar chromospheres exhibit a wide range of phenomena collectively called activity, stemming largely from the time evolution of their magnetic fields and the mass flux and transfer of radiation through the complex magnetic topology and the increasingly optically thin plasma of the outer stellar atmosphere. In this review, I will (1 outline the development of our understanding of chromospheric structure from 1960 to the present, (2 discuss the major observational programs and theoretical lines of inquiry, (3 review the origin and nature of both solar and stellar chromospheric activity and its relationship to, and effect on, stellar parameters including total energy output, and (4 summarize the outstanding problems today.

  3. A Chromospheric Conundrum?

    Science.gov (United States)

    Judge, Philip; Knölker, Michael; Schmidt, Wolfgang; Steiner, Oskar

    2010-09-01

    We examine spectra of the Ca II H line, obtained under good seeing conditions with the VTT Echelle Spectrograph in 2007 June, and higher resolution data of the Ca II λ8542 line from Fabry-Pérot instruments. The VTT targets were areas near disk center which included quiet Sun and some dispersed plage. The infrared data included quiet Sun and plage associated with small pores. Bright chromospheric network emission patches expand little with wavelength from line wing to line center, i.e., with increasing line opacity and height. We argue that this simple observation has implications for the force and energy balance of the chromosphere, since bright chromospheric network emission is traditionally associated with enhanced local mechanical heating which increases temperatures and pressures. Simple physical considerations then suggest that the network chromosphere may not be able to reach horizontal force balance with its surroundings, yet the network is a long-lived structure. We speculate on possible reasons for the observed behavior. By drawing attention to a potential conundrum, we hope to contribute to a better understanding of a long-standing unsolved problem: the heating of the chromospheric network.

  4. The chromosphere and prominence magnetometer

    OpenAIRE

    de Wijn, Alfred G.; Bethge, Christian; Tomczyk, Steven; McIntosh, Scott

    2012-01-01

    The Chromosphere and Prominence Magnetometer (ChroMag) is conceived with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro-polarimetry of the full solar disk. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will prov...

  5. The chromosphere during solar flares

    OpenAIRE

    Fletcher, Lyndsay

    2010-01-01

    The emphasis of observational and theoretical flare studies in the last decade or two has been on the flare corona, and attention has shifted substantially away from the flare's chromospheric aspects. However, although the pre-flare energy is stored in the corona, the radiative flare is primarily a chromospheric phenomenon, and its chromospheric emission presents a wealth of diagnostics for the thermal and non-thermal components of the flare. I will here review the chromospheric signatures of...

  6. A chromospheric conundrum?

    OpenAIRE

    Judge, Philip; Knoelker, Michael; Schmidt, Wolgang; Steiner, Oskar

    2010-01-01

    We examine spectra of the Ca II H line, obtained under good seeing conditions with the VTT Echelle Spectrograph in June of 2007, and higher resolution data of the Ca II 8542 Angstrom line from Fabry-Perot instruments. The VTT targets were areas near disk center which included quiet Sun and some dispersed plage. The infrared data included quiet Sun and plage associated with small pores. Bright chromospheric network emission patches expand little with wavelength from line wing to line center, i...

  7. Chromospheric activity as age indicator

    CERN Document Server

    Pace, Giancarlo

    2013-01-01

    Chromospheric activity has been calibrated and widely used as age indicator. However, it has been suggested that the viability of such an age indicator is, in the best case, limited to stars younger than about 1.5 Gyr. I aim to define the age range for which chromospheric activity is a robust astrophysical clock. I collected literature measurements of the S-index in field stars, which is a measure of the strength of the H and K lines of the Ca II and a proxy for chromospheric activity, and exploited the homogeneous database of temperature and age determinations for field stars provided by the Geneva-Copenhagen survey of the Solar neighbourhood. Field data, inclusive data previously used to calibrate chromospheric ages, confirm the result found using open cluster data, i.e. there is no decay of chromospheric activity after about 2 Gyr. The only existing indication supporting the viability of chromospheric ages larger than 2 Gyr, is the similarity of chromospheric activity levels in the components of 35 dwarf b...

  8. Connections: Photosphere -- Chromosphere - Corona

    Science.gov (United States)

    Gudiksen, B. V.

    2006-12-01

    The chromosphere is not only the region where the atmosphere goes from being optically thick to optically thin, but also the region where the dynamics changes from being controlled by the plasma to being controlled by the magnetic field. The magnetic field changes from being concentrated in small regions to being space filling. This expansion has traditionally been modeled by the magnetic funnel or wine-glass picture. For several reasons it is hard to gain any information about the magnetic field in this region, so this model remains unconfirmed. Three recent methods to acquire magnetic field information from this interesting region will be reviewed, and I will argue that the results from such investigations will require that we heavily revise the simplistic magnetic funnel picture.

  9. Stable umbral chromospheric structures

    Science.gov (United States)

    Henriques, V. M. J.; Scullion, E.; Mathioudakis, M.; Kiselman, D.; Gallagher, P. T.; Keenan, F. P.

    2015-02-01

    Aims: We seek to understand the morphology of the chromosphere in sunspot umbra. We investigate if the horizontal structures observed in the spectral core of the Ca II H line are ephemeral visuals caused by the shock dynamics of more stable structures, and examine their relationship with observables in the H-alpha line. Methods: Filtergrams in the core of the Ca II H and H-alpha lines as observed with the Swedish 1-m Solar Telescope are employed. We utilise a technique that creates composite images and tracks the flash propagation horizontally. Results: We find 0.̋15 wide horizontal structures, in all of the three target sunspots, for every flash where the seeing is moderate to good. Discrete dark structures are identified that are stable for at least two umbral flashes, as well as systems of structures that live for up to 24 min. We find cases of extremely extended structures with similar stability, with one such structure showing an extent of 5''. Some of these structures have a correspondence in H-alpha, but we were unable to find a one-to-one correspondence for every occurrence. If the dark streaks are formed at the same heights as umbral flashes, there are systems of structures with strong departures from the vertical for all three analysed sunspots. Conclusions: Long-lived Ca II H filamentary horizontal structures are a common and likely ever-present feature in the umbra of sunspots. If the magnetic field in the chromosphere of the umbra is indeed aligned with the structures, then the present theoretical understanding of the typical umbra needs to be revisited. Movies associated to Figs. 3 and 4 are available in electronic form at http://www.aanda.org

  10. Stable Umbral Chromospheric Structures

    CERN Document Server

    Henriques, V M J; Mathioudakis, M; Kiselman, D; Gallagher, P T; Keenan, F P

    2014-01-01

    Aims. To understand the morphology of the chromosphere in sunspot umbra. We investigate if the horizontal structures observed in the spectral core of the Ca II H line are ephemeral visuals caused by the shock dynamics of more stable structures, and examine their relationship with observables in the H-alpha line. Methods. Filtergrams in the core of the Ca II H and H-alpha lines as observed with the Swedish 1-m Solar Telescope are employed. We utilise a technique that creates composite images and tracks the flash propagation horizontally. Results. We find 0"15 wide horizontal structures, in all of the three target sunspots, for every flash where the seeing was moderate to good. Discrete dark structures are identified that are stable for at least two umbral flashes, as well as systems of structures that live for up to 24 minutes. We find cases of extremely extended structures with similar stability, with one such structure showing an extent of 5". Some of these structures have a correspondence in H-alpha but we ...

  11. Waves in the chromosphere: observations

    CERN Document Server

    Rutten, R J

    2010-01-01

    I review the literature on observational aspects of waves in the solar chromosphere in the first part of this contribution. High-frequency waves are invoked to build elaborate cool-star chromosphere heating theories but have not been detected decisively so far, neither as magnetic modes in network elements nor as acoustic modes in below-the-canopy internetwork regions. Three-minute upward-propagating acoustic shocks are thoroughly established through numerical simulation as the cause of intermittent bright internetwork grains, but their pistoning and their role in the low-chromosphere energy budget remain in debate. Three-minute wave interaction with magnetic canopies is a newer interest, presently progressing through numerical simulation. Three-minute umbral flashes and running penumbral waves seem a similar acoustic-shock phenomenon awaiting numerical simulation. The low-frequency network Doppler modulation remains enigmatic. In the second part, I address low-frequency ultraviolet brightness variations of t...

  12. CHROMOSPHERIC EVAPORATION VIA ALFVEN WAVES

    International Nuclear Information System (INIS)

    This paper presents a scenario for the chromospheric evaporation during solar flares, which is inspired by the chain of events leading to the formation of auroral arcs and ionospheric evacuation during magnetospheric substorms. The plasma, ejected from high coronal altitudes during a flare reconnection event, accumulates at the tops of coronal loops by braking of the reconnection flow, possibly by fast shock formation. A high-beta layer forms and distorts the magnetic field. Energy contained in magnetic shear stresses is transported as Alfven waves from the loop-top toward the chromosphere. It is shown that under these conditions the Alfven waves carry enough energy to feed the chromospheric evaporation process. The second subject of this investigation is identification of the most effective energy dumping or wave dissipation process. Several processes are being analyzed: ion-neutral collisions, classical and anomalous field-aligned current dissipation, and critical velocity ionization. All of them are being discarded, either because they turn out to be insufficient or imply very unlikely physical properties of the wave modes. It is finally concluded that turbulent fragmentation of the Alfven waves entering the chromosphere can generate the required damping. The basic process would be phase mixing caused by a strongly inhomogeneous distribution of Alfvenic phase speed and laminar flow breakup by Kelvin-Helmholtz (K-H) instability. The filamentary (fibril) structure of the chromosphere thus appears to be essential for the energy conversion, in which the K-H instability is the first step in a chain of processes leading to ion thermalization, electron heating, and neutral particle ionization. Quantitative estimates suggest that a transverse structure with scales not far below 100 km suffices to produce strong wave damping within a few seconds. Nonthermal broadening of some metallic ion lines observed during the pre-impulsive rise phase of a flare might be a residue of

  13. The Chromosphere and Prominence Magnetometer

    Science.gov (United States)

    de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk, Steven; Burkepile, Joan

    2013-04-01

    The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic instrument with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro-polarimetry of the full solar disk in a synoptic fashion. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An essential part of the ChroMag program is a commitment to develop and provide community access to the `inversion' tools necessary to interpret the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Advanced Technology Solar Telescope (ATST). A prototype is currently under construction at the High Altitude Observatory of the National Center for Atmospheric Research in Boulder, CO, USA. The heart of the ChroMag instrument is an electro-optically tunable wide-fielded narrow-band birefringent six-stage Lyot filter with a built-in polarimeter. We will present a progress update on the ChroMag design, and present results from the prototype instrument.

  14. Numerical studies of solar chromospheric jets

    Science.gov (United States)

    Iijima, Haruhisa

    2016-03-01

    The solar chromospheric jet is one of the most characteristic structures near the solar surface. The quantitative understanding of chromospheric jets is of substantial importance for not only the partially ionized phenomena in the chromosphere but also the energy input and dissipation processes in the corona. In this dissertation, the formation and dynamics of chromospheric jets are investigated using the radiation magnetohydrodynamic simulations. We newly develop a numerical code for the radiation magnetohydrodynamic simulations of the comprehensive modeling of solar atmosphere. Because the solar chromosphere is highly nonlinear, magnetic pressure dominated, and turbulent, a robust and high-resolution numerical scheme is required. In Chapter 2, we propose a new algorithm for the simulation of magnetohydrodynamics. Through the test problems and accuracy analyses, the proposed scheme is proved to satisfy the requirements. In Chapter 3, the effect of the non-local radiation energy transport, Spitzer-type thermal conduction, latent heat of partial ionization and molecule formation, and gravity are implemented to the magnetohydrodynamic code. The numerical schemes for the radiation transport and thermal conduction is carefully chosen in a view of the efficiency and compatibility with the parallel computation. Based on the developed radiation magnetohydrodynamic code, the formation and dynamics of chromospheric jets are investigated. In Chapter 4, we investigate the dependence of chromospheric jets on the coronal temperature in the two-dimensional simulations. Various scale of chromospheric jets with the parabolic trajectory are found with the maximum height of 2–8 Mm, lifetime of 2–7 min, maximum upward velocity of 10– 50 km/s, and deceleration of 100–350 m/s2. We find that chromospheric jets are more elongated under the cool corona and shorter under the hot corona. We also find that the pressure gradient force caused by the periodic shock waves accelerates

  15. Photospheric and chromospheric activity on EY Dra

    CERN Document Server

    Korhonen, H; Holhjem, K; Ramstedt, S; Rantala, J; Thoene, C C; Vida, K

    2007-01-01

    Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra is studied and possible correlations between the two are investigated using photometric observations in the V and R bands and optical and near infrared spectroscopy. The longitudinal spot configuration in the photosphere is obtained from the V band photometry, and the chromospheric structures are investigated using variations in the H alpha line profile and observations of the Paschen beta line. The shape of the V band light-curve indicates two active regions on the stellar surface, about 0.4 in phase apart. The spectroscopic observations show enhanced H alpha emission observed close to the phases of the photometrically detected starspots. This could indicate chromospheric plages associated with the photospheric starspots. Some indications of prominence structures are also seen. The chromospheric pressure is limited to logTR < -4 based on the non-detection of emission in the Paschen beta wavelength region.

  16. Photospheric and chromospheric activity on EY Dra

    OpenAIRE

    Korhonen, H.; Brogaard, K.; Holhjem, K.; Ramstedt, S.; Rantala, J.; Thoene, C. C.; Vida, K.

    2007-01-01

    Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra is studied and possible correlations between the two are investigated using photometric observations in the V and R bands and optical and near infrared spectroscopy. The longitudinal spot configuration in the photosphere is obtained from the V band photometry, and the chromospheric structures are investigated using variations in the H alpha line profile and observations of the Paschen beta line. The shape of the V ban...

  17. Wave Heating of the Solar Chromosphere

    Indian Academy of Sciences (India)

    Wolfgang Kalkofen

    2008-03-01

    The nonmagnetic interior of supergranulation cells has been thought since the 1940s to be heated by the dissipation of acoustic waves. But all attempts to measure the acoustic flux have failed to show sufficient energy for chromospheric heating. Recent space observations with TRACE, for example, have found 10% or less of the necessary flux. To explain the missing energy it has been speculated that the nonmagnetic chromosphere is heated mainly by waves related to the magnetic field. If that were correct, the whole chromosphere, magnetic as well as nonmagnetic, would be heated mainly by waves related to the magnetic field. But contrary to expectation, the radiation emerging from the nonmagnetic chromosphere shows none of the signatures of magnetic waves, only those of acoustic waves. Nearly all the heating of the nonmagnetic chromosphere must therefore be due to acoustic waves. In the magnetic network on the boundary of supergranulation cells, on the other hand, the small filling factor of the magnetic field in the photosphere implies that only a small fraction of the wave flux that travels upward to heat the chromosphere can be channeled by the magnetic field. Hence, while some of the energy that is dissipated in the magnetic network is in the form of magnetic waves, most of it must be in the form of acoustic waves. Thus, the quiet solar chromosphere, instead of being heated mainly by magneticwaves throughout, must be heated mainly by acoustic waves throughout. The full wave flux heating the quiet chromosphere must travel through the photosphere. In the nonmagnetic medium, this flux is essentially all in the form of acoustic waves; TRACE registers at most 10% of it, perhaps because of limited spatial resolution.

  18. Misalignment between chromospheric features and magnetic field

    CERN Document Server

    Martínez-Sykora, Juan; Carlsson, Mats; Hansteen, Viggo

    2016-01-01

    Observations of the upper chromosphere shows an enormous amount of intricate fine structure. Much of this comes in the form of linear features which are most often assumed to be well aligned with the direction of the magnetic field in the low plasma beta regime thought to dominate the upper chromosphere. We use advanced radiative MHD simulations including the effects of ion-neutral interactions (using the generalized Ohm's law) in the partially ionized chromosphere to show that the magnetic field is often not well aligned with chromospheric features. This occurs where the ambipolar diffusion is large, i.e., ions and neutral populations decouple as the ion-neutral collision frequency drops allowing the field to slip through the neutral population, currents perpendicular to the field are strong, and thermodynamic timescales are longer than or similar to the those of ambipolar diffusion. We find this often happens in dynamic spicule or fibril-like features at the top of the chromosphere. This has important conse...

  19. Detailed Chromospheric Activity Nature of KIC 9641031

    CERN Document Server

    Yoldaş, Ezgi

    2016-01-01

    This study depends on KIC 9641031 eclipsing binary system with a chromospherically active component. There are three type variations, such as geometrical variations due to eclipses, sinusoidal variations due to the rotational modulations and also flares, in the light curves obtained with the data taken from the Kepler Mission Database. Taking into account results obtained from KIC 9641031's observations in the Kepler Mission Database, we present and discuss the details of chromospheric activity. The sinusoidal light variations due to rotational modulation and the flare events were modelled separately. 92 different data subsets separated using the analytic models described in the literature were modelled separately to obtain the cool spot configuration. It is seen that just one component of the system is chromospherically active star. On this component, there are two active regions separated by about 180 deg longitudinally between the latitudes of +50 deg and +100 deg, whose locations and forms are rapidly cha...

  20. Modeling the Variable Chromosphere of α Orionis

    Science.gov (United States)

    Lobel, A.; Dupree, A. K.

    2000-12-01

    A spectral analysis of the prototypical red supergiant star α Ori that is based on near-UV, optical, and near-IR high-dispersion spectra obtained between 1992 September and 1999 July with the Space Telescope Imaging Spectrograph and the Goddard High Resolution Spectrograph on the Hubble Space Telescope, the Utrecht Echelle Spectrograph, and the SoFin Echelle Spectrograph is presented. With detailed non-LTE radiative transfer calculations in spherical geometry, we model the mean conditions in the stellar chromosphere from Hα and the Mg II resonance doublet. The Hα absorption line emerges from an extended chromosphere. Temporal changes of its velocity structure are determined from detailed fits to near-UV Si I lines, and chromospheric expansion velocities around 4 km s -1 are found in 1992, whereas the chromosphere was collapsing onto the photosphere with a velocity of 5 km s -1 in 1998-1999. The Hα core depth is correlated over time with weaker depression changes seen in prominent TiO band heads that dominate the optical spectrum. From elaborate spectral synthesis calculations, we isolate unblended metal absorption lines in the near-IR and determine Teff=3500 K and log(g)=-0.5 for solar metallicity and 12+/-0.5 km s -1 for macrobroadening and vsini. Semiempirical fits yield chromospheric temperatures not in excess of 5500 K, but with long-term changes by ~400 K. The model extends over 5000 Rsolar and requires supersonic microturbulence values ranging to 19 km s -1, in strong contrast with the photospheric value of only 2 km s -1. We observe Doppler shifts of 4-8 km s -1 in the scattering cores of many double-peaked near-UV emission lines which correlate with changes in the intensity ratio of their emission components. The red emission components were much stronger in 1992, indicating a phase of enhanced chromospheric outflow, for which we determine a spherical mass-loss rate of 6×10-7 Msolar yr -1. We present a discussion of chromospheric pulsation in this

  1. Structure and Organization of the Upper Chromosphere

    Science.gov (United States)

    Korendyke, C. M.; Landi, E.; Vourlidas, A.

    2005-05-01

    Over its past two flights, the VAULT sounding rocket instrument obtained a series of subarcsecond resolution images of the solar disk. These Lyman alpha images resolve and separate structures in the upper chromosphere. The observed plasmas are concentrated in larger diameter, optically thick loops. The images taken near the limb unambiguously identify the height of the upper chromosphere in the quiet sun. An unexpected level of evolution and activity is present in the "quiet sun" at small spatial scales. The third flight of the payload will investigate the interconnectivity of the observed structures with the photosphere.

  2. Observations of Chromospheric Flare Re-brightenings

    Czech Academy of Sciences Publication Activity Database

    Miklenic, C.H.; Veronig, A.; Vršnak, B.; Bárta, Miroslav

    2010-01-01

    Roč. 719, č. 2 (2010), s. 1750-1758. ISSN 0004-637X R&D Projects: GA ČR GA205/07/1100 Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * activity * chromosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 7.436, year: 2010

  3. The chromospheric structure of cool carbon stars

    International Nuclear Information System (INIS)

    The temperature-density structure of the outer atmospheres of the N-type carbon stars are investigated through computer generated synthetic spectra from model atmospheres. The synthetic spectra are compared to spectra obtained with the International Ultraviolet Explorer (IUE) spacecraft and ground-based photometry. The nature of the severe violet flux falloff seen in cool carbon stars is investigated through photospheric synthetic flux calculations with the assumption of local thermodynamic equilibrium (LTE). A new candidate for the unknown opacity source that causes this flux falloff is proposed-a preponderance of neutral metal bound-bound and bound-free transitions from low energy states. The chromospheric structure of these stars is also investigated through a semi-empirical modeling technique. Such a technique involves attaching a chromospheric temperature rise to a radiative equilibrium model photosphere and generating a synthetic spectrum of chromospheric spectral lines using non-LTE radiative transfer. The chromospheric temperature-density structure is then altered until the synthetic spectrum matches the IUE observations of the singly ionized magnesium resonance lines and the intercombination lines of singly ionized carbon. Through the above mentioned non-LTE analysis of the atmospheric structure of these stars, the excitation and ionization equilibria are investigated. The excited levels of H I, C I, Na I, Mg I, and Ca I are over-populated with respect to LTE in the middle and upper photosphere of these stars, and all are over-ionized with respect to LTE. Photons from the chromosphere greatly influence the excitation and ionization of H I, C I, and Mg I

  4. Chromospheric Dynamics and the FIP Flip

    OpenAIRE

    Rutten, R. J.

    2001-01-01

    This paper consists of two parts. The first, resembling many other SOHO contributions in this volume, reports on a recent campaign in which SUMER was employed simultaneously with groundbased tele- scopes. The campaign is described but results are not yet in hand. The second part differs by proposing SUMER measurements and analysis to be contributed by you. It calls attention to the FIP effect, a puzzling outer-atmosphere element segregation that may have to do with quiet-sun chromospheric dyn...

  5. Short dynamic fibrils in sunspot chromospheres

    CERN Document Server

    van der Voort, Luc Rouppe

    2013-01-01

    Sunspot chromospheres display vigorous oscillatory signature when observed in chromospheric diagnostics like the strong Ca II lines and H-alpha. New high-resolution sunspot observations from the Swedish 1-m Solar Telescope show the ubiquitous presence of small-scale periodic jet-like features that move up and down. This phenomenon has not been described before. Their typical width is about 0.3 arcsec and they display clear parabolic trajectories in space-time diagrams. The maximum extension of the top of the jets is lowest in the umbra, a few 100 km, and progressively longer further away from the umbra in the penumbra, with the longest more than 1000 km. These jets resemble dynamic fibrils found in plage regions but at smaller extensions. LTE inversion of spectro-polarimetric Ca II 8542 observations enabled for a comparison of the magnetic field inclination and the properties of these short jets. We find that the most extended of these jets also have longer periods and tend to be located in regions with more ...

  6. The Origin of Sequential Chromospheric Brightening

    Science.gov (United States)

    Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, Jason; Gilbert, Holly

    2016-05-01

    Sequential Chromospheric Brightenings (SCBs) are often observed in the immediate vicinity of erupting flares and are associated with coronal mass ejections. When SCBs are observed, they routinely appear before the peak emission of the flare and several hours before the first detection of a coupled CME. Since their initial discovery in 2005, there have been several subsequent investigations of SCBs. In each case, these sudden, small-scale brightenings provide vital clues regarding the mechanisms of large-scale energy release in the solar atmosphere. We make use of an automated detection algorithm developed by Kirk et al. (2013) to extract the physical qualities of SCBs in 11 flares of varying size and intensity. Using complementary magnetic field measurements, we also model the potential field beneath these brightenings. We conclude that SCBs originate in the lower corona around 0.1 R⊙ above the photosphere, propagate away from the flare center at speeds 35 ‑ 85 km s‑1, and have typical photosphere magnetic intensities 257± 37 G. In light of these measurements, we conclude that SCBs are distinctive chromospheric signatures of erupting coronal mass ejections.

  7. Characteristics of transverse waves in chromospheric mottles

    Energy Technology Data Exchange (ETDEWEB)

    Kuridze, D.; Mathioudakis, M.; Jess, D. B.; Keenan, F. P. [Astrophysics Research Center, School of Mathematics and Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); Verth, G.; Erdélyi, R. [Solar Physics and Space Plasma Research Center (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Morton, R. J. [Mathematics and Information Science, Northumbria University, Camden Street, Newcastle Upon Tyne NE1 8ST (United Kingdom); Christian, D. J., E-mail: dkuridze01@qub.ac.uk [Department of Physics and Astronomy, California State University, Northridge, CA 91330 (United States)

    2013-12-10

    Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structures near the solar disk center. The oscillations are interpreted in terms of propagating and standing magnetohydrodynamic kink waves. Wave characteristics including the maximum transverse velocity amplitude and the phase speed are measured as a function of distance along the structure's length. Solar magnetoseismology is applied to these measured parameters to obtain diagnostic information on key plasma parameters (e.g., magnetic field, density, temperature, flow speed) of these localized waveguides. The magnetic field strength of the mottle along the ∼2 Mm length is found to decrease by a factor of 12, while the local plasma density scale height is ∼280 ± 80 km.

  8. Magnetic tornadoes and chromospheric swirls -- Definition and classification

    CERN Document Server

    Wedemeyer, Sven; Steiner, Oskar; Rodriguez, Jaime de la Cruz; van der Voort, Luc Rouppe

    2013-01-01

    Chromospheric swirls are the observational signatures of rotating magnetic field structures in the solar atmosphere, also known as magnetic tornadoes. Swirls appear as dark rotating features in the core of the spectral line of singly ionized calcium at a wavelength of 854.2 nm. This signature can be very subtle and difficult to detect given the dynamic changes in the solar chromosphere. Important steps towards a systematic and objective detection method are the compilation and characterization of a statistically significant sample of observed and simulated chromospheric swirls. Here, we provide a more exact definition of the chromospheric swirl phenomenon and also present a first morphological classification of swirls with three types: (I) Ring, (II) Split, (III) Spiral. We also discuss the nature of the magnetic field structures connected to tornadoes and the influence of limited spatial resolution on the appearance of their photospheric footpoints.

  9. Magnetic tornadoes and chromospheric swirls – Definition and classification

    International Nuclear Information System (INIS)

    Chromospheric swirls are the observational signatures of rotating magnetic field structures in the solar atmosphere, also known as magnetic tornadoes. Swirls appear as dark rotating features in the core of the spectral line of singly ionized calcium at a wavelength of 854.2 nm. This signature can be very subtle and difficult to detect given the dynamic changes in the solar chromosphere. Important steps towards a systematic and objective detection method are the compilation and characterization of a statistically significant sample of observed and simulated chromospheric swirls. Here, we provide a more exact definition of the chromospheric swirl phenomenon and also present a first morphological classification of swirls with three types: (I) Ring, (II) Split, (III) Spiral. We also discuss the nature of the magnetic field structures connected to tornadoes and the influence of limited spatial resolution on the appearance of their photospheric footpoints.

  10. Magnetic tornadoes and chromospheric swirls -- Definition and classification

    OpenAIRE

    Wedemeyer, Sven; Scullion, Eamon; Steiner, Oskar; Rodriguez, Jaime de la Cruz; van der Voort, Luc Rouppe

    2013-01-01

    Chromospheric swirls are the observational signatures of rotating magnetic field structures in the solar atmosphere, also known as magnetic tornadoes. Swirls appear as dark rotating features in the core of the spectral line of singly ionized calcium at a wavelength of 854.2 nm. This signature can be very subtle and difficult to detect given the dynamic changes in the solar chromosphere. Important steps towards a systematic and objective detection method are the compilation and characterizatio...

  11. Simultaneous Observations of the Chromosphere with TRACE and SUMER

    Science.gov (United States)

    Pasachoff, Jay M.; Tingle, Evan D.; Dammasch, Ingolf E.; Sterling, Alphonse C.

    2011-01-01

    Using mainly the 1600 Å continuum channel and also the 1216 Å Lyman- α channel (which includes some UV continuum and C iv emission) aboard the TRACE satellite, we observed the complete lifetime of a transient, bright chromospheric loop. Simultaneous observations with the SUMER instrument aboard the SOHO spacecraft revealed interesting material velocities through the Doppler effect existing above the chromospheric loop imaged with TRACE, possibly corresponding to extended nonvisible loops, or the base of an X-ray jet.

  12. Simultaneous Observations of the Chromosphere with TRACE and SUMER

    OpenAIRE

    Pasachoff, J.M.; Tingle, E. D.; Dammasch, I. E.; Sterling, A. C.

    2011-01-01

    Using mainly the 1600 angstrom continuum channel, and also the 1216 angstrom Lyman-alpha channel (which includes some UV continuum and C IV emission), aboard the TRACE satellite, we observed the complete lifetime of a transient, bright chromospheric loop. Simultaneous observations with the SUMER instrument aboard the SOHO spacecraft revealed interesting material velocities through the Doppler effect existing above the chromospheric loop imaged with TRACE, possibly corresponding to extended no...

  13. Simultaneous Observations of the Chromosphere with TRACE and SUMER

    CERN Document Server

    Pasachoff, J M; Dammasch, I E; Sterling, A C

    2010-01-01

    Using mainly the 1600 angstrom continuum channel, and also the 1216 angstrom Lyman-alpha channel (which includes some UV continuum and C IV emission), aboard the TRACE satellite, we observed the complete lifetime of a transient, bright chromospheric loop. Simultaneous observations with the SUMER instrument aboard the SOHO spacecraft revealed interesting material velocities through the Doppler effect existing above the chromospheric loop imaged with TRACE, possibly corresponding to extended non-visible loops, or the base of an X-ray jet.

  14. Properties of Sequential Chromospheric Brightenings and Associated Flare Ribbons

    OpenAIRE

    Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, Jason; McAteer, R. T. James; Milligan, Ryan O.

    2012-01-01

    We report on the physical properties of solar sequential chromospheric brightenings (SCBs) observed in conjunction with moderate-sized chromospheric flares with associated CMEs. To characterize these ephemeral events, we developed automated procedures to identify and track subsections (kernels) of solar flares and associated SCBs using high resolution H-alpha images. Following the algorithmic identification and a statistical analysis, we compare and find the following: SCBs are distinctly dif...

  15. POSSIBLE CHROMOSPHERIC ACTIVITY CYCLES IN AD LEO

    Energy Technology Data Exchange (ETDEWEB)

    Buccino, Andrea P.; Petrucci, Romina; Mauas, Pablo J. D. [Instituto de Astronomía y Física del Espacio (CONICET-UBA), C.C. 67 Sucursal 28, C1428EHA-Buenos Aires (Argentina); Jofré, Emiliano [Observatorio Astronómico de Córdoba, Córdoba (Argentina)

    2014-01-20

    AD Leo (GJ 388) is an active dM3 flare star that has been extensively observed both in the quiescent and flaring states. Since this active star is near the fully convective boundary, studying its long-term chromospheric activity in detail could be an appreciable contribution to dynamo theory. Here, using the Lomb-Scargle periodogram, we analyze the Ca II K line-core fluxes derived from CASLEO spectra obtained between 2001 and 2013 and the V magnitude from the ASAS database between 2004 and 2010. From both of these totally independent time series, we obtain a possible activity cycle with a period of approximately seven years and a less significant shorter cycle of approximately two years. A tentative interpretation is that a dynamo operating near the surface could be generating the longer cycle, while a second dynamo operating in the deep convection zone could be responsible for the shorter one. Based on the long duration of our observing program at CASLEO and the fact that we observe different spectral features simultaneously, we also analyze the relation between simultaneous measurements of the Na I index (R{sub D}{sup ′}), Hα, and Ca II K fluxes at different activity levels of AD Leo, including flares.

  16. POSSIBLE CHROMOSPHERIC ACTIVITY CYCLES IN AD LEO

    International Nuclear Information System (INIS)

    AD Leo (GJ 388) is an active dM3 flare star that has been extensively observed both in the quiescent and flaring states. Since this active star is near the fully convective boundary, studying its long-term chromospheric activity in detail could be an appreciable contribution to dynamo theory. Here, using the Lomb-Scargle periodogram, we analyze the Ca II K line-core fluxes derived from CASLEO spectra obtained between 2001 and 2013 and the V magnitude from the ASAS database between 2004 and 2010. From both of these totally independent time series, we obtain a possible activity cycle with a period of approximately seven years and a less significant shorter cycle of approximately two years. A tentative interpretation is that a dynamo operating near the surface could be generating the longer cycle, while a second dynamo operating in the deep convection zone could be responsible for the shorter one. Based on the long duration of our observing program at CASLEO and the fact that we observe different spectral features simultaneously, we also analyze the relation between simultaneous measurements of the Na I index (RD′), Hα, and Ca II K fluxes at different activity levels of AD Leo, including flares

  17. Measurements of Photospheric and Chromospheric Magnetic Fields

    CERN Document Server

    Lagg, Andreas; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2015-01-01

    The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Conseque...

  18. Asymmetric Magnetic Reconnection in Weakly Ionized Chromospheric Plasmas

    CERN Document Server

    Murphy, Nicholas A

    2015-01-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral-ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak field (high ...

  19. Chromospheric, transition layer and coronal emission of metal deficient stars

    Science.gov (United States)

    Boehm-Vitense, E.

    1982-01-01

    It is shown that while MgII k line emission decreases for metal deficient stars, the Ly alpha emission increases. The sum of chromospheric hydrogen and metallic emission appears to be independent of metal abundances. The total chromospheric energy loss is estimated to be 0.0004 F sub bol. The chromospheric energy input does not seem to decrease for increasing age. The transition layer emission is reduced for metal deficient stars, but it is not known whether the reduction is larger than can be explained by curve of growth effects only. Coronal X-ray emission was measured for 4 metal deficient stars. Within a 12 limit it could still be consistent with the emission of solar abundance stars.

  20. Kinetic description of electron beams in the solar chromosphere

    Science.gov (United States)

    Gomez, Daniel O.; Mauas, Pablo J.

    1992-01-01

    We formulate the relativistic Fokker-Plank equation for a beam of accelerated electrons interacting with a partially ionized plasma. In our derivation we conserved those terms contributing to velocity diffusion and found that this effect cannot be neglected a priori. We compute the terms accounting for elastic and inelastic collisions with neutral hydrogen and helium. Collisions with neutral hydrogen are found to be dominant throughout the chromosphere, except at the uppermost layers close to the transition region. As an application, we compute the loss of energy and momentum for a power-law beam impinging on the solar chromosphere, for a particular case in which the Fokker-Planck equation can be integrated analytically. We find that most of the beam energy is deposited in a relatively thin region of the chromosphere, a result which is largely insensitive to the theoretical method employed to compute the energy deposition rate.

  1. Solar chromospheric fine scale structures: dynamics and energetics

    Science.gov (United States)

    Tziotziou, K.

    2012-01-01

    The solar chromosphere is a very inhomogeneous and dynamic layer of the solar atmosphere that exhibits several phenomena on a wide range of spatial and temporal scales. High-resolution and long-duration observations, employing mostly lines, such as Halpha, the Ca II infrared lines and the Ca II H and K lines, obtained both from ground-based telescope facilities (e.g. DST, VTT, THEMIS, SST, DOT), as well as state-of-the-art satellites (e.g. SOHO, TRACE, HINODE) reveal an incredibly rich, dynamic and highly structured chromospheric environment. What is known in literature as the chromospheric fine-scale structure mainly consists of small fibrilar-like features that connect various parts of quiet/active regions or span across the chromospheric network cell interiors, showing a large diversity of both physical and dynamic characteristics. The highly dynamic, fine-scale chromospheric structures are mostly governed by flows which reflect the complex geometry and dynamics of the local magnetic field and play an important role in the propagation and dissipation of waves. A comprehensive study of these structures requires deep understanding of the physical processes involved and investigation of their intricate link with structures/processes at lower photospheric levels. Furthermore, due to their large number present on the solar surface, it is essential to investigate their impact on the mass and energy transport to higher atmospheric layers through processes such as magnetic reconnection and propagation of waves. The in-depth study of all aforementioned characteristics and processes, with the further addition of non-LTE physics, as well as the use of three-dimensional numerical simulations poses a fascinating challenge for both theory and numerical modeling of chromospheric fine-scale structures.

  2. Chromospheric Polarization in the Photospheric Solar Oxygen Infrared Triplet

    Science.gov (United States)

    Del Pino Alemán, Tanausú; Trujillo Bueno, Javier

    2015-07-01

    We present multilevel radiative transfer modeling of the scattering polarization observed in the solar O i infrared triplet around 777 nm. We demonstrate that the scattering polarization pattern observed on the solar disk forms in the chromosphere, far above the photospheric region where the bulk of the emergent intensity profiles originate. We investigate the sensitivity of the polarization pattern to the thermal structure of the solar atmosphere and to the presence of weak magnetic fields (10-2-100 G) through the Hanle effect, showing that the scattering polarization signals of the oxygen infrared triplet encode information on the magnetism of the solar chromosphere.

  3. Chromospheric Polarization in the Photospheric Solar Oxygen Infrared Triplet

    CERN Document Server

    Alemán, T del Pino

    2015-01-01

    We present multilevel radiative transfer modeling of the scattering polarization observed in the solar O I infrared triplet around 777 nm. We demonstrate that the scattering polarization pattern observed on the solar disk forms in the chromosphere, far above the photospheric region where the bulk of the emergent intensity profiles originates. We study the sensitivity of the polarization pattern to the thermal structure of the solar atmosphere and to the presence of weak magnetic fields (0.01 - 100 G) through the Hanle effect, showing that the scattering polarization signals of the oxygen infrared triplet encode information on the magnetism of the solar chromosphere.

  4. An Estimate of Chromospheric Heating by Acoustic Waves

    Czech Academy of Sciences Publication Activity Database

    Sobotka, Michal; Švanda, Michal; Jurčák, Jan; Heinzel, Petr; Del Moro, D.; Berrilli, F.

    2014-01-01

    Roč. 38, č. 1 (2014), s. 53-58. ISSN 1845-8319 R&D Projects: GA ČR(CZ) GA14-04338S; GA ČR GPP209/12/P568; GA ČR GAP209/12/0287 Institutional support: RVO:67985815 Keywords : Sun * chromosphere * heating Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  5. The Role of Partial Ionization Effects in the Chromosphere

    CERN Document Server

    Martinez-Sykora, Juan; Hansteen, Viggo H; Carlsson, Mats

    2015-01-01

    The energy for the coronal heating must be provided from the convection zone. The amount and the method by which this energy is transferred into the corona depends on the properties of the lower atmosphere and the corona itself. We review: 1) how the energy could be built in the lower solar atmosphere; 2) how this energy is transferred through the solar atmosphere; and 3) how the energy is finally dissipated in the chromosphere and/or corona. Any mechanism of energy transport has to deal with the various physical processes in the lower atmosphere. We will focus on a physical process that seems to be highly important in the chromosphere and not deeply studied until recently: the ion-neutral interaction effects (INIE) in the chromosphere. We review the relevance and the role of the partial ionization in the chromosphere and show that this process actually impacts considerably the outer solar atmosphere. We include analysis of our 2.5D radiative MHD simulations with the Bifrost code (Gudiksen et al. 2011) includ...

  6. Recognizing Chromospheric Objects via Markov Chain Monte Carlo

    Science.gov (United States)

    Mukhtar, Saleem; Turmon, Michael J.

    1997-01-01

    The solar chromosphere consists of three classes which contribute differentially to ultraviolet radiation reaching the earth. We describe a data set of solar images, means of segmenting the images into the constituent classes, and a novel high-level representation for compact objects based on a triangulated spatial membership function.

  7. Spectral line formation and oscillations in the solar chromosphere

    International Nuclear Information System (INIS)

    This thesis is dedicated to two kind of models: the firsts, of semi-empiric type, seek to represent the vertical structure of the solar atmosphere and are treated in chapter II thru V. The others, of rather theoretical nature, have the ambition to simulate the oscillations of the chromosphere and are treated in chapter VI to X

  8. Chromospheric Lyman-alpha spectro-polarimeter (CLASP)

    Czech Academy of Sciences Publication Activity Database

    Kano, R.; Bando, T.; Narukage, N.; Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Hara, H.; Shimizu, T.; Suematsu, Y.; Ichimoto, K.; Sakao, T.; Goto, M.; Kato, Y.; Imada, S.; Kobayashi, K.; Holloway, T.; Winebarger, A.; Cirtain, J.; de Pontieu, B.; Casini, R.; Trujillo Bueno, J.; Štěpán, Jiří; Sainz, R.M.; Belluzzi, L.; Ramos, A.A.; Auchere, F.; Carlsson, M.

    Bellingham : International Society for Optical Engineering, 2012, 84434F/1-84434F/17. ISBN 9780819491442. - (Proceedings of SPIE. 8443). [Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray. Amsterdam (NL), 01.07.2012-06.07.2012] Institutional support: RVO:67985815 Keywords : chromospheric magnetic field Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  9. Solar chromospheric flares: energy release, transport and radiation

    OpenAIRE

    Fletcher, Lyndsay

    2012-01-01

    This paper presents an overview of some recent observational and theoretical results on solar flares, with an emphasis on flare impulsive-phase chromospheric properties, including: electron diagnostics, optical and UV emission, and discoveries made by the Hinode mission, especially in the EUV. A brief perspective on future observations and theoretical requirements is also given

  10. Chromospheric Activity, Tio Strength and Spectral Types in M Giants

    Science.gov (United States)

    Steiman-Cameron, Thomas Y.

    1984-07-01

    In an continuation of a study begun during the 6th year of the IUE guest observer program the IUE satellite will be used to study the ultraviolet spectra of cool giant stars that have well-determined angular diameters and effective temperatures. The stars to be observed have spectral classes ranging from K3 through M6 and are of luminosity class III. Low resolution observations in the long wavelength region will be made in order to study the photospheric continuum radiation in the UV and to determine the level of chromospheric activity in these stars. The absolute flux, as well as the slope of the continuum in the wavelength region 2200-3000 A, should be a sensitive probe of the extent of nonradiative heating in the upper photosphere. Chromospheric activity will be examined for the range of spectral subclasses observed to determine if the degree of chromospheric activity differs for stars of the same effective temperature. The Possibility exists that such a differential level of chromospheric activity could lead to the inhibition of TiO formation in the upper photosphere. Preliminary results from IUE observations made during this past year appear to support this hypothesis. This possibility will be examined along with the resultant consequences for comparisons of observed TiO bandstrengths with model predictions.

  11. On the minimum temperature of the quiet solar chromospheres

    NARCIS (Netherlands)

    Leenaarts, J.; Carlsson, M.; Hansteen, V.; Gudiksen, B.V.

    2011-01-01

    Aims. We aim to provide an estimate of the minimum temperature of the quiet solar chromosphere. Methods. We perform a 2D radiation-MHD simulation spanning the upper convection zone to the lower corona. The simulation includes non-LTE radiative transfer and an equation-of-state that includes non-equi

  12. Spectral analysis and modeling of solar flares chromospheric condensation

    Science.gov (United States)

    Cauzzi, Gianna; Graham, David; Kowalski, Adam; Zangrilli, Luca; Simoes, Paulo; Allred, Joel C.

    2016-05-01

    We follow up on our recent analysis of the X1.1 flare SOL2014-09-10T17:45, where we studied the impulsive phase dynamics of tens of individual flaring "kernels", in both coronal (Fe XXI) and chromospheric (MgII) lines observed at high cadence with IRIS.We concentrate here on the chromospheric aspect of the phenomenon, extending the analysis to multiple spectral lines of Mg II, Fe II, Si I, C II. We show that many flaring kernels display high velocity downflows in the spectra of all these chromospheric lines, exhibiting distinct, transient and strongly redshifted spectral components.From modeling using RADYN with the thick-target interpretation, the presence of two spectral components appears to be consistent with a high flux beam of accelerated electrons, characterized by a hard spectrum. In particular the highest energy electrons heat the denser, lower layers of the atmosphere, while the bulk of the beam energy, deposited higher in the atmosphere, is sufficient to produce chromospheric evaporation with a corresponding condensation.

  13. Chromospheric magnetic fields of an active region filament

    Science.gov (United States)

    Xu, Z.; Solanki, S.; Lagg, A.

    2012-06-01

    Vector magnetic fields of an active region filament are co-spatially and co-temporally mapped in photosphere and upper chromosphere, by using spectro-polarimetric observations made by Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A Zeeman-based ME inversion is performed on the full Stokes vectors of both the photospheric Si I 1082.7 nm and the chromospheric He I 1083.0 nm lines. We found that the strong magnetic fields, with the field strength of 600 - 800 G in the He I line formation height, are not uncommon among AR filaments. But such strong magnetic field is not always found in AR filaments.

  14. Conduction-driven chromospheric evaporation in a solar flare

    Science.gov (United States)

    Zarro, Dominic M.; Lemen, James R.

    1988-01-01

    Observations of gentle chromospheric evaporation during the cooling phase of a solar flare are presented. Line profiles of the low-temperature (T of about 6 x 10 to the 6th K) coronal Mg XI line, observed with the X-Ray Polychromator on the Solar Maximum Mission, show a blueshift that persisted for several minutes after the impulsive heating phase. This result represents the first detection of an evaporation signature in a soft X-ray line formed at this low temperature. By combining the Mg XI blueshift velocity data with simultaneous measurements of the flare temperature derived from Ca XIX observations, it is demonstrated that the upward flux of enthalpy transported by this gently evaporating plasma varies linearly with the downward flux of thermal energy conducted from the corona. This relationship is consistent with models of solar flares in which thermal conduction drives chromospheric evaporation during the early part of the cooling phase.

  15. The effects of transients on photospheric and chromospheric power distributions

    CERN Document Server

    Samanta, T; Banerjee, D; Prasad, S Krishna; Mathioudakis, M; Jess, D; Pant, V

    2016-01-01

    We have observed a quiet Sun region with the Swedish 1-meter Solar Telescope (SST) equipped with CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, H$\\alpha$ line scanning images were taken to observe different layers of the solar atmosphere from the photosphere to upper chromosphere. We study the distribution of power in different period-bands at different heights. Power maps of the upper photosphere and the lower chromosphere show suppressed power surrounding the magnetic-network elements, known as "magnetic shadows". These also show enhanced power close to the photosphere, traditionally referred to as "power halos". The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for these two effects. In this study we explore if small-scale transients can influence the distribution of power at different heights. We show that the presence of transients, like mottles, Rapid Blueshifted Excursions (RBEs) and Rapid Redshifted Excursions (RREs), can stro...

  16. Optimal Electron Energies for Driving Chromospheric Evaporation in Solar Flares

    CERN Document Server

    Reep, Jeffrey; Alexander, David

    2015-01-01

    In the standard model of solar flares, energy deposition by a beam of electrons drives strong chromospheric evaporation leading to a significantly denser corona and much brighter emission across the spectrum. Chromospheric evaporation was examined in great detail by Fisher, Canfield, & McClymont (1985a,b,c), who described a distinction between two different regimes, termed explosive and gentle evaporation. In this work, we examine the importance of electron energy and stopping depths on the two regimes and on the atmospheric response. We find that with explosive evaporation, the atmospheric response does not depend strongly on electron energy. In the case of gentle evaporation, lower energy electrons are significantly more efficient at heating the atmosphere and driving up-flows sooner than higher energy electrons. We also find that the threshold between explosive and gentle evaporation is not fixed at a given beam energy flux, but also depends strongly on the electron energy and duration of heating. Furt...

  17. Chromospheric Velocities of a C-class Flare

    OpenAIRE

    Keys, Peter H.; Jess, David B.; Mathioudakis, Mihalis; Keenan, Francis P

    2011-01-01

    We use high spatial and temporal resolution observations from the Swedish Solar Telescope to study the chromospheric velocities of a C-class flare originating from active region NOAA 10969. A time-distance analysis is employed to estimate directional velocity components in H-alpha and Ca II K image sequences. Also, imaging spectroscopy has allowed us to determine flare-induced line-of-sight velocities. A wavelet analysis is used to analyse the periodic nature of associated flare bursts. Time-...

  18. Stellar model chromospheres. III. Arcturus (K2 III)

    International Nuclear Information System (INIS)

    We construct models for the upper photosphere and chromosphere of Arcturus based on the H, K, and IR triplets lines of Ca II and the h and k lines of Mg ii. The chromosphere model is derived from complete redistribution solutions for a five-level Ca II ion and two-level Mg II ion. A photospheric model is derived from the Ca II wings using first the ''traditional'' complete redistribution limit and then the more realistic partial redistribution approximation. In particular, the temperature and mass column densities for the temperature minimum region and the chromosphere-transition region boundary are computed and the pressure P0 in the transition region and corona estimate. We find T/sub eff/T/sub min/approx. =0.77 for Arcturus, Procyon, and the Sun and a trend of increasing mass at the temperature minimum with decreasing gravity. We find P0 to be about 1 percent of the solar value and on this basis estimate the surface brightness of the Arcturus transition region and coronal spectrum to be much less than for the Sun. Finally, the partial redistibution calculation for the Ca II K line indicates that the emission width is at least partially determined by damping rather than Doppler broadening, suggesting a reexamination of previous explanations for the Wilson-Bappu effect

  19. Stellar model chromospheres. III - Arcturus /K2 III/

    Science.gov (United States)

    Ayres, T. R.; Linsky, J. L.

    1975-01-01

    Models are constructed for the upper photosphere and chromosphere of Arcturus based on the H, K, and IR triplet lines of Ca II and the h and k lines of Mg II. The chromosphere model is derived from complete redistribution solutions for a five-level Ca II ion and a two-level Mg II ion. A photospheric model is derived from the Ca II wings using first the 'traditional' complete-redistribution limit and then the more realistic partial-redistribution approximation. The temperature and mass column densities for the temperature-minimum region and the chromosphere-transition region boundary are computed, and the pressure in the transition region and corona are estimated. It is found that the ratio of minimum temperature to effective temperature is approximately 0.77 for Arcturus, Procyon, and the sun, and that mass tends to increase at the temperature minimum with decreasing gravity. The pressure is found to be about 1 percent of the solar value, and the surface brightness of the Arcturus transition region and coronal spectrum is estimated to be much less than for the sun. The partial-redistribution calculation for the Ca II K line indicates that the emission width is at least partially determined by damping rather than Doppler broadening, suggesting a reexamination of previous explanations for the Wilson-Bappu effect.

  20. Study of FK Comae Berenices: VII. Correlating photospheric and chromospheric activity

    OpenAIRE

    Vida, K.; Korhonen, H.; Ilyin, I. V.; Oláh, K.; Andersen, M. I.; Hackman, T.

    2015-01-01

    We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. We use spot temperature modelling, light curve inversion based on narrow- and wide-band photometric measurements, Halpha observations from 1997-2010, and Doppler maps from 2004-2010 to compare the behaviour of chromospheric and photospheric features. Investigating low-resolution Halpha spectra we find that the changes in the chromosphere seem to happen mainly on a time scale lon...

  1. Tracing Ca K grains through the chromosphere into the transition region

    Science.gov (United States)

    Steffens, S.; Deubner, F.-L.; Fleck, B.; Wilhelm, K.

    1997-01-01

    The propagation of Ca K grains from the lower chromosphere into the transition region is studied. Data from the solar ultraviolet measurement of emitted radiation (SUMER) and the VTT at Inzana (Tenerife) instruments were used. The purpose of the study was to investigate the formation of shock waves in the chromosphere. The most dynamical features in the chromosphere defined by the bright Ca II K emission in the filtergrams and spectrograms were analyzed.

  2. PROPAGATION OF ALFVÉNIC WAVES FROM CORONA TO CHROMOSPHERE AND CONSEQUENCES FOR SOLAR FLARES

    International Nuclear Information System (INIS)

    How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a two-fluid model (of plasma and neutrals) and used it to perform one-dimensional simulations of Alfvén waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra, and umbra) show that energy transmission from corona to chromosphere can exceed 20% of incident energy for wave periods of 1 s or less. Damping of waves in the chromosphere depends strongly on wave frequency: waves with periods 10 s or longer pass through the chromosphere with relatively little damping, however, for periods of 1 s or less, a substantial fraction (37%-100%) of wave energy entering the chromosphere is damped by ion-neutral friction in the mid- and upper chromosphere, with electron resistivity playing some role in the lower chromosphere and in umbras. We therefore conclude that Alfvénic waves with periods of a few seconds or less are capable of heating the chromosphere during solar flares, and speculate that they could also contribute to electron acceleration or exciting sunquakes.

  3. The Chromospheric Lyman Alpha SpectroPolarimeter (CLASP)

    Science.gov (United States)

    Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Cirtain, J. W.; Bando, T.; Kano, R.; Hara, H.; Fujimura, D.; Ueda, K.; Ishikawa, R.; Watanabe, H.; Ichimoto, K.; Sakao, T.; de Pontieu, B.; Carlsson, M.; Casini, R.

    2010-12-01

    Magnetic fields in the solar chromosphere play a key role in the energy transfer and dynamics of the solar atmosphere. Yet a direct observation of the chromospheric magnetic field remains one of the greatest challenges in solar physics. While some advances have been made for observing the Zeeman effect in strong chromospheric lines, the effect is small and difficult to detect outside sunspots. The Hanle effect offers a promising alternative; it is sensitive to weaker magnetic fields (e.g., 5-500 G for Ly-Alpha), and while its magnitude saturates at stronger magnetic fields, the linear polarization signals remain sensitive to the magnetic field orientation. The Hanle effect is not only limited to off-limb observations. Because the chromosphere is illuminated by an anisotropic radiation field, the Ly-Alpha line is predicted to show linear polarization for on-disk, near-limb regions, and magnetic field is predicted to cause a measurable depolarization. At disk center, the Ly-Alpha radiation is predicted to be negligible in the absence of magnetic field, and linearly polarized to an order of 0.3% in the presence of an inclined magnetic field. The proposed CLASP sounding rocket instrument is designed to detect 0.3% linear polarization of the Ly-Alpha line at 1.5 arcsecond spatial resolution (0.7’’ pixel size) and 10 pm spectral resolution. The instrument consists of a 30 cm aperture Cassegrain telescope and a dual-beam spectropolarimeter. The telescope employs a ``cold mirror’’ design that uses multilayer coatings to reflect only the target wavelength range into the spectropolarimeter. The polarization analyzer consists of a rotating waveplate and a polarizing beamsplitter that comprises MgF2 plates placed at Brewster’s Angle. Each output beam of the polarizing beamsplitter, representing two orthogonal linear polarizations, is dispersed and focused using a separate spherical varied-line-space grating, and imaged with a separate 512x512 CCD camera. Prototypes

  4. Numerical RHD simulations of flaring chromosphere with Flarix

    CERN Document Server

    Heinzel, P; Varady, M; Karlicky, M; Moravec, Z

    2016-01-01

    Flarix is a radiation-hydrodynamical (RHD) code for modeling of the response of the chromosphere to a beam bombardment during solar flares. It solves the set of hydrodynamic conservation equations coupled with non-LTE equations of radiative transfer. The simulations are driven by high energy electron beams. We present results of the Flarix simulations of a flaring loop relevant to the problem of continuum radiation during flares. In particular we focus on properties of the hydrogen Balmer continuum which was recently detected by IRIS.

  5. Analysis of the chromospheric spectrum of O I in Arcturus

    Science.gov (United States)

    Haisch, B. M.; Linsky, J. L.; Weinstein, A.; Shine, R. A.

    1977-01-01

    The ultraviolet and near-infrared spectra of O I in Arcturus are analyzed by a 15-level 14-transition model for O I and the Ayres-Linsky (1975) model chromosphere. It is found that the anomalously bright O I resonance lines at 1302, 1305, and 1306 A can be readily explained by a Ly-beta-pumped fluorescence mechanism as originally proposed by Bowen (1974). Observed equivalent widths of the near-infrared triplet and singlet lines are also consistent with the model predictions, but the intercombination lines at 1355 and 1359 A and near-infrared quintet lines may pose a problem.

  6. Chromospheric emission of planet candidate systems - a way to identify false positives

    CERN Document Server

    Karoff, Christoffer; Boxano, Alfio; Knudsen, Mads Faurschou

    2016-01-01

    It has been hypothesized that the presence of closely orbiting giant planets is associated with enhanced chromospheric emission of their host stars. The main cause for such a relation would likely be enhanced dynamo action induced by the planet. We present measurements of chromospheric emission in 234 planet candidate systems from the Kepler mission. This ensemble includes 37 systems with giant planet candidates, which show a clear emission enhancement. The enhancement, however, disappears when systems which are also identified as eclipsing binary candidates are removed from the ensemble. This suggests that a large fraction of the giant planet candidate systems with chromospheric emission stronger than the Sun are not giant planet system, but false positives. Such false-positive systems could be tidally interacting binaries with strong chromospheric emission. This hypotesis is supported by an analysis of 188 eclipsing binary candidates that show increasing chromospheric emission as function of decreasing orbi...

  7. Chromospheric Models and the Oxygen Abundance in Giant Stars

    Science.gov (United States)

    Dupree, A. K.; Avrett, E. H.; Kurucz, R. L.

    2016-04-01

    Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri, which include a chromosphere (CHR), influence the formation of optical lines of O i: the forbidden lines (λ6300, λ6363) and the infrared triplet (λλ7771‑7775). One-dimensional semi-empirical non-local thermodynamic equilibrium (LTE) models are constructed based on observed Balmer lines. A full non-LTE formulation is applied for evaluating the line strengths of O i, including photoionization by the Lyman continuum and photoexcitation by Lyα and Lyβ. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than those in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than those produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors of ∼3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate-mass AGB stars contribute to the observed abundance pattern in globular clusters. A change in the oxygen abundance of metal-poor field giants could affect models of deep mixing episodes on the red giant branch. Changes in the oxygen abundance can impact other abundance determinations that are critical to astrophysics, including chemical tagging techniques and galactic chemical evolution.

  8. Chromospheric Internetwork Oscillations at Various Locations of the Quiet Sun

    Institute of Scientific and Technical Information of China (English)

    Zong-Jun Ning; Ming-De Ding

    2005-01-01

    We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the CⅡ1334A line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) aboard Solar and Heliospheric Obse rvatory (SOHO). Three areas, 26 × 120arcsec2 each,at the various latitudes from the disk center to the north polar coronal hole, were rastered with a cadence of about 40-60 s in the solar minimum year. We obtained the time evolution of two-dimensional (2D) line intensity, continuum and line core shift. The continuum and the line shift show ~3 min chromospheric oscillations in the internetwork regions underlying the coronal hole as well as at the disk center. We find that the CⅡ1334A line shift oscillates with an average speed of ~1.7 km s-1, independent of the latitude, while its coherent scale decreases with latitude. On the other hand, the oscillation amplitude of the continuum around the 1334A and the phase delay between the Doppler shift and continuum slightly increase with latitude.

  9. ACCELERATION OF TYPE II SPICULES IN THE SOLAR CHROMOSPHERE

    International Nuclear Information System (INIS)

    A 2.5D, time-dependent magnetohydrodynamic model is used to test the proposition that observed type II spicule velocities can be generated by a Lorentz force under chromospheric conditions. It is found that current densities localized on observed space and time scales of type II spicules and that generate maximum magnetic field strengths ≤50 G can generate a Lorentz force that accelerates plasma to terminal velocities similar to those of type II spicules. Maximum vertical flow speeds are ∼150-460 km s–1, horizontally localized within ∼2.5-10 km from the vertical axis of the spicule, and comparable to slow solar wind speeds, suggesting that significant solar wind acceleration occurs in type II spicules. Horizontal speeds are ∼20 times smaller than vertical speeds. Terminal velocity is reached ∼100 s after acceleration begins. The increase in the mechanical and thermal energy of the plasma during acceleration is (2-3) × 1022 ergs. The radial component of the Lorentz force compresses the plasma during the acceleration process by factors as large as ∼100. The Joule heating flux generated during this process is essentially due to proton Pedersen current dissipation and can be ∼0.1-3.7 times the heating flux of ∼106 ergs cm–2 s–1 associated with middle-upper chromospheric emission. About 84%-94% of the magnetic energy that accelerates and heats the spicules is converted into bulk flow kinetic energy.

  10. Chromospheric Models and the Oxygen Abundance in Giant Stars

    CERN Document Server

    Dupree, A K; Kurucz, R L

    2016-01-01

    Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri that include a chromosphere influence the formation of optical lines of Oxygen I: the forbidden lines (630nm, 636nm) and the infrared triplet (777.1-777.5 nm). One-dimensional semi-empirical non-LTE models are constructed based on observed Balmer lines. A full non-LTE formulation is applied in evaluating line strengths of O I including photoionization by the Lyman continuum and photoexcitation by Ly-alpha and Ly-beta. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors ~3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate mass AGB stars contribute to the observed abundance pattern in globular cluste...

  11. Statistical comparison of the radio granulation and calcium chromospheric network

    International Nuclear Information System (INIS)

    The results of a statistical consideration of simultaneous observations of the radio granulation made with the RATAN-600 (wavelength λ=1.35 cm) and the chromospheric network (Ca II K line breifringent filter) are presented. The observations were made on July 21 and 28 and August 3, 1976, at the epoch of minimum phase of the solar cycle. Autocorrelation spectral analysis was used to find characteristics of the spatial structure. Characteristic lengths of 44 and 122 arcs (30 and 88x103 km) in the radio wavelength range and 29, 44 and 74 arcs (22, 30 and 53x103 km) in the optical region were revealed. Comparison of the two sets of data (radio and optical) was made using the cross-correlation analysis. The coherence amounts to 0.35; 0.80 and 0.75 for the spatial wavelength of 22, 30 and 53x103 km. These results confirm the earlier conclusion concerning physical relation between radio granulation and the calcium chromospheric network. However, the presence in the radio data of the period of about 120 arcs implies that both phenomena are not identical features of the solar atmosphere

  12. Chromospheric heating by acoustic waves compared to radiative cooling

    CERN Document Server

    Sobotka, M; Švanda, M; Jurčák, J; del Moro, D; Berrilli, F

    2016-01-01

    Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of solar atmosphere. A weak chromospheric plage near a large solar pore NOAA 11005 was observed on October 15, 2008 in the lines Fe I 617.3 nm and Ca II 853.2 nm with the Interferometric Bidimemsional Spectrometer (IBIS) attached to the Dunn Solar Telescope. Analyzing the Ca II observations with spatial and temporal resolutions of 0.4" and 52 s, the energy deposited by acoustic waves is compared with that released by radiative losses. The deposited acoustic flux is estimated from power spectra of Doppler oscillations measured in the Ca II line core. The radiative losses are calculated using a grid of seven 1D hydrostatic semi-empirical model atmospheres. The comparison shows that the spatial correlation of maps of radiative losses and acoustic flux is 72 %. In quiet chromosphere, the contribution of acoustic energy flux to radiative losses is small, only of about 15 %. In active areas with photospheric ma...

  13. Basal Chromospheric Flux and Maunder Minimum-type Stars: The quiet-Sun Chromosphere as a Universal Phenomenon

    CERN Document Server

    Schroeder, K -P; Martinez, M I Perez; Cuntz, M; Schmitt, J H M M

    2012-01-01

    Aims: We demonstrate the universal character of the quiet-Sun chromosphere among inactive stars (solar-type and giants). By assessing the main physical processes, we shed new light on some common observational phenomena. Methods: We discuss measurements of the solar Mt. Wilson S-index, obtained by the Hamburg Robotic Telescope around the extreme minimum year 2009, and compare the established chromospheric basal Ca II K line flux to the Mt. Wilson S-index data of inactive ("flat activity") stars, including giants. Results: During the unusually deep and extended activity minimum of 2009, the Sun reached S-index values considerably deeper than in any of its previously observed minima. In several brief periods, the Sun coincided exactly with the S-indices of inactive ("flat", presumed Maunder Minimum-type) solar analogues of the Mt. Wilson sample; at the same time, the solar visible surface was also free of any plages or remaining weak activity regions. The corresponding minimum Ca II K flux of the quiet Sun and ...

  14. Simulations of Alfven wave driving of the solar chromosphere - efficient heating and spicule launching

    CERN Document Server

    Brady, C S

    2016-01-01

    Two of the central problems in our understanding of the solar chromosphere are how the upper chromosphere is heated and what drives spicules. Estmates of the required chromospheric heating, based on radiative and conductive losses suggest a rate of $\\sim 0.1 \\mathrm{\\:erg\\:cm^{-3}\\:s^{-1}}$ in the lower chromosphere dropping to $\\sim 10^{-3} \\mathrm{\\:erg\\:cm^{-3}\\:s^{-1}}$ in the upper chromosphere (\\citet{Avrett1981}). The chromosphere is also permeated by spicules, higher density plasma from the lower atmosphere propelled upwards at speeds of $\\sim 10-20 \\mathrm{\\:km\\:s^{-1}}$, for so called Type-I spicules (\\citet{Pereira2012,Zhang2012}, reaching heights of $\\sim 3000-5000 \\mathrm{\\:km}$ above the photosphere. A clearer understanding of chromospheric dynamics, its heating and the formation of spicules, is thus of central importance to solar atmospheric science. For over thirty years it has been proposed that photospheric driving of MHD waves may be responsible for both heating and spicule formation. This ...

  15. Impact of the Ion-Neutral Interaction Effects in the Solar Chromosphere

    Science.gov (United States)

    Martínez-Sykora, J.; De Pontieu, B.; Hansteen, V. H.; Carlsson, M.

    2015-12-01

    The complexity of the chromosphere is due to various regime changes that take place across it. Consequently, the interpretation of chromospheric observations is a challenging task. It is thus crucial to combine these observations with advanced radiative-MHD numerical modeling. Because the photosphere, chromosphere and transition region are partially ionized, the interaction between ionized and neutral particles has important consequences on the magneto-thermodynamics of these regions. We implemented the effects of partial ionization using generalized Ohm's law in the Bifrost code (Gudiksen et al. 2011) which solves the full MHD equations with non-grey and non-LTE radiative transfer and thermal conduction along magnetic field lines. We perform 2.5D simulations which combines large and small scales structures. This leads to a highly dynamic chromosphere with large variety of physical processes which have not been reproduced with smaller simulations. The implementation of partial ionization effects impact our modeled radiative-MHD atmosphere, such as producing chromospheric heating and diffusion of photospheric magnetic field into the upper-chromosphere. We will also focus on which observables of these processes can be revealed with chromospheric observations.

  16. Chromospheric activity of ROSAT discovered weak-lined T Tauri stars

    OpenAIRE

    Montes, D.; Ramsey, L. W.

    1998-01-01

    We have started a high resolution optical observation program dedicated to the study of chromospheric activity in weak-lined T Tauri stars (WTTS) recently discovered by the ROSAT All-Sky Survey (RASS). It is our purpose to quantify the phenomenology of the chromospheric activity of each star determining stellar surface fluxes in the more important chromospheric activity indicators (Ca II H & K, H_beta, H_alpha, Ca II IRT) as well as obtain the Li I abundance, a better determination of the ste...

  17. Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath

    CERN Document Server

    Kato, Yoshiaki; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats

    2016-01-01

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab "pump" the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in ...

  18. The chromospheres of late-type stars: Pt. 1

    International Nuclear Information System (INIS)

    We derive a new model of the lower chromosphere of the dwarf K2 of star ε Eridani by matching flux profiles of the Ca IR triplet lines λλ8498 and 8542, Hα and Hβ lines and the Na D lines (all observed simultaneously at the AAT), and the Ca II K line. The coupled non-LTE equations of statistical equilibrium and radiative transfer are solved under the constraint of hydrostatic equilibrium. The extra constraints imposed by data from a large number of lines originating from different but overlapping atmospheric depths imply that previous models need to be changed in the photosphere, in the temperature minimum by raising it and placing it further out in the atmosphere, and by placing the base of the transition zone at log m = -4.54. (author)

  19. Sunspot Oscillations From The Chromosphere To The Corona

    Science.gov (United States)

    Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.

    The behavior of the 3 minute sunspot oscillations is studied as a function of temper- ature through the transition region using observations with CDS/SOHO and TRACE. The oscillations occur above the umbra, with amplitudes increasing to a maximum near 200 000 K, then decreasing towards higher temperatures. Deviations from pure linear oscillations are present in several cases. Power spectra of the oscillations are remarkably similar in the chromosphere and through the transition region in contra- diction to the predictions of the sunspot filter theory. The 3 minute oscillations pene- trate to the low temperature end of the corona, where they are channeled into smaller areas coinciding with the endpoints of sunspot coronal loops. This differs from the transition zone where the oscillating region covers the umbra.

  20. Effect of coronal temperature on the scale of solar chromospheric jets

    CERN Document Server

    Iijima, H

    2015-01-01

    We investigate the effect of coronal temperature on the formation process of solar chromospheric jets using two-dimensional magnetohydrodynamic simulations of the region from the upper convection zone to the lower corona. We develop a new radiative magnetohydrodynamic code for the dynamic modeling of the solar atmosphere, employing a LTE equation of state, optically thick radiative loss in the photosphere, optically thin radiative loss in the chromosphere and the corona, and thermal conduction along the magnetic field lines. Many chromospheric jets are produced in the simulations by shock waves passing through the transition region. We find that these jets are projected farther outward when the coronal temperature is lower (similar to that in coronal holes) and shorter when the coronal temperature is higher (similar to that in active regions). When the coronal temperature is high, the deceleration of the chromospheric jets is consistent with the model in which deceleration is determined by the periodic chromo...

  1. Sounding stellar cycles with Kepler - preliminary results from ground-based chromospheric activity measurements

    CERN Document Server

    Karoff, C; Chaplin, W J; Frandsen, S; Grundahl, F; Kjeldsen, H; Buzasi, D; Arentoft, T; Christensen-Dalsgaard, J

    2009-01-01

    Due to its unique long-term coverage and high photometric precision, observations from the Kepler asteroseismic investigation will provide us with the possibility to sound stellar cycles in a number of solar-type stars with asteroseismology. By comparing these measurements with conventional ground-based chromospheric activity measurements we might be able to increase our understanding of the relation between the chromospheric changes and the changes in the eigenmodes. In parallel with the Kepler observations we have therefore started a programme at the Nordic Optical Telescope to observe and monitor chromospheric activity in the stars that are most likely to be selected for observations for the whole satellite mission. The ground-based observations presented here can be used both to guide the selection of the special Kepler targets and as the first step in a monitoring programme for stellar cycles. Also, the chromospheric activity measurements obtained from the ground-based observations can be compared with s...

  2. The chromospheric and transition layer emission of stars with different metal abundances

    Science.gov (United States)

    Boehm-Vitense, E.

    1981-01-01

    Preliminary results on observations of chromospheric and transition layer emission of stars with different metal abundances are reported. Metal deficient stars generally show reduced emission in the Mg II resonance lines and also in the other chromospheric and transition layer emission lines. This is interpreted as showing that energy fluxes other than acoustic fluxes must at least be coresponsible for the coronal and transition layer heating.

  3. The Magnetic Coupling of Chromospheres and Winds From Late Type Evolved Stars: Role of MHD Waves

    Science.gov (United States)

    Airapetian, Vladimir; Leake, James; Carpenter, Kenneth

    2015-08-01

    Stellar chromospheres and winds represent universal attributes of stars on the cool portion of H-R diagram. In this paper we derive observational constrains for the chromospheric heating and wind acceleration from cool evolved stars and examine the role of Alfven waves as a viable source of energy dissipation and momentum deposition. We use a 1.5D magnetohydrodynamic code with a generalized Ohm's law to study propagation of Alfven waves generated along a diverging magnetic field in a stellar photosphere at a single frequency. We demonstrate that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfven waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of α Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere model due to resistive (Joule) dissipation of electric currents on Pedersen resistivity are consistent with observational constraints on the net radiative losses in UV lines and the continuum from α Tau. At the top of the chromosphere, Alfven waves experience significant reflection, producing downward propagating transverse waves that interact with upward propagating waves and produce velocity shear in the chromosphere. Our simulations also suggest that momentum deposition by non-linear Alfven waves becomes significant in the outer chromosphere within 1 stellar radius from the photosphere that initiates a slow and massive winds from red giants and supergiants.

  4. Three-Dimensional Propagation of Magnetohydrodynamic Waves in the Solar Chromosphere and Corona

    Institute of Scientific and Technical Information of China (English)

    李波; 郑惠南; 王水

    2002-01-01

    We study the three-dimensional magnetohydrodynamic (MHD) wave propagation in the solar atmosphere consisting of the chromosphere and corona. Pressure enhancement and velocity shear are implemented simultaneously at the bottom of the chromosphere. The global propagation of the incurred MHD waves, including fast-mode and slow-mode magnetoacoustic waves as well as Alfvén wave, can be identified. Wave front positions obtained numerically with respect to specific waves fit well with those calculated with local MHD wave speeds.

  5. Diagnostics of solar chromosphere plasma based on observations of millimeter radiation

    International Nuclear Information System (INIS)

    Graphical abstract: Observations of the solar chromosphere, the least understood layer of the Sun, at millimeter wavelengths provide new and perspective tests for atmospheric modeling. Comparison of the quiet Sun brightness temperatures observed at millimeter wavelengths with the model spectra calculated from the classical atmospheric models is presented as one of the results. Highlights: ► Classical solar atmospheric models are too warm for observations at mm wavelengths. ► Dynamic models are in agreement with the spatially averaged mm observational data. ► Mm interferometric observations confirm the complex structure of the chromosphere. ► Mm interferometric observations confirm the presence of chromospheric dynamics. - Abstract: In this paper we review the current knowledge of the solar chromosphere from its observations at millimeter wavelengths. We present the observational spectrum of the quiet Sun millimeter wave brightness temperature and its comparison with brightness temperatures computed from the standard static models and the dynamic simulations. Reporting on the findings regarding the structure and dynamics of the solar chromosphere from the best available interferometric data obtained at 3.5 mm we demonstrate a great potential of the mm observations for the study of the solar chromosphere.

  6. Chromospheric activity and rotational modulation on the young, single K2 dwarf LQ Hya

    International Nuclear Information System (INIS)

    High-resolution echelle spectra of LQ Hya, obtained during several observing runs from 2006 to 2012, have been analyzed to study its chromospheric activity. Using the spectral subtraction technique, we derived information about chromospheric activity of LQ Hya from several optical chromospheric activity indicators (including the Hβ, He I D3, Na I D1, D2, Hα, and Ca II infrared triplet (IRT) lines). No optical flares were found during our observations. The equivalent widths (EWs) of the excess emissions in the chromospheric activity lines have been measured. The ratios of EW8542/EW8498 are generally small, which indicates that the Ca II IRT emission arises from plage-like regions, while the E Hα/E Hβ values suggest that the emission of the Balmer lines is due to both plage and prominence structures for the observations in 2012. We find that clear rotational modulation of chromospheric emission exists, which suggests the presence and change of chromospheric active regions over the surface of LQ Hya. Moreover, the active regions were associated with the photospheric spots in spatial structure.

  7. The boundary line in the H-R diagram for stellar chromospheres and the theory of convection

    Science.gov (United States)

    Boehm-Vitense, E.; Dettmann, T.

    1980-01-01

    Ultraviolet emission-line spectra of A, F, and early G stars have been observed with the International Ultraviolet Explorer. For supergiants, classical chromospheric and transition-layer emission is seen only on the red side of the Cepheid instability strip. For luminosity classes III-V, chromospheric emission can be detected for spectral types F2 and later. For none of the A stars was normal chromospheric emission detected, regardless of their rotational velocities or peculiarities (i.e., Am or Ap).

  8. Chromospheric mass motions and intrinsic sunspot rotations for NOAA Active Regions 10484, 10486, and 10488 using ISOON data

    OpenAIRE

    Hardersen, Paul S.; Balasubramaniam, K. S.; Shkolyar, Svetlana

    2013-01-01

    This work utilizes Improved Solar Observing Optical Network (ISOON: Neidig et al. 2003) continuum (630.2 nm) and H{\\alpha} (656.2 nm) data to: 1) detect and measure intrinsic sunspot rotations occurring in the photosphere and chromosphere, 2) identify and measure chromospheric filament mass motions, and 3) assess any large-scale photospheric and chromospheric mass couplings. Significant results from October 27-29, 2003, using the techniques of Brown et al. (2003), indicate significant counter...

  9. Three-dimensional magnetohydrodynamic simulations of M-dwarf chromospheres

    CERN Document Server

    Wedemeyer, S; Steiner, O

    2012-01-01

    We present first results from three-dimensional radiation magnetohydrodynamic simulations of M-type dwarf stars with CO5BOLD. The local models include the top of the convection zone, the photosphere, and the chromosphere. The results are illustrated for models with an effective temperature of 3240 K and a gravitational acceleration of log g = 4.5, which represent analogues of AD Leo. The models have different initial magnetic field strengths and field topologies. This first generation of models demonstrates that the atmospheres of M-dwarfs are highly dynamic and intermittent. Magnetic fields and propagating shock waves produce a complicated fine-structure, which is clearly visible in synthetic intensity maps in the core of the Ca II K spectral line and also at millimeter wavelengths. The dynamic small-scale pattern cannot be described by means of one-dimensional models, which has important implications for the construction of semi-empirical model atmospheres and thus for the interpretation of observations in ...

  10. Flocculent flows in the chromospheric canopy of a sunspot

    CERN Document Server

    Vissers, Gregal

    2012-01-01

    High-quality imaging spectroscopy in the H{\\alpha} line, obtained with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST) at La Palma and covering a small sunspot and its surroundings, are studied. They exhibit ubiquitous flows both along fibrils making up the chromospheric canopy away from the spot and in the superpenumbra. We term these flows "flocculent" to describe their intermittent character, that is morphologically reminiscent of coronal rain. The flocculent flows are investigated further in order to determine their dynamic and morphological properties. For the measurement of their characteristic velocities, accelerations and sizes, we employ a new versatile analysis tool, the CRisp SPectral EXplorer (CRISPEX), which we describe in detail. Absolute velocities on the order of 7.2-82.4 km/s are found, with an average value of 36.5\\pm5.9 km/s and slightly higher typical velocities for features moving towards the sunspot than away. These velocities are much higher than th...

  11. High Resolution Observations of Chromospheric Jets in Sunspot Umbra

    CERN Document Server

    Yurchyshyn, V; Kosovichev, S; Goode, P

    2014-01-01

    Recent observations of sunspot's umbra suggested that it may be finely structured at a sub-arcsecond scale representing a mix of hot and cool plasma elements. In this study we report the first detailed observations of the umbral spikes, which are cool jet-like structures seen in the chromosphere of an umbra. The spikes are cone-shaped features with a typical height of 0.5-1.0 Mm and a width of about 0.1 Mm. Their life time ranges from 2 to 3 min and they tend to re-appear at the same location. The spikes are not associated with photospheric umbral dots and they rather tend to occur above darkest parts of the umbra, where magnetic fields are strongest. The spikes exhibit up and down oscillatory motions and their spectral evolution suggests that they might be driven by upward propagating shocks generated by photospheric oscillations. It is worth noting that triggering of the running penumbral waves seems to occur during the interval when the spikes reach their maximum height.

  12. Modeling the Chromosphere of a Sunspot and the Quiet Sun

    Science.gov (United States)

    Avrett, E.; Tian, H.; Landi, E.; Curdt, W.; Wülser, J.-P.

    2015-10-01

    Semiempirical atmospheric modeling attempts to match an observed spectrum by finding the temperature distribution and other physical parameters along the line of sight through the emitting region such that the calculated spectrum agrees with the observed one. In this paper we take the observed spectrum of a sunspot and the quiet Sun in the EUV wavelength range 668–1475 Å from the 2001 SUMER atlas of Curdt et al. to determine models of the two atmospheric regions, extending from the photosphere through the overlying chromosphere into the transition region. We solve the coupled statistical equilibrium and optically thick radiative transfer equations for a set of 32 atoms and ions. The atoms that are part of molecules are treated separately, and are excluded from the atomic abundances and atomic opacities. We compare the Mg ii k line profile observations from the Interface Region Imaging Spectrograph with the profiles calculated from the two models. The calculated profiles for the sunspot are substantially lower than the observed ones, based on the SUMER models. The only way we have found to raise the calculated Mg ii lines to agree with the observations is to introduce illumination of the sunspot from the surrounding active region.

  13. Estimating the Chromospheric Absorption of Transition Region Moss Emission

    CERN Document Server

    De Pontieu, Bart; McIntosh, Scott W; Patsourakos, Spiros

    2009-01-01

    Many models for coronal loops have difficulty explaining the observed EUV brightness of the transition region, which is often significantly less than theoretical models predict. This discrepancy has been addressed by a variety of approaches including filling factors and time-dependent heating. Here we focus on an effect that has been ignored so far: the absorption of EUV light with wavelengths below 912 {\\AA} by the resonance continua of neutral hydrogen and helium. Such absorption is expected to occur in the low-lying transition region of hot, active region loops, that is co-located with cool chromospheric features and called ``moss'' as a result of the reticulated appearance resulting from the absorption. We use co-temporal and co-spatial spectroheliograms obtained with SOHO/SUMER and Hinode/EIS of Fe XII 1242 {\\AA}, 195 {\\AA} and 186.88 {\\AA}, and compare the density determination from the 186/195 {\\AA} line ratio to that resulting from the 195/1242 {\\AA} line ratio. We find significant absorption of 195 {...

  14. Footpoint detection and mass-motion in chromospheric filaments

    Science.gov (United States)

    V, Aparna; Hardersen, P. S.; Martin, S. F.

    2013-07-01

    A quiescent region on the Sun containing three filaments is used to study the properties of mass motion. This study determines if the footpoints or end-points of the filaments are the locations from where mass gets injected into the filaments. Several hypotheses have been put forth in the past to determine how a filament acquires mass. Trapping of coronal mass in the filament channel due to condensation (Martin, 1996) and injection of mass into the filaments during magnetic reconnection (Priest, et al., 1995) are some of the speculations. This study looks for indications for injection of mass via chromospheric footpoints. The data consists of blue (Hα-0.5 Å) and red (Hα+0.5 Å) wing high resolution Hα images of the W29N37 region of the Sun taken on Oct 30, 2010, from 1200 - 1600 UT. The Dutch Open Telescope was used to obtain the data. The images are aligned and animated to see Doppler motion in the fibrils. Smaller fibrils merge to form longer ones; barbs appear and disappear in one of the long filaments and is seen moving along the length of the filament. A region with no typical filament-like absorption feature is observed to be continuously receiving mass. Fibrils appear to be converging from opposite sides along what appears to be a neutral line; mass motion is seen in these fibrils as well. An eruption occurs in a region of fibrils lumped together at the end of the first hour (1300 UT) followed by plage brightening at 1430 UT near one of the filament regions. Helioviewer (Panasenco, et al., 2011) is used for aligning the images; GIMP is used for precision alignment and animation. Each frame in the sequence is studied carefully to note changes in the filament regions. The footpoints of the filaments are determined by the changes observed in the position of the filament ‘legs’ in each frame. Variations in the magnetic polarity corresponding to changes observed in the chromosphere are analyzed using HMI magnetograms. Bright and dark points on the

  15. Stellar model chromospheres. VIII - 70 Ophiuchi A /K0 V/ and Epsilon Eridani /K2 V/

    Science.gov (United States)

    Kelch, W. L.

    1978-01-01

    Model atmospheres for the late-type active-chromosphere dwarf stars 70 Oph A and Epsilon Eri are computed from high-resolution Ca II K line profiles as well as Mg II h and k line fluxes. A method is used which determines a plane-parallel homogeneous hydrostatic-equilibrium model of the upper photosphere and chromosphere which differs from theoretical models by lacking the constraint of radiative equilibrium (RE). The determinations of surface gravities, metallicities, and effective temperatures are discussed, and the computational methods, model atoms, atomic data, and observations are described. Temperature distributions for the two stars are plotted and compared with RE models for the adopted effective temperatures and gravities. The previously investigated T min/T eff vs. T eff relation is extended to Epsilon Eri and 70 Oph A, observed and computed Ca II K and Mg II h and k integrated emission fluxes are compared, and full tabulations are given for the proposed models. It is suggested that if less than half the observed Mg II flux for the two stars is lost in noise, the difference between an active-chromosphere star and a quiet-chromosphere star lies in the lower-chromospheric temperature gradient.

  16. Stellar model chromospheres. VIII. 70 Ophiuchi A (K0 V) and epsilon Eridani (K2 V)

    International Nuclear Information System (INIS)

    High resolution Ca II K line profiles and Mg II h and k line fluxes are used to derive photosphere and chromosphere models of two K dwarf active chromosphere stars, epsilon Eri and 70 Oph A. These models are computed on the basis of partial redistribution diagnostics. The derived values of T/sub min//T/sub eff/ and m/sub o/ (the mass column density at the top of the chromosphere) confirm and extend the T/sub min//T/sub eff/ versus T/sub eff/ and the log m0 versus log g relations previously found in Paper VII. In particular, we find that T/sub min//T/sub eff/ is significantly larger in epsilon Eri and 70 Oph A than in α Cen B, presumably due to enhanced metal abundance and resultant larger CO line blanketing in α Cen B. The main-sequence models thus far derived strongly suggest that chromospheric activity correlates with the lower chromospheric temperature gradient rather than the value of m0

  17. Upper Chromospheric Magnetic Field of a Sunspot Penumbra: Observations of Fine Structure

    CERN Document Server

    Joshi, J; Solanki, S K; Feller, A; Collados, M; Suárez, D Orozco; Schlichenmaier, R; Franz, M; Balthasar, H; Denker, C; Berkefeld, T; Hofmann, A; Kiess, C; Nicklas, H; Yabar, A Pastor; Rezaei, R; Schmidt, D; Schmidt, W; Sobotka, M; Soltau, D; Staude, J; Strassmeier, K G; Volkmer, R; von der Lühe, O; Waldmann, T

    2016-01-01

    The fine-structure of magnetic field of a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere. High spatial resolution spectropolarimetric observations were recorded with the 1.5-meter GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The observed spectral domain includes the upper chromospheric He I triplet at 1083.0 nm and the photospheric Si I 1082.7 nm and Ca I 1083.3 nm spectral lines. The upper chromospheric magnetic field is obtained by inverting the He I triplet assuming a Milne-Eddington type model atmosphere. A height dependent inversion was applied to the Si I 1082.7 nm and Ca I 1083.3 nm lines to obtain the photospheric magnetic field. We find that the inclination of the magnetic field shows variations in the azimuthal direction both in the photosphere, but also in the upper chromosphere. The chromospheric variations remarkably well coincide with the variations in the inclination of the photospheric field and resemble the well-known sp...

  18. Key Properties of Solar Chromospheric Line Formation Process

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα, Hβ, CaIIH and CaII8542, in quiet Sun, faint and bright flares is explored in the unpolarized case. We stress four aspects characterising the property of line formation process: 1) width of line formation core; 2) lineformation region; 3) influence of the temperature minimum region; and 4) wavelength ranges within which one can obtain pure chromospheric and photospheric filtergrams. It is shown that the above four aspects depend strongly on the atmo spheric physical condition and the lines used. The formation regions of all the wave length points within a line may be continuously distributed over one depth domain or discretely distributed because of no contribution coming from the temperature minimum reg:on, an important domain in the solar atmosphere that determines the distribution pattern of escape photons. On the other hand, the formation region of one wavelength point may cover only one height range or spread over two domains which are separated again by the temperature minimum region. Different lines may form in different regions in the quiet Sun. However, these line formation regions be come closer ir. solar flaring regions. Finally, though the stratification of line-of-sight velocity can alter the position of the line formation core within the line band and result in the asymmetry of the line formation core about the shifted line center, it can only lead to negligible changes in the line formation region or the line formation core width. All these results can be instructive to solar filtering observations.

  19. Contribution to the study of velocity fields of chromosphere and solar transition zone

    International Nuclear Information System (INIS)

    The LPSP (Laboratoire de Physique Stellaire et Planetaire) experiment on board 0508 is described. The properties of the instrument are discussed together with their evolution with time. The chromospheric oscillations and transients were studied (sunspost and active regions, prominences, oscillations in the chromosphere, chromosphere-corona transition lines). Simultaneous time-resolved observations of the H Lα, Mg k 2795A, and Ca, K solar lines were made. They indicate that the temporal variations of wavelength of the reversal of the solar H Lα and Mg k lines are correlated. A narrow absorption on the red part of the solar H Lα profile was observed and attributed to atomic hydrogen of the nearby interplanetary gas

  20. MHD wave modes resolved in fine-scale chromospheric magnetic structures

    CERN Document Server

    Verth, G

    2015-01-01

    Within the last decade, due to significant improvements in the spatial and temporal resolution of chromospheric data, magnetohydrodynamic (MHD) wave studies in this fascinating region of the Sun's atmosphere have risen to the forefront of solar physics research. In this review we begin by reviewing the challenges and debates that have manifested in relation to MHD wave mode identification in fine-scale chromospheric magnetic structures, including spicules, fibrils and mottles. Next we go on to discuss how the process of accurately identifying MHD wave modes also has a crucial role to play in estimating their wave energy flux. This is of cardinal importance for estimating what the possible contribution of MHD waves is to solar atmospheric heating. Finally, we detail how such advances in chromospheric MHD wave studies have also allowed us, for the first time, to implement cutting-edge magnetoseismological techniques that provide new insight into the sub-resolution plasma structuring of the lower solar atmospher...

  1. On the spatial scales of wave heating in the solar chromosphere

    CERN Document Server

    Soler, Roberto; Ballester, Jose Luis

    2015-01-01

    Dissipation of magnetohydrodynamic (MHD) wave energy has been proposed as a viable heating mechanism in the solar chromospheric plasma. Here, we use a simplified one-dimensional model of the chromosphere to theoretically investigate the physical processes and the spatial scales that are required for the efficient dissipation of Alfv\\'en waves and slow magnetoacoustic waves. We consider the governing equations for a partially ionized hydrogen-helium plasma in the single-fluid MHD approximation and include realistic wave damping mechanisms that may operate in the chromosphere, namely Ohmic and ambipolar magnetic diffusion, viscosity, thermal conduction, and radiative losses. We perform an analytic local study in the limit of small amplitudes to approximately derive the lengthscales for critical damping and efficient dissipation of MHD wave energy. We find that the critical dissipation lengthscale for Alfv\\'en waves depends strongly on the magnetic field strength and ranges from 10~m to 1~km for realistic field ...

  2. NONPOTENTIALITY OF CHROMOSPHERIC FIBRILS IN NOAA ACTIVE REGIONS 11092 AND 9661

    International Nuclear Information System (INIS)

    In this paper, we present a method to automatically segment chromospheric fibrils from Hα observations and further identify their orientation. We assume that chromospheric fibrils are aligned with the magnetic field. By comparing the orientation of the fibrils with the azimuth of the embedding chromospheric magnetic field extrapolated from a potential field model, the shear angle, a measure of nonpotentiality, along the fibrils is readily deduced. Following this approach, we make a quantitative assessment of the nonpotentiality of fibrils in two NOAA active regions (ARs): (1) the relatively simple AR 11092, observed with very high resolution by Interferometric Bidimensional Spectrometer, and (2) a β-γ-δ AR 9661, observed with median resolution by Big Bear Solar Observatory before and after an X1.6 flare.

  3. Localizing Plages on BO Mic, First steps towards chromospheric Doppler imaging

    CERN Document Server

    Wolter, U

    2005-01-01

    We have obtained a densely sampled time series of CaII H&K line profiles of the ultrafast rotating K-dwarf star BO Mic. Taken at high resolution, the spectra reveal pronounced variations of the emission core profiles. We interpret these variations as signs of concentrated chromospherically active regions, in analogy to solar plages. We further interpret the variations as partly due to the rapid growth and decay of plages, while other variations appear to be caused by plages moved over the visible stellar disk by rotation. The equivalent width of the Ca K core emission changes approximately in anti-phase to the photospheric brightness, suggesting an association of the chromospheric plage regions with pronounced dark photospheric spots. We believe that further analysis of the presented spectral time series will lead to a chromospheric Doppler image of BO mic.

  4. Solar atmospheric dynamics. II - Nonlinear models of the photospheric and chromospheric oscillations

    Science.gov (United States)

    Leibacher, J.; Gouttebroze, P.; Stein, R. F.

    1982-01-01

    The one-dimensional, nonlinear dynamics of the solar atmosphere is investigated, and models of the observed photospheric (300 s) and chromospheric (200 s) oscillations are described. These are resonances of acoustic wave cavities formed by the variation of the temperature and ionization between the subphotospheric, hydrogen convection zone and the chromosphere-corona transition region. The dependence of the oscillations upon the excitation and boundary conditions leads to the conclusion that for the observed amplitudes, the modes are independently excited and, as trapped modes, transport little if any mechanical flux. In the upper photosphere and lower chromosphere, where the two modes have comparable energy density, interference between them leads to apparent vertical phase delays which might be interpreted as evidence of an energy flux.

  5. Patterns of photometric and chromospheric variation among Sun-like stars: A 20-year perspective

    CERN Document Server

    Lockwood, G W; Henry, G W; Henry, S; Radick, R R; Baliunas, S L; Donahue, R A; Soon, W; Henry, Gregory W.; Henry, Stephen

    2007-01-01

    We examine patterns of variation of 32 primarily main sequence stars, extending our previous 7-12 year time series to 13-20 years by combining b, y data from Lowell Observatory with similar data from Fairborn Observatory. Parallel chromospheric Ca II H and K emission data from the Mount Wilson Observatory span the entire interval. The extended data strengthen the relationship between chromospheric and photometric variation derived previously. Twenty-seven stars are deemed variable. On a year-to-year timescale young active stars become fainter when their Ca II emission increases while older less active stars such as the Sun become brighter when their Ca II emission increases. The Sun's total irradiance variation, scaled to the b and y filter photometry, still appears to be somewhat smaller than stars in our limited sample with similar mean chromospheric activity, but we now regard this discrepancy as probably due mainly to our limited stellar sample

  6. Tracing the Chromospheric and Coronal Magnetic Field with AIA, IRIS, IBIS, and ROSA Data

    Science.gov (United States)

    Aschwanden, Markus J.; Reardon, Kevin; Jess, Dave B.

    2016-07-01

    The aim of this study is to explore the suitability of chromospheric images for magnetic modeling of active regions. We use high-resolution images (≈ 0\\buildrel{\\prime\\prime}\\over{.} 2{--}0\\buildrel{\\prime\\prime}\\over{.} 3), from the Interferometric Bidimensional Spectrometer in the Ca ii 8542 Å line, the Rapid Oscillations in the Solar Atmosphere instrument in the Hα 6563 Å line, the Interface Region Imaging Spectrograph in the 2796 Å line, and compare non-potential magnetic field models obtained from those chromospheric images with those obtained from images of the Atmospheric Imaging Assembly in coronal (171 Å, etc.) and in chromospheric (304 Å) wavelengths. Curvi-linear structures are automatically traced in those images with the OCCULT-2 code, to which we forward-fitted magnetic field lines computed with the Vertical-current Approximation Nonlinear Force Free Field code. We find that the chromospheric images: (1) reveal crisp curvi-linear structures (fibrils, loop segments, spicules) that are extremely well-suited for constraining magnetic modeling; (2) that these curvi-linear structures are field-aligned with the best-fit solution by a median misalignment angle of {μ }2≈ 4^\\circ –7° (3) the free energy computed from coronal data may underestimate that obtained from cromospheric data by a factor of ≈ 2–4, (4) the height range of chromospheric features is confined to h≲ 4000 km, while coronal features are detected up to h = 35,000 km; and (5) the plasma-β parameter is β ≈ {10}-5{--}{10}-1 for all traced features. We conclude that chromospheric images reveal important magnetic structures that are complementary to coronal images and need to be included in comprehensive magnetic field models, something that is currently not accomodated in standard NLFFF codes.

  7. Tracing the Chromospheric and Coronal Magnetic Field with AIA, IRIS, IBIS, and ROSA Data

    CERN Document Server

    Aschwanden, M J; Jess, D

    2016-01-01

    The aim of this study is to explore the suitability of chromospheric images for magnetic modeling of active regions. We use high-resolution images (0.1") from the Interferometric Bidimensional Spectrometer (IBIS) in the Ca II 8542 A line, the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument in the H-alpha 6563 A line, the Interface Region Imaging Spectrograph (IRIS) in the 2796 A line, and compare non-potential magnetic field models obtained from those chromospheric images with those obtained from images of the Atmospheric Imaging Assembly (AIA) in coronal (171 A, etc.) and in chromospheric (304 A) wavelengths. Curvi-linear structures are automatically traced in those images with the OCCULT-2 code, to which we forward-fitted magnetic field lines computed with the Vertical-Current Approximation Non-Linear Force Free Field (VCA-NLFFF) code. We find that the chromospheric images: (1) reveal crisp curvi-linear structures (fibrils, loop segments, spicules) that are extremely well-suited for constrainin...

  8. Study of FK Comae Berenices: VII. Correlating photospheric and chromospheric activity

    CERN Document Server

    Vida, K; Ilyin, I V; Oláh, K; Andersen, M I; Hackman, T

    2015-01-01

    We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. We use spot temperature modelling, light curve inversion based on narrow- and wide-band photometric measurements, Halpha observations from 1997-2010, and Doppler maps from 2004-2010 to compare the behaviour of chromospheric and photospheric features. Investigating low-resolution Halpha spectra we find that the changes in the chromosphere seem to happen mainly on a time scale longer than a few hours, but shorter variations were also observed. According to the Halpha measurements prominences are often found in the chromosphere that reach to more than a stellar radius and are stable for weeks, and which seem to be often, but not every time connected with dark photospheric spots. The rotational modulation of the Halpha emission seems to typically be anticorrelated with the light curve, but we did not find convincing evidence of a clear connection in the long-term trends of the Halpha emission and th...

  9. Dynamic Models of the Sun from the Convection Zone to the Chromosphere

    CERN Document Server

    Wedemeyer-B"ohm, S

    2006-01-01

    The chromosphere in internetwork regions of the quiet Sun was regarded as a static and homogeneous layer for a long time. Thanks to advances in observations and numerical modelling, the wave nature of these atmospheric regions received increasing attention during the last decade. Recent three-dimensional radiation magnetohydrodynamic simulations with CO5BOLD feature the chromosphere of internetwork regions as a dynamic and intermittent phenomenon. It is a direct product of interacting waves that form a mesh-like pattern of hot shock fronts and cool post-shock regions. The waves are excited self-consistently at the top of the convection zone. In the middle chromosphere above an average height of 1000 km, plasma beta gets larger than one and magnetic fields become more important. The model chromosphere exhibits a magnetic field that is much more homogeneous than in the layers below and evolves much faster. That includes fast propagating (MHD) waves. Further improvements of the simulations like time-dependent hy...

  10. On the correlation between stellar chromospheric flux and the surface gravity of close-in planets

    CERN Document Server

    Lanza, A F

    2014-01-01

    The chromospheric emission of stars with close-by transiting planets has been found to correlate with the surface gravity of their planets. Stars with low-gravity planets have an average lower chromospheric flux. We propose that such a correlation is due to the absorption by circumstellar matter that comes from the evaporation of the planets. Planets with a lower gravity have a greater mass loss rate that leads to a higher column density of circumstellar absorption thus explaining the lower level of chromospheric emission observed in their host stars. We estimate the required column density and find that planetary evaporation can account for it. A theoretical relationship between the chromospheric emission as measured in the core of the Ca II H&K lines and the planet gravity is derived. We apply our relationship to a sample of transiting systems for which both the stellar Ca II H&K emission and the planetary surface gravity are known and find a good agreement, given the various sources of uncertaintie...

  11. Qualities of Sequential Chromospheric Brightenings Observed in Hα and UV Images

    Science.gov (United States)

    Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, Jason; McAteer, R. T. James

    2014-12-01

    Chromospheric flare ribbons observed in Hα appear well-organized when first examined: ribbons impulsively brighten, morphologically evolve, and exponentially decay back to pre-flare levels. Upon closer inspection of the Hα flares, there is often a significant number of compact areas brightening in concert with the flare eruption but are spatially separated from the evolving flare ribbon. One class of these brightenings is known as sequential chromospheric brightenings (SCBs). SCBs are often observed in the immediate vicinity of erupting flares and are associated with coronal mass ejections. In the past decade there have been several previous investigations of SCBs. These studies have exclusively relied upon Hα images to discover and analyze these ephemeral brightenings. This work employs the automated detection algorithm of Kirk et al. to extract the physical qualities of SCBs in observations of ground-based Hα images and complementary Atmospheric Imaging Assembly images in He II, C IV, and 1700 Å. The metadata produced in this tracking process are then culled using complementary Doppler velocities to isolate three distinguishable types of SCBs. From a statistical analysis, we find that the SCBs at the chromospheric Hα layer appear earlier and last longer than their corresponding signatures measured in AIA. From this multi-layer analysis, we infer that SCBs are spatially constrained to the mid-chromosphere. We also derive an energy budget to explain SCBs which have a postulated energy of not more than 0.01% of the total flare energy.

  12. Diagnostics of Dark Chromospheric Mottles Based on High Resolution Spectra. I - Observational Data

    Czech Academy of Sciences Publication Activity Database

    Kotrč, Pavel; Schwartz, Pavol; Heinzel, Petr; Tsiropoula, G.; Tziotziou, K.

    2005-01-01

    Roč. 29, č. 1 (2005), s. 289-298. ISSN 0351-2657. [Hvar astrophysical colloquium /7./: Solar activity cycle and global phenomena. Hvar, 20.09.2004-24.09.2004] Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * chromosphere * dark mottles Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  13. Toward A Self Consistent MHD Model of Chromospheres and Winds From Late Type Evolved Stars

    CERN Document Server

    Airapetian, V S; Carpenter, K G

    2014-01-01

    We present the first magnetohydrodynamic model of the stellar chromospheric heating and acceleration of the outer atmospheres of cool evolved stars, using alpha Tau as a case study. We used a 1.5D MHD code with a generalized Ohm's law that accounts for the effects of partial ionization in the stellar atmosphere to study Alfven wave dissipation and wave reflection. We have demonstrated that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfven waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of alpha Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere due to resistive (Joule) dissipation of electric currents, induced by ...

  14. Chromospheric Nanoflares as a Source of Coronal Plasma: II. Repeating Nanoflares

    CERN Document Server

    Bradshaw, Stephen J

    2016-01-01

    The million degree plasma of the solar corona must be supplied by the underlying layers of the atmosphere. The mechanism and location of energy release, and the precise source of coronal plasma, remain unresolved. In earlier work we pursued the idea that warm plasma is supplied to the corona via direct heating of the chromosphere by nanoflares, contrary to the prevailing belief that the corona is heated in-situ and the chromosphere is subsequently energized and ablated by thermal conduction. We found that single (low-frequency) chromospheric nanoflares could not explain the observed intensities, Doppler-shifts, and red/blue asymmetries in Fe XII and XIV emission lines. In the present work we follow up on another suggestion that the corona could be powered by chromospheric nanoflares that repeat on a timescale substantially shorter than the cooling/draining timescale. That is, a single magnetic strand is re-supplied with coronal plasma before the existing plasma has time to cool and drain. We perform a series ...

  15. An active region filament studied simultaneously in the chromosphere and photosphere. II. Doppler velocities

    CERN Document Server

    Kuckein, C; Centeno, R

    2012-01-01

    Paper I presents the magnetic structure of a filament that developed in active region (AR) NOAA 10781. In this paper we complement those results with the velocities retrieved from Doppler shifts measured at the chromosphere and the photosphere in the AR filament area. Various inversion methods with different numbers of atmospheric components and different weighting schemes of the Stokes profiles were used. The velocities were calibrated on an absolute scale. A ubiquitous chromospheric downflow is found in the faculae surrounding the filament, with an average velocity of 1.6 km/s. The filament region, however, displays upflows in the photosphere on both days, when the linear polarization (which samples the transverse component of the fields) is given more weight in the inversions. The upflow speeds of the transverse fields in the filament region average -0.15 km/s. In the chromosphere, the situation is different for the two days of observation. On July 3, the chromospheric portion of the filament is moving upw...

  16. The multi-species Farley-Buneman instability in the solar chromosphere

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, Chad A.; Dimant, Yakov S.; Oppenheim, Meers M. [Center for Space Physics, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Fontenla, Juan M., E-mail: cmadsen@bu.edu [Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 1234 Innovation Drive, Boulder, CO 80303 (United States)

    2014-03-10

    Empirical models of the solar chromosphere show intense electron heating immediately above its temperature minimum. Mechanisms such as resistive dissipation and shock waves appear insufficient to account for the persistence and uniformity of this heating as inferred from both UV lines and continuum measurements. This paper further develops the theory of the Farley-Buneman instability (FBI) which could contribute substantially to this heating. It expands upon the single-ion theory presented by Fontenla by developing a multiple-ion-species approach that better models the diverse, metal-dominated ion plasma of the solar chromosphere. This analysis generates a linear dispersion relationship that predicts the critical electron drift velocity needed to trigger the instability. Using careful estimates of collision frequencies and a one-dimensional, semi-empirical model of the chromosphere, this new theory predicts that the instability may be triggered by velocities as low as 4 km s{sup -1}, well below the neutral acoustic speed. In the Earth's ionosphere, the FBI occurs frequently in situations where the instability trigger speed significantly exceeds the neutral acoustic speed. From this, we expect neutral flows rising from the photosphere to have enough energy to easily create electric fields and electron Hall drifts with sufficient amplitude to make the FBI common in the chromosphere. If so, this process will provide a mechanism to convert neutral flow and turbulence energy into electron thermal energy in the quiet Sun.

  17. Study of FK Comae Berenices. VII. Correlating photospheric and chromospheric activity

    Science.gov (United States)

    Vida, K.; Korhonen, H.; Ilyin, I. V.; Oláh, K.; Andersen, M. I.; Hackman, T.

    2015-08-01

    Aims: We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. Methods: We use spot temperature modelling, light curve inversion based on narrow- and wide-band photometric measurements, Hα observations from 1997-2010, and Doppler maps from 2004-2010 to compare the behaviour of chromospheric and photospheric features. Results: Investigating low-resolution Hα spectra, we find that the changes in the chromosphere seem to happen mainly on a time scale longer than a few hours, but shorter variations are also observed. According to the Hα measurements, prominences are often found in the chromosphere that reach to more than a stellar radius and are stable for weeks, and they seem to be often, but not always connected to dark photospheric spots. The rotational modulation of the Hα emission typically seems to be anticorrelated with the light curve, but we did not find convincing evidence of a clear connection in the long-term trends of the Hα emission and the brightness of the star. In addition, FK Com seems to be in an unusually quiet state in 2009-2010 with very little chromospheric activity and low spot contrast, which might indicate the long-term decrease in activity. Based on the observations obtained at the Nordic Optical Telescope, Observatorio Roque de los Muchachos, La Palma, Canary Islands, Spain; Kitt Peak National Observatory, USA.Figures 12, 13, and Appendix A are available in electronic form at http://www.aanda.orgNew data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A64

  18. Ca II 854.2 nm Spectromagnetograms: A Powerful Chromospheric Diagnostic

    Science.gov (United States)

    Harvey, J. W.; Bertello, Luca; Branston, D.; Britanik, J.; Bulau, S.; Cole, L.; Gosain, Sanjay; Harker, Brian; Jones, Harrison P.; Marble, A.; Martinez Pillet, V.; Pevtsov, A.; Schramm, K.; Streander, Kim; Villegas, H.

    2016-05-01

    The transition from physical dominance by plasma flows in the photosphere to magnetic pressure in the solar chromosphere motivates as many diagnostic observations as possible across this important region. Among the few ground-accessible spectral lines formed within the chromosphere, the Ca II 854.2 nm line has the desirable properties of presence everywhere on the solar disk, Zeeman sensitivity, and narrow line width. Mapped observations of circular polarization within this line (spectromagnetograms) have been made at NSO infrequently since 1974, with regular daily full-disk observations starting in August 1996. Full-disk spectral observations of the complete Stokes polarization vector are now being made regularly since November 2015. It is not easy to estimate chromospheric magnetic field properties from the 854.2 nm line profile polarization. To provide rough quick-look vector field maps we found that the weak-field approximation provides a fair first estimate of the line-of-sight component but appears to be too simple to interpret the transverse magnetic field from frequently asymmetric, linearly-polarized line profiles. More realistic estimates of the chromospheric vector field, short of extremely lengthy, full 3D, non-local radiative transfer inversions, are being investigated. We briefly introduce recent instrumental modifications and observational characteristics, sample observations, and results concerning the expansion of the chromospheric field with increasing height, the presence of large areas of weak, nearly horizontal fields, and field estimates in plages, sunspots, flares, filaments, and filament channels. The Stokes spectra will be freely available to the community.This work utilizes SOLIS data obtained by the NSO Integrated Synoptic Program (NISP), managed by the National Solar Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation.

  19. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere VI. Helium in the Chromosphere

    OpenAIRE

    Robitaille P.-M.

    2013-01-01

    Molecular hydrogen and hydrides have recently been advanced as vital agents in the generation of emission spectra in the chromosphere. This is a result of the role they play in the formation of condensed hydrogen structures (CHS) within the chromosphere (P.M. Robitaille. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere IV. On the Nature of the Chromosphere. Progr. Phys., 2013, v. 3, 15–21). Next to hydrogen, helium is perhaps the most intriguing component in this region ...

  20. Full-Disk Chromospheric Vector Magnetograms with Ca II 854.2 nm line: Some Promising Applications

    Science.gov (United States)

    Gosain, Sanjay; Harvey, J. W.; Harker, Brian; Pillet, V. M.; Pevtsov, Alexei A.; Marble, Andrew R.; Bertello, Luca; + SOLIS-Team

    2016-05-01

    Over the last decade, the focus of solar magnetometry has shifted outward from the photosphere to the chromospheric layers. The reasons for this are many. With regards to instrumentation faster detectors with more sensitivity have become available, as have fast electro-optic modulators. Also, there are several potential benefits of observing vector fields in the chromospheric layer as the magnetic field is more force-free in this layer as compared to the photosphere. Coronal force-free field extrapolations are more reliable using chromospheric fields as the lower boundary condition and free magnetic energy is readily computed using the magnetic virial theorem. Recently, a full Stokes polarimeter for the chromospheric Ca II 854.2 nm spectral line was developed and installed in the Vector Spectromagnetograph (VSM) instrument on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) telescope. We present details of this new polarimeter, full disk spectropolarimetric observations and vector magnetograms of the chromosphere, and examples of some promising applications (e.g., maps of normal component of electric current density in the chromosphere, free magnetic energy estimated using virial theorem, and non-potentiality parameter magnetic shear angle).This work utilizes SOLIS data obtained by the NSO Integrated Synoptic Program (NISP), managed by the National Solar Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation

  1. Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation

    CERN Document Server

    Kuridze, D; Henriques, V; Mathioudakis, M; Keenan, F P; Hanslmeier, A

    2016-01-01

    Using data obtained by the high resolution CRisp Imaging SpectroPolarimeter instrument on the Swedish 1-m Solar Telescope, we investigate the dynamics and stability of quiet-Sun chromospheric jets observed at disk center. Small-scale features, such as Rapid Redshifted and Blueshifted Excursions, appearing as high speed jets in the wings of the H$\\alpha$ line, are characterized by short lifetimes and rapid fading without any descending behavior. To study the theoretical aspects of their stability without considering their formation mechanism, we model chromospheric jets as twisted magnetic flux tubes moving along their axis, and use the ideal linear incompressible magnetohydrodynamic approximation to derive the governing dispersion equation. Analytical solutions of the dispersion equation indicate that this type of jet is unstable to Kelvin-Helmholtz instability (KHI), with a very short (few seconds) instability growth time at high upflow speeds. The generated vortices and unresolved turbulent flows associated...

  2. Chromospheres in Metal-Poor Stars Evidenced from the He I 10830A Line

    CERN Document Server

    Takeda, Yoichi

    2011-01-01

    Based on the near-IR spectra of 33 late-type stars in the wide metallicity range (mainly dwarfs and partly giants) obtained with IRCS+AO188 of the Subaru Telescope, we confirmed that He I 10830A line is seen in absorption in almost all moderately to extremely metal-poor stars of thick disk and halo population (from [Fe/H]~ -0.5 down to [Fe/H]~ -3.7), the strength of which is almost constant irrespective of the metallicity. This is an evidence that chromospheric activity at a basal level persists even for such old stars, despite that their rotations are considered to be slowed down and incapable of sustaining a dynamo, suggesting that some kind of chromospheric heating mechanism independent of rotation/magnetism (e.g., acoustic heating) may take place.

  3. Nonlinear Instability and Intermittent Nature of Magnetic Reconnection in Solar Chromosphere

    CERN Document Server

    Singh, K A P; Isobe, H; Shibata, K

    2016-01-01

    The recent observations of Singh et al. (2012) have shown multiple plasma ejections and the intermittent nature of magnetic reconnection in the solar chromosphere, highlighting the need for fast reconnection to occur in highly collisional plasma. However, the physical process through which fast magnetic reconnection occurs in partially ionized plasma, like the solar chromosphere, is still poorly understood. It has been shown that for sufficiently high magnetic Reynolds numbers, Sweet-Parker current sheets can become unstable leading to tearing mode instability and plasmoid formation, but when dealing with a partially ionized plasma the strength of coupling between the ions and neutrals plays a fundamental role in determining the dynamics of the system. We propose that as the reconnecting current sheet thins and the tearing instability develops, plasmoid formation passes through strongly, intermediately, and weakly coupled (or decoupled) regimes, with the time scale for the tearing mode instability depending o...

  4. Spicules and their on-disk counterparts, the main driver for solar chromospheric heating?

    CERN Document Server

    Puschmann, Klaus Gerhard

    2016-01-01

    The question how the outer solar atmosphere is heated from solar photospheric temperatures of about 5800K up to solar chromospheric and coronal temperatures of about 20 000K and millions of degrees respectively, remained without any satisfying answer for centuries. On 4 May 2005, I recorded several time series of Halpha line scans with the GREGOR Fabry-Perot Interferometer, still deployed at the German Vacuum Tower Telescope (VTT), for different solar limb and on-disc positions as well for quiet sun at solar disk center. The spatially and temporally highly resolved time series of Halpha line parameters reveal the entire and detailed complexity as well as the overwhelming dynamics of spicules covering the entire solar disk, thus apparently confirming spicules as the potential driver for chromospheric heating of both the Sun and sun-like stars.

  5. Coronal heating in coupled photosphere-chromosphere-coronal systems: turbulence and leakage

    CERN Document Server

    Verdini, Andrea; Velli, Marco

    2011-01-01

    Coronal loops act as resonant cavities for low frequency fluctuations that are transmitted from the deeper layers of the solar atmosphere and are amplified in the corona, triggering nonlinear interactions. However trapping is not perfect, some energy leaks down to the chromosphere, thus limiting the turbulence development and the associated heating. We consider the combined effects of turbulence and leakage in determining the energy level and associated heating rate in models of coronal loops which include the chromosphere and transition region. We use a piece-wise constant model for the Alfven speed and a Reduced MHD - Shell model to describe the interplay between turbulent dynamics in the direction perpendicular to the mean field and propagation along the field. Turbulence is sustained by incoming fluctuations which are equivalent, in the line-tied case, to forcing by the photospheric shear flows. While varying the turbulence strength, we compare systematically the average coronal energy level (E) and dissi...

  6. Heating of the partially ionized solar chromosphere by waves in magnetic structures

    CERN Document Server

    Shelyag, S; de Vicente, A; Przybylski, D

    2016-01-01

    In this paper, we show a "proof of concept" of the heating mechanism of the solar chromosphere due to wave dissipation caused by the effects of partial ionization. Numerical modeling of non-linear wave propagation in a magnetic flux tube, embedded in the solar atmosphere, is performed by solving a system of single-fluid quasi-MHD equations, which take into account the ambipolar term from the generalized Ohm's law. It is shown that perturbations caused by magnetic waves can be effectively dissipated due to ambipolar diffusion. The energy input by this mechanism is continuous and shown to be more efficient than dissipation of static currents, ultimately leading to chromospheric temperature increase in magnetic structures.

  7. The role of magnetic fields in stellar chromospheres and transition regions

    International Nuclear Information System (INIS)

    In this review based largely on observations with the IUE and Einstein satellites, the author summarizes the different roles that magnetic fields play in controlling the structure and energy balance in the chromospheres and transition regions of late-type stars. The author proposes that the existence of a boundary between solar-like stars and those with little or no hot plasma, as well as the different types of G-K giants and supergiants, can be understood in terms of the fractional surface coverage by closed magnetic structures. Transition region downflows, the chromospheric heating mechanism, and the relative heating rates at different layers can be simply explained by the control of the energy balance by magnetic fields. Finally, models computed for active and quiet regions on the Sun are compared with similar models computed for active and quiet stars, that is stars with intrinsically bright or weak emission lines. (Auth.)

  8. Skylab and solar exploration. [chromosphere-corona structure, energy production and heat transport processes

    Science.gov (United States)

    Von Puttkamer, J.

    1973-01-01

    Review of some of the findings concerning solar structure, energy production, and heat transport obtained with the aid of the manned Skylab space station observatory launched on May 14, 1973. Among the topics discussed are the observation of thermonuclear fusion processes which cannot be simulated on earth, the observation of short-wave solar radiation not visible to observers on earth, and the investigation of energy-transport processes occurring in the photosphere, chromosphere, and corona. An apparent paradox is noted in that the cooler chromosphere is heating the hotter corona, seemingly in defiance of the second law of thermodynamics, thus suggesting that a nonthermal mechanism underlies the energy transport. Understanding of this nonthermal mechanism is regarded as an indispensable prerequisite for future development of plasma systems for terrestrial applications.

  9. Heating of the Partially Ionized Solar Chromosphere by Waves in Magnetic Structures

    Science.gov (United States)

    Shelyag, S.; Khomenko, E.; de Vicente, A.; Przybylski, D.

    2016-03-01

    In this paper, we show a “proof of concept” of the heating mechanism of the solar chromosphere due to wave dissipation caused by the effects of partial ionization. Numerical modeling of non-linear wave propagation in a magnetic flux tube, embedded in the solar atmosphere, is performed by solving a system of single-fluid quasi-MHD equations, which take into account the ambipolar term from the generalized Ohm’s law. It is shown that perturbations caused by magnetic waves can be effectively dissipated due to ambipolar diffusion. The energy input by this mechanism is continuous and shown to be more efficient than dissipation of static currents, ultimately leading to chromospheric temperature increase in magnetic structures.

  10. Chromospheric and transition region structure of the Herbig emission stars HR 5999 and BN Ori

    Science.gov (United States)

    Brown, A.; Tjinadjie, H. R. E.; The, P. S.

    1986-01-01

    The IUE spectra of HR 5999 and BN Ori were analyzed, showing strong emission lines of C II, C IV, O I, and Si IV (also Mg II in HR 5999), indicating the presence of chromospheres and transition regions around these high mass premain sequence (PMS) stars. Infrared, optical, and ultraviolet observations show that BN Ori has a spectral type of FO-2 IIIe, a bolometric luminosity of 36 L, age 1.5 million yr, and mass 2 to 2.5 solar mass. As HR 5999 fades, the ratio of total to selective absorption increases indicating the appearance of larger grains or changes in grain alignment. Emission measure distributions are used to investigate the atmospheric structure of the stars. As HR 5999 fades the emission measure distribution rises systematically and the inferred transition region pressures increase. The transition region and chromospheric radiative losses are large and imply input mechanical energy fluxes similar to those of lower mass PMS stars.

  11. IUE observations of HR 6902 - Effect of luminosity on supergiant chromospheres

    Science.gov (United States)

    Ahmad, Imad A.

    1990-01-01

    IUE observations of the most recently discovered Zeta Aurigae system, HR 6902, are reported to reveal profound differences in the spectrum of the chromosphere of the cool primary from those of all other Zeta Aurigae systems. Unlike its sister systems, HR 6902 shows evidence of neither strong wind nor an extended chromosphere for the cool primary. Instead, the spectrum is like that of a single blue dwarf. The most likely reason for this contrast to all other Zeta Aur systems observed with IUE is the lower luminosity of the HR 6902 primary: a type-II 'bright giant' as opposed to the type I (or Ib-II in the case of 22 Vul) 'supergiants' in the other Zeta Aur systems.

  12. Millimeter radiation from a 3D model of the solar atmosphere I. Diagnosing chromospheric thermal structure

    CERN Document Server

    Loukitcheva, Maria; Carlsson, Mats; White, Stephen

    2015-01-01

    Aims. We use advanced 3D NLTE radiative magnetohydrodynamic simulations of the solar atmosphere to carry out detailed tests of chromospheric diagnostics at millimeter and submillimeter wavelengths. Methods. We focused on the diagnostics of the thermal structure of the chromosphere in the wavelength bands from 0.4 mm up to 9.6 mm that can be accessed with the Atacama Large Millimeter/Submillimeter Array (ALMA) and investigated how these diagnostics are affected by the instrumental resolution. Results. We find that the formation height range of the millimeter radiation depends on the location in the simulation domain and is related to the underlying magnetic structure. Nonetheless, the brightness temperature is a reasonable measure of the gas temperature at the effective formation height at a given location on the solar surface. There is considerable scatter in this relationship, but this is significantly reduced when very weak magnetic fields are avoided. Our results indicate that although instrumental smearin...

  13. Chromospheric Sunspot Oscillations in H-alpha and Ca II 8542A

    CERN Document Server

    Maurya, Ram Ajor; Park, Hyungmin; Yang, Heesu; Song, Donguk; Cho, Kyuhyoun

    2013-01-01

    We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region (AR) using scanning spectroscopy in H-alpha and Ca II 8542A, with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler velocity maps. Temporal sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands.

  14. SOLAR HARD X-RAY SOURCE SIZES IN A BEAM-HEATED AND IONIZED CHROMOSPHERE

    International Nuclear Information System (INIS)

    Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ∼3 Mm and ∼0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources

  15. The influence of the magnetic field on running penumbral waves in the solar chromosphere

    International Nuclear Information System (INIS)

    We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar chromosphere. Analysis of a near-circular sunspot, close to the center of the solar disk, reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter. However, in one directional quadrant, corresponding to the north direction, a pronounced kink in the period-distance diagram is found. Utilizing a combination of the inversion of magnetic Stokes vectors and force-free field extrapolations, we attribute this behavior to the cut-off frequency imposed by the magnetic field geometry in this location. A rapid, localized inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut-off frequency. For the first time, we reveal how the spatial distribution of dominant wave periods, obtained with one of the highest resolution solar instruments currently available, directly reflects the magnetic geometry of the underlying sunspot, thus opening up a wealth of possibilities in future magnetohydrodynamic seismology studies. In addition, the intrinsic relationships we find between the underlying magnetic field geometries connecting the photosphere to the chromosphere, and the characteristics of running penumbral waves observed in the upper chromosphere, directly supports the interpretation that running penumbral wave phenomena are the chromospheric signature of upwardly propagating magneto-acoustic waves generated in the photosphere.

  16. Propagation of Alfv\\'enic Waves From Corona to Chromosphere and Consequences for Solar Flares

    OpenAIRE

    Russell, A. J. B.; Fletcher, L.

    2013-01-01

    How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a 2-fluid model (of plasma and neutrals) and used it to perform 1D simulations of Alfv\\'en waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra and umbra) show that energy transmis...

  17. SOLAR HARD X-RAY SOURCE SIZES IN A BEAM-HEATED AND IONIZED CHROMOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    O' Flannagain, Aidan M.; Gallagher, Peter T. [Astrophysics Research Group, School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Brown, John C. [Astronomy and Astrophysics Group, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2015-02-01

    Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ∼3 Mm and ∼0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources.

  18. Simulations of the Mg II k and Ca II 8542 lines from an Alfv\\'en Wave-heated flare chromosphere

    CERN Document Server

    Kerr, Graham S; Russell, Alexander J B; Allred, Joel C

    2016-01-01

    We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfv\\'en wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show that the distinctive atmospheric evolution in the mid-to-upper chromosphere results in Mg II k-line emission that should be observably different between wave-heated and beam-heated simulations. We also present Ca II 8542A profiles which are formed slightly deeper in the chromosphere. The Mg II k-line profiles from our wave-heated simulation are quite different from those from a beam-heated model and are more consistent with IRIS observations. The predicted differences between the Ca II 8542A in the two models are small. We conclude that careful observational and theoretical study of lines formed in the mid-to-upper chromosphere holds genuine promise for distinguishing between competing models for chromospheric heating in flares.

  19. A bimodal correlation between host star chromospheric emission and the surface gravity of hot Jupiters

    CERN Document Server

    Fossati, L; Lanza, A F

    2015-01-01

    The chromospheric activity index logR'HK of stars hosting transiting hot Jupiters appears to be correlated with the planets' surface gravity. One of the possible explanations is based on the presence of condensations of planetary evaporated material located in a circumstellar cloud that absorbs the CaII H&K and MgII h&k resonance line emission flux, used to measure chromospheric activity. A larger column density in the condensations, or equivalently a stronger absorption in the chromospheric lines, is obtained when the evaporation rate of the planet is larger, which occurs for a lower gravity of the planet. We analyze here a sample of stars hosting transiting hot Jupiters tuned in order to minimize systematic effects (e.g., interstellar medium absorption). Using a mixture model, we find that the data are best fit by a two-linear-regression model. We interpret this result in terms of the Vaughan-Preston gap. We use a Monte Carlo approach to best take into account the uncertainties, finding that the two...

  20. Mass motion in upper solar chromosphere detected from solar eclipse observation

    Science.gov (United States)

    Li, Zhi; Qu, Zhongquan; Yan, Xiaoli; Dun, Guangtao; Chang, Liang

    2016-05-01

    The eclipse-observed emission lines formed in the upper solar atmosphere can be used to diagnose the atmosphere dynamics which provides an insight to the energy balance of the outer atmosphere. In this paper, we analyze the spectra formed in the upper chromospheric region by a new instrument called Fiber Arrayed Solar Optic Telescope (FASOT) around the Gabon total solar eclipse on November 3, 2013. The double Gaussian fits of the observed profiles are adopted to show enhanced emission in line wings, while red-blue (RB) asymmetry analysis informs that the cool line (about 104 K) profiles can be decomposed into two components and the secondary component is revealed to have a relative velocity of about 16-45 km s^{-1}. The other profiles can be reproduced approximately with single Gaussian fits. From these fittings, it is found that the matter in the upper solar chromosphere is highly dynamic. The motion component along the line-of-sight has a pattern asymmetric about the local solar radius. Most materials undergo significant red shift motions while a little matter show blue shift. Despite the discrepancy of the motion in different lines, we find that the width and the Doppler shifts both are function of the wavelength. These results may help us to understand the complex mass cycle between chromosphere and corona.

  1. Relationship between chromospheric evaporation and magnetic field topology in M-class solar flare

    CERN Document Server

    Sadykov, V M; Sharykin, I N; Zimovets, I V; Dominguez, S Vargas

    2016-01-01

    Chromospheric evaporation is observed as Doppler blueshift during solar flares. It plays one of key roles in 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 the NASA's IRIS (Interface Region Imaging Spectrograph) and HMI/SDO (Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory) telescopes, and VIS/NST (Visible Imaging Spectrometer at New Solar Telescope) high-resolution observations, covering the temperature range from 10^4 K to 10^7 K. The results show that the averaged over the region Fe XXI blueshift of the hot evaporating plasma is delayed relative to the C II redshift of the relatively cold chromospheric plasma by about 1 min. The spatial distribution of the delays is not uniform across the region and can be as long as 2 min in several zones. Using vector magne...

  2. First Detection of Chromospheric Magnetic Field Changes During an X1-Flare

    CERN Document Server

    Kleint, Lucia

    2016-01-01

    Stepwise changes of the photospheric magnetic field, which often becomes more horizontal, have been observed during many flares. Previous interpretations include coronal loops that contract and it has been speculated that such jerks could be responsible for sunquakes. Here we report the detection of stepwise chromospheric line-of-sight magnetic field (B$_{\\rm LOS}$) changes obtained through spectropolarimetry of Ca II 8542 \\AA\\ with DST/IBIS during the X1-flare SOL20140329T17:48. They are stronger ($<$640 Mx cm$^{-2}$) and appear in larger areas than their photospheric counterparts ($<$320 Mx cm$^{-2}$). The absolute value of B$_{\\rm LOS}$ more often decreases than increases. Photospheric changes are predominantly located near a polarity inversion line, chromospheric changes near footpoints of loops. The locations of changes are near, but not exactly co-spatial to hard X-ray (HXR) emission and neither to enhanced continuum emission, nor a small sunquake. Enhanced chromospheric and coronal emission is ob...

  3. Observation and numerical modeling of chromospheric evaporation during the impulsive phase of a solar flare

    Energy Technology Data Exchange (ETDEWEB)

    Imada, Shinsuke, E-mail: shinimada@stelab.nagoya-u.ac.jp [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Murakami, Izumi, E-mail: murakami.izumi@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan); Department of Fusion Science, SOKENDAI (The Graduate University of Advanced Studies), Toki, Gifu 509-5292 (Japan); Watanabe, Tetsuya, E-mail: watanabe.tetsuya@nao.ac.jp [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Department of Astronomical Science, SOKENDAI (The Graduate University of Advanced Studies), Mitaka, Tokyo 181-8588 (Japan)

    2015-10-15

    We have studied the chromospheric evaporation flow during the impulsive phase of the flare by using the Hinode/EUV Imaging Spectrometer observation and 1D hydrodynamic numerical simulation coupled to the time-dependent ionization. The observation clearly shows that the strong redshift can be observed at the base of the flaring loop only during the impulsive phase. We performed two different numerical simulations to reproduce the strong downflows in FeXII and FeXV during the impulsive phase. By changing the thermal conduction coefficient, we carried out the numerical calculation of chromospheric evaporation in the thermal conduction dominant regime (conductivity coefficient κ{sub 0} = classical value) and the enthalpy flux dominant regime (κ{sub 0} = 0.1 × classical value). The chromospheric evaporation calculation in the enthalpy flux dominant regime could reproduce the strong redshift at the base of the flare during the impulsive phase. This result might indicate that the thermal conduction can be strongly suppressed in some cases of flare. We also find that time-dependent ionization effect is important to reproduce the strong downflows in Fe XII and Fe XV.

  4. Two step chromospheric Moreton wave excitation in a blast-wave scenario. A case study: Simulation of the December $06$, $2006$ event

    CERN Document Server

    Krause, G; Francile, C; Costa, A; Elaskar, S; Schneiter, M

    2015-01-01

    We examine the capability of a coronal flare ignited blast wave scenario to reproduce the chromospheric phenomenon. We numerically simulate the Moreton event of December 06, 2006 considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock -able to generate a detectable chromospheric Moreton wave- a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that the flare ignited blast wave scenario is capable to reproduce the observations.

  5. What does C II lambda 2325 A emission tell us about chromospheres of red supergiants? - A critical test using Zeta Aurigae-type K supergiants

    Science.gov (United States)

    Schroeder, K.-P.; Reimers, D.; Carpenter, K. G.; Brown, A.

    1988-01-01

    The limitations of the Carpenter et al. (1985) C II intercombination multiplet method of determining the density and geometric extent of red giant chromospheres are presently tested through observation of the C II 2325 A emission of two K-type supergiants whose empirical model chromospheres have been derived by high-resolution IUE observations at eclipse phases. While the observed C II emission fluxes are well reproduced, much of this emission originates in the high-density lower chromosphere.

  6. Numerical simulation of the three-dimensional structure and dynamics of the non-magnetic solar chromosphere

    CERN Document Server

    Wedemeyer, S; Steffen, M; Ludwig, H G; Holweger, H; Wedemeyer, Sven; Freytag, Bernd; Steffen, Matthias; Ludwig, Hans-G\\"unter; Holweger, Hartmut

    2004-01-01

    Three-dimensional numerical simulations with CO5BOLD, a new radiation hydrodynamics code, result in a dynamic, thermally bifurcated model of the non-magnetic chromosphere of the quiet Sun. The 3-D model includes the middle and low chromosphere, the photosphere, and the top of the convection zone, where acoustic waves are excited by convective motions. While the waves propagate upwards, they steepen into shocks, dissipate, and deposit their mechanical energy as heat in the chromosphere. Our numerical simulations show for the first time a complex 3-D structure of the chromospheric layers, formed by the interaction of shock waves. Horizontal temperature cross-sections of the model chromosphere exhibit a network of hot filaments and enclosed cool regions. The horizontal pattern evolves on short time-scales of the order of typically 20 - 25 seconds, and has spatial scales comparable to those of the underlying granulation. The resulting thermal bifurcation, i.e., the co-existence of cold and hot regions, provides t...

  7. NUMERICAL SIMULATIONS OF CHROMOSPHERIC ANEMONE JETS ASSOCIATED WITH MOVING MAGNETIC FEATURES

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Liping; He, Jiansen; Tu, Chuanyi; Zhang, Lei [School of Earth and Space Sciences, Peking University, 100871 Beijing (China); Peter, Hardi [Max Planck Institute for Solar System Research, D-37191 Katlenburg-Lindau (Germany); Feng, Xueshang [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, 100871 Beijing (China); Zhang, Shaohua, E-mail: jshept@gmail.com [Institute of Geology and Geophysics, Chinese Academy of Sciences, 100871 Beijing (China)

    2013-11-01

    Observations with the space-based solar observatory Hinode show that small-scale magnetic structures in the photosphere are found to be associated with a particular class of jets of plasma in the chromosphere called anemone jets. The goal of our study is to conduct a numerical experiment of such chromospheric anemone jets related to the moving magnetic features (MMFs). We construct a 2.5 dimensional numerical MHD model to describe the process of magnetic reconnection between the MMFs and the pre-existing ambient magnetic field, which is driven by the horizontal motion of the magnetic structure in the photosphere. We include thermal conduction parallel to the magnetic field and optically thin radiative losses in the corona to account for a self-consistent description of the evaporation process during the heating of the plasma due to the reconnection process. The motion of the MMFs leads to the expected jet and our numerical results can reproduce many observed characteristics of chromospheric anemone jets, topologically and quantitatively. As a result of the tearing instability, plasmoids are generated in the reconnection process that are consistent with the observed bright moving blobs in the anemone jets. An increase in the thermal pressure at the base of the jet is also driven by the reconnection, which induces a train of slow-mode shocks propagating upward. These shocks are a secondary effect, and only modulate the outflow of the anemone jet. The jet itself is driven by the energy input due to the reconnection of the MMFs and the ambient magnetic field.

  8. FAST MAGNETIC RECONNECTION IN THE SOLAR CHROMOSPHERE MEDIATED BY THE PLASMOID INSTABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Lei; Kliem, Bernhard; Lin, Jun [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Wu, Ning, E-mail: leini@ynao.ac.cn [School of Tourism and Geography, Yunnan Normal University, Kunming 650031 (China)

    2015-01-20

    Magnetic reconnection in the partially ionized solar chromosphere is studied in 2.5 dimensional magnetohydrodynamic simulations including radiative cooling and ambipolar diffusion. A Harris current sheet with and without a guide field is considered. Characteristic values of the parameters in the middle chromosphere imply a high magnetic Reynolds number of ∼10{sup 6}-10{sup 7} in the present simulations. Fast magnetic reconnection then develops as a consequence of the plasmoid instability without the need to invoke anomalous resistivity enhancements. Multiple levels of the instability are followed as it cascades to smaller scales, which approach the ion inertial length. The reconnection rate, normalized to the asymptotic values of magnetic field and Alfvén velocity in the inflow region, reaches values in the range ∼0.01-0.03 throughout the cascading plasmoid formation and for zero as well as for strong guide field. The outflow velocity reaches ≈40 km s{sup –1}. Slow-mode shocks extend from the X-points, heating the plasmoids up to ∼8 × 10{sup 4} K. In the case of zero guide field, the inclusion of both ambipolar diffusion and radiative cooling causes a rapid thinning of the current sheet (down to ∼30 m) and early formation of secondary islands. Both of these processes have very little effect on the plasmoid instability for a strong guide field. The reconnection rates, temperature enhancements, and upward outflow velocities from the vertical current sheet correspond well to their characteristic values in chromospheric jets.

  9. The Solar Surface Differential Rotation from Disk-Integrated Chromospheric Fluxes

    Science.gov (United States)

    Donahue, Robert A.; Keil, Steven L.

    1995-06-01

    Disk-integrated solar chromospheric Ca ii K-line (3933.68 Å) fluxes have been measured almost daily at Sacramento Peak Observatory since 1977. Using observing windows selected to mimic seasonal windows for chromospheric measurements of lower Main-Sequence stars such as those observed by Mount Wilson Observatory's HK Project, we have measured the solar rotation from the modulation of the Ca ii K-line flux. We track the change of rotation period from the decline of cycle 21 through the maximum of cycle 22. This variation in rotation period is shown to behave as expected from the migration of active regions in latitude according to Maunder's ‘butterfly diagram’, including an abrupt change in rotation period at the transition from cycle 21 to cycle 22. These results indicate the successful detection of solar surface differential rotation from disk-integrated observations. We argue that the success of our study compared to previous investigations of the solar surface differential rotation from disk-integrated fluxes lies primarily with the choice of the length of the time-series window. Our selection of 200 days is shorter than in previous studies whose windows are typically on the order of one year. The 200-day window is long enough to permit an accurate determination of the rotation period, yet short enough to avoid complications arising from active region evolution. Thus, measurements of the variation of rotation period in lower Main-Sequence stars, especially those that appear to be correlated with long-term changes in chromospheric activity (i.e., cycles), are probably evidence for stellar surface differential rotation.

  10. A Comparative Study of Magnetic Fields in the Solar Photosphere and Chromosphere at Equatorial and Polar Latitudes

    CERN Document Server

    Petrie, Gordon J D; 10.1088/0004-637X/699/1/871

    2010-01-01

    Besides their own intrinsic interest, correct interpretation of solar surface magnetic field observations is crucial to our ability to describe the global magnetic structure of the solar atmosphere. Photospheric magnetograms are often used as lower boundary conditions in models of the corona, but not data from the nearly force-free chromosphere. National Solar Observatory's (NSO) Synoptic Optical Long-term Investigations of the Sun VSM (Vector Spectromagnetograph) produces full-disk line-of-sight magnetic flux images deriving from both photospheric and chromospheric layers on a daily basis. In this paper, we investigate key properties of the magnetic field in these two layers using more than five years of VSM data. We find from near-equatorial measurements that the east-west inclination angle of most photospheric fields is less than about 12{\\deg}, while chromospheric fields expand in all directions to a significant degree. Using a simple stereoscopic inversion, we find evidence that photospheric polar fields...

  11. CHROMOSPHERIC MASS MOTIONS AND INTRINSIC SUNSPOT ROTATIONS FOR NOAA ACTIVE REGIONS 10484, 10486, AND 10488 USING ISOON DATA

    International Nuclear Information System (INIS)

    This work utilizes Improved Solar Observing Optical Network continuum (630.2 nm) and Hα (656.2 nm) data to: (1) detect and measure intrinsic sunspot rotations occurring in the photosphere and chromosphere, (2) identify and measure chromospheric filament mass motions, and (3) assess any large-scale photospheric and chromospheric mass couplings. Significant results from 2003 October 27-29, using the techniques of Brown et al., indicate significant counter-rotation between the two large sunspots in NOAA AR 10486 on October 29, as well as discrete filament mass motions in NOAA AR 10484 on October 27 that appear to be associated with at least one C-class solar flare

  12. YSO accretion shocks: magnetic, chromospheric or stochastic flow effects can suppress fluctuations of X-ray emission

    CERN Document Server

    Matsakos, T; Stehlé, C; González, M; Ibgui, L; de Sá, L; Lanz, T; Orlando, S; Bonito, R; Argiroffi, C; Reale, F; Peres, G

    2013-01-01

    Context. Theoretical arguments and numerical simulations of radiative shocks produced by the impact of the accreting gas onto young stars predict quasi-periodic oscillations in the emitted radiation. However, observational data do not show evidence of such periodicity. Aims. We investigate whether physically plausible perturbations in the accretion column or in the chromosphere could disrupt the shock structure influencing the observability of the oscillatory behavior. Methods. We performed local 2D magneto-hydrodynamical simulations of an accretion shock impacting a chromosphere, taking optically thin radiation losses and thermal conduction into account. We investigated the effects of several perturbation types, such as clumps in the accretion stream or chromospheric fluctuations, and also explored a wide range of plasma-\\beta values. Results. In the case of a weak magnetic field, the post-shock region shows chaotic motion and mixing, smoothing out the perturbations and retaining a global periodic signature....

  13. Acceleration of Type 2 Spicules in the Solar Chromosphere - 2: Viscous Braking and Upper Bounds on Coronal Energy Input

    CERN Document Server

    Goodman, Michael L

    2014-01-01

    A magnetohydrodynamic model is used to determine conditions under which the Lorentz force accelerates plasma to type 2 spicule speeds in the chromosphere. The model generalizes a previous model to include a more realistic pre-spicule state, and the vertical viscous force. Two cases of acceleration under upper chromospheric conditions are considered. The magnetic field strength for these cases is ~ this energy. Compressive heating dominates during the early phase of acceleration. The maximum energy injected into the corona by type 2 spicules, defined as the energy flux in the upper chromosphere, may largely balance total coronal energy losses in quiet regions, possibly also in coronal holes, but not in active regions. It is proposed that magnetic flux emergence in inter-granular regions drives type 2 spicules.

  14. Formation of the O I resonance triplet and intercombination doublet in the solar chromosphere

    Science.gov (United States)

    Skelton, D. L.; Shine, R. A.

    1982-01-01

    Spectrum synthesis calculations are presented for the O I resonance triplet at 1304 A and the intercombination doublet at 1358 A for the solar atmosphere and several variants, allowing for triplet fluorescence by the Ly-beta emission of H I. Profiles, synthesized from a seven-level plus continuum O I atom are compared to observations taken with the high-resolution spectrometer on OSO 8. It is found that the O I triplet emission is dominated by the Ly-beta fluorescence and that the agreement between observations and profiles computed with current chromospheric models is much improved over earlier studies.

  15. Chemical enrichment and star formation in the Milky Way disk. I. Sample description and chromospheric age-metallicity relation

    Science.gov (United States)

    Rocha-Pinto, H. J.; Maciel, W. J.; Scalo, J.; Flynn, C.

    2000-06-01

    The age-metallicity relation of the solar neighbourhood is studied using a sample of 552 late-type dwarfs. This sample was built from the intersection of photometric catalogues with chromospheric activity surveys of the Mount Wilson group. For these stars, metallicities were estimated from uvby data, and ages were calculated from their chromospheric emission levels using a new metallicity-dependent chromospheric activity-age relation developed by Rocha-Pinto & Maciel (\\cite{RPM98}). A careful estimate of the errors in the chromospheric age is made. The errors in the chromospheric indices are shown to include partially the effects of the stellar magnetic cycles, although a detailed treatment of this error is still beyond our knowledge. It is shown that the results are not affected by the presence of unresolved binaries in the sample. We derive an age-metallicity relation which confirms the mean trend found by previous workers. The mean metallicity shows a slow, steady increase with time, amounting at least 0.56 dex in 15 Gyr. The initial metallicity of the disk is around -0.70 dex, in agreement with the G dwarf metallicity distribution (Rocha-Pinto & Maciel \\cite{RPM96}). According to our data, the intrinsic cosmic dispersion in metal abundances is around 0.13 dex, a factor of two smaller than that found by Edvardsson et al. (\\cite{Edv}). We show that chromospheric ages are compatible with isochrone ages, within the expected errors, so that the difference in the scatter cannot be caused by the accuracy of our ages and metallicities. This reinforces some suggestions that the Edvarsson et al.'s sample is not suitable to the determination of the age-metallicity relation.

  16. Oscillatory Response of the Solar Chromosphere to a Strong Downflow above a Sunspot

    CERN Document Server

    Kwak, Hannah; Song, Donguk; Kim, Yeon-Han; Lim, Eun-Kyung; Madjarska, Maria S

    2016-01-01

    We report three-minute oscillations in the solar chromosphere driven by a strong downflow event in a sunspot. We used the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope and the Interface Region Imaging Spectrograph (IRIS). The strong downflow event is identified in the chromospheric and transition region lines above the sunspot umbra. After the event, oscillations occur at the same region. The amplitude of the Doppler velocity oscillations is 2 km/s, and gradually decreases with time. In addition, the period of the oscillations gradually increases from 2.7 minutes to 3.3 minutes. In the IRIS 1330 slit-jaw images, we identify a transient brightening near the footpoint of the downflow detected in the Ha+0.5A image. The characteristics of the downflowing material are consistent with those of sunspot plumes. Based on our findings, we suggest that the gravitationally stratified atmosphere came to oscillate with three minute period in response to the impulsive downflow event as was theoretically i...

  17. A Tale Of Two Spicules: The Impact of Spicules on the Magnetic Chromosphere

    CERN Document Server

    De Pontieu, Bart; Hansteen, Viggo H; Carlsson, Mats; Schrijver, C J; Tarbell, T D; Title, A M; Shine, R A; Suematsu, Y; Tsuneta, S; Katsukawa, Y; Ichimoto, K; Shimizu, T; Nagata, S

    2007-01-01

    We use high-resolution observations of the Sun in Ca II H 3968 A from the Solar Optical Telescope on Hinode to show that there are at least two types of spicules that dominate the structure of the magnetic solar chromosphere. Both types are tied to the relentless magnetoconvective driving in the photosphere, but have very different dynamic properties. ``Type-I'' spicules are driven by shock waves that form when global oscillations and convective flows leak into the upper atmosphere along magnetic field lines on 3-7 minute timescales. ``Type-II'' spicules are much more dynamic: they form rapidly (in ~10s), are very thin (<200km wide), have lifetimes of 10-150s (at any one height) and seem to be rapidly heated to (at least) transition region temperatures, sending material through the chromosphere at speeds of order 50-150 km/s. The properties of Type II spicules suggest a formation process that is a consequence of magnetic reconnection, typically in the vicinity of magnetic flux concentrations in plage and n...

  18. Line Profile Variations of Solar Analog Stars: Chromospheric Indexes vs. Li Abundance. The Host Star Search.

    Science.gov (United States)

    Amazo-Gómez, E. M.; Harutyunyan, G.; Alvarado-Gómez, J. D.; Strassmeier, K. G.; Weber, M.; Carroll, T. A.

    2015-10-01

    PolarBase contains stellar spectropolarimetric data collected with the NARVAL & ESPaDOnS instruments (Petit et al. 2014). Their respective spectral resolutions are 65 000 and 68 000, in spectropolarimetric mode. As the first part of this work, we use the NARVAL spectropolarimetric repositories. We selected spectra from a sample of cool stars with effective Temperature (T eff) ranging between 4900 to 6000 K. This sample contains stellar systems with and without reported exoplanets. We exploit the full wavelength range from 380 to 900 nm in order to obtain chromospheric indexes such as the Ca ii H&K S-Index, and a Ca ii IRT and Hα index. We calibrated our measurements using the Mount Wilson S-Index values. Furthermore, we employ lithium (Li) abundance measurements from the literature (Gonzalez et al. 2010; Delgado Mena et al. 2014; Israelian et al. 2004), investigating in this way a possible correlation between the chromospheric activity measurements and the Li abundance in 32 selected cool stars.

  19. The solar chromosphere observed at 1 Hz and 0.''2 resolution

    International Nuclear Information System (INIS)

    We recently reported extremely rapid changes in chromospheric fine structure observed using the IBIS instrument in the red wing of Hα. Here, we examine data obtained during the same observing run (2010 August 7), of a mature active region NOAA 11094. We analyze more IBIS data including wavelength scans and data from the Solar Dynamics Observatory, all from within a 30 minute interval. Using a slab radiative transfer model, we investigate the physical nature of fibrils in terms of tube-like versus sheet-like structures. Principal Component Analysis shows that the very rapid Hα variations in the line wings depend mostly on changes of line width and line shift, but for Ca II 854.2 the variations are dominated by changes in column densities. The tube model must be rejected for a small but significant class of fibrils undergoing very rapid changes. If our wing data arise from the same structures leading to 'type II spicules', our analysis calls into question much recent work. Instead, the data do not reject the hypothesis that some fibrils are optical superpositions of plasma collected into sheets. We review how Parker's theory of tangential discontinuities naturally leads to plasma collecting into sheets, and show that the sheet picture is falsifiable. Chromospheric fine structures seem to be populated by both tubes and sheets. We assess the merits of spectral imaging versus slit spectroscopy for future studies.

  20. The energy input mechanism into the lower transition regions between stellar chromospheres and coronae

    Science.gov (United States)

    Boehm-Vitense, Erika

    1988-01-01

    The ratio of the emission line fluxes for the C II and C IV lines in the lower transition regions (T = 30,000 to 100,000 K) between stellar chromospheres and transition layers is shown to depend mainly on the temperature gradient in the line emitting regions which can therefore be determined from this line ratio. From the observed constant (within the limits of observational error) ratio of the emission line fluxes of the C II (1335 A) and C IV (1550 A) lines it is concluded that the temperature gradients in the lower transition layers are similar for the large majority of stars independently of T sub eff, L, and degree of activity. This means that the temperature dependence of the damping length for the mechanical flux must be the same for all these stars. Since for different kinds of mechanical fluxes the dependence of the damping length on gas pressure and temperature is quite different, it is concluded that the same heating mechanism must be responsible for the heating of all the lower transition layers of these stars, regardless of their chromospheric activity. Only the amount of mechanical flux changes. The T Tauri stars are exceptions: their emission lines are probably mainly due to circumstellar material.

  1. Magnetic and Velocity Field of Sunspots in the Photosphere and Upper Chromosphere

    Science.gov (United States)

    Joshi, Jayant

    2014-03-01

    Sunspots, the dark blemishes on the solar surface have been widely studied for the past 400 years. Sunspots are the most readily identifiable manifestation of magnetic field concentrations on the solar surface. Interaction of the sunspot magnetic field with the plasma makes them one of the most interesting objects for research in solar physics. This thesis presents a study of the photospheric and upper chromospheric velocity and magnetic field structure of sunspots by analyzing spectro-polarimetric observations. These observations comprise different spectral lines obtained with two ground based telescopes and a space borne telescope. The lower brightness of sunspots on the solar surface is due to the presence of strong magnetic fields (up to 4 kG in the umbra), which makes the overturning convection inefficient. Convection is the main heat transport mechanism in the quiet Sun. The Penumbra, the annular part around the umbra has a brightness of about 75% of that in the quiet Sun. At the same time it has an average magnetic field strength of around 1.5 kG. The brightness of penumbrae has been an enigma for solar physicists for a long time. Theoretical models like the gappy penumbra model and the convective roll model as well as magnetohydrodynamic (MHD) simulations suggest that the heat transport in penumbrae is based on the presence of overturning convection. Direct observational evidence for the presence of convective flows in penumbral filaments was missing so far. In Chapter 3 we present observations of a penumbra in the C i 5380 Å spectral line formed in the deep photosphere. These high spatial resolution observations (0. '' 14) are obtained with the Swedish 1-m Solar Telescope (SST). Doppler map clearly shows the presence of several dark downflow lanes at the edges of the penumbral filaments which surround the bright upflows at the center of the filaments, supporting overturning convection as a mechanism of heat transport in penumbrae. Chapter 4 analyses the

  2. Coronal and Chromospheric Signatures of Large-Scale Disturbances Associated with a Major Solar Eruption

    CERN Document Server

    Zong, Weiguo

    2015-01-01

    We present both coronal and chromospheric observations of large-scale disturbances associated with a major solar eruption on 2005 September 7. In GOES/SXI, arclike coronal brightenings are recorded propagating in the southern hemisphere. The SXI front shows an initially constant speed of 730 km s$^{-1}$ and decelerates later on, and its center is near the central position angle of the associated coronal mass ejection (CME) but away from flare site. Chromospheric signatures of the disturbances are observed in both MLSO/PICS H$\\alpha$ and MLSO/CHIP He I 10830 {\\AA}, and can be divided into two parts. The southern signatures occur in regions where the SXI front sweeps over, with the H$\\alpha$ bright front coincident with the SXI front while the He I dark front lagging the SXI front but showing a similar kinematics. Ahead of the path of the southern signatures, oscillations of a filament are observed. The northern signatures occur near the equator, with the H$\\alpha$ and He I fronts coincident with each other. Th...

  3. Fast magnetic reconnection in the solar chromosphere mediated by the plasmoid instability

    CERN Document Server

    Ni, Lei; Lin, Jun; Wu, Ning

    2015-01-01

    Magnetic reconnection in the partially ionized solar chromosphere is studied in 2.5-dimensional magnetohydrodynamic simulations including radiative cooling and ambipolar diffusion. A Harris current sheet with and without a guide field is considered. Characteristic values of the parameters in the middle chromosphere imply a high magnetic Reynolds number of $\\sim10^{6}\\mbox{--}10^7$ in the present simulations. Fast magnetic reconnection then develops as a consequence of the plasmoid instability without the need to invoke anomalous resistivity enhancements. Multiple levels of the instability are followed as it cascades to smaller scales, which approach the ion inertial length. The reconnection rate, normalized to the asymptotic values of magnetic field and Alfv\\'en velocity in the inflow region, reaches values in the range $\\sim0.01\\mbox{--}0.03$ throughout the cascading plasmoid formation and for zero as well as for strong guide field. The out-flow velocity reaches $\\approx40$~km\\,s$^{-1}$. Slow-mode shocks ext...

  4. The Chromospheric Structure and Wind of the K-Supergiant Lambda Velorum

    Science.gov (United States)

    Carpenter, Kenneth G.; Ayres, T. R.; Brown, A.; Harper, G. M.; Wahlgren, G. M.

    2011-01-01

    Recently, the 1326-1466 Å region of the FUV spectrum of the K4 Ib-II supergiant Lambda Vel was observed with the Cosmic Origins Spectrograph (COS) on HST, as part of the Ayres and Redfield Cycle 17 SNAP program "SNAPing Coronal Iron.” This spectrum covers a region not previously recorded in Lambda Vel at high resolution and, in a mere 20 minutes of exposure, reveals an amazing treasure trove of information. It shows a wide variety of strong atomic and molecular emission lines formed in the chromosphere and multiple atomic absorption lines formed in the stellar wind, both superposed on a bright chromospheric continuum. Further evidence of the stellar wind is seen in the P Cygni profiles presented by the C II (UV 1) lines near 1335 Å. We combine this COS data with archival GHRS spectra of other selected FUV and NUV regions to better characterize the outer atmospheric structure of the star and its massive, outflowing wind.

  5. On fibrils and field lines: The nature of H$\\alpha$ fibrils in the solar chromosphere

    CERN Document Server

    Leenaarts, Jorrit; van der Voort, Luc Rouppe

    2015-01-01

    Observations of the solar chromosphere in the line-core of the \\Halpha\\ line show dark elongated structures called fibrils that show swaying motion. We performed a 3D radiation-MHD simulation of a network region, and computed synthetic \\Halpha\\ images from this simulation to investigate the relation between fibrils and the magnetic field lines in the chromosphere. The periods, amplitudes and phase-speeds of the synthetic fibrils are consistent with those observed. We analyse the relation between the synthetic fibrils and the field lines threading through them, and find that some fibrils trace out the same field line along the fibril's length, but there are also fibrils that sample different field lines at different locations along their length. Fibrils sample the same field lines on a time scale of $\\sim200$~s. This is shorter than their own lifetime. We analysed the evolution of the atmosphere along a number of field lines that thread through fibrils and find that they carry slow-mode waves that load mass in...

  6. First Direct Detection of Magnetic Fields in Starspots and Stellar Chromospheres

    CERN Document Server

    Berdyugina, S V; Afram, N; Suwald, F; Petit, P; Arnaud, J; Harrington, D M; Kuhn, J R

    2007-01-01

    Here we report on the first detection of circular polarization in molecular lines formed in cool magnetic regions (starspots) and in chromospheric emission lines formed in hot plages on the surfaces of active stars. Our survey of G-K-M stars included young main-sequence dwarfs and RS CVn-type giants and subgiants. All stars were found to possess surface magnetic fields producing Stokes V LSD signals in atomic lines of 0.05 to 0.5%. Several stars clearly showed circular polarization in molecular lines of 0.1 to 1%. The molecular Stokes V signal is reminiscent of that observed in sunspots. Chromospheric magnetic fields were detected on most active targets in Stokes V profiles of emission lines with peak polarization up to 2%. The observed molecular circular polarization on M dwarfs indicates single-polarity magnetic fields covering at least 10% of the stellar disk. Smaller signals on K stars imply that their magnetic fields are apparently weaker, more entangled than on M dwarfs, or more diluted by the bright ph...

  7. Can We Improve the Preprocessing of Photospheric Vector Magnetograms by the Inclusion of Chromospheric Observations?

    CERN Document Server

    Wiegelmann, T; Schrijver, C J; Derosa, M L; Metcalf, T R

    2008-01-01

    The solar magnetic field is key to understanding the physical processes in the solar atmosphere. Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field upward from underlying vector boundary data. However, we can only measure the magnetic field vector routinely with high accuracy in the photosphere, and unfortunately these data do not fulfill the force-free condition. We must therefore apply some transformations to these data before nonlinear force-free extrapolation codes can be self-consistently applied. To this end, we have developed a minimization procedure that yields a more chromosphere-like field, using the measured photospheric field vectors as input. The procedure includes force-free consistency integrals, spatial smoothing, and -- newly included in the version presented here -- an improved match to the field direction as inferred from fibrils as can be observed in, e.g., chromospheric H$\\alpha$ images. We test the procedure using a model active-region field that i...

  8. Overdamped Alfven waves due to ion-neutral collisions in the solar chromosphere

    CERN Document Server

    Soler, R; Zaqarashvili, T V

    2014-01-01

    Alfvenic waves are ubiquitous in the solar atmosphere and their dissipation may play an important role in atmospheric heating. In the partially ionized solar chromosphere, collisions between ions and neutrals are an efficient dissipative mechanism for Alfven waves with frequencies near the ion-neutral collision frequency. The collision frequency is proportional to the ion-neutral collision cross section for momentum transfer. Here, we investigate Alfven wave damping as a function of height in a simplified chromospheric model and compare the results for two sets of collision cross sections, namely those of the classic hard-sphere model and those based on recent quantum-mechanical computations. We find important differences between the results for the two sets of cross sections. There is a critical interval of wavelengths for which impulsively excited Alfven waves are overdamped as a result of the strong ion-neutral dissipation. The critical wavelengths are in the range from 1 km to 50 km for the hard-sphere cr...

  9. Qualities of Sequential Chromospheric Brightenings Observed in Optical and UV Images

    CERN Document Server

    Kirk, Michael S; Jackiewicz, Jason; McAteer, R T James

    2014-01-01

    Chromospheric flare ribbons observed in H-alpha appear well-organized when first examined: ribbons impulsively brighten, morphologically evolve, and exponentially decay back to pre-flare levels. Upon closer inspection of H-alpha flares, there is often a significant number of compact areas brightening in concert with the flare eruption but are spatially separated from the evolving flare ribbon. One class of these brightenings is known as sequential chromospheric brightenings (SCBs). SCBs are often observed in the intimidate vicinity of erupting flares and are associated with coronal mass ejections. In the past decade there have been several previous investigations of SCBs. These studies have exclusively relied upon H-alphaimages to discover and analyze these ephemeral brightenings. This work employs the automated detection algorithm of Kirk et al. (2011) to extract the physical qualities of SCBs in observations of ground-based H-alpha images and complementary AIA images in HeII, Civ, and 1700 \\AA. The meta-dat...

  10. Chromospheric activity among fast rotating M-dwarfs in the open cluster NGC 2516

    CERN Document Server

    Jackson, R J

    2010-01-01

    We report radial velocities (RVs), projected equatorial velocities (v sin i) and CaII triplet (CaT) chromospheric activity indices for 237 late-K to mid-M candidate members of the young open cluster NGC 2516. These stars have rotation periods between 0.1 and 15 days. Intermediate resolution spectra were obtained using the Giraffe spectrograph at the Very Large Telescope. Membership was confirmed on the basis of RVs for 210 targets. We see a marked increase in the fraction of rapidly rotators as we move to cooler spectral types. About 20 per cent of M0-M1 stars have v sin i >15km/s, increasing to 90 per cent of M4 stars. Activity indices derived from the first two lines of the CaT (8498A and 8542A) show differing dependencies on rotation period and mass for stars lying above and below the fully convective boundary. Higher mass stars, of spectral type K3-M2.5, show chromospheric activity which increases with decreasing Rossby number (the ratio of period to convective turnover time), saturating for Rossby number...

  11. Oscillation of Newly Formed Loops After Magnetic Reconnection in the Solar Chromosphere

    CERN Document Server

    Yang, Shuhong

    2016-01-01

    With the high spatial and temporal resolution H$\\alpha$ images from the New Vacuum Solar Telescope, we focus on two groups of loops with a X-shaped configuration in the dynamic chromosphere. We find that the anti-directed loops approach each other and reconnect continually. The connectivity of the loops is changed and new loops are formed and stack together. The stacked loops are sharply bent, implying that they are greatly impacted by the magnetic tension force. When another more reconnection process takes place, one new loop is formed and stacks with the previously formed ones. Meanwhile, the stacked loops retract suddenly and move toward the balance position, performing an overshoot movement, which led to an oscillation with an average period of about 45 s. The oscillation of newly formed loops after magnetic reconnection in the chromosphere is observed for the first time. We suggest that the stability of the stacked loops is destroyed due to the join of the last new loop and then suddenly retract under th...

  12. Observational Searches for Chromospheric -Mode Oscillations from CaII H-Line Observations

    Indian Academy of Sciences (India)

    R. Kariyappa; L. Damé; K. M. Hiremath

    2006-06-01

    We have used a high spatial and temporal resolution of long time sequence of spectra in CaII H-line obtained at the Vacuum Tower Telescope (VTT) of the Sacramento Peak Observatory on a quiet region at the center of the solar disk over a large number of bright points and network elements to search for atmospheric (chromospheric) -mode oscillations. An important parameter of the H-line profile, intensity at H2V(IH2V), has been derived from a large number of line profiles. We derived the light curves of all the bright points and network elements. The light curves represent the main pulse with large intensity amplitude and followed by several follower pulses with lower intensity amplitudes. The light curves of these bright points would give an impression that one can as well draw curves towards and away from the highest peak (main pulse) showing an exponential growth and decay of the amplitudes. An exponential decaying function has been fitted for all the light curves of the bright points to determine the damping time of the modes that are more or less the same, and one value of the coefficient of exponent can represent reasonably well the decay for all the cases. The FFT analysis of temporal variation of both the bright points and the network elements indicates around 10-min periodicity. We speculate that this longer period of oscillation may be related to chromospheric -mode oscillations.

  13. Supergranulation-driven Alfven waves in the solar chromosphere and related phenomena.

    Science.gov (United States)

    Hollweg, J. V.

    1972-01-01

    It has recently been recognized that Alfven waves frequently dominate the microstructure of the solar wind at the orbit of the earth. We seek a solar source for these waves, and consider here their excitation by the supergranular motions. The wave equation is solved in a horizontally stratified, bi-exponential solar atmosphere. The interaction of Alfven wave motions associated with adjacent supergranules is discussed qualitatively. The Alfven wave effectively conveys the supergranular motions to great heights in the chromosphere. These motions are oppositely directed above intersupergranule boundaries, and compress the magnetic field there. A naive calculation of the compression, based on balancing dynamic and magnetic pressures, leads to adequate agreement with observations of the chromospheric network. We find that the magnetic field is appreciably compressed only below about 1500 km, and on this basis we reject theories of spicule formation which require large vertical magnetic fields at the heights reached by spicules. We advance a theory for spicule formation, in which spicules form as a result of matter being squeezed upward, out of the compression region between adjacent supergranules.

  14. Oscillations of the Sun's chromosphere. VIII. Horizontal motions of CA II K bright points

    Science.gov (United States)

    Wellstein, S.; Kneer, F.; von Uexkuell, M.

    1998-07-01

    We present a re-analysis of a time series of solar disc centre Ca ii K2v filtergrams taken with the Vacuum Tower Telescope at the Observatorio del Teide/Tenerife. We concentrate on the measurements of proper motions of K grains in the internetwork regions and of bright points in the chromospheric network. For the K grains we find horizontal velocities of 2-15 km s(-1) , values much lower than those deduced by Steffens et al. (1996) from a smaller sample, analyzed differently. In accord with our earlier conclusion from k-omega diagrams (Kneer & von Uexkuell 1993) and with numerical simulations by Carlsson & Stein (1997) high-frequency (pseudo-) p-modes can viably explain the K grains. Yet, the rareness of the K grains may indicate a connection to magnetic fields. The proper motions of the network bright points are non-periodic, very impulsive, with velocities of 7-10 km s(-1) . Estimating the energy flux if these motions are magnetic kink waves (cf. Choudhuri et al. 1993, Muller et al. 1994), we find it sufficient to heat the solar corona, but too small to cover the radiative losses of the chromospheric network.

  15. Chromospheric features of LQ Hydrae from H-alpha line profiles

    CERN Document Server

    Frasca, A; Strassmeier, K G; Biazzo, K

    2008-01-01

    We analyze the H-alpha spectral variability of the rapidly-rotating K1-dwarf LQ Hya using high-resolution H-alpha spectra recorded during April-May 2000. Chromospheric parameters were computed from the H-alpha profile as a function of rotational phase. We find that all these parameters vary in phase, with a higher chromospheric electron density coinciding with the maximum H-alpha emission. We find a clear rotational modulation of the H-alpha emission that is better emphasized by subtracting a reference photospheric template built up with a spectrum of a non-active star of the same spectral type. A geometrical plage model applied to the H-alpha variation curve allows us to derive the location of the active regions that come out to be close in longitude to the most pronounced photospheric spots found with Doppler imaging applied to the photospheric lines in the same spectra. Our analysis suggests that the H-alpha features observed in LQ Hya in 2000 are a scaled-up version of the solar plages as regards dimensio...

  16. 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.

  17. An active region filament studied simultaneously in the chromosphere and photosphere: I - Magnetic structure

    CERN Document Server

    Kuckein, C; Pillet, V Martinez

    2011-01-01

    A thorough multiwavelength, multiheight study of the vector magnetic field in a compact active region (AR) filament (NOAA10781) is presented. We suggest an evolutionary scenario for this filament. Full Stokes vectors were acquired with TIP-II in a spectral range which comprises the chromospheric He I 10830 A multiplet and the photospheric Si I 10827 A line. An AR filament (that was formed before our observing run) was detected in the He I absorption images on 2005 July 3rd. The chromospheric vector magnetic field in this portion of the filament was strongly sheared whereas the photospheric field lines underneath had an inverse polarity configuration. From July 3rd to July 5th, an opening and closing of the polarities at either side of the polarity inversion line (PIL) was recorded, resembling the recently discovered process of the sliding door effect seen by Hinode. During this time, a newly created region that contained pores and orphan penumbrae at the PIL was observed.On July 5th, a normal polarity configu...

  18. Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum in Microwaves

    Science.gov (United States)

    Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2011-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radio-heliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  19. Polar Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum

    Science.gov (United States)

    Gopalswamy, N.; Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2010-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radioheliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approximately 250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  20. GENERATION OF ELECTRIC CURRENTS IN THE CHROMOSPHERE VIA NEUTRAL-ION DRAG

    International Nuclear Information System (INIS)

    We consider the generation of electric currents in the solar chromosphere where the ionization level is typically low. We show that ambient electrons become magnetized even for weak magnetic fields (30 G); that is, their gyrofrequency becomes larger than the collision frequency while ion motions continue to be dominated by ion-neutral collisions. Under such conditions, ions are dragged by neutrals, and the magnetic field acts as if it is frozen-in to the dynamics of the neutral gas. However, magnetized electrons drift under the action of the electric and magnetic fields induced in the reference frame of ions moving with the neutral gas. We find that this relative motion of electrons and ions results in the generation of quite intense electric currents. The dissipation of these currents leads to resistive electron heating and efficient gas ionization. Ionization by electron-neutral impact does not alter the dynamics of the heavy particles; thus, the gas turbulent motions continue even when the plasma becomes fully ionized, and resistive dissipation continues to heat electrons and ions. This heating process is so efficient that it can result in typical temperature increases with altitude as large as 0.1-0.3 eV km-1. We conclude that this process can play a major role in the heating of the chromosphere and corona.

  1. The solar chromosphere observed at 1 Hz and 0.''2 resolution

    Energy Technology Data Exchange (ETDEWEB)

    Lipartito, Isabel [Smith College, 99 Paradise Road, Northampton, MA 01063 (United States); Judge, Philip G. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Reardon, Kevin [National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349 (United States); Cauzzi, Gianna, E-mail: iliparti@smith.edu, E-mail: judge@ucar.edu, E-mail: kreardon@arcetri.astro.it, E-mail: gcauzzi@arcetri.astro.it [INAF-Ossevatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)

    2014-04-20

    We recently reported extremely rapid changes in chromospheric fine structure observed using the IBIS instrument in the red wing of Hα. Here, we examine data obtained during the same observing run (2010 August 7), of a mature active region NOAA 11094. We analyze more IBIS data including wavelength scans and data from the Solar Dynamics Observatory, all from within a 30 minute interval. Using a slab radiative transfer model, we investigate the physical nature of fibrils in terms of tube-like versus sheet-like structures. Principal Component Analysis shows that the very rapid Hα variations in the line wings depend mostly on changes of line width and line shift, but for Ca II 854.2 the variations are dominated by changes in column densities. The tube model must be rejected for a small but significant class of fibrils undergoing very rapid changes. If our wing data arise from the same structures leading to 'type II spicules', our analysis calls into question much recent work. Instead, the data do not reject the hypothesis that some fibrils are optical superpositions of plasma collected into sheets. We review how Parker's theory of tangential discontinuities naturally leads to plasma collecting into sheets, and show that the sheet picture is falsifiable. Chromospheric fine structures seem to be populated by both tubes and sheets. We assess the merits of spectral imaging versus slit spectroscopy for future studies.

  2. THE CHROMOSPHERIC SOLAR MILLIMETER-WAVE CAVITY ORIGINATES IN THE TEMPERATURE MINIMUM REGION

    Energy Technology Data Exchange (ETDEWEB)

    De la Luz, Victor [Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla, Puebla, Mexico, Apdo. Postal 51 y 216, 72000 (Mexico); Raulin, Jean-Pierre [CRAAM, Universidade Presbiteriana Mackenzie, Sao Paulo, SP 01302-907 (Brazil); Lara, Alejandro [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico 04510 (Mexico)

    2013-01-10

    We present a detailed theoretical analysis of the local radio emission at the lower part of the solar atmosphere. To accomplish this, we have used a numerical code to simulate the emission and transport of high-frequency electromagnetic waves from 2 GHz up to 10 THz. As initial conditions, we used VALC, SEL05, and C7 solar chromospheric models. In this way, the generated synthetic spectra allow us to study the local emission and absorption processes with high resolution in both altitude and frequency. Associated with the temperature minimum predicted by these models, we found that the local optical depth at millimeter wavelengths remains constant, producing an optically thin layer that is surrounded by two layers of high local emission. We call this structure the Chromospheric Solar Millimeter-wave Cavity (CSMC). The temperature profile, which features temperature minimum layers and a subsequent temperature rise, produces the CSMC phenomenon. The CSMC shows the complexity of the relation between the theoretical temperature profile and the observed brightness temperature and may help us to understand the dispersion of the observed brightness temperature in the millimeter wavelength range.

  3. IUE observations of rapidly rotating low-mass stars in young clusters - The relation between chromospheric activity and rotation

    International Nuclear Information System (INIS)

    If the rapid spindown of low-mass stars immediately following their arrival on the ZAMS results from magnetic braking by coronal winds, an equally sharp decline in their chromospheric emission may be expected. To search for evidence of this effect, the IUE spacecraft was used to observe the chromospheric Mg II emission lines of G-M dwarfs in the nearby IC 2391, Alpha Persei, Pleiades, and Hyades clusters. Similar observations were made of a group of X-ray-selected naked T Tauri stars in Taurus-Auriga. The existence of a decline in activity cannot be confirmed from the resulting data. However, the strength of the chromospheric emission in the Mg II lines of the cluster stars is found to be correlated with rotation rate, being strongest for the stars with the shortest rotation periods and weakest for those with the longest periods. This provides indirect support for such an evolutionary change in activity. Chromospheric activity may thus be only an implicit function of age. 31 refs

  4. Parent Stars of Extrasolar Planets. XII. Additional evidence for trends with vsini, condensation temperature, and chromospheric activity

    CERN Document Server

    Gonzalez, Guillermo

    2011-01-01

    Several recent studies have reported differences in vsini, abundance-condensation temperature trends, and chromospheric activity between samples of stars with and without Doppler-detected planets. These findings have been disputed, and the status of these results remains uncertain. We evaluate these claims using additional published data and find support for all three.

  5. A COMPARATIVE STUDY OF MAGNETIC FIELDS IN THE SOLAR PHOTOSPHERE AND CHROMOSPHERE AT EQUATORIAL AND POLAR LATITUDES

    International Nuclear Information System (INIS)

    Besides their own intrinsic interest, correct interpretation of solar surface magnetic field observations is crucial to our ability to describe the global magnetic structure of the solar atmosphere. Photospheric magnetograms are often used as lower boundary conditions in models of the corona, but not data from the nearly force-free chromosphere. National Solar Observatory's (NSO) Synoptic Optical Long-term Investigations of the Sun VSM (Vector Spectromagnetograph) produces full-disk line-of-sight magnetic flux images deriving from both photospheric and chromospheric layers on a daily basis. In this paper, we investigate key properties of the magnetic field in these two layers using more than five years of VSM data. We find from near-equatorial measurements that the east-west inclination angle of most photospheric fields is less than about 12 deg., while chromospheric fields expand in all directions to a significant degree. Using a simple stereoscopic inversion, we find evidence that photospheric polar fields are also nearly radial but that during 2008 the chromospheric field in the south pole was expanding superradially. We obtain a spatially resolved polar photospheric flux distribution up to 80 deg. latitude whose strength increases poleward approximately as cosine(colatitude) to the power 9-10. This distribution would give a polar field strength of 5-6 G. We briefly discuss implications for future synoptic map construction and modeling.

  6. A Signature of Chromospheric Activity in Brown Dwarfs Revealed by 2.5-5.0 Micron AKARI Spectra

    CERN Document Server

    Sorahana, Satoko; Yamamura, Issei

    2014-01-01

    We propose that the 2.7 micron H_2O, 3.3 micron CH_4 and 4.6 micron CO absorption bands can be good tracers of chromospheric activity in brown dwarfs. In our previous study, we found that there are difficulties in explaining entire spectra between 1.0 and 5.0 microns with the Unified Cloudy Model (UCM), a brown dwarf atmosphere model. Based on simple radiative equilibrium, temperature in a model atmosphere usually decreases monotonically with height. However, if a brown dwarf has a chromosphere, as inferred by some observations, the temperature in the upper atmosphere is higher. We construct a simple model that takes into account heating due to chromospheric activity by setting a temperature floor in an upper atmosphere, and find that the model spectra of 3 brown dwarfs with moderate H-alpha emission, an indicator of chromospheric activity, are considerably improved to match the AKARI spectra. Because of the higher temperatures in the upper atmospheres, the amount of CH_4 molecules is reduced and the absorpti...

  7. On the Chromospheric Response At The Pre-CME Phase Of The 18 March 2003 Solar Flare

    Czech Academy of Sciences Publication Activity Database

    Kashapova, L. K.; Kotrč, Pavel; Kupryakov, Yu. A.

    2011-01-01

    Roč. 35, č. 1 (2011), s. 125-134. ISSN 1845-8319 R&D Projects: GA ČR(CZ) GA205/09/1469; GA ČR GA205/09/1705 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flare * chromosphere and corona * CME Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  8. Tracers of Chromospheric Structure. I. Observations of Ca II K and Hα in M Dwarfs

    Science.gov (United States)

    Walkowicz, Lucianne M.; Hawley, Suzanne L.

    2009-02-01

    We report on our observing program4This paper is based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. to capture simultaneous spectra of Ca II and Balmer lines in a sample of nearby M3 dwarfs. Our goal is to investigate the chromospheric temperature structure required to produce these lines at the observed levels. We find a strong positive correlation between instantaneous measurements of Ca II K and the Balmer lines in active stars, although these lines may not be positively correlated in time-resolved measurements. The relationship between Hα and Ca II K remains ambiguous for weak and intermediate activity stars, with Hα absorption corresponding to a range of Ca II K emission. A similar relationship is also observed between Ca II K and the higher-order Balmer lines. As our sample consists of a single spectral type, correlations between these important chromospheric tracers cannot be ascribed to continuum effects, as suggested by other authors. These data confirm prior nonsimultaneous observations of the Hα line behavior with increasing activity, showing an initial increase in the Hα absorption with increasing Ca II K emission, prior to Hα filling in and eventually becoming a pure emission line in the most active stars. We also compare our optical measurements with archival UV and X-ray measurements, finding a positive correlation between the chromospheric and coronal emission for both high and intermediate activity stars. We compare our results with previous determinations of the active fraction of low-mass stars

  9. The resonance lines of MG2 as diagnostics of the upper solar chromosphere

    Science.gov (United States)

    Avrett, Eugene H.

    1994-01-01

    The resonance lines of singly ionized magnesium, the MgII h&k lines at about 280 nm, are two of the small number of lines in the solar spectrum that are optically thick in the chromospheric part of the solar atmosphere. Potentially these lines contain information on the initial temperature rise that occurs at the top of the photosphere. Unfortunately, few good observations of the lines exist due to their wavelength near 280 nm the ultraviolet. However, a fair number of observations (on the order of 200) are available from the data base of the UltraViolet Polarimeter and Spectrometer (UVSP) instrument that flew on board of NASA's Solar Maximum Mission (SMM) satellite. In addition, this data base contains a number of spectra that include the Mg I resonance line at (lambda)285.2nm, just longward of the h&k lines. The neutral magnesium line is not as strong as its ionic counterparts and samples slightly lower parts of the atmosphere. Its width is a sensitive diagnostic of the ionization balance between neutral and singly ionized magnesium, which determines the opacity scale (and formation height) of other diagnostically important MgI lines like the 457.1 nm intercombination line, the magnesium b lines and the infrared MgI emission lines near 12 microns. Analysis of the observed line profiles shows that it is necessary to include the effects of partial frequency redistribution (PRD) in the formation of the line as in the case of the h&k lines. This implies that the core of the line is very sensitive to the way scattering is treated in the modeling of the line, and in turn this allows us to separate the uncertain effects in the atomic data (viz. the Van der Waals broadening) from the uncertainties in the underlying atmospheric model. The main objective of this research was to compare observed spectra of the magnesium resonance lines against theoretical line profiles calculated from recent models of the solar atmosphere by Fontenla et al., hereafter called FAL. These

  10. Transition Region and Chromospheric Signatures of Impulsive Heating Events. II. Modeling

    CERN Document Server

    Reep, Jeffrey W; Crump, Nicholas A; Simoes, Paulo J A

    2016-01-01

    Results from the Solar Maximum Mission showed a close connection between the hard X-ray and transition region emission in solar flares. Analogously, the modern combination of RHESSI and IRIS data can inform the details of heating processes in ways never before possible. We study a small event that was observed with RHESSI, IRIS, SDO, and Hinode, allowing us to strongly constrain the heating and hydrodynamical properties of the flare, with detailed observations presented in a previous paper. Long duration red-shifts of transition region lines observed in this event, as well as many other events, are fundamentally incompatible with chromospheric condensation on a single loop. We combine RHESSI and IRIS data to measure the energy partition among the many magnetic strands that comprise the flare. Using that observationally determined energy partition, we show that a proper multi-threaded model can reproduce these red-shifts in magnitude, duration, and line intensity, while simultaneously being well constrained by...

  11. Dynamical Processes in Flux Tubes and their Role in Chromospheric Heating

    Indian Academy of Sciences (India)

    S. S. Hasan

    2000-09-01

    We model the dynamical interaction between magnetic flux tubes and granules in the solar photosphere which leads to the excitation of transverse (kink) and longitudinal (sausage) tube waves. The investigation is motivated by the interpretation of network oscillations in terms of flux tube waves. The calculations show that for magnetic field strengths typical of the network, the energy flux in transverse waves is higher than in longitudinal waves by an order of magnitude. But for weaker fields, such as those that might be found in internetwork regions, the energy fluxes in the two modes are comparable. Using observations of footpoint motions, the energy flux in transverse waves is calculated and the implications for chromospheric heating are pointed out.

  12. Forced Field Extrapolation of the Magnetic Structure of the Hα fibrils in the Solar Chromosphere

    Science.gov (United States)

    Xiaoshuai, Zhu; Huaning, Wang; Zhanle, Du; Han, He

    2016-07-01

    We present a careful assessment of forced field extrapolation using the Solar Dynamics Observatory/Helioseismic and Magnetic Imager magnetogram. We use several metrics to check the convergence property. The extrapolated field lines below 3600 km appear to be aligned with most of the Hα fibrils observed by the New Vacuum Solar Telescope. In the region where magnetic energy is far larger than potential energy, the field lines computed by forced field extrapolation are still consistent with the patterns of Hα fibrils while the nonlinear force-free field results show a large misalignment. The horizontal average of the lorentz force ratio shows that the forced region where the force-free assumption fails can reach heights of 1400–1800 km. The non-force-free state of the chromosphere is also confirmed based on recent radiation magnetohydrodynamics simulations.

  13. Forced field extrapolation of the magnetic structure of the Halpha fibrils in solar chromosphere

    CERN Document Server

    Zhu, Xiaoshuai; Du, Zhanle; He, Han

    2016-01-01

    We present a careful assess of the forced field extrapolation using Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) magnetogram. The convergence property is checked by several metrics. The extrapolated field lines below 3600km appear to be aligned with most Halpha fibrils observed by New Vacuum Solar Telescope (NVST). In the region where magnetic energy far larger than potential energy, field lines computed by forced field extrapolation still consistent with the patterns of Halpha fibrils while non-linear force free field (NLFFF) results show large misalignment. The horizontal average of lorentz force ratio shows the forced region where force-free assumption is failed can reach the height of $1400-1800km$. The non-force-free state of the chromosphere is also confirmed by recent radiation magnetohydrodynamics (MHD) simulation.

  14. Observation of Chromospheric Sunspot at Millimeter Range with the Nobeyama 45 m Telescope

    CERN Document Server

    Iwai, Kazumasa

    2015-01-01

    The brightness temperature of the radio free-free emission at millimeter range is an effective tool for characterizing the vertical structure of the solar chromosphere. In this paper, we report on the first single-dish observation of a sunspot at 85 and 115 GHz with sufficient spatial resolution for resolving the sunspot umbra using the Nobeyama 45 m telescope. We used radio attenuation material, i.e. a solar filter, to prevent the saturation of the receivers. Considering the contamination from the plage by the side-lobes, we found that the brightness temperature of the umbra should be lower than that of the quiet region. This result is inconsistent with the preexisting atmospheric models. We also found that the brightness temperature distribution at millimeter range strongly corresponds to the ultraviolet (UV) continuum emission at 1700 {\\AA}, especially at the quiet region.

  15. Formation of the O I resonance triplet and intercombination doublet in the solar chromosphere

    International Nuclear Information System (INIS)

    Spectrum synthesis calculations are presented for the O I resonance triplet at 1304 A and the intercombination doublet at 1358 A for the solar atmosphere of Vernazza, Avrett, and Loeser and several variants, allowing for triplet fluorescence by the Lyβ emission of H I. Profiles, synthesized from a seven-level plus continuum O I atom are compared to observations taken with the high-resolution spectrometer on OSO 8, calibrated with the irradiance measurements of Heroux and Higgins. We find tha the O I triplet emission is dominated by the Lyβ fluorescence and that the agreement between observations and profiles computed with current chromospheric models is much improved over earlier studies

  16. The solar chromosphere as induction disk and the inverse Joule-Thomson effect

    CERN Document Server

    Vita-Finzi, Claudio

    2016-01-01

    The connection between nuclear fusion in the Sun's core and solar irradiance is obscured among other things by uncertainty over the mechanism of coronal heating. Data for solar wind density and velocity, sunspot number, and EUV flux suggest that electromagnetic energy from the Sun's convection zone is converted by induction through the chromosphere into thermal energy. The helium and hydrogen mixture exhaled by the Sun is then heated by the inverse Joule-Thomson effect when it expands via the corona into space. The almost complete shutdown of the solar wind on 10-11 May 1999 demonstrated that its velocity is a more faithful indicator of solar activity than are sunspots as it reflects short-term variations in coronal heating rather than quasicyclical fluctuations in the Sun's magnetism. Its reconstruction from the cosmic ray flux using isotopes spanning over 800,000 yr should therefore benefit the analysis and long-term forecasting of Earth and space weather.

  17. CHROMOSPHERICALLY ACTIVE STARS IN THE RADIAL VELOCITY EXPERIMENT (RAVE) SURVEY. I. THE CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Žerjal, M.; Zwitter, T. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Matijevič, G. [Department of Astronomy and Astrophysics, Villanova University, 800 E Lancaster Avenue, Villanova, PA 19085 (United States); Strassmeier, K. G.; Siviero, A.; Steinmetz, M. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Bienaymé, O. [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, 11 rue de l' Université, F-67000 Strasbourg (France); Bland-Hawthorn, J. [Sydney Institute for Astronomy, School of Physics A28, Sydney, NSW 2006 (Australia); Boeche, C.; Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Freeman, K. C. [Research School of Astronomy and Astrophysics, Australia National University, Weston Creek, Canberra, ACT 2611 (Australia); Kordopatis, G. [Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA (United Kingdom); Munari, U. [INAF Osservatorio Astronomico di Padova, I-36012 Asiago (Italy); Navarro, J. F. [Department of Physics and Astronomy, University of Victoria, Victoria BC, V8P 5C2 (Canada); Parker, Q. A.; Reid, W. [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Seabroke, G. [Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, RH5 6NT (United Kingdom); Wyse, R. F. G., E-mail: marusa.zerjal@fmf.uni-lj.si [Johns Hopkins University, Homewood Campus, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2013-10-20

    RAVE, the unbiased magnitude limited survey of southern sky stars, contained 456,676 medium-resolution spectra at the time of our analysis. Spectra cover the Ca II infrared triplet (IRT) range, which is a known indicator of chromospheric activity. Our previous work classified all spectra using locally linear embedding. It identified 53,347 cases with a suggested emission component in calcium lines. Here, we use a spectral subtraction technique to measure the properties of this emission. Synthetic templates are replaced by the observed spectra of non-active stars to bypass the difficult computations of non-local thermal equilibrium profiles of the line cores and stellar parameter dependence. We derive both the equivalent width of the excess emission for each calcium line on a 5 Å wide interval and their sum EW{sub IRT} for ∼44,000 candidate active dwarf stars with signal-to-noise ratio >20, with no cuts on the basis of the source of their emission flux. From these, ∼14,000 show a detectable chromospheric flux with at least a 2σ confidence level. Our set of active stars vastly enlarges previously known samples. Atmospheric parameters and, in some cases, radial velocities of active stars derived from automatic pipelines suffer from systematic shifts due to their shallower calcium lines. We re-estimate the effective temperature, metallicity, and radial velocities for candidate active stars. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with non-active stars and the second with the pre-main-sequence cases. The catalog will be made publicly available with the next RAVE public data releases.

  18. EVIDENCE FOR TWO SEPARATE BUT INTERLACED COMPONENTS OF THE CHROMOSPHERIC MAGNETIC FIELD

    International Nuclear Information System (INIS)

    Chromospheric fibrils are generally thought to trace out low-lying, mainly horizontal magnetic fields that fan out from flux concentrations in the photosphere. A high-resolution (∼0.''1 pixel–1) image, taken in the core of the Ca II 854.2 nm line and covering an unusually large area, shows the dark fibrils within an active region remnant as fine, looplike features that are aligned parallel to each other and have lengths comparable to a supergranular diameter. Comparison with simultaneous line-of-sight magnetograms confirms that the fibrils are centered above intranetwork areas (supergranular cell interiors), with one end rooted just inside the neighboring plage or strong unipolar network but the other endpoint less clearly defined. Focusing on a particular arcade-like structure lying entirely on one side of a filament channel (large-scale polarity inversion), we find that the total amount of positive-polarity flux underlying this 'fibril arcade' is ∼50 times greater than the total amount of negative-polarity flux. Thus, if the fibrils represent closed loops, they must consist of very weak fields (in terms of total magnetic flux), which are interpenetrated by a more vertical field that contains most of the flux. This surprising result suggests that the fibrils in unipolar regions connect the network to the nearby intranetwork flux, while the bulk of the network flux links to remote regions of the opposite polarity, forming a second, higher canopy above the fibril canopy. The chromospheric field near the edge of the network thus has an interlaced structure resembling that in sunspot penumbrae.

  19. Precision VUV Spectro-Polarimetry for Solar Chromospheric Magnetic Field Measurements

    Science.gov (United States)

    Ishikawa, R.; Bando, T.; Hara, H.; Ishikawa, S.; Kano, R.; Kubo, M.; Katsukawa, Y.; Kobiki, T.; Narukage, N.; Suematsu, Y.; Tsuneta, S.; Aoki, K.; Miyagawa, K.; Ichimoto, K.; Kobayashi, K.; Auchère, F.; Clasp Team

    2014-10-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a VUV spectro-polarimeter optimized for measuring the linear polarization of the Lyman-α line (121.6 nm) to be launched in 2015 with NASA's sounding rocket (Ishikawa et al. 2011; Narukage et al. 2011; Kano et al. 2012; Kobayashi et al. 2012). With this experiment, we aim to (1) observe the scattering polarization in the Lyman-α line, (2) detect the Hanle effect, and (3) assess the magnetic fields in the upper chromosphere and transition region for the first time. The polarization measurement error consists of scale error δ a (error in amplitude of linear polarization), azimuth error Δφ (error in the direction of linear polarization), and spurious polarization ɛ (false linear polarization signals). The error ɛ should be suppressed below 0.1% in the Lyman-α core (121.567 nm ±0.02 nm), and 0.5% in the Lyman-α wing (121.567 nm ±0.05 nm), based on our scientific requirements shown in Table 2 of Kubo et al. (2014). From scientific justification, we adopt Δ φzero at the Sun center due to symmetric geometry. In order to clarify whether we will be able to achieve the required polarization sensitivity and accuracy via these steps, we exercise polarization error budget, by investigating all the possible causes and their magnitudes of polarization errors, all of which are not necessarily verified by the polarization calibration. Based on these error budgets, we conclude that a polarization sensitivity of 0.1% in the line core, δ abudgets throughout the course of these tests.

  20. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere IV. On the Nature of the Chromosphere

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-07-01

    Full Text Available The chromosphere is the site of weak emission lines characterizing the flash spectrum observed for a few seconds during a total eclipse. This layer of the solar atmosphere is known to possess an opaque Hα emission and a great number of spicules, which can extend well above the photosphere. A stunning variety of hydrogen emission lines have been observed in this region. The production of these lines has provided the seventeenth line of evidence that the Sun is comprised of condensed matter (Robitaille P.M. Liquid Metallic Hydrogen II: A critical assessment of current and primordial helium levels in Sun. Progr. Phys., 2013, v. 2, 35–47. Contrary to the gaseous solar models, the simplest mechanism for the production of emission lines is the evaporation of excited atoms from condensed surfaces existing within the chromosphere, as found in spicules. This is reminiscent of the chemiluminescence which occurs during the condensation of silver clusters (Konig L., Rabin I., Schultze W., and Ertl G. Chemiluminescence in the Agglomeration of Metal Clusters. Science, v. 274, no. 5291, 1353–1355. The process associated with spicule formation is an exothermic one, requiring the transport of energy away from the site of condensation. As atoms leave localized surfaces, their electrons can occupy any energy level and, hence, a wide variety of emission lines are produced. In this regard, it is hypothesized that the presence of hydrides on the Sun can also facilitate hydrogen condensation in the chromosphere. The associated line emission from main group and transition elements constitutes the thirtieth line of evidence that the Sun is condensed matter. Condensation processes also help to explain why spicules manifest an apparently constant temperature over their entire length. Since the corona supports magnetic field lines, the random orientations associated with spicule formation suggests that the hydrogen condensates in the chromosphere are not metallic in

  1. Fine structure of the age-chromospheric activity relation in solar-type stars I: The Ca II infrared triplet: Absolute flux calibration

    CERN Document Server

    Lorenzo-Oliveira, Diego; Dutra-Ferreira, Letícia; Ribas, Ignasi

    2016-01-01

    Strong spectral lines are useful indicators of stellar chromospheric activity. They are physically linked to the convection efficiency, differential rotation, and angular momentum evolution and are a potential indicator of age. However, for ages > 2 Gyr, the age-activity relationship remains poorly constrained thus hampering its full application. The Ca II infrared triplet (IRT lines) has been poorly studied compared to classical chromospheric indicators. We report in this paper absolute chromospheric fluxes in the three Ca II IRT lines, based on a new calibration tied to up-to-date model atmospheres. We obtain the Ca II IRT absolute fluxes for 113 FGK stars from high signal-to-noise ratio and high-resolution spectra covering an extensive domain of chromospheric activity levels. We perform an absolute continuum flux calibration for the Ca II IRT lines anchored in atmospheric models calculated as an explicit function of effective temperatures, metallicity, and gravities avoiding the degeneracy present in photo...

  2. Temporal Evolution of the Scattering Polarization of the CaII IR Triplet in Hydrodynamical Models of the Solar Chromosphere

    CERN Document Server

    Carlin, E S; Bueno, J Trujillo

    2012-01-01

    Velocity gradients in a stellar atmospheric plasma have an impact on the anisotropy of the radiation field that illuminates each point within the medium, and this may in principle influence the scattering line polarization that results from the induced atomic level polarization. Here we analyze the emergent linear polarization profiles of the Ca II infrared triplet after solving the radiative transfer problem of scattering polarization in time-dependent hydrodynamical models of the solar chromosphere, taking into account the impact of the plasma macroscopic velocity on the atomic level polarization. We discuss the influence that the velocity and temperature shocks in the considered chromospheric models have on the temporal evolution of the scattering polarization signals of the Ca II infrared lines, as well as on the temporally averaged profiles. Our results indicate that the increase of the linear polarization amplitudes caused by macroscopic velocity gradients may be significant in realistic situations. We ...

  3. Reflection and Conversion of Magneto-Gravity Waves in the Solar Chromosphere: Windows to the Upper Atmosphere

    CERN Document Server

    Newington, Marie

    2009-01-01

    The detection of upward propagating internal gravity waves in the Sun's chromosphere has recently been reported by Straus et al., who postulated that these may efficiently couple to Alfven waves in magnetic regions. This may be important in transporting energy to higher levels. Here we explore the propagation, reflection and mode conversion of linear gravity waves in a VAL C atmosphere, and find that even weak magnetic fields usually reflect gravity waves back downward as slow magnetoacoustic waves well before they reach the Alfven/acoustic equipartition height at which mode conversion might occur. However, for certain highly inclined magnetic field orientations in which the gravity waves manage to penetrate near or through the equipartition level, there can be substantial conversion to either or both upgoing Alfven and acoustic waves. Wave energy fluxes comparable to the chromospheric radiative losses are expected.

  4. Magnetic cycles of Sun-like stars with different levels of coronal and chromospheric activity -- comparison with the Sun

    CERN Document Server

    Bruevich, E A; Shimanovskaya, E V

    2016-01-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of F, G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycles, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of the chromospheric and coronal activity confirms that the Sun belongs to stars with the low level of the chromospheric activity and stands apart among these stars by the minimum level of its coronal radiation and the minimum level of its variations of the photospheric flux.

  5. Resolving the Fan-spine Reconnection Geometry of a Small-scale Chromospheric Jet Event with the New Solar Telescope

    Science.gov (United States)

    Zeng, Zhicheng; Chen, Bin; Ji, Haisheng; Goode, Philip R.; Cao, Wenda

    2016-03-01

    Jets are ubiquitously present in both quiet and active regions on the Sun. They are widely believed to be driven by magnetic reconnection. A fan-spine structure has been frequently reported in some coronal jets and flares, and has been regarded as a signature of ongoing magnetic reconnection in a topology consisting of a magnetic null connected by a fan-like separatrix surface and a spine. However, for small-scale chromospheric jets, clear evidence of such structures is rather rare, although it has been implied in earlier works that showed an inverted-Y-shaped feature. Here we report high-resolution (0.″16) observations of a small-scale chromospheric jet obtained by the New Solar Telescope (NST) using 10830 Å filtergrams. Bi-directional flows were observed across the separatrix regions in the 10830 Å images, suggesting that the jet was produced due to magnetic reconnection. At the base of the jet, a fan-spine structure was clearly resolved by the NST, including the spine and the fan-like surface, as well as the loops before and after the reconnection. A major part of this fan-spine structure, with the exception of its bright footpoints and part of the base arc, was invisible in the extreme ultraviolet and soft X-ray images (observed by the Atmosphere Imaging Assembly and the X-Ray Telescope, respectively), indicating that the reconnection occurred in the upper chromosphere. Our observations suggest that the evolution of this chromospheric jet is consistent with a two-step reconnection scenario proposed by Török et al.

  6. Optical Alignment of the Chromospheric Lyman-Alpha SpectroPolarimeter using Sophisticated Methods to Minimize Activities under Vacuum

    Science.gov (United States)

    Giono, G.; Katsukawa, Y.; Ishikawa, R.; Narukage, N.; Kano, R.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.

    2016-01-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument developed at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. The in- strument main scientific goal is to achieve polarization measurement of the Lyman-alpha line at 121.56 nm emitted from the solar upper-chromosphere and transition region with an unprecedented 0.1% accuracy. For this purpose, the optics are composed of a Cassegrain telescope coated with a "cold mirror" coating optimized for UV reflection and a dual-channel spectrograph allowing for simultaneous observation of the two orthogonal states of polarization. Although the polarization sensitivity is the most important aspect of the instrument, the spatial and spectral resolutions of the instrument are also crucial to observe the chromospheric features and resolve the Ly- pro les. A precise alignment of the optics is required to ensure the resolutions, but experiments under vacuum conditions are needed since Ly-alpha is absorbed by air, making the alignment experiments difficult. To bypass this issue, we developed methods to align the telescope and the spectrograph separately in visible light. We will explain these methods and present the results for the optical alignment of the CLASP telescope and spectrograph. We will then discuss the combined performances of both parts to derive the expected resolutions of the instrument, and compare them with the flight observations performed on September 3rd 2015.

  7. Formation and Eruption of a Small Flux Rope in the Chromosphere Observed by NST, IRIS, and SDO

    CERN Document Server

    Kumar, Pankaj; Wang, Haimin; Cho, Kyung-Suk

    2015-01-01

    Using high-resolution images from 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), we report the direct evidence of chromospheric reconnection at the polarity inversion line (PIL) between two small opposite polarity sunspots. Small jet-like structures (with velocities of ~20-55 km/s) were observed at the reconnection site before the onset of the first M1.0 flare. The slow rise of untwisting jets was followed by the onset of cool plasma inflow (~10 km/s) at the reconnection site, causing the onset of a two-ribbon flare. The reconnection between two sheared J-shaped cool H$\\alpha$ loops causes the formation of a small twisted flux rope (S shaped) in the chromosphere. In addition, Helioseismic and Magnetic Imager (HMI) magnetograms show the flux cancellation (both positive and negative) during the first M1.0 flare. The emergence of negative flux and cancellation of positive flux (with shear flows) continue until the successful eruption of the flux rope. The newly formed chromospheric flux ro...

  8. Acceleration of type 2 spicules in the solar chromosphere. II. Viscous braking and upper bounds on coronal energy input

    International Nuclear Information System (INIS)

    A magnetohydrodynamic model is used to determine conditions under which the Lorentz force accelerates plasma to type 2 spicule speeds in the chromosphere. The model generalizes a previous model to include a more realistic pre-spicule state, and the vertical viscous force. Two cases of acceleration under upper chromospheric conditions are considered. The magnetic field strength for these cases is ≤12.5 and 25 G. Plasma is accelerated to terminal vertical speeds of 66 and 78 km s–1 in 100 s, compared with 124 and 397 km s–1 for the case of zero viscosity. The flows are localized within horizontal diameters ∼80 and 50 km. The total thermal energy generated by viscous dissipation is ∼10 times larger than that due to Joule dissipation, but the magnitude of the total cooling due to rarefaction is ≳ this energy. Compressive heating dominates during the early phase of acceleration. The maximum energy injected into the corona by type 2 spicules, defined as the energy flux in the upper chromosphere, may largely balance total coronal energy losses in quiet regions, possibly also in coronal holes, but not in active regions. It is proposed that magnetic flux emergence in intergranular regions drives type 2 spicules.

  9. The quiescent chromospheres and transition regions of active dwarf stars: what are we learning from recent observations and models

    International Nuclear Information System (INIS)

    The rapid progress in understanding active dwarf stars, which has been stimulated by recent IUE, Einstein and ground-based observations, is reviewed. Active phenomena in late-type dwarf stars are seen as somehow a direct consequence of strong magnetic fields. The nonflare phenomena in the chromosphere and transition regions of these stars are discussed, while some suggestions are given about the way in which magnetic fields control these phenomena. Especially, the review deals with a description and comparison of those activities which are similar in active and quiescent dwarf stars and summarizes the various roles which magnetic fields likely play in modifying the chromospheres and transition regions of active stars. Successively, the following subjects are discussed: the basic structure of the stars, the enhanced heating and solar-like flux tubes, the consequences of plasma flows, heating rates in different layers, heating mechanism of chromosphere and transition region, semi-empirical models. The author finishes with some suggestions for future work. (G.J.P.)

  10. Acceleration of type 2 spicules in the solar chromosphere. II. Viscous braking and upper bounds on coronal energy input

    Energy Technology Data Exchange (ETDEWEB)

    Goodman, Michael L., E-mail: mgoodman@wvhtf.org [Advanced Technologies Group, West Virginia High Technology Consortium Foundation, 1000 Galliher Drive, Fairmont, WV 26554 (United States)

    2014-04-20

    A magnetohydrodynamic model is used to determine conditions under which the Lorentz force accelerates plasma to type 2 spicule speeds in the chromosphere. The model generalizes a previous model to include a more realistic pre-spicule state, and the vertical viscous force. Two cases of acceleration under upper chromospheric conditions are considered. The magnetic field strength for these cases is ≤12.5 and 25 G. Plasma is accelerated to terminal vertical speeds of 66 and 78 km s{sup –1} in 100 s, compared with 124 and 397 km s{sup –1} for the case of zero viscosity. The flows are localized within horizontal diameters ∼80 and 50 km. The total thermal energy generated by viscous dissipation is ∼10 times larger than that due to Joule dissipation, but the magnitude of the total cooling due to rarefaction is ≳ this energy. Compressive heating dominates during the early phase of acceleration. The maximum energy injected into the corona by type 2 spicules, defined as the energy flux in the upper chromosphere, may largely balance total coronal energy losses in quiet regions, possibly also in coronal holes, but not in active regions. It is proposed that magnetic flux emergence in intergranular regions drives type 2 spicules.

  11. X-Shooter spectroscopy of young stellar objects: II. Impact of chromospheric emission on accretion rate estimates

    CERN Document Server

    Manara, C F; Rigliaco, E; Alcala, J M; Natta, A; Stelzer, B; Biazzo, K; Covino, E; Covino, S; Cupani, G; D'Elia, V; Randich, S

    2013-01-01

    Context. The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) Young Stellar Objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is still missing. This can be undertaken using samples of young diskless (Class III) K and M-type stars. Aims. Our goal is to measure the chromospheric activity of Class III pre main sequence stars to determine its effect on the estimates of accretion luminosity (Lacc) and mass accretion rate (Macc) in young stellar objects with disks. Methods. Using VLT/X-Shooter spectra we have analyzed a sample of 24 non-accreting young stellar objects of spectral type between K5 and M9.5. We identify the main emission lines normally used as tracers of accretion in Class II objects, and we determine their fluxes in order to estimate the contribution of ...

  12. Non-linear propagation of kink waves to the solar chromosphere

    CERN Document Server

    Stangalini, M; Jafarzadeh, S

    2015-01-01

    Small-scale magnetic field concentrations (magnetic elements) in the quiet Sun are believed to contribute to the energy budget of the upper layers of the Sun's atmosphere, as they are observed to support a large number of MHD modes. In recent years, kink waves in magnetic elements were observed at different heights in the solar atmosphere, from the photosphere to the corona. However, the propagation of these waves has not been fully evaluated. Our aim is to investigate the propagation of kink waves in small magnetic elements in the solar atmosphere. We analysed spectropolarimetric data of high-quality and long duration of a photospheric quiet Sun region observed near the disk center with the spectropolarimeter CRISP at the Swedish Solar Telescope (SST), and complemented by simultaneous and co-spatial broad-band chromospheric observations of the same region. Our findings reveal a clear upward propagation of kink waves with frequency above $~2.6$ mHz. Moreover, the signature of a non-linear propagation process ...

  13. Oscillatory behavior of chromospheric fine structures in a network and a semi-active regions

    CERN Document Server

    Bostanci, Z F; Al, N

    2014-01-01

    In the present work, we study the periodicities of oscillations in dark fine structures using observations of a network and a semi-active region close to the solar disk center. We simultaneously obtained spatially high resolution time series of white light images and narrow band images in the H$\\alpha$ line using the 2D G\\"ottingen spectrometer, which were based on two Fabry-Perot interferometers and mounted in the VTT/Observatorio del Teide/Tenerife. During the observations, the H$\\alpha$ line was scanned at 18 wavelength positions with steps of 125 m\\AA. We computed series of Doppler and intensity images by subtraction and addition of the H$\\alpha$ $\\pm$ 0.3 \\AA\\ and $\\pm$ 0.7 \\AA\\ pairs, sampling the upper chromosphere and the upper photosphere, respectively. Then we obtained power, coherence and phase difference spectra by performing a wavelet analysis to the Doppler fluctuations. Here, we present comparative results of oscillatory properties of dark fine structures seen in a network and a semi-active reg...

  14. The 3D structure of an active region filament as extrapolated from photospheric and chromospheric observations

    CERN Document Server

    Chaouche, L Yelles; Pillet, V Martínez; Moreno-Insertis, F

    2012-01-01

    The 3D structure of an active region (AR) filament is studied using nonlinear force-free field (NLFFF) extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 \\AA\\ line and the He I 10830 \\AA\\ triplet obtained with the Tenerife Infrared Polarimeter (TIP) at the VTT (Tenerife). The two extrapolations have been carried out independently from each other and their respective spatial domains overlap in a considerable height range. This opens up new possibilities for diagnostics in addition to the usual ones obtained through a single extrapolation from, typically, a photospheric layer. Among those possibilities, this method allows the determination of an average formation height of the He I 10830 \\AA\\ signal of \\approx 2 Mm above the surface of the sun. It allows, as well, to cross-check the obtained 3D magnetic structures in view of verifying a possible deviation from the force- free condition especially at the photosphere. The extrapolati...

  15. Solar granulation from photosphere to low chromosphere observed in BaII 4554 A line

    CERN Document Server

    Kostik, R; Shchukina, N

    2009-01-01

    The purpose of this paper is to characterize the statistical properties of solar granulation in the photosphere and low chromosphere up to 650 km. We use velocity and intensity variations obtained at different atmospheric heights from observations in BaII 4554 A. The observations were done during good seeing conditions at the VTT at the Observatorio del Teide on Tenerife. The line core forms rather high in the atmosphere and allows granulation properties to be studied at heights that have been not accessed before in similar studies. In addition, we analyze the synthetic profiles of the BaII 4554 A line by the same method computed taking NLTE effects into account in the 3D hydrodynamical model atmosphere. We suggest a 16-column model of solar granulation depending on the direction of motion and on the intensity contrast measured in the continuum and in the uppermost layer. We calculate the heights of intensity contrast sign reversal and velocity sign reversal. We show that both parameters depend strongly on th...

  16. Chromospheric activity and evolutionary age of the Sun and four solar twins

    CERN Document Server

    Mittag, M; Hempelmann, A; González-Pérez, J N; Schmitt, J H M M

    2016-01-01

    The activity levels of the solar-twin candidates HD 101364 and HD 197027 are measured and compared with the Sun, the known solar twin 18 Sco, and the solar-like star 51 Peg. Furthermore, the absolute ages of these five objects are estimated from their positions in the HR diagram and the evolutionary (relative) age compared with their activity levels. To represent the activity level of these stars, the Mount Wilson S-indices were used. To obtain consistent ages and evolutionary advance on the main sequence, we used evolutionary tracks calculated with the Cambridge Stellar Evolution Code. From our spectroscopic observations of HD 101364 and HD 197027 and based on the established calibration procedures, the respective Mount Wilson S-indices are determined. We find that the chromospheric activity of both stars is comparable with the present activity level of the Sun and that of 18 Sco, at least for the period in consideration. Furthermore, the absolute age of HD 101364, HD 197027, 51 Peg, and 18 Sco are found to ...

  17. Transition Region and Chromospheric Signatures of Impulsive Heating Events. I. Observations

    CERN Document Server

    Warren, Harry P; Crump, Nicholas A; Simoes, Paulo J A

    2016-01-01

    We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from RHESSI provide constraints on the energetic electrons precipitating into the flare footpoints while observations of XRT, AIA, and EIS allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event the intensities in each pixel for the Si IV 1402.770, C II 1334.535, Mg II 2796.354 and O I 1355.598 emission lines are characterized by numerous, small-scale bursts typically lasting 60s or less. Red shifts are observed in Si IV, C II, and Mg II during the impulsive phase. Mg II shows red-shifts during the bursts and stationary emission at other times. The Si IV and C II profiles, in contrast, are ...

  18. Doppler tomography of XTE J1118+480 revealing chromospheric emission from the secondary star

    Science.gov (United States)

    Zurita, C.; González Hernández, J. I.; Escorza, A.; Casares, J.

    2016-08-01

    Doppler tomography of emission lines in low-mass X-ray binaries allows us to investigate the structure and variability of the accretion discs as well as possible activity arising from the secondary stars. We present Doppler maps of the black hole binary XTE J1118+480 from spectra obtained using OSIRIS@GTC during quiescence on four different nights in 2011 and 2012. Doppler imaging of the Hα line shows, for the first time, a narrow component from the secondary star with observed equivalent widths varying in the range 1.2-2.9 Å but not correlated with the veiling of the accretion disc. The Hα flux of the secondary star is too large to be powered by X-ray irradiation, supporting chromospheric activity, possibly induced by rapid rotation, as the most likely origin of this feature in the black hole X-ray binary XTE J1118+480. In addition, we detect variations in the centroid of the Hα line on nightly basis. These are likely caused by a precessing accretion disc, although with a much lower amplitude (˜50 km s-1) than previously observed.

  19. Time-dependent hydrogen ionisation in the solar chromosphere. I: Methods and first results

    CERN Document Server

    Wedemeyer-Boehm, J L S

    2006-01-01

    An approximate method for solving the rate equations for the hydrogen populations was extended and implemented in the three-dimensional radiation (magneto-)hydrodynamics code CO5BOLD. The method is based on a model atom with six energy levels and fixed radiative rates. It has been tested extensively in one-dimensional simulations. The extended method has been used to create a three-dimensional model that extends from the upper convection zone to the chromosphere. The ionisation degree of hydrogen in our time-dependent simulation is comparable to the corresponding equilibrium value up to 500 km above optical depth unity. Above this height, the non-equilibrium ionisation degree is fairly constant over time and space, and tends to be at a value set by hot propagating shock waves. The hydrogen level populations and electron density are much more constant than the corresponding values for statistical equilibrium, too. In contrast, the equilibrium ionisation degree varies by more than 20 orders of magnitude between...

  20. Chromospheric and Coronal Structure of Polar Plumes. 1; Magnetic Structure and Radiative Energy Balance

    Science.gov (United States)

    Allen, Maxwell J.; Oluseyi, Hakeem M.; Walker, Arthur B. C.; Hoover, Richard B.; Barbee, Troy W., Jr.

    1997-01-01

    The Multi-Spectral Solar Telescope Array (MSSTA), a rocket-borne solar observatory, was successfully launched from White Sands Missile Range, New Mexico, on May 13, 1991 at 19:05 UT. The telescope systems onboard the MSSTA obtained several full disk solar images in narrow bandpasses centered around strong soft X-ray, EUV, and FUV emission lines. Each telescope was designed to be sensitive to the coronal plasmas at a particular temperature, for seven temperatures ranging from 20,000 K to 4,000,000 K. We report here on the images obtained during the initial flight of the MSSTA, and on the chromospheric and coronal structure of polar plumes observed over both poles of the Sun. We have also co-aligned the MSSTA images with Kitt Peak magnetograms taken on the same day. We are able to positively identify the magnetic structures underlying the polar plumes we analyze as unipolar. We discuss the plume observations and present a radiative energy balance model derived from them.

  1. Mass motions and chromospheres of RGB stars in the globular cluster NGC 2808

    CERN Document Server

    Cacciari, C; Rossetti, E; Pecci, F F; Mulas, G; Carretta, E; Gratton, R G; Momany, Y; Pasquini, L

    2004-01-01

    We present the results of the first observations, taken with FLAMES during Science Verification, of red giant branch (RGB) stars in the globular cluster NGC 2808. A total of 137 stars was observed, of which 20 at high resolution (R=47,000) with UVES and the others at lower resolution (R=19,000-29,000) with GIRAFFE in MEDUSA mode, monitoring ~ 3 mag down from the RGB tip. Spectra were taken of the Halpha, Na I D and Ca II H and K lines. This is by far the largest and most complete collection of such data in globular cluster giants, both for the number of stars observed within one cluster, and for monitoring all the most important optical diagnostics of chromospheric activity/mass motions.Evidence of mass motions in the atmospheres was searched from asymmetry in the profiles and coreshifts of the Halpha, Na I D and Ca II K lines, as well as from Halpha emission wings. We have set the detection thresholds for the onset of Halpha emission, negative Na D_2 coreshifts and negative K_3 coreshifts at log L/Lsun ~ 2.5...

  2. Chromospheric Rapid Blueshifted Excursions Observed with IBIS and Their Association with Photospheric Magnetic Field Evolution

    CERN Document Server

    Deng, Na; Liu, Chang; Jing, Ju; Tritschler, Alexandra; Reardon, Kevin P; Lamb, Derek A; Deforest, Craig E; Denker, Carsten; Wang, Shuo; Liu, Rui; Wang, Haimin

    2014-01-01

    Chromospheric rapid blueshifted excursions (RBEs) are suggested to be the disk counterparts of type II spicules at the limb and believed to contribute to the coronal heating process. Previous identification of RBEs was mainly based on feature detection using Dopplergrams. In this paper, we study RBEs on 2011 October 21 in a very quiet region at the disk center, which were observed with the high-cadence imaging spectroscopy of the Ca II 8542 A line from the Interferometric Bidimensional Spectrometer (IBIS). By using an automatic spectral analysis algorithm, a total of 98 RBEs are identified during a 11 minute period. Most of these RBEs have either a round or elongated shape, with an average area of 1.2 arcsec^2. The detailed temporal evolution of spectra from IBIS makes possible a quantitative determination of the velocity (~16 km/s) and acceleration (~400 m/s^2) of Ca II 8542 RBEs, and reveal an additional deceleration (~-160 m/s^2) phase that usually follows the initial acceleration. In addition, we also inv...

  3. IMAGING AND SPECTROSCOPIC OBSERVATIONS OF MAGNETIC RECONNECTION AND CHROMOSPHERIC EVAPORATION IN A SOLAR FLARE

    International Nuclear Information System (INIS)

    Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfvén speed. Yet, spectroscopic observations of such outflows, especially the downflows, are extremely rare. With observations of the newly launched Interface Region Imaging Spectrograph (IRIS), we report the detection of a greatly redshifted (∼125 km s–1 along the line of sight) Fe XXI 1354.08 Å emission line with a ∼100 km s–1 nonthermal width at the reconnection site of a flare. The redshifted Fe XXI feature coincides spatially with the loop-top X-ray source observed by RHESSI. We interpret this large redshift as the signature of downward-moving reconnection outflow/hot retracting loops. Imaging observations from both IRIS and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory also reveal the eruption and reconnection processes. Fast downward-propagating blobs along these loops are also found from cool emission lines (e.g., Si IV, O IV, C II, Mg II) and images of AIA and IRIS. Furthermore, the entire Fe XXI line is blueshifted by ∼260 km s–1 at the loop footpoints, where the cool lines mentioned above all exhibit obvious redshift, a result that is consistent with the scenario of chromospheric evaporation induced by downward-propagating nonthermal electrons from the reconnection site

  4. A Study of Surges: II. On the Relationship between Chromospheric Surges and Coronal Mass Ejections

    Science.gov (United States)

    Liu, Yu

    2008-05-01

    Liu et al. ( Astrophys. J. 628, 1056, 2005a) described one surge coronal mass ejection (CME) event showing a close relationship between solar chromospheric surge ejection and CME that had not been noted before. In this work, large Hα surges (>72 Mm, or 100 arcsec) are studied. Eight of these were associated with CMEs. According to their distinct morphological features, Hα surges can be classified into three types: jetlike, diffuse, and closed loop. It was found that all of the jetlike surges were associated with jetlike CMEs (with angular widths ≤30 degrees); the diffuse surges were all associated with wide-angle CMEs ( e.g., halo); the closed-loop surges were not associated with CMEs. The exclusive relation between Hα surges and CMEs indicates difference in magnetic field configurations. The jetlike surges and related narrow CMEs propagate along coronal fields that are originally open. The unusual transverse mass motions in the diffuse surges are suggested to be due to magnetic reconnections in the corona that produce wide-angle CMEs. For the closed-loop surges, their paths are just outlining stable closed loops close to the solar surface. Thus no CMEs are associated with them.

  5. IMAGING AND SPECTROSCOPIC OBSERVATIONS OF MAGNETIC RECONNECTION AND CHROMOSPHERIC EVAPORATION IN A SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Hui; Reeves, Katharine K.; Raymond, John C.; Chen, Bin; Murphy, Nicholas A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Li, Gang [Department of Physics and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Guo, Fan [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States); Liu, Wei, E-mail: hui.tian@cfa.harvard.edu [Lockheed Martin Solar and Astrophysics Laboratory, Building 252, 3251 Hanover Street, Palo Alto, CA 94305 (United States)

    2014-12-20

    Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfvén speed. Yet, spectroscopic observations of such outflows, especially the downflows, are extremely rare. With observations of the newly launched Interface Region Imaging Spectrograph (IRIS), we report the detection of a greatly redshifted (∼125 km s{sup –1} along the line of sight) Fe XXI 1354.08 Å emission line with a ∼100 km s{sup –1} nonthermal width at the reconnection site of a flare. The redshifted Fe XXI feature coincides spatially with the loop-top X-ray source observed by RHESSI. We interpret this large redshift as the signature of downward-moving reconnection outflow/hot retracting loops. Imaging observations from both IRIS and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory also reveal the eruption and reconnection processes. Fast downward-propagating blobs along these loops are also found from cool emission lines (e.g., Si IV, O IV, C II, Mg II) and images of AIA and IRIS. Furthermore, the entire Fe XXI line is blueshifted by ∼260 km s{sup –1} at the loop footpoints, where the cool lines mentioned above all exhibit obvious redshift, a result that is consistent with the scenario of chromospheric evaporation induced by downward-propagating nonthermal electrons from the reconnection site.

  6. Observations, analysis and interpretation with non-LTE of chromospheric structures of the Sun

    CERN Document Server

    Nuño, Bruno Sánchez-Andrade

    2008-01-01

    This thesis is based on observations performed at the Vacuum Tower Telescope (Tenerife). We have used an infrared spectropolarimeter (TIP) and a Fabry-Perot spectrometer (G-FPI) from years 2004 to 2006. We have applied several imaging speckle reconstruction techniques, and compared them. We have studied chromospheric dynamics inside the solar disc and at the limb using H\\alpha with very high spatial, spectral and temporal resolution. Keywords (see full abstract for details): fibrils, surge, MHD waves, speckle, blind deconvolution, Fabry-Perot, mini-flares, cloud model, spicules in Halpha, spicules continuing on the disc) Using He I 10830 we studied the offlimb spicular spectral I profiles with height over the limb. The analysis shows the variation of the off-limb emission profiles as a function of the distance to the visible solar limb. The intensity ratio of the multiplet (which is related to the optical thickness and coronal irradiation) is studied and compared with standard atmospheric models. We report ob...

  7. Chromospheric Condensation and Quasi-periodic Pulsations in a Circular-ribbon Flare

    CERN Document Server

    Zhang, Q M; Ning, Z J

    2016-01-01

    In this paper, we report our multiwavelength observations of the C3.1 circular-ribbon flare SOL2015-10-16T10:20 in AR 12434. The flare consisted of a circular flare ribbon (CFR), an inner flare ribbon (IFR) inside, and a pair of short parallel flare ribbons (PFRs). During the impulsive phase of the flare, "two-step" raster observations of \\textit{IRIS} with a cadence of 6 s and an exposure time of 2 s show plasma downflow at the CFR in the Si {\\sc iv} $\\lambda$1402.77 line, suggesting chromospheric condensation. The downflow speeds first increased rapidly from a few km s$^{-1}$ to the peak values of 45$-$52 km s$^{-1}$, before decreasing gradually to the initial levels. The decay timescales of condensation were 3$-$4 minutes, indicating ongoing magnetic reconnection. Interestingly, the downflow speeds are positively correlated with logarithm of the Si {\\sc iv} line intensity and time derivative of the \\textit{GOES} soft X-ray (SXR) flux in 1$-$8 {\\AA}. The radio dynamic spectra are characterized by a type \\Rm...

  8. The Chromospheric Solar Limb Brightening at Radio, Millimeter, Sub-millimeter, and Infrared Wavelengths

    CERN Document Server

    De la Luz, Victor

    2016-01-01

    Observations of the emission at radio, millimeter, sub-millimeter, and infrared wavelengths in the center of the solar disk validate the auto-consistence of semi-empirical models of the chromosphere. Theoretically, these models must reproduce the emission at the solar limb. In this work, we tested both the VALC and the C7 semi-empirical models by computing their emission spectrum in the frequency range from 2 GHz to 10 THz, at solar limb altitudes. We calculate the Sun's theoretical radii as well as their limb brightening. Non-Local Thermodynamic Equilibrium (NLTE) was computed for hydrogen, electron density, and H-. In order to solve the radiative transfer equation a 3D geometry was employed to determine the ray paths and Bremsstrahlung, H-, and inverse Bremsstrahlung opacity sources were integrated in the optical depth. We compared the computed solar radii with high resolution observations at the limb obtained by Clark (1994). We found that there are differences between observed and computed solar radii of ...

  9. Magnetic Diagnostics of the Chromosphere with the Mg II h-k Lines

    CERN Document Server

    Alemán, Tanausú del Pino; Sainz, Rafael Manso

    2016-01-01

    We developed a numerical code for polarized radiative transfer in a plane-parallel geometry that implements a recent formulation of partially coherent scattering by polarized multi-term atoms in arbitrary magnetic field regimes. This code allows the realistic modeling of the scattering polarization of important chromospheric lines, such as the Mg II h-k doublet, the Ca II H-K doublet and IR triplet, and lines of the H I Lyman and Balmer series. We present explicit results of the Mg II h-k doublet in a weakly magnetized atmosphere (20-100 G). These confirm the importance of partial redistribution effects in the formation of these lines, as pointed out by previous work in the non-magnetic case. We show that the presence of a magnetic field can produce measurable modifications of the broadband linear polarization even for relatively small field strengths (~10 G), while the circular polarization remains well represented by the classical magnetograph formula. Both these results open an important new window for the...

  10. Calculation of theoretical chromospheric models and the interpretation of solar spectra from rockets and spacecraft. Semiannual Report, 1 January-31 December 1985

    International Nuclear Information System (INIS)

    Calculated results based on two chromospheric flare models F1 and F2 of Machado, et al., (1980) are presented. Two additional models are included: F1*, which has enhanced temperatures relative to the weak-flare model F1 in the upper photosphere and low chromosphere, and F3 which has enhanced temperatures relative to the strong flare model F2 in the upper chromosphere. Each model is specified by means of a given variation of the temperature as a function of column mass. The corresponding variation of particle density and the geometrical height scale are determined by assuming hydrostatic equilibrium. The coupled equations of statistical equilibrium is solved as is 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. The overall absorption and emission of radiation by lines throughout the spectrum is determined by means of a reduced set of opacities sampled from a compilation of over 10 to the 7th power individual lines. That the white flight flare continuum may arise by extreme chromospheric overheating as well as by an enhancement of the minimum temperature region is also shown. The radiative cooling rate calculations for our brightest flare model suggest that chromospheric overheating provides enhanced radiation that could cause significant heating deep in the flare atmosphere

  11. Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation

    CERN Document Server

    Gálvez, M C; Fernández-Figueroa, M J; De Castro, E; Cornide, M

    2007-01-01

    This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution i...

  12. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere VII. Further Insights into the Chromosphere and Corona

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-07-01

    Full Text Available In the liquid metallic hydrogen model of the Sun, the chromosphere is responsible for the capture of atomic hydrogen in the solar atmosphere and its eventual re-entry onto the photospheric surface (P.M. Robitaille. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere IV. On the Nature of the Chromosphere. Prog. Phys., 2013, v. 3, L15–L21. As for the corona, it represents a diffuse region containing both gaseous plasma and condensed matter with elevated electron affinity (P.M. Robitaille. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere V. On the Nature of the Corona. Prog. Phys., 2013, v. 3, L22–L25. Metallic hydrogen in the corona is thought to enable the continual harvest of electrons from the outer reaches of the Sun, thereby preserving the neutrality of the solar body. The rigid rotation of the corona is offered as the thirty-third line of evidence that the Sun is comprised of condensed matter. Within the context of the gaseous models of the Sun, a 100 km thick transition zone has been hypothesized to exist wherein temperatures increase dramatically from 104–106 K. Such extreme transitional temperatures are not reasonable given the trivial physical scale of the proposed transition zone, a region adopted to account for the ultra-violet emission lines of ions such as C IV, O IV, and Si IV. In this work, it will be argued that the transition zone does not exist. Rather, the intermediate ionization states observed in the solar atmosphere should be viewed as the result of the simultaneous transfer of protons and electrons onto condensed hydrogen structures, CHS. Line emissions from ions such as C IV, O IV, and Si IV are likely to be the result of condensation reactions, manifesting the involvement of species such as CH4, SiH4, H3O+ in the synthesis of CHS in the chromosphere. In addition, given the presence of a true solar surface at the level of the photosphere in the liquid metallic hydrogen model

  13. Where is the chromospheric response to conductive energy input from a hot pre-flare coronal loop?

    CERN Document Server

    Battaglia, Marina; Simões, Paulo J A

    2014-01-01

    Before the onset of a flare is observed in hard X-rays there is often a prolonged pre-flare or pre-heating phase with no detectable hard X-ray emission but pronounced soft X-ray emission suggesting that energy is being released and deposited into the corona and chromosphere already at this stage. This work analyses the temporal evolution of coronal source heating and the chromospheric response during this pre-heating phase to investigate the origin and nature of early energy release and transport during a solar flare. Simultaneous X-ray, EUV, and microwave observations of a well observed flare with a prolonged pre-heating phase are analysed to study the time evolution of the thermal emission and to determine the onset of particle acceleration. During the 20 minutes duration of the pre-heating phase we find no hint of accelerated electrons, neither in hard X-rays nor in microwave emission. However, the total energy budget during the pre-heating phase suggests that energy must be supplied to the flaring loop to...

  14. Resolving the Fan-Spine Reconnection Geometry of a Small-Scale Chromospheric Jet Event with the New Solar Telescope

    CERN Document Server

    Zeng, Zhicheng; Ji, Haisheng; Goode, Philip R; Cao, Wenda

    2016-01-01

    Jets present ubiquitously in both quiet and active regions on the Sun. They are widely believed to be driven by magnetic reconnection. A fan-spine structure has been frequently reported in some coronal jets and flares, regarded as a signature of ongoing magnetic reconnection in a topology consisting of a magnetic null connected by a fan-like separatrix surface and a spine. However, for small-scale chromospheric jets, clear evidence of such structures is rather rare, although they are implied in earlier works that show an inverted-Y-shaped feature. Here we report high-resolution (0$"$.16) observations of a small-scale chromospheric jet obtained by the New Solar Telescope (NST) using 10830~{\\AA} filtergrams. Bi-directional flows were observed across the separatrix regions in the 10830~\\AA{} images, suggesting that the jet was produced due to magnetic reconnection. At the base of the jet, a fan-spine structure was clearly resolved by the NST, including the spine and the fan-like surface, as well as the loops bef...

  15. Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare

    Science.gov (United States)

    Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay, Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio; Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte

    2016-05-01

    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‑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.

  16. Chromospheric Jet and Growing "Loop" Observed by Hinode: New Evidence of Fan-Spine Magnetic Topology Resulting From Flux Emergence

    CERN Document Server

    Liu, Wei; Title, Alan M; Tarbell, Theodore D; Low, B C

    2010-01-01

    We present observations of a chromospheric jet and growing "loop" system that show new evidence of a fan-spine topology resulting from magnetic flux emergence. This event, occurring in an equatorial coronal hole on 2007 February 9, was observed by the Hinode Solar Optical Telescope in the Ca II H line in unprecedented detail. The predecessor of the jet is a bundle of fine material threads that extend above the chromosphere and appear to rotate about the bundle axis at ~50 km/s (period <200 s). These rotations or transverse oscillations propagate upward at velocities up to 786 km/s. The bundle first slowly and then rapidly swings up, with the transition occurring at the onset of an A4.9 flare. A loop expands simultaneously in these two phases (velocity: 16-135 km/s). Near the peak of the flare, the loop appears to rupture; simultaneous upward ejecta and mass downflows faster than free-fall appear in one of the loop legs. The material bundle then swings back in a whiplike manner and develops into a collimate...

  17. Hinode and IRIS observations of the magnetohydrodynamic waves propagating from the photosphere to the chromosphere in a sunspot

    CERN Document Server

    Kanoh, Ryuichi; Imada, Shinsuke

    2016-01-01

    Magnetohydrodynamic (MHD) waves have been considered as energy sources for heating the solar chromosphere and the corona. Although MHD waves have been observed in the solar atmosphere, there are lack of quantitative estimates on the energy transfer and dissipation in the atmosphere. We performed simultaneous Hinode and IRIS observations of a sunspot umbra to derive the upward energy fluxes at two different atmospheric layers (photosphere and lower transition region) and estimate the energy dissipation. The observations revealed some properties of the observed periodic oscillations in physical quantities, such as their phase relations, temporal behaviors, and power spectra, making a conclusion that standing slow-mode waves are dominant at the photosphere with their high frequency leakage, which is observed as upward waves at the chromosphere and the lower transition region. Our estimate of upward energy fluxes are $2.0\\times10^7$ erg cm$^{-2}$ s$^{-1}$ at the photospheric level and $8.3\\times10^4$ erg cm$^{-2}...

  18. Chromospheric activity and evolutionary age of the Sun and four solar twins

    Science.gov (United States)

    Mittag, M.; Schröder, K.-P.; Hempelmann, A.; González-Pérez, J. N.; Schmitt, J. H. M. M.

    2016-06-01

    Aims: The activity levels of the solar-twin candidates HD 101364 and HD 197027 are measured and compared with the Sun, the known solar twin 18 Sco, and the solar-like star 51 Peg. Furthermore, the absolute ages of these five objects are estimated from their positions in the HR diagram and the evolutionary (relative) age compared with their activity levels. Methods: To represent the activity level of these stars, the Mount Wilson S-indices were used. To obtain consistent ages and evolutionary advance on the main sequence, we used evolutionary tracks calculated with the Cambridge Stellar Evolution Code. Results: From our spectroscopic observations of HD 101364 and HD 197027 and based on the established calibration procedures, the respective Mount Wilson S-indices are determined. We find that the chromospheric activity of both stars is comparable with the present activity level of the Sun and that of 18 Sco, at least for the period in consideration. Furthermore, the absolute age of HD 101364, HD 197027, 51 Peg, and 18 Sco are found to be 7.2, 7.1, 6.1, and 5.1 Gyr, respectively. Conclusions: With the exception of 51 Peg, which has a significantly higher metallicity and a mass higher by about 10% than the Sun, the present Sun and its twins compare relatively well in their activity levels, even though the other twins are somewhat older. Even though 51 Peg has a similar age of 6.1 Gyr, this star is significantly less active. Only when we compare it on a relative age scale (which is about 20% shorter for 51 Peg than for the Sun in absolute terms) and use the higher-than-present long-term SMWO average of 0.18 for the Sun, does the S-index show a good correlation with evolutionary (relative) age. This shows that in the search for a suitably similar solar twin, the relative main-sequence age matters for obtaining a comparable activity level.

  19. Heating and ionization of stellar chromospheres by nonthermal proton beams: Implications for impulsive phase, redshifted Lyman-alpha radiation in stellar flares

    Science.gov (United States)

    Brosius, Jeffrey W.; Robinson, Richard D.; Maran, Stephen P.

    1995-01-01

    We investigate the physical basis for the timescale of impulsive-phase, redshifted Lyman-alpha emission in stellar flares on the assumption that it is determined by energy losses in a nonthermal proton beam that is penetrating the chromosphere from above. The temporal evolution of ionization and heating in representative model chromospheres subjected to such beams is calculated. The treatment of 'stopping' of beam protons takes into account their interactions with (1) electrons bound in neutral hydrogen, (2) nuclei of neutral hydrogen, (3) free electrons, and (4) ambient thermal protons. We find that, for constant incident beam flux, the system attains an equilibrium with the beam energy input to the chromosphere balanced by radiative losses. In equilibrium, the beam penetration depth is constant, and erosion of the chromosphere ceases. If the redshifted, impulsive-phase stellar flare Lyman-alpha emission is produced by downstreaming hydrogen formed through charge exchange between beam protons and ambient hydrogen, then the emission should end when the beam no longer reaches neutral hydrogen. The durations of representative emission events calculated on this assumption range from 0.1 to 14 s. The stronger the beam, the shorter the timescale over which the redshifted Lyman-alpha emission can be observed.

  20. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere VI. Helium in the Chromosphere

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-07-01

    Full Text Available Molecular hydrogen and hydrides have recently been advanced as vital agents in the generation of emission spectra in the chromosphere. This is a result of the role they play in the formation of condensed hydrogen structures (CHS within the chromosphere (P.M. Robitaille. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere IV. On the Nature of the Chromosphere. Progr. Phys., 2013, v. 3, 15–21. Next to hydrogen, helium is perhaps the most intriguing component in this region of the Sun. Much like other elements, which combine with hydrogen to produce hydrides, helium can form the well-known helium hydride molecular ion, HeH+, and the excited neutral helium hydride molecule, HeH∗. While HeH+ is hypothesized to be a key cosmologicalmolecule, its possible presence in the Sun, and that of its excited neutral counterpart, has not been considered. Still, these hydrides are likely to play a role in the synthesis of CHS, as the He I and He II emission lines strongly suggest. In this regard, the study of helium emission spectra can provide insight into the condensed nature of the Sun, especially when considering the 10830 Å line associated with the 23P→2 3S triplet state transition. This line is strong in solar prominences and can be seen clearly on the disk. The excessive population of helium triplet states cannot be adequately explained using the gaseous models, since these states should be depopulated by collisional processes. Conversely, when He-based molecules are used to build CHS in a liquid metallic hydrogen model, an ever increasing population of the 23S and 23P states might be expected. The overpopulation of these triplet states leads to the conclusion that these emission lines are unlikely to be produced through random collisional or photon excitation, as required by the gaseous models. This provides a significant hurdle for these models. Thus, the strong 23P→2 3S lines and the overpopulation of the helium triplet

  1. Studying Ca uc(ii) K Line Profile Shapes and Dynamic Processes in the Solar Chromosphere at the Base of a Coronal Hole

    Science.gov (United States)

    Grigoryeva, S. A.; Turova, I. P.; Ozhogina, O. A.

    2016-07-01

    We study Ca uc(ii) K profiles in structural features of the quiet chromosphere and plages using observations of two time series for two regions at the base of a coronal hole. One of the regions that we study has a low-brightness area where the reversal-free profile shape remains the same even over a spatial extent of about 16 arcsec. Such a profile shape is typical of low-temperature areas. The analysis of the spectral composition of oscillations has revealed that all the chromospheric structures feature various combinations of periods: 3, 4, 5, and long. One rarely finds only a single period. In same-type structures, we cannot single out a dominant highest-power period; such may be any of the above periods. Periodic brightenings of the violet peak in the Ca uc(ii) K wing occur in both internetwork and network areas. Moreover, they do not arise from purely 3-min oscillations. The integrated spectral power of oscillations throughout the whole area cut out by the spectrograph slit decreases with height from the temperature minimum region to the lower and middle chromosphere in 4.0 - 5.2 (4-min oscillations), 2.4 - 4.0 (5-min oscillations) and 1.1 - 16.0 mHz frequency bands. The oscillation power in the low-frequency band demonstrates a reverse tendency. The oscillation power in 5.2 - 6.8 mHz (3-min oscillations) decreases from the lower to middle chromosphere. This is the case for both regions at the base of a coronal hole. The integrated spectral power distribution in different chromospheric structures is complicated. Low-frequency oscillations are enhanced more often in peripheral areas of structures. Our observations do not corroborate the belief that 3-min oscillations prevail in internetwork and 5-min oscillations in network areas.

  2. Chromospheric imaging of the active binary system V 711 Tauri = HR 1099 in December 1992

    Science.gov (United States)

    Busà, I.; Pagano, I.; Rodonò, M.; Neff, J. E.; Lanzafame, A. C.

    1999-10-01

    Spectroscopic observations of the bright RS CVn-type system V 711 Tau = HR 1099 (K1 IV + G5 V) were obtained by IUE during the same period of a Multi-Site Continuous Spectroscopy (MUSICOS) campaign between 12-18 December 1992 (Huang et al. 1995). We report on the results of a ``Doppler Imaging" analysis of the Mg II h line. Broad, variable and extended wings have been detected and successfully fitted using a broad Gaussian, which accounts for a large fraction of flux from the global stellar Mg II h emission. This broad component is present in all spectra and presents velocity shifts with respect to the K1 star rest-frame that are variable in the range between -19 and +44 km s(-1) . Similar results have been obtained from Doppler Imaging of the other relevant chromospheric line (H_α) in other RS CVn stars ({c.f.} Hatzes, 1995 and Hatzes, 1998). Furthermore, our analysis suggests that these shifts could be due to rotational modulation produced by an active region, that essentially straddles the pole of the K1 star in which down-flows dominate on up-flows. Finally, emitting matter between the two stars has been detected, indicating that mass-exchange is present in the binary system. Five flare episodes with strong flux enhancements in several transition region lines were observed. These flares were preliminarily reported by Neff et al. (1995). We analyse in this paper the Mg II h and k line emission during the major of these five flare (1992 December 14), since only a weak enhancement was observed in the Mg II h and k lines during the other four flares. Spectral imaging of the Mg II lines during this flare indicates a flaring site on the visible K1 star hemisphere with mass ejection from the K1 star towards the G5 companion. The Mg II emission shows a large broadening with FWHM reaching 1000 km s(-1) at flare peak and decreasing to 700 km s(-1) two hours after the peak. Our analysis have been carried out using both IUESIPS and NEWSIPS processed spectra. We find that

  3. The quiescent chromospheres and transition regions of active dwarf stars - What are we learning from recent observations and models?

    Science.gov (United States)

    Linsky, J. L.

    1983-01-01

    Progress in understanding active dwarf stars based on recent IUE, Einstein, and ground-based observations is reviewed. The extent of magnetic field control over nonflare phenomena in active dwarf stars is considered, and the spatial homogeneity and time variability of active dwarf atmospheres is discussed. The possibility that solar like flux tubes can explain enhanced heating in active dwarf stars in examined, and the roles of systematic flows in active dwarf star atmospheres are considered. The relation between heating rates in different layers of active dwarf stars is summarized, and the mechanism of chromosphere and transition region heating in these stars are discussed. The results of one-component and two-component models of active dwarf stars are addressed.

  4. The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations

    Science.gov (United States)

    Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.; Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.; Nestoras, I.

    2010-01-01

    The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT succeeded in obtaining the first ever subarcsecond ( 0.5^'' ) images of this region with high sensitivity and cadence. Detailed analyses of those observations contributed significantly to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly α atmosphere as revealed by the VAULT observations and bring together past results and new analyses from the second VAULT flight to create a synthesis of our current knowledge of the high-resolution Ly α Sun. We hope that this work will serve as a good reference for the design of upcoming Ly α telescopes and observing plans.

  5. The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations

    CERN Document Server

    Vourlidas, A; Landi, E; Patsourakos, S; Teriaca, L; Schühle, U; Korendyke, C M; Nestoras, I

    2009-01-01

    The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly-a line at 1216 {\\AA}. In two flights, VAULT succeeded in obtaining the first ever sub-arcsecond (0.5") images of this region with high sensitivity and cadence. Detailed analyses of those observations have contributed significantly to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly-a atmosphere as revealed by the VAULT observations, and bring together past results and new analyses from the second VAULT flight to create a synthesis of our current knowledge of the high-resolution Ly-a Sun. We hope that this work will serve as a good reference for the design of upcoming Ly-a telescopes and observing plans.

  6. RHESSI AND SDO/AIA OBSERVATIONS OF THE CHROMOSPHERIC AND CORONAL PLASMA PARAMETERS DURING A SOLAR FLARE

    International Nuclear Information System (INIS)

    X-ray and extreme ultraviolet (EUV) observations are an important diagnostic of various plasma parameters of the solar atmosphere during solar flares. Soft X-ray and EUV observations often show coronal sources near the top of flaring loops, while hard X-ray emission is mostly observed from chromospheric footpoints. Combining RHESSI with simultaneous Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) observations, it is possible for the first time to determine the density, temperature, and emission profile of the solar atmosphere over a wide range of heights during a flare, using two independent methods. Here we analyze a near limb event during the first of three hard X-ray peaks. The emission measure, temperature, and density of the coronal source is found using soft X-ray RHESSI images while the chromospheric density is determined using RHESSI visibility analysis of the hard X-ray footpoints. A regularized inversion technique is applied to AIA images of the flare to find the differential emission measure (DEM). Using DEM maps, we determine the emission and temperature structure of the loop, as well as the density, and compare it with RHESSI results. The soft X-ray and hard X-ray sources are spatially coincident with the top and bottom of the EUV loop, but the bulk of the EUV emission originates from a region without cospatial RHESSI emission. The temperature analysis along the loop indicates that the hottest plasma is found near the coronal loop-top source. The EUV observations suggest that the density in the loop legs increases with increasing height while the temperature remains constant within uncertainties.

  7. Chromospheric Jet and Growing "Loop" Observed by Hinode: New Evidence of Fan-spine Magnetic Topology Resulting from Flux Emergence

    Science.gov (United States)

    Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell, Theodore D.; Low, B. C.

    2011-02-01

    We present observations of a chromospheric jet and growing "loop" system that show new evidence of a fan-spine topology resulting from magnetic flux emergence. This event, occurring in an equatorial coronal hole on 2007 February 9, was observed by the Hinode Solar Optical Telescope in the Ca II H line in unprecedented detail. The predecessor of the jet is a bundle of fine material threads that extend above the chromosphere and appear to rotate about the bundle axis at ~50 km s-1 (period lsim200 s). These rotations or transverse oscillations propagate upward at velocities up to 786 km s-1. The bundle first slowly and then rapidly swings up, with the transition occurring at the onset of an A4.9 flare. A loop expands simultaneously in these two phases (velocity: 16-135 km s-1). Near the peak of the flare, the loop appears to rupture; simultaneous upward ejecta and mass downflows faster than free-fall appear in one of the loop legs. The material bundle then swings back in a whip-like manner and develops into a collimated jet, which is orientated along the inferred open-field lines with transverse oscillations continuing at slower rates. Some material falls back along smooth streamlines, showing no more oscillations. At low altitudes, the streamlines bifurcate at presumably a magnetic null point and bypass an inferred dome, depicting an inverted-Y geometry. These streamlines closely match in space the late Ca II H loop and X-ray flare loop. These observations are consistent with the model that flux emergence in an open-field region leads to magnetic reconnection, forming a jet and fan-spine topology. We propose that the material bundle and collimated jet represent the outer spine in quasi-static and eruptive stages, respectively, and the growing loop is a two-dimensional projection of the three-dimensional fan surface.

  8. The collisional interaction of a beam of charged particles with a hydrogen target of arbitrary ionization level. [chromospheric heating during solar flares

    Science.gov (United States)

    Emslie, A. G.

    1978-01-01

    The classical theory of scattering under the Coulomb potential of both charged and neutral particles is used to derive formulae for the energy deposition rate and mean scattering of a beam of charged particles interacting with a cold hydrogen target of arbitrary ionization level as a function of the column density traversed by the beam. These general results hold for any form of stable injection energy spectrum, and their relevance to the existing literature on chromospheric heating during solar flares is discussed.

  9. Analysis of flares in the chromosphere and corona of main- and pre-main-sequence M-type stars

    Science.gov (United States)

    Crespo-Chacón, I.

    2015-11-01

    This Ph.D. Thesis revolves around flares on main- and pre-main-sequence M-type stars. We use observations in different wavelength ranges with the aim of analysing the effects of flares at different layers of stellar atmospheres. In particular, optical and X-ray observations are used so that we can study how flares affect, respectively, the chromosphere and the corona of stars. In the optical range we carry out a high temporal resolution spectroscopic monitoring of UV Ceti-type stars aimed at detecting non-white-light flares (the most typical kind of solar flares) in stars other than the Sun. With these data we confirm that non-white-light flares are a frequent phenomenon in UV Ceti-type stars, as observed in the Sun. We study and interpret the behaviour of different chromospheric lines during the flares detected on AD Leo. By using a simplified slab model of flares (Jevremović et al. 1998), we are able to determine the physical parameters of the chromospheric flaring plasma (electron density and electron temperature), the temperature of the underlying source, and the surface area covered by the flaring plasma. We also search for possible relationships between the physical parameters of the flaring plasma and other properties such as the flare duration, area, maximum flux and released energy. This work considerably extends the existing sample of stellar flares analysed with good quality spectroscopy in the optical range. In X-rays we take advantage of the great sensitivity, wide energy range, high energy resolution, and continuous time coverage of the EPIC detectors - on-board the XMMNewton satellite - in order to perform time-resolved spectral analysis of coronal flares. In particular, in the UV Ceti-type star CC Eri we study two flares that are weaker than those typically reported in the literature (allowing us to speculate about the role of flares as heating agents of stellar atmospheres); while in the pre-main-sequence M-type star TWA 11B (with no signatures of

  10. Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

    Science.gov (United States)

    Gömöry, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K.

    2016-04-01

    Aims: We study the response of the solar atmosphere during a GOES M1.6 flare using spectroscopic and imaging observations. In particular, we examine the evolution of the mass flows and electron density together with the energy input derived from hard X-ray (HXR) in the context of chromospheric evaporation. Methods: We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer in the Fe xiii 202.044 Å (log T = 6.2) and Fe xvi 262.980 Å (log T = 6.4) spectral lines to derive temporal variations of the line intensity, Doppler shifts, and electron density during the flare. We combined these data with HXR measurements acquired with RHESSI to derive the energy input to the lower atmosphere by flare-accelerated electrons. Results: During the flare impulsive phase, we observe no significant flows in the cooler Fe xiii line but strong upflows, up to 80-150 km s-1, in the hotter Fe xvi line. The largest Doppler shifts observed in the Fe xvi line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe xiii line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01 × 109 cm-3 to 3.16 × 1010 cm-3 during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34 × 1010 erg s-1 cm-2 for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of ~15 km s-1 that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km s-1 for the upflowing filament material. Conclusions: The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the

  11. Temporal Evolution of Chromospheric Evaporation: Case Studies of the M1.1 Flare on 2014 September 6 and X1.6 Flare on 2014 September 10

    Science.gov (United States)

    Tian, Hui; Young, Peter R.; Reeves, Katharine K.; Chen, Bin; Liu, Wei; McKillop, Sean

    2015-10-01

    With observations from the Interface Region Imaging Spectrograph, we track the complete evolution of ˜11 MK evaporation flows in an M1.1 flare on 2014 September 6 and an X1.6 flare on 2014 September 10. These hot flows, as indicated by the blueshifted Fe xxi 1354.08 Å line, evolve smoothly with a velocity decreasing exponentially from ˜200 km s-1 to almost stationary within a few minutes. We find a good correlation between the flow velocity and energy deposition rate as represented by the hard X-ray flux observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager, or time derivative of the soft X-ray flux observed with the Geostationary Operational Environmental Satellites and the HINODE X-ray Telescope, which is in general agreement with models of nonthermal electron heating. The maximum blueshift of Fe xxi appears approximately at the same time as or slightly after the impulsive enhancement of the ultraviolet continuum and the Mg ii 2798.8 Å line emission, demonstrating that the evaporation flow is closely related to heating of the lower chromosphere. Finally, while the hot Fe xxi 1354.08 Å line is entirely blueshifted with no obvious rest component, cool chromospheric and transition region lines like Si iv 1402.77 Å are often not entirely redshifted but just reveal an obvious red wing enhancement at the ribbons, suggesting that the speed of chromospheric condensation might be larger than previously thought.

  12. The chromospheric Ca II and Mg II radiative losses in late-type stars: a computational comparison between two-level and multi-level atomic models

    Science.gov (United States)

    Fawzy, Diaa E.

    2015-06-01

    In the current study we present radiation correction factors to compute the radiative losses by Mg II and Ca II ions during the process of constructing theoretical models for the chromospheres in late-type stars (spectral type in the range F5V-K8V). We combine the two-level atom approach with the multi-level atom method to accurately compute the radiation correction factors. The procedure is fast and reasonably accurate to be implemented in the time-dependent computations. In the current computations we implement what is called pseudo-partial frequency redistribution and the time-dependent ionization in regard to hydrogen. The radiative correction factors for Mg II show very slight variation for the different spectral types with average value of 1.5. The values we obtained for Ca II show very strong dependence on spectral types and the basic parameters, with values range between 5.58 to 4.22 for F5V and K8V spectral types, respectively. The obtained results accelerate the process of constructing theoretical model chromospheres based on mechanical heating by monochromatic and wave spectra. The current study is an initial step in establishing hybrid multi-dimensional models of stellar chromospheres.

  13. HiRISE/NEOCE: an ESA M5 formation flying proposed mission combining high resolution and coronagraphy for ultimate observations of the chromosphere, corona and interface

    Science.gov (United States)

    Damé, Luc; Von Fay-Siebenburgen (Erdélyi), Robert

    2016-07-01

    The global understanding of the solar environment through the magnetic field emergence and dissipation, and its influence on Earth, is at the centre of the four major thematics addressed by HiRISE/NEOCE (High Resolution Imaging and Spectroscopy Explorer/New Externally Occulted Coronagraph Experiment). They are interlinked and also complementary: the internal structure of the Sun determines the surface activity and dynamics that trigger magnetic field structuring which evolution, variation and dissipation will, in turn, explain the coronal heating onset and the major energy releases that feed the influence of the Sun on Earth. The 4 major themes of HiRISE/NEOCE are: - fine structure of the chromosphere-corona interface by 2D spectroscopy in FUV at very high resolution; - coronal heating roots in inner corona by ultimate externally-occulted coronagraphy; - resolved and global helioseismology thanks to continuity and stability of observing at L1 Lagrange point; - solar variability and space climate with a global comprehensive view of UV variability as well. Recent missions have shown the definite role of waves and of the magnetic field deep in the inner corona, at the chromosphere-corona interface, where dramatic changes occur. The dynamics of the chromosphere and corona is controlled by the emerging magnetic field, guided by the coronal magnetic field. Accordingly, the direct measurement of the chromospheric and coronal magnetic fields is of prime importance. This is implemented in HiRISE/NEOCE, to be proposed for ESA M5 ideally placed at the L1 Lagrangian point, providing FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, and ultimate coronagraphy by a remote external occulter (two satellites in formation flying 375 m apart minimizing scattered light) allowing to characterize temperature, densities and velocities up to the solar upper chromosphere, transition zone and inner corona with, in particular, 2D very high resolution multi

  14. Photometric properties of solar H alpha Fabry-Perot etalons. Application to the analysis of the chromospheric fringe

    CERN Document Server

    Bazin, Cyril

    2012-01-01

    We consider the use of the commercially available Fabry-Perot etalons (FP) for the imaging of the solar chromosphere in the H line of HI. Three etalons of 40, 60 and 90 mm of diameter were evaluated and accurately analysed. At normal incidence the maximum transmission wavelength is 656.285 nm for the 60 and 40 mm etalons FP. The finesse has been evaluated at 13.3 for the FP 60mm, 8.7 for the FP 40 and 13.9 for the FP 90 mm. Shifts of the central wavelength as a function of the incidence angle were accurately measured. Polynomial curves precisely giving the transmitted central wavelength variations when using a quasi-parallel beam from a point-like source are presented. Further calibrations have been done with a photometric accuracy using i/ a 16 bits CCD camera; ii/ a Littrow spectrograph of a spectral power 110000, a linear dispersion giving a 0.0058 nm/pixel resolution and iii/ feed by an artificial Sun used as a light source and iv/ precisely adjustable in position optical components. The precise laborator...

  15. Retrospective Conversion of Solar Data Printed in "Synoptic Maps of the Solar Chromosphere": A Scientific and Librarianship Project

    Science.gov (United States)

    Laurenceau, A.; Aboudarham, J.; Renié, C.

    2015-04-01

    Between 1928 and 2003, the Observatoire de Paris published solar activity maps and their corresponding data tables, first in the Annals of the Meudon Observatory, then in the Synoptic Maps of the Solar Chromosphere. These maps represent the main solar structures in a single view and spread out on a complete Carrington rotation as well as tables of associated data, containing various information on these structures such as positions, length, morphological characteristics, and behavior. Since 2003, these maps and data tables have not been released in print, as they are only published on the online BASS2000 database, the solar database maintained by LESIA (Laboratory for space studies and astrophysical instruments). In order to make the first 80 years of observations which were available only in paper accessible and usable, the LESIA and the Library of the Observatory have started a project to digitize the publications, enter the data with the assistance of a specialized company, and then migrate the files obtained in BASS2000 and in the Heliophysics Features Catalog created in the framework of the European project HELIO.

  16. Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare

    CERN Document Server

    Dudik, Jaroslav; Janvier, Miho; Mulay, Sargam M; Karlicky, Marian; Aulanier, Guillaume; Del Zanna, Giulio; Dzifcakova, Elena; Mason, Helen E; Schmieder, Brigitte

    2016-01-01

    We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. The slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions towards both ends of the ribbons. Velocities of 20--40 km\\,s$^{-1}$ 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 \\textit{IRIS} slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromosph...

  17. Radial Velocity Variations of Photometrically Quiet, Chromospherically Inactive Kepler Stars: A Link Between RV Jitter and Photometric Flicker

    CERN Document Server

    Bastien, Fabienne A; Pepper, Joshua; Wright, Jason T; Aigrain, Suzanne; Basri, Gibor; Johnson, John A; Howard, Andrew W; Walkowicz, Lucianne M

    2013-01-01

    We compare stellar photometric variability, as measured from Kepler light curves by Basri et al. (2011), with measurements of radial velocity (RV) root-mean-square (RMS) variations of all California Planet Search overlap stars. We newly derive rotation periods from the Kepler light curves for all of the stars in our study sample. The RV variations reported herein range from less than 4 m/s to 135 m/s, yet the stars all have amplitudes of photometric variability less than 3 mmag, reflecting the preference of the RV program for chromospherically "quiet" stars. Despite the small size of our sample, we find with high statistical significance that the RV RMS manifests strongly in the Fourier power spectrum of the light curve: stars that are noisier in RV have a greater number of frequency components in the light curve. We also find that spot models of the observed light curves systematically underpredict the observed RV variations by factors of ~2--1000, likely because the low level photometric variations in our s...

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

    International Nuclear Information System (INIS)

    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 × 1031 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 × 1030 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.

  19. Radial velocity variations of photometrically quiet, chromospherically inactive Kepler stars: A link between RV jitter and photometric flicker

    Energy Technology Data Exchange (ETDEWEB)

    Bastien, Fabienne A.; Stassun, Keivan G.; Pepper, Joshua [Physics and Astronomy Department, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Wright, Jason T. [Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16803 (United States); Aigrain, Suzanne [Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom); Basri, Gibor [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Johnson, John A. [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States)

    2014-02-01

    We compare stellar photometric variability, as measured from Kepler light curves by Basri et al., with measurements of radial velocity (RV) rms variations of all California Planet Search overlap stars. We newly derive rotation periods from the Kepler light curves for all of the stars in our study sample. The RV variations reported herein range from less than 4 to 135 m s{sup –1}, yet the stars all have amplitudes of photometric variability less than 3 mmag, reflecting the preference of the RV program for chromospherically 'quiet' stars. Despite the small size of our sample, we find with high statistical significance that the RV rms manifests strongly in the Fourier power spectrum of the light curve: stars that are noisier in RV have a greater number of frequency components in the light curve. We also find that spot models of the observed light curves systematically underpredict the observed RV variations by factors of ∼2-1000, likely because the low-level photometric variations in our sample are driven by processes not included in simple spot models. The stars best fit by these models tend to have simpler light curves, dominated by a single relatively high-amplitude component of variability. Finally, we demonstrate that the RV rms behavior of our sample can be explained in the context of the photometric variability evolutionary diagram introduced by Bastien et al. We use this diagram to derive the surface gravities of the stars in our sample, revealing many of them to have moved off the main sequence. More generally, we find that the stars with the largest RV rms are those that have evolved onto the 'flicker floor' sequence in that diagram, characterized by relatively low amplitude but highly complex photometric variations which grow as the stars evolve to become subgiants.

  20. 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.

  1. Radial velocity variations of photometrically quiet, chromospherically inactive Kepler stars: A link between RV jitter and photometric flicker

    International Nuclear Information System (INIS)

    We compare stellar photometric variability, as measured from Kepler light curves by Basri et al., with measurements of radial velocity (RV) rms variations of all California Planet Search overlap stars. We newly derive rotation periods from the Kepler light curves for all of the stars in our study sample. The RV variations reported herein range from less than 4 to 135 m s–1, yet the stars all have amplitudes of photometric variability less than 3 mmag, reflecting the preference of the RV program for chromospherically 'quiet' stars. Despite the small size of our sample, we find with high statistical significance that the RV rms manifests strongly in the Fourier power spectrum of the light curve: stars that are noisier in RV have a greater number of frequency components in the light curve. We also find that spot models of the observed light curves systematically underpredict the observed RV variations by factors of ∼2-1000, likely because the low-level photometric variations in our sample are driven by processes not included in simple spot models. The stars best fit by these models tend to have simpler light curves, dominated by a single relatively high-amplitude component of variability. Finally, we demonstrate that the RV rms behavior of our sample can be explained in the context of the photometric variability evolutionary diagram introduced by Bastien et al. We use this diagram to derive the surface gravities of the stars in our sample, revealing many of them to have moved off the main sequence. More generally, we find that the stars with the largest RV rms are those that have evolved onto the 'flicker floor' sequence in that diagram, characterized by relatively low amplitude but highly complex photometric variations which grow as the stars evolve to become subgiants.

  2. The VAULT2.0 Observing Campaign: A Comprehensive Investigation of the Chromosphere-Corona Interface at Sub-arcsecond scales

    Science.gov (United States)

    Vourlidas, A.; Korendyke, C.; Tun-Beltran, S. D.; Ugarte-Urra, I.; Morrill, J. S.; Warren, H. P.; Young, P.; De Pontieu, B.; Gauzzi, G.; Reardon, K.

    2014-12-01

    We report the first results from an observing campaign in support of the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0 is a Lya (1216Å) spectroheliograph capable of 0.3" (~250 km) spatial resolution. The objective of the VAULT2.0 project is the study of the chromosphere-corona interface. This interface has acquired renewed emphasis over the last few years, thanks to high-resolution observations from Hinode/SOT and EIS instruments and the Lya imaging from the two VAULT flights. The observations have shown that the upper chromosphere may play a more important role in heating the corona and in affecting EUV observations that previously thought: (1) by supplying the mass via Type-II spicules and, (2) by absorbing coronal emission. Many of the required clues for further progress are located in sub-arcsecond structures with temperatures between 10000 and 50000 K, a regime not accessible by Hinode or SDO. Lyman-alpha observations are, therefore, ideal, for filling in this gap. The observing campaign in support of the VAULT2.0 is closely coordinated with the Hinode and IRIS missions to study the mass/energy flow from the chromosphere to the corona with joint observations of type-II spicules, and the magnetic connectivity of coronal loops using the full imaging and spectral capabilities of IRIS, Hinode and SDO. Several ground-based observatories also provide important observations (IBIS, BBSO, SOLIS). The VAULT2.0 project is funded by the NASA LCAS program.

  3. The VAULT2.0 Observing Campaign: The First Comprehensive Investigation of the Chromosphere-Corona Interface at Sub-arcsecond scales

    Science.gov (United States)

    Vourlidas, A.; Korendyke, C.; Tun, S.; Ugarte-Urra, I.; Chua, D. H.; Morrill, J. S.; Warren, H. P.; Young, P.; Landi, E.; De Pontieu, B.; Cauzzi, G.; Reardon, K.

    2013-12-01

    We report the first results from an observing campaign in support of the VAULT2.0 sounding rocket launch. VAULT2.0 is a Lya (1216Å) spectroheliograph capable of 0.3' (~250 km) spatial resolution. The objective of the VAULT2.0 project is the study of the chromosphere-corona interface. This interface has acquired renewed emphasis over the last few years, thanks to high-resolution observations from Hinode/SOT and EIS instruments and the Lya imaging from the two VAULT flights. The observations have shown that the upper chromosphere may play a more important role in heating the corona and in affecting EUV observations that previously thought: (1) by supplying the mass via Type-II spicules and, (2) by absorbing coronal emission. Many of the required clues for further progress are located in sub-arcsecond structures with temperatures between 10000 and 50000 K, a regime not accessible by Hinode or SDO. Lyman-alpha observations are, therefore, ideal, for filling in this gap. The observing campaign in support of the VAULT2.0 is closely coordinated with the Hinode and IRIS missions to study the mass/energy flow from the chromosphere to the corona with joint observations of type-II spicules, and the magnetic connectivity of coronal loops using the full imaging and spectral capabilities of IRIS, Hinode and SDO. Several ground-based observatories also provide important observations (IBIS, BBSO, SOLIS). The VAULT2.0 project is funded by the NASA LCAS program. The upgraded payload, VAULT2.0, is ideally suited to address this questions because it observes in a unique line, unavailable elsewhere, it's the only other space telescope with spatial resolution comparable to that of the Hinode instruments, and the science objectives are well suited to the short time span of a rocket flight.

  4. Stellar model chromospheres. IV - The formation of the H-epsilon feature in the sun /G2 V/ and Arcturus /K2 III/

    Science.gov (United States)

    Ayres, T. R.; Linsky, J. L.

    1975-01-01

    The formation of the Balmer-series member H-epsilon in the near-red wing of the Ca II H line is discussed for two cases: the sun (H-epsilon absorption profile) and Arcturus (H-epsilon emission profile). It is shown that although the H-epsilon source functions in both stars are dominated by the Balmer-continuum radiation field through photoionizations, the line-formation problems in the two stars are quantitatively different, owing to a substantial difference in the relative importance of the stellar chromosphere temperature inversion as compared with the stellar photosphere.

  5. Stellar model chromospheres. IV. The formation of the Hepsilon feature in the Sun (G2 V) and Arcturus (K2 III)

    International Nuclear Information System (INIS)

    The formation of the Balmer series member Hepsilon in the near red wing of the Ca ii H line is discussed for two cases: the Sun (Hepsilon absorption profile) and Arcturus (Hepsilon absorption profile). It is shown that although the Hepsilon source functions in both stars are dominated by the Balmer continuum radiation field through photoionizations, the line formation problems in the two stars are quantitatively different, owing to a substantial difference in the relative importance of the stellar chromosphere temperature inversion compared with the stellar photosphere

  6. What Goes Up Doesn't Necessarily Come Down! - Connecting the Dynamics of the Chromosphere and Transition Region with TRACE, Hinode and SUMER

    OpenAIRE

    McIntosh, S. W.; Pontieu, Bart de

    2009-01-01

    We explore joint observations of the South-East limb made by Hinode, TRACE and SOHO/SUMER on April 12, 2008 as part of the Whole Heliosphere Interval (WHI) Quiet Sun Characterization targeted observing program. During the sequence a large, 10Mm long, macro-spicule was sent upward and crossed the line-of-sight of the SUMER slit, an event that affords us an opportunity to study the coupling of cooler chromospheric material to transition region emission formed as hot as 600,000K. This short arti...

  7. What Goes Up Doesn't Necessarily Come Down! - Connecting the Dynamics of the Chromosphere and Transition Region with TRACE, Hinode and SUMER

    CERN Document Server

    McIntosh, S W

    2009-01-01

    We explore joint observations of the South-East limb made by Hinode, TRACE and SOHO/SUMER on April 12, 2008 as part of the Whole Heliosphere Interval (WHI) Quiet Sun Characterization targeted observing program. During the sequence a large, 10Mm long, macro-spicule was sent upward and crossed the line-of-sight of the SUMER slit, an event that affords us an opportunity to study the coupling of cooler chromospheric material to transition region emission formed as hot as 600,000K. This short article provides preliminary results of the data analysis.

  8. A coordinated optical and X-ray spectroscopic campaign on HD179949: searching for planet-induced chromospheric and coronal activity

    OpenAIRE

    Scandariato, G.; Maggio, A.; Lanza, A. F.; Pagano, I.; Fares, R.; Shkolnik, E. L.; Bohlender, D.; Cameron, A. C.; Dieters, S.; Donati, J.-F.; Martínez Fiorenzano, A. F.; Jardine, M.; Moutou, C.

    2013-01-01

    Context. HD 179949 is an F8V star, orbited by a close-in giant planet with a period of ~3 days. Previous studies suggested that the planet enhances the magnetic activity of the parent star, producing a chromospheric hot spot which rotates in phase with the planet orbit. However, this phenomenon is intermittent since it was observed in several but not all seasons. Aims. A long-term monitoring of the magnetic activity of HD 179949 is required to study the amplitude and time scales of star-plane...

  9. Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832

    CERN Document Server

    Fontenla, J M; Witbrod, Jesse; France, Kevin; Buccino, A; Mauas, Pablo; Vietes, Mariela; Walkowicz, Lucianne M

    2016-01-01

    Stellar radiation from X-rays to the visible provides the energy that controls the photochemistry and mass loss from exoplanet atmospheres. The important extreme ultraviolet (EUV) region (10--91.2~nm) is inaccessible and should be computed from a reliable stellar model. It is essential to understand the formation regions and physical processes responsible for the various stellar emission features in order to predict how the spectral energy distribution varies with age and activity levels. We compute a state-of-the-art semi-empirical atmospheric model and the emergent high-resolution synthetic spectrum of the moderately active M2~V star GJ~832 as the first of a series of models for stars with different activity levels. Using non-LTE radiative transfer techniques and including many molecular lines, we construct a one-dimensional simple model for the physical structure of the star's chromosphere, chromosphere-corona transition region, and corona. The synthesized spectrum for this model fits the continuum and lin...

  10. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere I. Continuous Emission and Condensed Matter Within the Chromosphere

    Directory of Open Access Journals (Sweden)

    Robitaille P.-M.

    2013-07-01

    Full Text Available The continuous spectrum of the solar photosphere stands as the paramount observation with regard to the condensed nature of the solar body. Studies relative to Kirchhoff’s law of thermal emission (e.g. Robitaille P.-M. Kirchhoff’s law of thermal emission: 150 years. Progr. Phys., 2009, v. 4, 3–13. and a detailed analysis of the stellar opacity problem (Robitaille P.M. Stellar opacity: The Achilles’ heel of the gaseous Sun. Progr. Phys., 2011, v. 3, 93–99 have revealed that gaseous models remain unable to properly account for the generation of this spectrum. Therefore, it can be stated with certainty that the photosphere is comprised of condensed matter. Beyond the solar surface, the chromospheric layer of the Sun also generates a weak continuous spectrum in the visible region. This emission exposes the presence of material in the condensed state. As a result, above the level of the photosphere, matter exists in both gaseous and condensed forms, much like within the atmosphere of the Earth. The continuous visible spectrum associated with the chromosphere provides the twenty-sixth line of evidence that the Sun is condensed matter.

  11. Separation of low first ionization potential ions from high first ionization potential neutrals in the low chromosphere

    Science.gov (United States)

    Athay, R. Grant

    1994-03-01

    Spectroscopic data from two flights of the Naval Research Laboratory's High Resolution Telescope and Spectrograph (HRTS) are analyzed for evidence of variations in relative abundances in the low chromosphere. Comparisons of sunspot, active region, and quiet-Sun data from HRTS II reveal decreases of intensities of sunspot lines from the first ionization stages of elements with low first ionization potential relative to both the active region and the quiet Sun. C I lines, however, are more intense in the sunspot than either the active region or the quiet Sun. Within a sunspot in Spacelab II data, the C I line at 156.1 nm is near its average intensity, whereas the Fe II line at 156.3 is much weaker than average. Both spots suggest a relative high value for the C I/Fe II abundance ratio. Within the zone of the same magnetic polarity as the sunspot (leading polarity) in the Spacelab II data, the brightest plages in C I show large C I/Fe II intensity ratios similar to those found in the sunspot. By contrast, the zones of following polarity on either side of the leading polarity show several well-defined areas of unusually low C I/Fe II intensity ratios associated with dark features in C I. The plages within these same zones have near normal or somewhat enhanced values for the C I/Fe II intensity ratios. It is noteworthy, also, that many of the brightest areas in C I do not coincide spatially with the brightest regions in Fe II. Neither do the darkest areas in C I align well with the darkest areas in Fe II. The association of high C I/Fe II intensity ratios with the zone of leading polarity and low-intensity ratios with zones of following polarity suggests that the iron abundance is dependent on the field polarity and is relatively low in the sunspot and the brighter plages in the zone of leading polarity and relatively high in C I dark flocculi in zones of following polarity. Failure of the brightest and darkest features in C I to align with the brightest and darkest

  12. Solar Imagery - Chromosphere - Calcium

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of full-disk images of the sun in Calcium (Ca) II K wavelength (393.4 nm). Ca II K imagery reveal magnetic structures of the sun from about...

  13. Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response

    International Nuclear Information System (INIS)

    State-of-the-art solar instrumentation is now revealing magnetic activity of the Sun with unprecedented temporal and spatial resolutions. Observations with the 1.6 m aperture New Solar Telescope (NST) of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research topics of high-resolution solar physics. As part of a joint observing program with NASA's Interface Region Imaging Spectrograph (IRIS) mission on 2013 August 7, the NST observed active region NOAA 11,810 in the photospheric TiO 7057 Å band with a resolution of pixel size of 0.''034 and chromospheric He I 10830 Å and Hα 6563 Å wavelengths. Complementary data are provided by the Solar Dynamics Observatory (SDO) and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing granular alignments and interacting with the preexisting ambient field in the upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the He I 10830 Å data (bandpass of 0.05 Å). The IRIS transition region imaging caught ejection of a hot plasma jet associated with the He I surge. The SDO/HMI data used to study the evolution of the magnetic and Doppler velocity fields reveal emerging magnetic loop-like structures. Hinode/Ca II H and IRIS filtergrams detail the connectivities of the newly emerged magnetic field in the lower solar chromosphere. From these data, we find that the orientation of the emerging magnetic field lines from a twisted flux tube formed an angle of ∼45° with the overlying ambient field. Nevertheless, the interaction of emerging magnetic field lines with the pre-existing overlying field generates high-temperature emission regions and boosts the

  14. Temporal evolution of chromospheric evaporation: case studies of the M1.1 flare on 2014 September 6 and X1.6 flare on 2014 September 10

    CERN Document Server

    Tian, Hui; Reeves, Katharine K; Chen, Bin; Liu, Wei; McKillop, Sean

    2015-01-01

    Observations from IRIS allow us to study the chromospheric heating and evaporation processes during solar flares with unprecedented high resolution and high cadence. We track the complete evolution of ~11 MK evaporation flows in the M1.1 flare on 2014 September 6 and the X1.6 flare on 2014 September 10. These hot flows, as indicated by the entirely blueshifted Fe xxi 1354.08 emission line, evolve smoothly with a velocity decreasing from ~200 km/s to almost stationary within a few minutes. The velocity decrease appears to be exponential in time, especially for the X1.6 flare. There is a good correlation between the flow velocity and the energy deposition rate as represented by the RHESSI hard X-Ray flux, or the time derivative of the soft X-Ray flux observed by GOES and the HINODE/XRT, which is in general agreement with models of nonthermal electron heating. The maximum blue shift of Fe xxi appears approximately at the same time as or slightly after the impulsive enhancement of the UV continuum and the Mg ii 2...

  15. Photospheric and chromospheric magnetic activity of seismic solar analogs. Observational inputs on the solar/stellar connection from Kepler and Hermes

    CERN Document Server

    Salabert, D; Beck, P G; Egeland, R; Palle, P L; Mathur, S; Metcalfe, T S; Nascimento, J -D do; Ceillier, T; Andersen, M F; Hage, A Trivino

    2016-01-01

    We identify a set of 18 solar analogs among the seismic sample of solar-like stars observed by the Kepler satellite rotating between 10 and 40 days. This set is constructed using the asteroseismic stellar properties derived using either the global oscillation properties or the individual acoustic frequencies. We measure the magnetic activity properties of these stars using observations collected by the photometric Kepler satellite and by the ground-based, high-resolution Hermes spectrograph mounted on the Mercator telescope. The photospheric (Sph) and chromospheric (S index) magnetic activity levels of these seismic solar analogs are estimated and compared in relation to the solar activity. We show that the activity of the Sun is comparable to the activity of the seismic solar analogs, within the maximum-to-minimum temporal variations of the 11-year solar activity cycle 23. In agreement with previous studies, the youngest stars and fastest rotators in our sample are actually the most active. The activity of s...

  16. Chromospheric magnetic field of an active region filament using the He I triplet and the primary observation of filaments (prominences) using New Vacuum Solar Tower of China

    Science.gov (United States)

    Xu, Zhi; Lagg, A.; Solanki, S.; Liu, Z.; New Vacuum Solar Telescope Observers

    2013-07-01

    There are two parts in my presentation. In the first part I present the magnetic field measurement of an active region filament using the full Stokes profiles of He I 10830 and Si I 10827 band when the filament in its stable phase. This observation was fulfilled using German Vacuum Tower Telescope (VTT). The vector magnetic field and Doppler velocity map both in the photosphere and chromosphere were observed and analyzed co-temporally and co-spatially. The observation findings reveal that we were observing the emergence of a flux rope with a subsequent formation of a filament. In the second part, I would like to exhibit another ground-based observation facility, 1m New Vacuum Solar Telescope (NVST) located in Fu-Xian Lake Solar Observatory of China. After the basic introduction including the location and instrumentations, I give some high lights including granulation, faculae, micro-flares, jets, and filaments or prominence since the first running in 2010, showing our potential ability to do high-resolution solar observation from the ground. Observation proposals from the international solar community are well appreciated in future.

  17. Numerical MHD Simulation of the Coupled Evolution of Collisional Plasma and Magnetic Field in the Solar Chromosphere. I. Gradual and Impulsive Energisation

    CERN Document Server

    Alekseeva, L M

    2015-01-01

    The dynamical coupling between the solar chromospheric plasma and magnetic field is investigated by numerically solving a fully self-consistent, two-dimensional initial-value problem for the nonlinear collisional MHD equations including electric resistivity, thermal conduction, and, in some cases, gas-dynamic viscosity. The processes in the contact zone between two horizontal magnetic fields of opposite polarities are considered. The plasma is assumed to be initially motionless and having a temperature of 50,000 K uniform throughout the plasma volume; the characteristic magnetic field corresponds to a plasma $\\beta\\gtrsim 1$. In a physical-time interval of 17~seconds typically covered by a computational run, the plasma temperature gradually increases by a factor of two to three. Against this background, an impulsive (in 0.1 seconds or less) increase in the current-aligned plasma velocity occurs at the site of the current-layer thinning (sausage-type deformation, or $m=0$ pinch instability). Such a "velocity b...

  18. Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response

    CERN Document Server

    Dominguez, Santiago Vargas; Yurchyshyn, Vasyl

    2014-01-01

    State-of-the-art solar instrumentation is revealing magnetic activity of the Sun with unprecedented resolution. Observations with the 1.6m New Solar Telescope of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research. As part of a joint observing program with NASA's IRIS mission, the NST observed active region NOAA 11810 in photospheric and chromospheric wavelengths. Complimentary data are provided by SDO and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing abnormal granulation and interacting with the pre-existing ambient field in upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the HeI data. IRIS catched ejection of a hot plasma jet...

  19. The Sub-arcsecond Structure Of The Upper Chromosphere: Results From The 2nd Flight Of The Nrl Vault Sounding Rocket Payload

    Science.gov (United States)

    Sanchez-Andrade Nuno, Bruno; Vourlidas, A.; Korendyke, C.

    2009-05-01

    The Very high Angular resolution ULtraviolet Telescope (VAULT) is an Lya spectroheliograph flown on a sounding rocket. The payload is capable of obtaining Lya filtergrams with a spatial resolution of around 0.33'' ( 200 km) over an extended field of view (535'' x 235'') . The instrument is tuned to the Ly-a line because it forms at the boundary of the upper chromosphere low corona. On its last flight, on 14 June 2002, VAULT observed an area around NOAA AR 9997 & 9998 with a rich variety of features: quiet Sun network, limb spicules, filaments, prominences and plage. The observing campaign incorporated a wide variety of ground-based and space-borne instruments. The level 0.9 VAULT data is open and available from http://wwwsolar.nrl.navy.mil/rockets/vault .We have recently releseased SolarSoft-compatible software for easy access and processing of the data. This contribution showcases the data capabilities and availability. We present contrast-enhanced images by means of wavelet image processing. The images reveal in extraordinary detail the dynamics of the smallest solar scales (200-300 km). We observe flows along thin threads on the prominence, exploding events on the plage and even in the quiet sun regions.

  20. Chromospheric Variability: Analysis of 36 years of Time Series from the National Solar Observatory/Sacramento Peak Ca II K-line Monitoring Program

    Science.gov (United States)

    Scargle, Jeffrey D.; Keil, Stephen L.; Worden, Simon P.

    2014-01-01

    Analysis of more than 36 years of time series of seven parameters measured in the NSO/AFRL/Sac Peak K-line monitoring program elucidates five elucidates five components of the variation: (1) the solar cycle (period approx. 11 years), (2) quasi-periodic variations (periods approx 100 days), (3) a broad band stochastic process (wide range of periods), (4) rotational modulation, and (5) random observational errors. Correlation and power spectrum analyses elucidate periodic and aperiodic variation of the chromospheric parameters. Time-frequency analysis illuminates periodic and quasi periodic signals, details of frequency modulation due to differential rotation, and in particular elucidates the rather complex harmonic structure (1) and (2) at time scales in the range approx 0.1 - 10 years. These results using only full-disk data further suggest that similar analyses will be useful at detecting and characterizing differential rotation in stars from stellar light-curves such as those being produced by NASA's Kepler observatory. Component (3) consists of variations over a range of timescales, in the manner of a 1/f random noise process. A timedependent Wilson-Bappu effect appears to be present in the solar cycle variations (1), but not in the stochastic process (3). Component (4) characterizes differential rotation of the active regions, and (5) is of course not characteristic of solar variability, but the fact that the observational errors are quite small greatly facilitates the analysis of the other components. The recent data suggest that the current cycle is starting late and may be relatively weak. The data analyzed in this paper can be found at the National Solar Observatory web site http://nsosp.nso.edu/cak_mon/, or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters.

  1. Solar Activity and Motions in the Solar Chromosphere and Corona at the 2012 and 2013 Total and Annular Eclipses in the U.S., Australia, and Africa

    Science.gov (United States)

    Pasachoff, Jay M.; Babcock, B. A.; Davis, A. B.; Demianski, M.; Lucas, R.; Lu, M.; Dantowitz, R.; Rusin, V.; Saniga, M.; Seaton, D. B.; Gaintatzis, P.; Voulgaris, A.; Seiradakis, J. H.; Gary, D. E.; Shaik, S. B.

    2014-01-01

    Our studies of the solar chromosphere and corona at the 2012 and 2013 eclipses shortly after cycle maximum 24 (2011/2012) of solar activity (see: http://www.swpc.noaa.gov/SolarCycle/) involved radio observations of the 2012 annular eclipse with the Jansky Very Large Array, optical observations of the 2012 total eclipse from Australia, optical observations of the 2013 annular eclipse from Tennant Creek, Australia, and the 3 November 2013 total solar eclipse from Gabon. Our observations are coordinated with those from solar spacecraft: Solar Dynamics Observatory AIA and HMI, Hinode XRT and SOT, SOHO LASCO and EIT, PROBA2 SWAP, and STEREO SECCHI. Our 2012 totality observations include a CME whose motion was observed with a 37-minute interval. We include first results from the expedition to Gabon for the 3 November 2013 eclipse, a summary of eclipse results from along the path of totality across Africa, and a summary of the concomitant spacecraft observations. The Williams College 2012 expeditions were supported in part by NSF grant AGS-1047726 from Solar Terrestrial Research/NSF AGS, and by the Rob Spring Fund and Science Center funds at Williams. The JVLA is supported by the NSF. The Williams College 2013 total-eclipse expedition was supported in part by grant 9327-13 from the Committee for Research and Exploration of the National Geographic Society. ML was also supported in part by a Grant-In-Aid of Research from the National Academy of Sciences, administered by Sigma Xi, The Scientific Research Society (Grant ID: G20120315159311). VR and MS acknowledge support for 2012 from projects VEGA 2/0003/13 and NGS-3139-12 of the National Geographic Society. We are grateful to K. Shiota (Japan) for kindly providing us with some of his 2012 eclipse coronal images. We thank Alec Engell (Montana State U) for assistance on site, and Terry Cuttle (Queensland Amateur Astronomers) for help with site arrangements. We thank Aram Friedman (Ansible Technologies), Michael Kentrianakis

  2. Long term changes in EUV and X-ray emissions from the solar corona and chromosphere as measured by the response of the Earth’s ionosphere during total solar eclipses from 1932 to 1999

    Directory of Open Access Journals (Sweden)

    C. J. Davis

    Full Text Available Measurements of the ionospheric E region during total solar eclipses in the period 1932–1999 have been used to investigate the fraction of Extreme Ultra Violet and soft X-ray radiation, 8, that is emitted from the limb corona and chromosphere. The relative apparent sizes of the Moon and the Sun are different for each eclipse, and techniques are presented which correct the measurements and, therefore, allow direct comparisons between different eclipses. The results show that the fraction of ionising radiation emitted by the limb corona has a clear solar cycle variation and that the underlying trend shows this fraction has been increasing since 1932. Data from the SOHO spacecraft are used to study the effects of short-term variability and it is shown that the observed long-term rise in 8 has a negligible probability of being a chance occurrence.

    Key words. Ionosphere (solar radiation and cosmic ray effects – Solar physics, astrophysics, and astronomy (corona and transition region

  3. Chromospheric oscillations observed by SUMER/SOHO

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Curdt, W.

    San Francisco: Astronomical Society of the Pacific, 1999 - (Schmieder, B.; Hofmann, A.; Staude, J.), s. 201-205 [Advances in solar physics: magnetic fields and oscillations /3./. Potsdam (DE), 22.09.1998-25.09.1998] R&D Projects: GA AV ČR IAA3003707 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  4. Chromospheric Dynamics and the FIP Flip

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This paper consists of two parts. The first, resembling many other SOHO contributions in this volume, reports on a recent campaign in which SUMER was employed simultaneously with groundbased tele- scopes. The campaign is described but results are not yet in hand. The second part differs by proposing

  5. Solar Imagery - Chromosphere - H-Alpha

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of H-alpha photographic datasets contributed by a number of national and private solar observatories located worldwide. Solar...

  6. Explosive Chromospheric Evaporation in a Circular-ribbon Flare

    CERN Document Server

    Zhang, Q M; Ning, Z J; Su, Y N; Ji, H S; Guo, Y

    2016-01-01

    In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the \\textit{Interface Region Imaging Spectrograph} (\\textit{IRIS}) show plasma upflow at speed of 35$-$120 km s$^{-1}$ in the Fe {\\sc xxi} 1354.09 {\\AA} line ($\\log T\\approx7.05$) and downflow at speed of 10$-$60 km s$^{-1}$ i...

  7. Active region evolution in the chromosphere and transtition region

    International Nuclear Information System (INIS)

    Images in the C IV 1548 A and the Si II 1526 S lines taken with the ultraviolet spectrometer polarimeter (UVSP) instrument on board the Solar Maximum Mission (SMM) satellite were combined into movies showing the evolution of active regions and the neighboring supergranulation over several days. The data sets generally consist of 240 by 240 arc second rasters with 3 arc second pixels taken one per orbit (about every 90 minutes). The images are projected on a latitude/longitude grid to remove the forshortening as the region rotates across the solar disk and further processed to remove jitter and gain variations. Movies were made with and without differential rotation. Although there are occasional missing orbits, these series do not suffer from the long nighttime gaps that occur in observations taken at a single groundbased observatory and are excellent for studying changes on time scales of several hours. The longest sequence processed to date runs from 20 Oct. 1980 to 25 Oct. 1980. This was taken during an SMM flare buildup study on AR 2744. Several shorter sequences taken in 1980 and 1984 will also be shown. The results will be presented on a video disk which can be interactively controlled to view the movies

  8. About the magnetic origin of Chromospheric Spicules and Coronal Jets

    Science.gov (United States)

    Koutchmy, S.; Filippov, B.; Tavabi, E.

    2012-06-01

    Observations of jet- like phenomena near the solar limb are reported for a long time, first in Hα (Secchi observations of spicules in the 1870 ies), and after, from eclipse high resolution coronal images taken in white-light (1920-1973) as spiky structures. EUV jets were reported in the 70 ies from rocket and space-borne CIV filtergrams and finally X-EUV jets were reported from SXT observations of Yohkoh and from EIT and CDS SoHO observations. There is now little doubt that they are of magnetic origin although no magnetic field measurements exist for these regions and thermo-dynamical models are still work out. New observations of both spicules and jets with the SOT/SXT of Hinode were subjected to an analysis showing the influence of the null point(s) of the magnetic field. The collective behavior of the H CaII SOT(Hinode) time sequences of processed with the Madmax operator images of limb spicules show the torsional effects which were partly suggested before from the interpretation of high resolution limb spectra taken on Russian coronagraphs and the VTT at SacPeak. 100 s and shorter period waves are recorded. We propose a reconnection process occurring at the top of an emerging twisted flux tube for explaining some peculiarities of the spicular eruptions and possibly, as a viable mechanism for explaining the SXR jet eruptions. The result of a numerical 3D modeling illustrates this erupting mechanism although the behavior of the magneto-plasma structure near a null point, as shown by coronal filtergrams, does not necessary imply reconnections, especially the case of jets making a long coronal ray we observed in white-light with Lasco C2.

  9. Halpha line profile asymmetries and the chromospheric flare velocity field

    CERN Document Server

    Kuridze, D; Simões, P J A; van der Voort, L Rouppe; Carlsson, M; Jafarzadeh, S; Allred, J C; Kowalski, A F; Kennedy, M; Fletcher, L; Graham, D; Keenan, F P

    2015-01-01

    The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Halpha and Ca II 8542 {\\AA} lines are studied using high spatial, temporal and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1-m Solar Telescope. The temporal evolution of the Halpha line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum, and excess in the blue wing (blue asymmetry) after maximum. However, the Ca II 8542 {\\AA} line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesise spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Halpha is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, w...

  10. Doppler Images and Chromospheric Variability of TWA 6

    OpenAIRE

    Skelly, M. B.; Unruh, Y. C.; Cameron, A. Collier; Barnes, J. R.; Donati, J.-F; Lawson, W. A.; Carter, B. D.

    2008-01-01

    We present Doppler imaging and Balmer line analysis of the weak-line T Tauri star TWA 6. Using this data we have made one of the first attempts to measure differential rotation in a T Tauri star, and the first detection of a slingshot prominence in such a star. We also show the most direct evidence to date of the existence of solar-type plages in a star other than the Sun. Observations were made over six nights: 11-13th February 2006 and 18-20th February 2006, when spectra were taken with the...

  11. Mode conversion of radiatively damped magnetogravity waves in the solar chromosphere

    OpenAIRE

    Newington, Marie E.; Cally, Paul S.

    2011-01-01

    Modelling of adiabatic gravity wave propagation in the solar atmosphere showed that mode conversion to field guided acoustic waves or Alfv\\'en waves was possible in the presence of highly inclined magnetic fields. This work aims to extend the previous adiabatic study, exploring the consequences of radiative damping on the propagation and mode conversion of gravity waves in the solar atmosphere. We model gravity waves in a VAL-C atmosphere, subject to a uniform, and arbitrarily orientated magn...

  12. Photospheric, Chromospheric and Helioseismic Signatures of a Large Flare in Super-active Region NOAA 10486

    Indian Academy of Sciences (India)

    Ashok Ambastha

    2006-06-01

    NOAA 10486 produced several powerful flares, including the 4B/X17.2 superflare of October 28, 2003/11:10 UT. This flare was extensively covered by the H and GONG instruments operated at the Udaipur Solar Observatory (USO). The central location of the active region on October 28, 2003was well-suited for the ring diagram analysis to obtain the 3-D power spectra and search for helioseismic response of this large flare on the amplitude, frequency and width of the p-modes. Further, using USO observations, we have identified the sites of new flux emergences, large proper motions and line-of-sight velocity flows in the active region and their relationship with the flare.

  13. Mg I as a probe of the solar chromosphere - The atomic model

    Science.gov (United States)

    Mauas, Pablo J.; Avrett, Eugene H.; Loeser, Rudolf

    1988-01-01

    This paper presents a complete atomic model for Mg I line synthesis, where all the atomic parameters are based on recent experimental and theoretical data. It is shown how the computed profiles at 4571 A and 5173 A are influenced by the choice of these parameters and the number of levels included in the model atom. In addition, observed profiles of the 5173 A b2 line and theoretical profiles for comparison (based on a recent atmospheric model for the average quiet sun) are presented.

  14. Chromospheric and transition-region heating phenomena: coordinated GBO and SOHO observations

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Kotrč, Pavel; Karlický, Marian; Nejezchleba, Tomáš; Knížek, Miloslav

    Paris : European Space Agency, 1994, s. 369-374. - (European Space Agency. SP-373). [SOHO Workshop - Solar Dynamic Phenomena and Solar Wind Consequences /3./. Estes Park, Colorado (US), 26.09.1994-29.09.1994] R&D Projects: GA ČR GA205/94/1577

  15. Ca II H sunspot tomography from the photosphere to the chromosphere

    Science.gov (United States)

    Henriques, V. M. J.; Kiselman, D.

    2013-09-01

    Aims: We aim at gaining insight into the thermal properties of different small-scale structures related to sunspots. Methods: We use filtergrams in the Ca ii H filter at the Swedish 1-m Solar Telescope to study the relationship between fine structure at different heights in a sunspot. Results: The methods for destretching and aligning the different image data work well. The magnetic spine structure in the outer parts of the sunspot penumbra is found to be associated with higher intensities in the Ca ii H wing passbands but with less steep vertical temperature gradients. Dark lanes in a light bridge behave very similarly to dark cores in penumbral filaments. Fibril structures are seen in the line-core images over the umbra and penumbra. Conclusions: The observations add support to the idea that penumbral filaments, light bridges, and umbral dots are caused by similar processes of overturning convection. Observations in the Ca ii H & K wings are a promising observable, complementing others, for testing simulation results for sunspots at high spatial resolution.

  16. Chromospheric, transition layer and X-ray emission for stars with different rotational velocities

    Science.gov (United States)

    Boehm-Vitense, E.

    1982-01-01

    In agreement with previous findings for the MgII k line emission in F stars an increase of Lya and transition layer emission with increasing V sub r sin i, if v sub r sin i greater than 30 km/sec. was not found. For V sub r sin i 30 km/sec., the measured line intensities are consistent with an increase in emission with increasing V sub r sin i. Such a relation between emission and rotation for single stars is also in agreement with X-ray observations. For the young F stars in the Hyades we find generally enhanced emission independently of rotational velocities. The enhancement is most pronounced for low excitation lines.

  17. Three-dimensional simulations of scattering polarization and the Hanle effect in MHD chromospheric models

    CERN Document Server

    Štěpán, Jiří

    2015-01-01

    Scattering line polarization and the Hanle effect are among the most important mechanisms for diagnostics of the solar and stellar atmospheres. The fact that real stellar atmospheres are horizontally inhomogeneous makes the spectral synthesis and interpretation very challenging because the effect of thermodynamic fluctuations on spectral line polarization is entangled with the action of magnetic fields. This applies to the spatially resolved as well as to the averaged spectra. The necessary step towards the interpretation of such spectra is to study the line formation in sufficiently realistic 3D MHD models and comparison of the synthetic spectra with observations. This paper gives an overview of recent progress in the field of 3D NLTE synthesis of polarized spectral lines resulting from investigations with the radiative transfer code PORTA.

  18. Simultaneous observations of chromospheric and transition region oscillations in HI Lyman transitions and in optical lines

    Czech Academy of Sciences Publication Activity Database

    Curdt, W.; Heinzel, Petr; Schnidt, W.; Tarbell, T.

    Noordwijk: ESA Publications Division, 1999 - (Wilson, A.), s. 177-182 ISBN 92-9092-792-5. [European meeting on solar physics /9./. Florence (IT), 12.09.1999-18.09.1999] R&D Projects: GA AV ČR IAA3003902 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  19. Chromospheric activity above changign photospheric magnetic and velocity fields of developing active regions

    Czech Academy of Sciences Publication Activity Database

    Bumba, Václav; Klvaňa, Miroslav; Kálmán, B.; Rompolt, B.; Rudawy, P.

    San Francisco: Astronomical Society of the Pacific, 1998, s. 224-228. (ASP Conference series.. 155). [Euroconference : Three-dimensional structure of solar active regions : Advaces in solar physics. Preveza (GR), 07.10.1997-12.10.1997] Institutional research plan: CEZ:AV0Z1003909 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  20. Determining Energy Balance in the Flaring Chromosphere from Oxygen V Line Ratios

    CERN Document Server

    Graham, David R; Labrosse, Nicolas

    2014-01-01

    The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. We use an O V density diagnostic formed of the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a constraint on the properties of the heated transition region. Hinode EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionization and optically thin radiation for the O V lines were found to be acceptable. Properties of the electron distribution, for one event, were deduced from earlier RHESSI hard X-ray observations and used to calculate the ...

  1. Determination of the chromospheric quiet network element area index and its variation between 2008 and 2011

    Institute of Scientific and Technical Information of China (English)

    Jagdev Singh; Ravindra Belur; Selvendran Raju; Kumaravel Pichaimani; Muthu Priyal; Thambaje Gopalan Priya; Amareswari Kotikalapudi

    2012-01-01

    In general,it is believed that plages and sunspots are the main contributors to solar irradiance.There are small-scale structures on the Sun with intermediate magnetic fields that could also contribute to solar irradiance,but it has not yet been quantified how many of these small scale structures contribute and how much this varies over the solar cycle.We used Ca Ⅱ K images obtained from the telescope at the Kodaikanal observatory.We report a method to separate the network elements from the background structure and plage regions,and compute the changes in the network element area index during the minimum phase of the solar cycle and part of the ascending phase of cycle 24.The measured area occupied by the network elements is about 30% and the plages cover less than 1% of the solar disk during the observation period from February 2008 to 2011.During the extended period of minimum activity,it is observed that the network element area index decreases by about 7% compared to the area occupied by the network elements in 2008.A long term study of the network element area index is required to understand the variations over the solar cycle.

  2. Detection of mesogranulation at the upper chromosphere from SOHO/SUMER observations

    CERN Document Server

    Kariyappa, R; Curdt, W

    2008-01-01

    We have analyzed a time series of spectra in the hydrogen Lyman lines and the Lyman continuum obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the SOlar Heliospheric Observatory (SOHO). The time series of about 2 hours and 22 minutes was obtained on 1999 March 9 in a quiet region near the center of the solar disk. For our analysis, we have selected a Lyman continuum window around 907 A, and the five Lyman lines: Ly5 (937.8 A), Ly7 (926.2 A), Ly9 (920.9 A), Ly11 (918.1 A), and Ly15 (915.3 A). A Fast Fourier analysis has been performed in the spatial domain, all along the slit length used, for all the spectra and for the total duration of the observations. We have detected a significant periodic spatial variations with Fourier transform power peaks around 9-10 arcsec and at 4 arcsec. They correspond to the scale of the mesogranulation structure and the width of the supergranular boundary, respectively. For the first time, this provides evidence for the existence of a m...

  3. Three-dimensional simulations of scattering polarization and the Hanle effect in MHD chromospheric models

    Czech Academy of Sciences Publication Activity Database

    Štěpán, Jiří

    Cambridge : Cambridge University Press, 2015, s. 360-367 ISBN 9781107078550. - (Proceedings of the International Astronomical Union. S305). [Symposium of the International Astronomical Union /305./. Punta Leona (CR), 30.11.2014-05.12.2014] R&D Projects: GA ČR GPP209/12/P741 Institutional support: RVO:67985815 Keywords : polarization * radiati ve transfer * scattering Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  4. Time-Dependent Turbulent Heating of Open Flux Tubes in the Chromosphere, Corona, and Solar Wind

    CERN Document Server

    Woolsey, Lauren N

    2015-01-01

    We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfven-wave-driven turbulence for three typical open magnetic field structures: a polar coronal hole, an open flux tube neighboring an equatorial streamer, and an open flux tube near a strong-field active region. We compare time-steady, one-dimensional turbulent heating models (Cranmer et al., 2007) against fully time-dependent three-dimensional reduced-magnetohydrodynamics modeling of BRAID (van Ballegooijen et al., 2011). We find that the time-steady results agree well with time-averaged results from BRAID. The time-dependence allows us to investigate the variability of the magnetic fluctuations and of the heating in the corona. The high-frequency tail of the power spectrum of fluctuations forms a power law whose exponent varies with height, and we discuss the possible physical explanation for this behavior. The variability in the heating rate is bursty...

  5. Self-heating and its possible relationship to chromospheric heating in slowly rotating stars

    OpenAIRE

    Rogava, A; Poedts, Stefaan; Osmanov, Zaza

    2010-01-01

    The efficiency of nonmodal self-heating by acoustic wave perturbations is examined. Considering different kinds of kinematically complex velocity patterns we show that nonmodal instabilities arising in these inhomogeneous flows may lead to significant amplification of acoustic waves. Subsequently, the presence of viscous dissipation damps these amplified waves and causes the energy transfer back to the background flow in the form of heat; viz. closes the "self-heating" cycle and contributes t...

  6. Numerical Modeling of the Solar Chromosphere and Corona: What Has Been Done? What Should Be Done?

    Science.gov (United States)

    Hansteen, V.; Carlsson, M.; Gudiksen, B.

    2015-10-01

    A number of increasingly sophisticated numerical simulations spanning the solar atmosphere from below the photosphere in the convection zone to far above in the corona have shed considerable insight into the role of the magnetic field in the structure and energetics of the Sun's outer layers. This development is strengthened by the wealth of observational data now coming on-line from both ground and space based observatories. In this talk we will concentrate on the successes and failures of the modeling effort thus far and discuss the inclusion of various effects not traditionally considered in the MHD description such as time dependent ionization, non-LTE radiative transfer, and generalized Ohm's law.

  7. A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    Czech Academy of Sciences Publication Activity Database

    Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.; Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway, T.; Winebarger, A.; Cirtain, J.; de Pontieu, B.; Casini, R.; Auchere, F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; AsensioRamos, A.; Štěpán, Jiří; Carlsson, M.

    San Francisco : Astronomical Society of the Pacific, 2014 - (Nagendra, K.), s. 307-317 ISBN 9781583818633. - (ASP Conference Series. 489). [ Solar Polarization 7. Kunning (CN), 09.09.2013-13.09.2013] R&D Projects: GA ČR GPP209/12/P741 Institutional support: RVO:67985815 Keywords : magnetic fields * polarization * scattering Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  8. NEAR-ULTRAVIOLET ABSORPTION, CHROMOSPHERIC ACTIVITY, AND STAR-PLANET INTERACTIONS IN THE WASP-12 SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Haswell, C. A.; Fossati, L.; Holmes, S.; Kolb, U. C.; Busuttil, R.; Carter, A. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Ayres, T.; France, K.; Froning, C. S. [Center for Astrophysics and Space Astronomy, University of Colorado, 593 UCB, Boulder, CO 80309-0593 (United States); Street, R. A. [Las Cumbres Observatory Global Telescope Network, Inc., 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Hebb, L. [Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center Nashville, TN 37235 (United States); Cameron, A. Collier; Enoch, B. [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom); Burwitz, V. [Max Planck Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Rodriguez, J. [Observatori Astronomic de Mallorca, Cami de l' Observatori, E-07144 Costitx, Mallorca (Spain); West, R. G. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Pollacco, D.; Wheatley, P. J., E-mail: C.A.Haswell@open.ac.uk, E-mail: l.fossati@open.ac.uk, E-mail: cynthia.froning@colorado.edu, E-mail: leslie.hebb@vanderbilt.edu [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2012-11-20

    Extended gas clouds have been previously detected surrounding the brightest known close-in transiting hot Jupiter exoplanets, HD 209458 b and HD 189733 b; we observed the distant but more extreme close-in hot Jupiter system, WASP-12, with Hubble Space Telescope (HST). Near-UV (NUV) transits up to three times deeper than the optical transit of WASP-12 b reveal extensive diffuse gas, extending well beyond the Roche lobe. The distribution of absorbing gas varies between visits. The deepest NUV transits are at wavelength ranges with strong stellar photospheric absorption, implying that the absorbing gas may have temperature and composition similar to those of the stellar photosphere. Our spectra reveal significantly enhanced absorption (greater than 3{sigma} below the median) at {approx}200 individual wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching that excludes matches with velocity shifts exceeding {approx}20 km s{sup -1}. Excess transit depths are robustly detected throughout the inner wings of the Mg II resonance lines independently on both HST visits. We detected absorption in Fe II {lambda}2586, the heaviest species yet detected in an exoplanet transit. The Mg II line cores have zero flux, emission cores exhibited by every other observed star of similar age and spectral type are conspicuously absent. WASP-12 probably produces normal Mg II profiles, but the inner portions of these strong resonance lines are likely affected by extrinsic absorption. The required Mg{sup +} column is an order of magnitude greater than expected from the interstellar medium, though we cannot completely dismiss that possibility. A more plausible source of absorption is gas lost by WASP-12 b. We show that planetary mass loss can produce the required column. Our Visit 2 NUV light curves show evidence for a stellar flare. We show that some of the possible transit detections in resonance lines of rare elements may be due instead to non-resonant transitions in common species. We present optical observations and update the transit ephemeris.

  9. Near-UV Absorption, Chromospheric Activity, and Star-Planet Interactions in the WASP-12 system

    CERN Document Server

    Haswell, C A; Ayres, T; France, K; Froning, C S; Holmes, S; Kolb, U C; Busuttil, R; Street, R A; Hebb, L; Cameron, A Collier; Enoch, B; Burwitz, V; Rodriguez, J; West, R G; Pollacco, D; Wheatley, P J; Carter, A; 10.1088/0004-637X/760/1/79

    2013-01-01

    We observed the extreme close-in hot Jupiter system, WASP-12, with HST. Near-UV transits up to three times deeper than the optical transit of WASP-12b reveal extensive diffuse gas, extending well beyond the Roche lobe. The distribution of absorbing gas varies between visits. The deepest NUV transits are at wavelength ranges with strong photospheric absorption, implying the absorbing gas may have temperature and composition similar to the stellar photosphere. Our spectra reveal significantly enhanced absorption (greater than 3 \\sigma below the median) at ~200 wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching which excludes matches with velocity shifts exceeding ~20 km/s. Excess transit depths are robustly detected throughout the inner wings of the MgII resonance lines independently on both HST visits. We detected absorption in FeII 2586A, the heaviest species yet detected in an exoplanet transit. The MgII line co...

  10. Imaging and Spectra of the Chromosphere and Corona at the 2013 Total Eclipse in Gabon

    Science.gov (United States)

    Pasachoff, Jay M.; Davis, Allen B.; Demianski, Marek; Rusin, Vojtech; Saniga, Metod; Seaton, Daniel B; Gaintatzis, Pavlos; Voulgaris, Aristeidis; Lucas, Robert; Edwards, Zophia; Zeiler, Michael; Kentrianakis, Michael

    2014-06-01

    We successfully observed the 3 November 2013 eclipse's 59 s of totality in clear sky from the centerline of totality where it exited La Lope National Park in Gabon, close to the maximum totality available on land. Our wide-field imaging showed two CMEs and an erupting prominence. We compare our images with those obtained elsewhere in totality to assess motion and dynamics. Our imaging observations are also compared with near-simultaneous observations from SDO/AIA, SDO/HMI, Hinode/XRT, SOHO/LASCO, SOHO/EIT, PROBA2/SWAP, and STEREO/SECCHI. We also have flash and coronal spectra, which continue to show overall warming of the corona in 2012 and 2013 through studies we have made over the solar cycle that include the ratio of intensities of the coronal red (Fe X 637.4 nm) and green (Fe XIV 530.3 nm) forbidden lines.The Williams College 2013 total-eclipse expedition was supported in part by grant 9327-13 from the Committee for Research and Exploration of the National Geographic Society. Our continued work on the 2012 eclipse results is supported in part by grant AGS-1047726 from Solar Terrestrial Research/NSF AGS.

  11. Imaging and spectroscopic observations of magnetic reconnection and chromospheric evaporation in a solar flare

    CERN Document Server

    Tian, Hui; Reeves, Katharine K; Raymond, John C; Guo, Fan; Liu, Wei; Chen, Bin; Murphy, Nicholas A

    2014-01-01

    Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfv\\'{e}n speed. Yet, spectroscopic observations of such outflows, especially the downflows, are extremely rare. With observations of the newly launched Interface Region Imaging Spectrograph (IRIS), we report the detection of greatly redshifted ($\\sim$125 km s$^{-1}$ along line of sight) Fe {\\sc{xxi}} 1354.08\\AA{} emission line with a $\\sim$100 km s$^{-1}$ nonthermal width at the reconnection site of a flare. The redshifted Fe {\\sc{xxi}} feature coincides spatially with the loop-top X-Ray source observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We interpret this large redshift as the signature of downward-moving reconnection outflow/hot retracting loops. Imaging observations from both IRIS and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) also...

  12. The energy of waves in the photosphere and lower chromosphere: II. Intensity statistics

    OpenAIRE

    Beck, C; Rezaei, R.; Puschmann, K. G.

    2012-01-01

    We investigate the statistics of the intensity distributions as function of the wavelength for Ca II H and the CA II IR line at 854.2 nm to estimate the energy content. We derived the intensity variations at different heights of the solar atmosphere as given by the line wings and line cores of the two spectral lines. We converted the observed intensities to absolute energy units employing reference profiles calculated in NLTE. We also converted the observed intensity fluctuations to brightnes...

  13. The energy of waves in the photosphere and lower chromosphere: II. Intensity statistics

    CERN Document Server

    Beck, C; Puschmann, K G

    2012-01-01

    We investigate the statistics of the intensity distributions as function of the wavelength for Ca II H and the CA II IR line at 854.2 nm to estimate the energy content. We derived the intensity variations at different heights of the solar atmosphere as given by the line wings and line cores of the two spectral lines. We converted the observed intensities to absolute energy units employing reference profiles calculated in NLTE. We also converted the observed intensity fluctuations to brightness temperatures assuming LTE. The rms fluctuations of the emitted intensity are about 0.6 (1.2) W/m2 ster pm near the core of the Ca IR line (Ca II H), corresponding to intensity fluctuations of about 20% (30%). For the line wing, we find rms values of about 0.3 W/ m2 ster pm for both lines, corresponding to relative fluctuations below 5%. The rms shows a local minimum for wavelengths forming at about 130 km height, but otherwise increases from the wing to the core. The rms brightness temperature fluctuations are below 100...

  14. Using Sdo's AIA to Investigate Energy Transport from a Flare's Energy Release Site to the Chromosphere

    Science.gov (United States)

    Brosius, Jeffrey W.; Holman, Gordon D.

    2012-01-01

    Coordinated observations of a GOES B4.8 microflare with SDOs Atmospheric Imaging Assembly (AIA) and the RamatyHigh Energy Solar Spectroscopic Imager (RHESSI) on 2010 July 31 show that emission in all seven of AIAs EUV channels brightened simultaneously nearly 6 min before RHESSI or GOES detected emission from plasma at temperatures around 10 MK. Aims. To help interpret these and AIA flare observations in general, we characterized the expected temporal responses of AIAs 94, 131, 171, 193, 211, and 335 channels to solar flare brightenings by combining (1) AIAs nominal temperature response functions available through SSWIDL with (2) EUV spectral line data observed in a flare loop Coordinated observations of a GOES B4.8 microflare with SDOs Atmospheric Imaging Assembly (AIA) and the RamatyHigh Energy Solar Spectroscopic Imager (RHESSI) on 2010 July 31 show that emission in all seven of AIAs EUV channels brightenedsimultaneously nearly 6 min before RHESSI or GOES detected emission from plasma at temperatures around 10 MK.Aims. To help interpret these and AIA flare observations in general, we characterized the expected temporal responses of AIAs 94,131, 171, 193, 211, and 335 channels to solar flare brightenings by combining (1) AIAs nominal temperature response functionsavailable through SSWIDL with (2) EUV spectral line data observed in a flare loop

  15. Two-Dimensional Helioseismic Power, Phase, and Coherence Spectra of {\\it Solar Dynamics Observatory} Photospheric and Chromospheric Observables

    CERN Document Server

    Howe, Rachel; Bogart, Richard S; Haber, Deborah A; Baldner, Charles S

    2012-01-01

    While the {\\it Helioseismic and Magnetic Imager} (HMI) onboard the {\\it Solar Dynamics Observatory} (SDO) provides Doppler velocity [$V$], continuum intensity [$I_C$], and line-depth [$Ld$] observations, each of which is sensitive to the five-minute acoustic spectrum, the {\\it Atmospheric Imaging Array} (AIA) also observes at wavelengths -- specifically the 1600 and 1700 Angstrom bands -- that are partly formed in the upper photosphere and have good sensitivity to acoustic modes. In this article we consider the characteristics of the spatio--temporal Fourier spectra in AIA and HMI observables for a 15-degree region around NOAA Active Region 11072. We map the spatio--temporal-power distribution for the different observables and the HMI Line Core [$I_L$], or Continuum minus Line Depth, and the phase and coherence functions for selected observable pairs, as a function of position and frequency. Five-minute oscillation power in all observables is suppressed in the sunspot and also in plage areas. Above the acoust...

  16. PHOTOMETRIC STUDY TO UNDERSTAND THE AMBIGUITY BETWEEN ACCRETION AND CHROMOSPHERIC ACTIVITY PRESENT IN LOW-MASS STARS

    Directory of Open Access Journals (Sweden)

    O. A. Restrepo

    2014-01-01

    Full Text Available Realizamos un estudio fotom ́trico de una muestra de estrellas de la pre-secuencia principal y T Tauri en el e intervalo espectral G-K y algunas M tempranas, de masas desde 0.5 hasta 3 masas solares, en asociaciones cercanas al Sol (20–200 pc. Medimos el exceso presente en el ultravioleta y vemos que para estrellas de tipo espectral M temprano y K tard ́ ıas, ́ste aumenta notablemente. Se presentan dos posibles escenarios para e dicho aumento: (1 Actividad cromosf ́rica, debido a que las estrellas presentan n ́cleo radiativo y convectivo e u dando lugar a la actividad magn ́tica lo que genera este exceso presente en el continuo y (2 a los procesos e o de acreci ́n presentes en las estrellas que poseen alrededor de ellas un disco de gas y polvo que es acrecido hacia ellas por medio de las l ́ ıneas de campo magn ́tico. Debido a la ambig ̈edad presente en los dos efectos, e u ya que estos afectan las mismas l ́ ıneas de emisi ́n, es dif ́ distinguir cu ́l de estos procesos est ́ dominando. o ıcil a a Nosotros proponemos una cota m ́ ınima de 0.22 magnitudes de exceso en la banda U para nuestra muestra y as ́ podemos distinguir cuando se est ́n dando los dos procesos o cuando s ́lo el de actividad cromosf ́rica, ya ı a o e que el de acreci ́n tiene sus finales en edades muy tempranas, ∼10 millones de a ̃os.

  17. Full-disk Synoptic Observations of the Chromosphere Using H$_{\\alpha}$ Telescope at the Kodaikanal Observatory

    CERN Document Server

    Ravindra, B; Rangarajan, K E; Bagare, S P; Jagdev, Singh; Kemkar, P M M; Lancelot, J P; Thulasidharen, K C; Gabriel, F; Selvendran, R

    2016-01-01

    This paper reports on the installation and observations of a new solar telescope installed on 7th October, 2014 at the Kodaikanal Observatory. The telescope is a refractive type equipped with a tunable Lyot H$_{\\alpha}$ filter. A CCD camera of 2k$\\times$2k size makes the image of the Sun with a pixel size of 1.21$^{\\prime\\prime}$ pixel$^{-1}$ with a full field-of-view of 41$^{\\prime}$. The telescope is equipped with a guiding system which keeps the image of the Sun within a few pixels throughout the observations. The FWHM of the Lyot filter is 0.4\\AA~and the filter is motorized, capable of scanning the H$_{\\alpha}$ line profile at a smaller step size of 0.01\\AA. Partial-disk imaging covering about 10$^{\\prime}$, is also possible with the help of a relay lens kept in front of the CCD camera. In this paper, we report the detailed specifications of the telescope, filter unit, its installation, observations and the procedures we have followed to calibrate and align the data. We also present preliminary results wi...

  18. The Gaia-ESO Survey: Chromospheric Emission, Accretion Properties, and Rotation in $\\gamma$ Velorum and Chamaeleon I

    CERN Document Server

    Frasca, A; Lanzafame, A C; Alcalá, J M; Brugaletta, E; Klutsch, A; Stelzer, B; Sacco, G G; Spina, L; Jeffries, R D; Montes, D; Alfaro, E J; Barentsen, G; Bonito, R; Gameiro, J F; Lopez-Santiago, J; Pace, G; Pasquini, L; Prisinzano, L; Sousa, S G; Gilmore, G; Randich, S; Micela, G; Bragaglia, A; Flaccomio, E; Bayo, A; Costado, M T; Franciosini, E; Hill, V; Hourihane, A; Jofre', P; Lardo, C; Maiorca, E; Masseron, T; Morbidelli, L; Worley, C C

    2014-01-01

    We use the fundamental parameters delivered by the GES consortium in the first internal data release to select the members of $\\gamma$ Vel and Cha I among the UVES and GIRAFFE spectroscopic observations. A total of 140 $\\gamma$ Vel members and 74 Cha I members were studied. We calculated stellar luminosities through spectral energy distributions, while stellar masses were derived by comparison with evolutionary tracks. The spectral subtraction of low-activity and slowly rotating templates, which are rotationally broadened to match the $v\\sin i$ of the targets, enabled us to measure the equivalent widths (EWs) and the fluxes in the H$\\alpha$ and H$\\beta$ lines. The H$\\alpha$ line was also used for identifying accreting objects and for evaluating the mass accretion rate ($\\dot M_{\\rm acc}$). The distribution of $v\\sin i$ for the members of $\\gamma$ Vel displays a peak at about 10 km s$^{-1}$ with a tail toward faster rotators. There is also some indication of a different $v\\sin i$ distribution for the members o...

  19. Fibrillar Chromospheric Spicule-Like Counterparts to an EUV and Soft X-Ray Blowout Coronal Jet

    Science.gov (United States)

    Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.

    2010-01-01

    We observe an erupting jet feature in a solar polar coronal hole, using data from Hinode/SOT, EIS, and XRT, with supplemental data from STEREO/EUVI. From EUV and soft X-ray (SXR) images we identify the erupting feature as a blowout coronal jet: in SXRs it is a jet with bright base, and in EUV it appears as an eruption of relatively cool (approximately 50,000 K) material of horizontal size scale approximately 30" originating from the base of the SXR jet. In SOT Ca II H images the most pronounced analog is a pair of thin (approximately 1") ejections, at the locations of either of the two legs of the erupting EUV jet. These Ca II features eventually rise beyond 45", leaving the SOT field of view, and have an appearance similar to standard spicules except that they are much taller. They have velocities similar to that of "type II" spicules, approximately 100 kilometers per second, and they appear to have spicule-like substructures splitting off from them with horizontal velocity approximately 50 kilometers per second, similar to the velocities of splitting spicules measured by Sterling et al. (2010). Motions of splitting features and of other substructures suggest that the macroscopic EUV jet is spinning or unwinding as it is ejected. This and earlier work suggests that a sub-population of Ca II type II spicules are the Ca II manifestation of portions of larger-scale erupting magnetic jets. A different sub-population of type II spicules could be blowout jets occurring on a much smaller horizontal size scale than the event we observe here.

  20. Coronal vs chromospheric heating through co-spatial return currents during the 19 and 20 Jan 2005 solar flare

    Science.gov (United States)

    Alaoui, Meriem; Holman, Gordon D.

    2016-05-01

    The high electron flux required to explain the bremsstrahlung X-ray emission observed from solar flares is expected to be accompanied by a neutralizing co-spatial return current. In addition to resupplying the acceleration region with electrons, this return current will both heat the coronal plasma and flatten the electron distribution at lower energies. This flattening in the electron distribution in turn flattens the X-ray spectrum. We have found that return-current collisional thick-target model (RCCTTM) of Holman (2012) provides an acceptable fit to X-ray spectra with strong breaks for 18 flares observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). This is a 1D model similar to the collisional thick-target model (CTTM) with two additional assumptions: (1) electrons lose some of their energy through return current losses along their path to the thick target, where they lose all their remaining energy through Coulomb collisions; (2) the non-thermal beam is streaming in a warm target, which means that electrons will be thermalized at a non-zero energy. We assume this energy to be equal to the analytical value derived by Kontar et al. 2015. We show that return-current heating in the corona is about an order of magnitude higher than the heating at the footpoints at times during the flare.

  1. The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced From Multi-Wavelength Observations

    CERN Document Server

    Milligan, Ryan O; Dennis, Brian R; Hudson, Hugh S; Fletcher, Lyndsay; Allred, Joel C; Chamberlin, Phillip C; Ireland, Jack; Mathioudakis, Mihalis; Keenan, Francis P

    2014-01-01

    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 $>2\\times10^{31}$ 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\\AA\\ and H I (Ly$\\alpha$) at 1216\\AA\\ by SDO/EVE, the UV continua at 1600\\AA\\ and 1700\\AA\\ by SDO/AIA, and the WL continuum at 4504\\AA, 5550\\AA, and 6684\\AA, along with the Ca II H line at 3968\\AA\\ using Hinode/SOT. The summed energy detected by these in...

  2. Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

    CERN Document Server

    Gömöry, P; Su, Y; Temmer, M; Thalmann, J K

    2016-01-01

    We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler Fe XIII line but strong upflows, up to 80-150 km/s, in the hotter Fe XVI line. The largest Doppler shifts observed in the Fe XVI line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe XIII line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01x10^(9) cm^(-3) to 3.16x10^(10) cm^(-3) during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34x10^(10) erg/s/cm^(2) for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of 15 km/s that were detected in both ...

  3. Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

    OpenAIRE

    Gömöry, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K.

    2016-01-01

    We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler Fe XIII line but strong upflows, up to 80-150 km/s, in the hotter Fe XVI line. The largest Doppler shifts observed in the Fe XVI line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe XIII line pair ratio exhibited fas...

  4. Photospheric and chromospheric activity in V405 And: An M dwarf binary with components on the two sides of the full convection limit

    CERN Document Server

    Vida, K; Kővári, Zs; Korhonen, H; Bartus, J; Hurta, Zs; Posztobányi, K

    2009-01-01

    We investigate the fast rotating (P_orb=P_rot=0.465d) active dwarf binary V405 And (M0V+M5V) using photometric BV(RI)_C and optical spectroscopic data. The light variation is caused by the combined effect of spottedness and binarity with a small eclipse. From the available light and radial velocity curves we estimate the system parameters. Three flare events happened during the observations: two were found in the spectroscopic data and one was observed photometrically in BV(RI)_C colours. An interesting eruptive phenomenon emerged from the photometric measurements which can be interpreted as a series of post-flare eruptions lasting for at least 3 orbits (rotations) of the system, originating from trans-equatorial magnetic loops, which connect the active regions in the two hemispheres. The two components of V405 And have masses well over and below the theoretical limit of full convection. This rare property makes the binary an ideal target for observing and testing models for stellar dynamo action.

  5. Photospheric and chromospheric activity in V405 And: An M dwarf binary with components on the two sides of the full convection limit

    OpenAIRE

    Vida, K.; Oláh, K.; Kővári, Zs.; Korhonen, H.; Bartus, J.; Hurta, Zs.; Posztobányi, K.

    2009-01-01

    We investigate the fast-rotating (P_orb=P_rot=0.465d), active dwarf binary V405 And (M0V+M5V) using photometric BV(RI)_C and optical spectroscopic data. The light variation is caused by the combined effect of spottedness and binarity with a small eclipse. We estimate the system parameters from the available light and radial velocity curves. Three flare events occurred during the observations: two were found in the spectroscopic data and one was observed photometrically in BV(RI)_C colours. An...

  6. Investigation of the Chromosphere-Corona Interface with the Upgraded Very high angular Resolution ULtraviolet Telescope (VAULT2.0) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a three-year effort to upgrade our existing sub-arcsecond Lyman-alpha telescope payload to improve the observing cadence by a factor of 2, increase the...

  7. The Liquid Metallic Hydrogen Model of the Sun and the Solar Atmosphere VIII. "Futile" Processes in the Chromosphere (Letters to Progress in Physics

    Directory of Open Access Journals (Sweden)

    Robitaille L.

    2014-01-01

    Full Text Available In the liquid metallic hydrogen solar model (LMHSM, the chr omosphere is the site of hydrogen condensation (P.M. Robitaille. The Liquid Metall ic Hydrogen Model of the Sun and the Solar Atmosphere IV. On the Nature of the Chromosp here. Progr. Phys. , 2013, v. 3, L15–L21. Line emission is associated with the di ssipation of energy from condensed hydrogen structures, CHS. Previously considere d reactions resulted in hy- drogen atom or cluster addition to the site of condensation. In this work, an additional mechanism is presented, wherein atomic or molecular specie s interact with CHS, but do not deposit hydrogen. These reactions channel heat away f rom CHS, enabling them to cool even more rapidly. As a result, this new class of proce sses could complement true hydrogen condensation reactions by providing an auxil iary mechanism for the re- moval of heat. Such ‘futile’ reactions lead to the formation of activated atoms, ions, or molecules and might contribute to line emission from such sp ecies. Evidence that com- plimentary ‘futile’ reactions might be important in the chr omosphere can be extracted from lineshape analysis.

  8. Three-dimensional Radiative Transfer Simulations of the Scattering Polarization of the Hydrogen Lyalpha Line in a Magnetohydrodynamic Model of the Chromosphere-Corona Transition Region

    Czech Academy of Sciences Publication Activity Database

    Štěpán, Jiří; Trujillo Bueno, J.; Leenaarts, J.; Carlsson, M.

    2015-01-01

    Roč. 803, č. 2 (2015), 65/1-65/15. ISSN 0004-637X R&D Projects: GA ČR GPP209/12/P741 Grant ostatní: EU(XE) COST action MP1104 Institutional support: RVO:67985815 Keywords : polarization * radiative transfer * scattering Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.993, year: 2014

  9. Evolution of chromospheres and coronae in solar mass stars: A far-ultraviolet and soft x-ray comparison of Arcturus (K2III) and Alpha Centauri A (G2 V)

    International Nuclear Information System (INIS)

    We compare IUE far-ultraviolet and Einstein soft X-ray observations of the red giant Arcturus (α Bootis, K2III) and the nearby yellow dwarf α Centauri A (G2 V), which are archetypes of solar mass stars in very different stages of evolution. We find no evidence for coronal (Troughly-equal106 K) soft X-ray emission from the red giant at surface flux levels of only 0.0006 (3sigma) that detected previously for α Cen A, and no evidence for C IV lambdalambda1548, 1551 (Troughly-equal105 K) or C II lambdalambda1335, 1336 (Troughly-equal2 x 104 K) resonance line emission at surface flux levels of only 0.02 (3sigma) those of the yellow dwarf. Instead of a solar-like hot corona and warm (Troughly-equal105 K) transition region, the resonance line upper limits and previous detections of the C II intersystem UV multiplet 0.01 near 2325 A provide evidence that the outer atmosphere of Arcturus is geometrically extended (Δhapprox.R/sub */), tenuous (n/sub e/roughly-equal3 x 108 cm-3), and cool (T4 K)

  10. On the plasma flow inside magnetic tornadoes on the Sun

    OpenAIRE

    Wedemeyer, Sven; Steiner, Oskar

    2014-01-01

    High-resolution observations with the Swedish 1-m Solar Telescope (SST) and the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures that extend from the solar surface into the chromosphere and the corona. These so-called magnetic tornadoes are primarily detected as rings or spirals of rotating plasma in the Ca II 854.2 nm line core (also known as chromospheric swirls). Detailed numerical simulations show that the observed chromospheric plasma motion is caused by the rot...

  11. Photometric analysis of Ellerman bombs

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Berlicki, Arkadiusz; Avrett, E.H.

    2010-01-01

    Roč. 81, č. 2 (2010), s. 646-652. ISSN 0037-8720. [Chromospheric structure and dynamics: From old wisdom to new insights. Sunspot,, 31.08.2009-4.09.2009] Institutional research plan: CEZ:AV0Z10030501 Keywords : line formation * Sun * chromosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  12. Chromosperic oscillations

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This review concentrates on the quiet-Sun chromosphere. Its internetwork areas are dynamically dominated by the so-called chromospheric three-minute oscillation. They are interpretationally dominated by the so-called Ca II K 2V and H 2V grains. The main points of this review are that the one phenome

  13. Atmospheric Heating and Wind Acceleration in Cool Evolved Stars

    CERN Document Server

    Airapetian, Vladimir S

    2014-01-01

    A chromosphere is a universal attribute of stars of spectral type later than ~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This chapter provides a review of the observational requirements and theoretical approaches for modeling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma...

  14. Waves, shocks and non-stationary phenomena in the outer solar atmosphere

    Science.gov (United States)

    Hansteen, V. H.

    1997-01-01

    The dynamics of the solar chromosphere, transition region and corona were investigated. The consequences of the solar dynamics on the formation of spectral features in solar atmosphere regions are discussed. Data mainly from the solar ultraviolet measurement of emitted radiation (SUMER) instrument, showing signatures of non-stationary processes, are presented. These data are compared to the predictions of numerical models of the chromosphere and transition region. The observations seem to support the importance of upwardly propagating acoustic shocks in the heating of the chromosphere.

  15. Two step mechanism for Moreton wave excitations in a blast-wave scenario: the 2006 December 06 case study

    Science.gov (United States)

    Krause, G.; Cécere, M.; Francile, C.; Costa, A.; Elaskar, S.; Schneiter, M.

    2015-11-01

    We examine the capability of a blast-wave scenario - associated with a coronal flare or to the expansion of CME flanks - to reproduce a chromospheric Moreton phenomenon. We also simulate the Moreton event of 2006 December 06, considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock - able to generate a detectable chromospheric Moreton wave - a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that a flare ignited blast-wave or the expansion of the CME flanks emulated as an instantaneous or a temporal piston model, respectively, are capable to reproduce the observations.

  16. A kinematic model of a solar flare.

    Science.gov (United States)

    Nakagawa, Y.; Wu, S. T.; Han, S. M.

    1973-01-01

    Hyder advocated the idea that the optical (H-alpha) flares can be identified with the response of the solar chromosphere to an infalling material stream resulting from the 'disparition brusque' of a prominence. Since some flares are observed without any apparent association with infalling streams, in this paper we examine the possibility of identifying the optical flare with the response of the chromosphere to a supersonic disturbance, i.e., a shock, propagating downward. The undisturbed chromosphere is represented by the Harvard-Smithsonian Reference Atmosphere and the evolution of the shock is evaluated with the use of the CCW (Chisnell, Chester, Whitham) approximation based on the theory of characteristics. It is shown that the chromosphere is heated by the shock, that radiation is enhanced, and that the enhanced radiation terminates the shock around the height of the temperature minimum.

  17. The Mg II resonance line emission at 2800 A in stars with different rotational velocities and different metal abundances

    Science.gov (United States)

    Boehm-Vitense, E.

    1982-01-01

    In many investigations, a study of the Mg II 2800 A emission was conducted in order to derive more information about the correlation of chromospheric emission with the properties of the convection zone. It has been suggested by Ayres and Linsky (1980) that there is a positive correlation between rotation and chromospheric emission at least for binary stars. The present investigation is concerned with such a correlation between rotation and chromospheric emission. Since large differences in rotational velocities are observed for F stars for which also strong chromospheric emission is observable, this particular study deals mainly with F stars. On the basis of observations of the Mg II emission in F and G stars, it is found that the emission is abnormally strong in close binary F stars. This may be explained by the generation of a large differential rotation due to tidal effects which may give very efficient dynamo generation of a surface magnetic field.

  18. On Tripolar Magnetic Reconnection and Coronal Heating

    CERN Document Server

    Pandey, K; Lohani, N K; Pandey, Kumud; Narain, Udit

    2003-01-01

    Using recent data for the photosphere-chromosphere region of the solar atmosphere the magnetic reconnection in tripolar geometry has been investigated through the procedure of Sturrock (1999). Particular attention has been given to the width of the reconnecting region, wave number of the rapidly growing tearing mode, island length scales, frequency of MHD fluctuations, tearing mode growth rate, energy dissipation rate and minimum magnetic field strength required to heat chromospheric plasma to coronal temperatures. It is found that small length scales are formed in the upper chromosphere. The maximum growth rate of tearing mode instability coincides with the peak in the energy dissipation rate both of which occur in the upper chromosphere at the same height. It is realized that the distribution of magnetic field with height is essential for a better understanding of the coronal heating problem.

  19. Dynamics of the solar atmosphere above a pore with a light bridge

    CERN Document Server

    Sobotka, M; Jurcak, J; Heinzel, P; Del Moro, D; Berrilli, F

    2013-01-01

    Context: Solar pores are small sunspots lacking penumbra with prevailing vertical magnetic field component. They can include light bridges at places with locally reduced magnetic field. Like sunspots, they exhibit a wide range of oscillatory phenomena. Aims: A large isolated pore with a light bridge (NOAA 11005) is studied to obtain characteristics of a chromospheric filamentary structure around the pore, to analyse oscillations and waves in and around the pore, and to understand the structure and brightness of the light bridge. Methods: Spectral imaging observations in the line Ca II 854.2 nm and a complementary spectropolarimetry in Fe I lines, obtained with the DST/IBIS spectrometer and HINODE/SOT spectropolarimeter, are used to measure photospheric and chromospheric velocity fields, oscillations, waves, magnetic field in the photosphere, and acoustic energy flux and radiative losses in the chromosphere. Results: The chromospheric filamentary structure around the pore has all important characteristics of a...

  20. Multi-wavelength analysis of Ellerman Bomb Light Curves

    Czech Academy of Sciences Publication Activity Database

    Herlender, M.; Berlicki, Arkadiusz

    2011-01-01

    Roč. 35, č. 1 (2011), s. 181-186. ISSN 1845-8319 Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * chromosphere * Ellerman bomb Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  1. The Source of Alfven Waves That Heat the Solar Corona

    Science.gov (United States)

    Ruzmaikin, A.; Berger, M. A.

    1998-01-01

    We suggest a source for high-frequency Alfven waves invoked in coronal heating and acceleration of the solar wind. The source is associated with small-scale magnetic loops in the chromospheric network.

  2. A Possible Scenario of Energy Transport in the 17th May 2002 Flare

    Czech Academy of Sciences Publication Activity Database

    Kotrč, Pavel; Kashapova, L. K.; Frolova, A.S.; Kupryjakov, Ju. A.

    2009-01-01

    Roč. 33, č. 1 (2009), s. 207-215. ISSN 1845-8319 Institutional research plan: CEZ:AV0Z10030501 Keywords : solar flare * accelerated particles * chromosphere and corona Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  3. Solar Features - Prominences and Filaments

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Prominences and filaments are two manifestations of the same phenomenon. Both prominences and filaments are features formed above the chromosphere by cool dense...

  4. CIV Interferometer for a Solar Sounding Rocket Program

    Science.gov (United States)

    Gary, G. A.; West, E. A.; Davis, J. M.; Rees, D.

    2007-01-01

    A sounding rocket instrument consisting of two vacuum ultraviolet Fabry-Perot filters in series would allow high-spectral resolution over an extended field of view for solar observations of the transition region between the chromosphere and the corona.

  5. On the 3D Structure of the Magnetic Field in Regions of Emerging Flux

    CERN Document Server

    Ramos, A Asensio

    2010-01-01

    We explore the photospheric and chromospheric magnetic field in an emerging flux region. An image of the equivalent width of the He I 10830 A red blended component shows the presence of filamentary structures that might be interpreted as magnetic loops. We point out that the magnetic field strength in the chromosphere resembles a smoothed version of that found in the photosphere and that it is not correlated at all with the above-mentioned equivalent width map. Lacking other diagnostics, this suggests that one cannot discard the possibility that the chromospheric field we infer from the observations is tracing the lower chromosphere of the active region instead of tracing the magnetic field along loops. If the He I line is formed within magnetic loops, we point out a potential problem that appears when interpreting observations using only one component along the line-of-sight.

  6. The dynamics and magnetism of the X1 flare on 2014-03-29

    Science.gov (United States)

    Kleint, Lucia; Heinzel, Petr; Philip, Judge; Krucker, Sam

    2016-05-01

    The X1 flare on 2014-03-29 was observed with an unprecedented number of instruments including chromospheric polarimetry and spectroscopy from the UV to the IR. By combining data from these instruments, we can answer several open questions: Where is the observed continuum emission during flares formed and through which physical processes? How does the magnetic field structure in the photosphere and in the chromosphere change during a flare? We discuss the implications of our findings on standard flare models.

  7. Magnetic Reconnection resulting from Flux Emergence: Implications for Jet Formation in the lower solar atmosphere?

    OpenAIRE

    Ding, J. Y.; Madjarska, M. S.; Doyle, J. G.; Lu, Q. M.; Vanninathan, K.; Huang, Z

    2011-01-01

    We aim at investigating the formation of jet-like features in the lower solar atmosphere, e.g. chromosphere and transition region, as a result of magnetic reconnection. Magnetic reconnection as occurring at chromospheric and transition regions densities and triggered by magnetic flux emergence is studied using a 2.5D MHD code. The initial atmosphere is static and isothermal, with a temperature of 20,000 K. The initial magnetic field is uniform and vertical. Two physical environments with diff...

  8. Small Scale Dynamo Magnetism And the Heating of the Quiet Sun Solar Atmosphere.

    Science.gov (United States)

    Amari, T.

    2015-12-01

    The longstanding problem of the solar atmosphere heating has been addressed by many theoretical studies. Two specific mechanisms have been shown to play a key role in those : magnetic reconnection and waves. On the other hand the necessity of treating together chromosphere and corona has also been been stressed, with debates going on about the possibility of heating coronal plasma by energetic phenomena observed in the chromosphere,based on many key observations such as spicules, tornadoes…. We present some recent results about the modeling of quiet Sun heating in which magnetic fields are generated by a subphotospheric fluid dynamo which is connected to granulation. The model shows a topologically complex magnetic field of 160 G on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations.Those generated magnetic fields emerge into the chromosphere, providing the required energy flux and then small-scale eruptions releasing magnetic energy and driving sonic motions. Some of the more energetic eruptions can affect the very low corona only.It is also found that taking into account a vertical weak network magnetic field then allows to provide energy higher in the corona, while leaving unchanged the physics of chromospheric eruptions. The coronal heating mechanism rests on the eventual dissipation of Alfven waves generated inside the chromosphere and carrying upwards an adequate energy flux, while more energetic phenomena contribute only weakly to the heating of the corona.

  9. Observations of the forward scattering Hanle effect in the Ca i 4227 {\\AA} line

    CERN Document Server

    Bianda, M; Anusha, L S; Stenflo, J O; Nagendra, K N; Holzreuter, R; Sampoorna, M; Frisch, H; Smitha, H N

    2011-01-01

    Chromospheric magnetic fields are notoriously diffcult to measure. The chromospheric lines are broad, while the fields are producing a minuscule Zeeman-effect polarization. A promising diagnostic alternative is provided by the forward-scattering Hanle effect, which can be recorded in chromospheric lines such as the He i 10830 {\\AA} and the Ca i 4227 {\\AA} lines. We present a set of spectropolarimetric observations of the full Stokes vector obtained near the center of the solar disk in the Ca i 4227 {\\AA} line with the ZIMPOL polarimeter at the IRSOL observatory.We detect a number of interesting forward-scattering Hanle effect signatures, which we model successfully using polarized radiative transfer. Here we focus on the observational aspects, while a separate companion paper deals with the theoretical modeling.

  10. Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars

    CERN Document Server

    Orlando, S; Argiroffi, C; Reale, F; Peres, G; Miceli, M; Matsakos, T; Stehle', C; Ibgui, L; de Sa, L; Chie`ze, J P; Lanz, T

    2013-01-01

    (abridged) AIMS. We investigate the dynamics and stability of post-shock plasma streaming along nonuniform stellar magnetic fields at the impact region of accretion columns. We study how the magnetic field configuration and strength determine the structure, geometry, and location of the shock-heated plasma. METHODS. We model the impact of an accretion stream onto the chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our model takes into account the gravity, the radiative cooling, and the magnetic-field-oriented thermal conduction. RESULTS. The structure, stability, and location of the shocked plasma strongly depend on the configuration and strength of the magnetic field. For weak magnetic fields, a large component of B may develop perpendicular to the stream at the base of the accretion column, limiting the sinking of the shocked plasma into the chromosphere. An envelope of dense and cold chromospheric material may also develop around the shocked column. For strong magnetic fields, th...

  11. Magnetic field reconstruction based on sunspot oscillations

    CERN Document Server

    Löhner-Böttcher, J; Schmidt, W

    2016-01-01

    The magnetic field of a sunspot guides magnetohydrodynamic waves toward higher atmospheric layers. In the upper photosphere and lower chromosphere, wave modes with periods longer than the acoustic cut-off period become evanescent. The cut-off period essentially changes due to the atmospheric properties, e.g., increases for larger zenith inclinations of the magnetic field. In this work, we aim at introducing a novel technique of reconstructing the magnetic field inclination on the basis of the dominating wave periods in the sunspot chromosphere and upper photosphere. On 2013 August 21st, we observed an isolated, circular sunspot (NOAA11823) for 58 min in a purely spectroscopic multi-wavelength mode with the Interferometric Bidimensional Spectro-polarimeter (IBIS) at the Dunn Solar Telescope. By means of a wavelet power analysis, we retrieved the dominating wave periods and reconstructed the zenith inclinations in the chromosphere and upper photosphere. The results are in good agreement with the lower photosphe...

  12. The multi-thermal and multi-stranded nature of coronal rain

    CERN Document Server

    Antolin, P; Pereira, T M D; van der Voort, L Rouppe; Scullion, E

    2015-01-01

    In this work, we analyse coordinated observations spanning chromospheric, TR and coronal temperatures at very high resolution which reveal essential characteristics of thermally unstable plasmas. Coronal rain is found to be a highly multi-thermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated to coronal rain showers. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. A fast-slow two-step catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, mainly due to a funnel effect from the observed expansion of the magnetic field. Strong density inhomogeneities on spatial scales of 0.2"-0.5" are found, in which TR to chromospheric temperature ...

  13. Numerical simulations of magnetic reconnection in the lower solar atmosphere

    Institute of Scientific and Technical Information of China (English)

    Xiao-Yan Xu; Cheng Fang; Ming-De Ding; Dan-Hui Gao

    2011-01-01

    Observations indicate that Ellerman bombs (EBs) and chromospheric microflares both occur in the lower solar atmosphere, and share many common features,such as temperature enhancements, accompanying jet-like mass motions, short lifetime, and so on. These strongly suggest that EBs and chromospheric microflares could both probably be induced by magnetic reconnection in the lower solar atmosphere.With gravity, ionization and radiation considered, we perform two-dimensional numerical simulations of magnetic reconnection in the lower solar atmosphere. The influence of different parameters, such as intensity of the magnetic field and anomalous resistivity, on the results are investigated. Our result demonstrates that the temperature increases are mainly due to the joule dissipation caused by magnetic reconnection.The spectral profiles of EBs and chromospheric microflares are calculated with the non-LTE radiative transfer theory and compared with observations. It is found that the typical features of the two phenomena can be qualitatively reproduced.

  14. Magnetic structure of an activated filament in a flaring active region

    CERN Document Server

    Sasso, C; Solanki, S K

    2013-01-01

    While the magnetic field in quiescent prominences has been widely investigated, less is known about the field in activated prominences. We introduce observational results on the magnetic field structure of an activated filament in a flaring active region. We study, in particular, its magnetic structure and line-of-sight flows during its early activated phase, shortly before it displays signs of rotation. We invert the Stokes profiles of the chromospheric He I 10830 A triplet and the photospheric Si I 10827 A line observed in this filament by the VTT on Tenerife. Using these inversion results we present and interpret the first maps of velocity and magnetic field obtained in an activated filament, both in the photosphere and the chromosphere. Up to 5 different magnetic components are found in the chromospheric layers of the filament, while outside the filament a single component is sufficient to reproduce the observations. Magnetic components displaying an upflow are preferentially located towards the centre of...

  15. K2-Dwarf V471 TAU: a stellar version of solar variability

    International Nuclear Information System (INIS)

    Simultaneous observations of the rotational modulation with a 1/2 day period of chromospheric H alpha emission and of broadband irradiance for the K2-dwarf in V471 Tau are presented. The observations cover eight rotation periods but do not cover the full surface of the dwarf because of timing constraints. Preliminary results show a phase relation between enhanced chromospheric emission and continuum darkening similar to that observed on the Sun. A comparison with chromospheric Mg II resonance emission modulation observed about 2 1/4 years earlier by Guinan and Sion shows that the same active longitude is involved. This is either coincidental due to lucky phasing or it signifies a stable longitude that has persisted for hundreds of rotations

  16. The K2-dwarf V471 TAU: a Stellar Version of Solar Variability

    Science.gov (United States)

    Skumanich, A.; Young, A.

    1984-01-01

    Simultaneous observations of the rotational modulation with a 1/2 day period of chromospheric H alpha emission and of broadband irradiance for the K2-dwarf in V471 Tau are presented. The observations cover eight rotation periods but do not cover the full surface of the dwarf because of timing constraints. Preliminary results show a phase relation between enhanced chromospheric emission and continuum darkening similar to that observed on the Sun. A comparison with chromospheric Mg II resonance emission modulation observed about 2 1/4 years earlier by Guinan and Sion shows that the same active longitude is involved. This is either coincidental due to lucky phasing or it signifies a stable longitude that has persisted for hundreds of rotations.

  17. He I vector magnetic field maps of a sunspot and its superpenumbral fine-structure

    CERN Document Server

    Schad, T A; Lin, H; Tritschler, A

    2015-01-01

    Advanced inversions of high-resolution spectropolarimetric observations of the He I triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions, as superpenumbral Stokes profiles are dominated by atomic-level polarization while sunspot profiles are Zeeman-dominated but also exhibit signatures perhaps induced by symmetry breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere, and further show that the superpenumbral magnetic field does not appear finely structured, unlike the observed intensity structure. This suggests fibrils are not concentrations of magnetic flux but rather distinguished by individualized thermalization. We also dire...

  18. IUE and IRAS observations of luminous M stars with varying gas-to dust ratios

    International Nuclear Information System (INIS)

    Circumstellar gas and dust surrounding M giants and supergiants show luminous M stars to split into two distinct classes. Stars with a high gas to dust ratio all show chromospheric Ca II, H, and K emission. Stars with a high dust to gas ratio do not show chromospheric Ca II emission but are the only ones to show Balmer emission indicative of atmospheric shocks and are also the only ones to show maser emission. In order to determine whether all chromospheric indicators disappear in high dust to gas ratio stars, a survey of stars in both these classes was conducted with the IUE satellite. Long wavelength infrared fluxes for the program stars were obtained from the IRAS point source catalog. There is no obvious difference in the long wavelength observations between the two groups of stars. The long wavelength excess tends to follow the 10 micron excess and not the dust to gas ratio

  19. Reappraising Transition Region Line Widths in light of Recent Alfv\\'{e}n Wave Discoveries

    CERN Document Server

    McIntosh, Scott W; Tarbell, Theodore D

    2008-01-01

    We provide a new interpretation of ultraviolet transition region emission line widths observed by the SUMER instrument on the Solar and Heliospheric Observatory (SOHO). This investigation is prompted by observations of the chromosphere at unprecedented spatial and temporal resolution from the Solar Optical Telescope (SOT) on Hinode revealing that all chromospheric structures above the limb display significant transverse (Alfvenic) perturbations. We demonstrate that the magnitude, network sensitivity and apparent center-to-limb isotropy of the measured line widths (formed below 250,000K) can be explained by an observationally constrained forward-model in which the line width is caused by the line-of-sight superposition of longitudinal and Alfvenic motions on the small-scale (spicular) structures that dominate the chromosphere and low transition region.

  20. Evidence for short-period acoustic waves in the solar atmosphere

    Science.gov (United States)

    Wunnenberg, M.; Kneer, F.; Hirzberger, J.

    2002-11-01

    Short-period acoustic waves are thought to supply the energy for the radiative losses of the non-magnetic chromosphere of the Sun and, in general, of late-type stars. Here, we present evidence for the existence of waves in the solar atmosphere with periods in the range of 50 s Tower Telescope at the Observatorio del Teide/Tenerife. They are subjected to speckle reconstruction and to a wavelet analysis. The atmospheric ranges forming the velocity signals are narrowed by linear combinations of Doppler maps from wavelengths near line center. The power in the short-period range is concentrated above intergranular spaces. We estimate an acoustic flux into the chromosphere of approximately 3*E6 erg cm-2 s-1, as needed for the chromospheric radiative losses.

  1. From GHz to mHz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare

    CERN Document Server

    Martinez-Oliveros, J C; Besliu-Ionescu, D; Donea, A -C; Cally, P S; Lindsey, C

    2007-01-01

    We carried out an electromagnetic acoustic analysis of the solar flare of 14 August 2004 in active region AR10656 from the radio to the hard X-ray spectrum. The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake, confirming earlier inferences that relatively low-energy flares may be able to generate sun quakes. We introduce the hypothesis that the seismicity of the active region is closely related to the heights of coronal magnetic loops that conduct high-energy particles from the flare. In the case of relatively short magnetic loops, chromospheric evaporation populates the loop interior with ionized gas relatively rapidly, expediting the scattering of remaining trapped high-energy electrons into the magnetic loss cone and their rapid precipitation into the chromosphere. This increases both the intensity and suddenness of the chromospheric heating, satisfying the basic conditions for an acoustic emission that penetrates into the solar interior.

  2. Wave propagation and shock formation in different magnetic structures

    CERN Document Server

    Centeno, Rebecca; Bueno, Javier Trujillo

    2008-01-01

    Velocity oscillations "measured" simultaneously at the photosphere and the chromosphere -from time series of spectropolarimetric data in the 10830 A region- of different solar magnetic features allow us to study the properties of wave propagation as a function of the magnetic flux of the structure (i.e. two different-sized sunspots, a tiny pore and a facular region). While photospheric oscillations have similar characteristics everywhere, oscillations measured at chromospheric heights show different amplitudes, frequencies and stages of shock development depending on the observed magnetic feature. The analysis of the power and the phase spectra, together with simple theoretical modeling, lead to a series of results concerning wave propagation within the range of heights of this study. We find that, while the atmospheric cut-off frequency and the propagation properties of the different oscillating modes depend on the magnetic feature, in all the cases the power that reaches the high chromosphere above the atmo...

  3. Magnetoacoustic Waves in the Solar Stratified Atmosphere

    Institute of Scientific and Technical Information of China (English)

    郑惠南; 王水; 吴式灿; 李波

    2001-01-01

    The propagation of magnetoacoustic waves in the solar atmosphere consisting of the photosphere, chromosphere and corona has been studied numerically by time-dependent multi-dimensional magnetohydrodynamic (MHD) simulation. Pressure disturbances are introduced at the bottom of the chromosphere and at the bottom of the corona, respectively. The computational results show that incurred fast and slow MHD waves propagate away from the source of the disturbances. The fast MHD wave propagates as an expansive wave in the radial direction, while the slow one steepens and it may evolve into a slow shock. We suggest that the extreme ultraviolet imaging telescope wave observed by the SOHO and Moreton wave are a fast MHD wave propagating in the corona and in the chromosphere, respectively.

  4. Small-scale dynamo magnetism as the driver for heating the solar atmosphere

    Science.gov (United States)

    Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques

    2015-06-01

    The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes.

  5. Multiwavelength spectropolarimetric observations of an Ellerman bomb

    Science.gov (United States)

    Rezaei, R.; Beck, C.

    2015-10-01

    Context. Ellerman bombs (EBs) are enhanced emission in the wings of the Hα line in the solar spectrum. Aims: We study the structure of an EB in the photosphere and chromosphere. Methods: We analyze simultaneous observations of four chromospheric lines (Hα, Ca ii H, Ca ii IR 854 nm, and He i 1083 nm) as well as two photospheric lines (Fe i 630 and Si i 1082.7 nm) along with high-cadence 160 and 170 nm ultraviolet (UV) continuum filtergrams. Full Stokes data from the Helioseismic and Magnetic Imager (HMI) are used to trace the temporal evolution of the magnetic structure. Results: We identify the EB by excess emission in the wings of the Hα line, a brightening in the UV continuum, and large emission peaks in the core of the two Ca ii lines. The EB shows a blueshift in all chromospheric lines, while no shifts are observed in the photospheric lines. The blueshift in the chromospheric layer causes very asymmetric emission peaks in the Ca ii H line. The photospheric Si i spectral line shows a shallower line depth at the location of the EB. The UV continuum maps show that the EB was substantially brighter than its surroundings for about 30 min. The continuum contrast of the EB from 170 nm to 1080 nm shows a power-law dependency on the wavelength. The temperature enhancement amounts to 130 K in the low photosphere and 400 K at the temperature minimum level. This temperature excess is also seen in an LTE inversion of the Ca ii spectra. The total thermal and radiative energy content of the EB is about 1020 J and 1018 J in the photosphere and chromosphere, respectively. The HMI data hints at a photospheric magnetic flux cancellation as the driver of the EB. Conclusions: Ellerman bombs release the energy in a height range of several pressure scale heights around the temperature minimum such that they affect both the photosphere and the lower chromosphere.

  6. CaII Κ Imaging to Understand UV Irradiance Variability

    Indian Academy of Sciences (India)

    R. Kariyappa

    2000-09-01

    To identify and understand the underlying physical mechanisms of total solar and UV irradiance variability and to estimate the contribution of various chromospheric features to UV irradiance, detailed analysis of spatially resolved data is required. The various chromospheric features have been segregated and different parameters have been derived from CaII Κ Spectroheliograms of NSO/Sac Peak and Kodaikanal Observatory and compared with UV irradiance flux measured in MgII h and k lines by NOAA 9 satellite. The important results of this detailed analysis of CaII Κ Images of 1992 together with UV irradiance data will be discussed in this paper.

  7. Kink waves in an active region dynamic fibril

    CERN Document Server

    Pietarila, A; Hirzberger, J; Solanki, S K

    2011-01-01

    We present high spatial and temporal resolution Ca II 8542 observations of a kink wave in an on-disk chromospheric active region fibril. The properties of the wave are similar to those observed in off-limb spicules. From the observed phase and period of the wave we determine a lower limit for the field strength in the chromospheric active region fibril located at the edge of a sunspot to be a few hundred Gauss. We find indications that the event was triggered by a small-scale reconnection event higher up in the atmosphere.

  8. The presence of Si I series in the ultraviolet solar spectrum - 3000 to 1200 A

    Science.gov (United States)

    Moore, C. E.; Brown, C. M.; Sandlin, G. D.; Tilford, S. G.; Tousey, R.

    1977-01-01

    Laboratory and solar data are presented which form the basis for identifying chromospheric Si I absorption lines in UV rocket spectra of the solar limb. Prints of the Si I laboratory spectrum between 1520 and 1570 A are matched with those of the chromospheric spectrum, and a striking line-to-line coincidence is observed. Individual absorption series of Si I covering the 3p(2), 3P, 1D, and 1S ground terms are tabulated in multiplet form over the wavelength range from 1517 to 3069 A. It is noted that many of the solar lines are blended with both other Si I lines and lines of other spectra.

  9. Ly-alpha polarimeter design for CLASP rocket experiment

    CERN Document Server

    Watanabe, H; Kubo, M; Ishikawa, R; Bando, T; Kano, R; Tsuneta, S; Kobayashi, K; Ichimoto, K; Trujillo-Bueno, J

    2014-01-01

    A sounding-rocket program called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is proposed to be launched in the summer of 2014. CLASP will observe the solar chromosphere in Ly-alpha (121.567 nm), aiming to detect the linear polarization signal produced by scattering processes and the Hanle effect for the first time. The polarimeter of CLASP consists of a rotating half-waveplate, a beam splitter, and a polarization analyzer. Magnesium Fluoride (MgF2) is used for these optical components, because MgF2 exhibits birefringent property and high transparency at ultraviolet wavelength.

  10. The development of activity in Hale region 17098 (28 August - 8 September 1980)

    International Nuclear Information System (INIS)

    Proper motions and some respects of chromospheric activities of a relatively simple large sunspot group were studied based on full-disc white light photoheliograms and Hsub(α) filtergrams. The large sunspot group consisted of two subsequently developing groups. In the course of their development, the umbrae of the two groups collided with each other, three times a delta-configuration developed by convergent motions of opposite polarity umbrae of the two groups of different age creating a common penumbra. In spite of this complexity, the observed chromospheric activity was relatively low. (author)

  11. A search for star-planet interactions in the upsilon Andromedae system at X-ray and optical wavelengths

    OpenAIRE

    Poppenhaeger, K.; Lenz, L. F.; Reiners, A.; Schmitt, J. H. M. M.; Shkolnik, E.

    2010-01-01

    Context. Close-in, giant planets are expected to influence their host stars via tidal or magnetic interaction. But are these effects in X-rays strong enough in suitable targets known so far to be observed with today’s instrumentation? Aims. The υ And system, an F8V star with a Hot Jupiter, was observed to undergo cyclic changes in chromospheric activity indicators with its innermost planet’s period. We aim to investigate the stellar chromospheric and coronal activity over several mon...

  12. 13CO mapping study for massive molecular cloud cores

    Institute of Scientific and Technical Information of China (English)

    WU; Yuefang

    2001-01-01

    [1] Zirin, H., Astrophysics of the Sun, Chapter 7, Cambridge: Cambridge University Press, 1988.[2] Shine, R. A., Linsky, J. L., Physical properties of solar chromospheric plages II. Chromospheric plage models, Solar Phys., 1974, 39: 49.[3] Kelch, W. L., Linsky, J. L., Physical properties of solar chromospheric plages III. Models based on CaII and MgII observations, Solar Phys., 1978, 58: 37.[4] Lemaire, P., Goutlebroze, J. C., Vial, J. C. et al., Physical properties of the solar chromosphere deduced from optically thick lines, A & A, 1981, 103: 160.[5] Fontenla, J. M., Avrett, E. H., Loeser, R., Energy balance in the solar transition region II. Effects of pressure and energy input on hydrostatic models, ApJ, 1991, 377: 712.[6] Fontenla, J. M., Avrett, E. H., Loeser, R., Energy balance in the solar transition region III. Helium emission in hydrostatic, constant-abundance models with diffusion, ApJ, 1993, 406: 319.[7] Pierce, A. K., Slaughter, C., Solar limb darkening I: λλ(30337297), Solar Phys., 1977, 51: 25.[8] Pierce, A. K., Slaughter, C., Weinberger, D., Solar limb darkening in the interval 740424018*!, II, Solar Phys., 1977, 52: 179.[9] Nechel, H., Labs, D., The solar radiation between 3300 and 12500*!, Solar Phys., 1984, 90: 205.[10] Vernazza, J. E., Avrett, E. H., Loeser, R., Structure of the solar chromosphere I. Basic computations and summary of the results, ApJ, 1973, 184: 605.[11] Mihalas, D., Stellar Atmospheres, San Francisco: W. H. Freeman and Company, 1978.[12] Fang, C., Hnoux, J. -C., Self-consistent model of flare heated solar chromosphere, A & A, 1983, 118: 139.[13] Ding, M. D., Fang, C., A semi-empirical model of sunspot penumbra, A & A, 1989, 225: 204.[14] Vernazza, J. E., Avrett, E. H., Loeser, R., Structure of the solar chromosphere III. Models of the EUV brightness components of the quiet Sun, ApJ Suppl., 1981, 45: 635.[15] Canfield, R. C., Athey, R

  13. Semi-empirical model of solar plages

    Institute of Scientific and Technical Information of China (English)

    FANG; Cheng

    2001-01-01

    [1] Zirin, H., Astrophysics of the Sun, Chapter 7, Cambridge: Cambridge University Press, 1988.[2] Shine, R. A., Linsky, J. L., Physical properties of solar chromospheric plages II. Chromospheric plage models, Solar Phys., 1974, 39: 49.[3] Kelch, W. L., Linsky, J. L., Physical properties of solar chromospheric plages III. Models based on CaII and MgII observations, Solar Phys., 1978, 58: 37.[4] Lemaire, P., Goutlebroze, J. C., Vial, J. C. et al., Physical properties of the solar chromosphere deduced from optically thick lines, A & A, 1981, 103: 160.[5] Fontenla, J. M., Avrett, E. H., Loeser, R., Energy balance in the solar transition region II. Effects of pressure and energy input on hydrostatic models, ApJ, 1991, 377: 712.[6] Fontenla, J. M., Avrett, E. H., Loeser, R., Energy balance in the solar transition region III. Helium emission in hydrostatic, constant-abundance models with diffusion, ApJ, 1993, 406: 319.[7] Pierce, A. K., Slaughter, C., Solar limb darkening I: λλ(30337297), Solar Phys., 1977, 51: 25.[8] Pierce, A. K., Slaughter, C., Weinberger, D., Solar limb darkening in the interval 740424018*!, II, Solar Phys., 1977, 52: 179.[9] Nechel, H., Labs, D., The solar radiation between 3300 and 12500*!, Solar Phys., 1984, 90: 205.[10] Vernazza, J. E., Avrett, E. H., Loeser, R., Structure of the solar chromosphere I. Basic computations and summary of the results, ApJ, 1973, 184: 605.[11] Mihalas, D., Stellar Atmospheres, San Francisco: W. H. Freeman and Company, 1978.[12] Fang, C., Hnoux, J. -C., Self-consistent model of flare heated solar chromosphere, A & A, 1983, 118: 139.[13] Ding, M. D., Fang, C., A semi-empirical model of sunspot penumbra, A & A, 1989, 225: 204.[14] Vernazza, J. E., Avrett, E. H., Loeser, R., Structure of the solar chromosphere III. Models of the EUV brightness components of the quiet Sun, ApJ Suppl., 1981, 45: 635.[15] Canfield, R. C., Athey, R

  14. Energy balance in the solar transition region. II - Effects of pressure and energy input on hydrostatic models

    Science.gov (United States)

    Fontenla, J. M.; Avrett, E. H.; Loeser, R.

    1991-01-01

    The radiation of energy by hydrogen lines and continua in hydrostatic energy-balance models of the transition region between the solar chromosphere and corona is studied using models which assume that mechanical or magnetic energy is dissipated in the hot corona and is then transported toward the chromosphere down the steep temperature gradient of the transition region. These models explain the average quiet sun and also the entire range of variability of the Ly-alpha lines. The relations between the downward energy flux, the pressure of the transition region, and the different hydrogen emission are described.

  15. Continuum and line emission of flares on red dwarf stars: origin of the blue continuum radiation

    CERN Document Server

    Morchenko, E S

    2016-01-01

    There are two types of models that explain the appearance of the blue continuum radiation during the impulsive phase of stellar flares. Grinin and Sobolev (Astrophysics, vol. 13, 348, 1977) argue that this component of the optical continuum is formed in "the transition layer between the chromosphere and the photosphere". Katsova et al. (Astrophysics, vol. 17, 156, 1981) have "raised" the source of the white-light continuum up to the dense region in the perturbed chromosphere. In the present contribution (the main paper was submitted to journal "Astrophysics"), we show that the statement by Katsova et al. is erroneous.

  16. Stellar magnetic activity

    International Nuclear Information System (INIS)

    The stellar emission in the chromospheric Ca II H+K lines is compared with the coronal soft X-ray emission, measuring the effects of non-radiative heating in the outer atmosphere at temperatures differing two orders of magnitude. The comparison of stellar flux densities in Ca II H+K and X-rays is extended to fluxes from the transition-region and the high-temperature chromosphere. The stellar magnetic field is probably generated in the differentially rotating convective envelope. The relation between rotation rate and the stellar level of activity measured in chromospheric, transition-region, and coronal radiative diagnostics is discovered. X-ray observations of the binary λ Andromedae are discussed. The departure of M-type dwarfs from the main relations, and the implications for the structure of the chromospheres of these stars are discussed. Variations of the average surface flux densities of the Sun during the 11-year activity cycle agree with flux-flux relations derived for other cool stars, suggesting that the interpretation of the stellar relations may be furthered by studying the solar analogue in more detail. (Auth.)

  17. The Evolution of Cyclic Activity of the Sun in the Context of Physical Processes on Late-Type Stars

    Science.gov (United States)

    Katsova, Maria M.

    Features of the solar cycle in the context of stellar activity are investigated. We discovered reliably differential rotation in chromospheres of some stars and presented the first stellar butterfly diagrams. These stars possess less regular variability and do not demonstrate excellent cycles. This is the first evidence for differences of the solar activity from processes on stars with Excellent cycles. We compare indices of the chromospheric activity of the Sun with that for above 1,300 northern and southern stars whose activity revealed during planet search programs. We argue the matter pro and con for two possible ways of an evolution of activity from a contraction phase to 10Gyrs. When a young star brakes down, the chromospheric and the coronal activity weaken synchronously. The solar-like activity of the most main sequence F and early G stars does evolve by this path. The activity of the later stars from G5 to K7 after a definite level evolves by another way: the chromospheric activity diminishes up to the solar level, while coronae stay stronger than the solar one. Two possible paths of the evolution of activity are associated with the different depth of the convective zone of these stars. Physically this means that the relative input of small- and large-scale of magnetic fields differs for F-G and K stars.

  18. THE QUIET SOLAR ATMOSPHERE OBSERVED AND SIMULATED IN Na I D1

    International Nuclear Information System (INIS)

    The Na I D1 line in the solar spectrum is sometimes attributed to the solar chromosphere. We study its formation in quiet-Sun network and internetwork. We first present high-resolution profile-resolved images taken in this line with the imaging spectrometer Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope and compare these to simultaneous chromospheric images taken in Ca II 8542 A and Hα. We then model Na I D1 formation by performing three-dimensional (3D) non-local thermodynamic equilibrium profile synthesis for a snapshot from a 3D radiation-magnetohydrodynamics simulation. We find that most Na I D1 brightness is not chromospheric but samples the magnetic concentrations that make up the quiet-Sun network in the photosphere, well below the height where they merge into chromospheric canopies, with aureoles from 3D resonance scattering. The line core is sensitive to magneto-acoustic shocks in and near magnetic concentrations, where shocks occur deeper than elsewhere, and may provide evidence of heating deep within magnetic concentrations.

  19. Observations of On-Disk Type I and II Spicules

    Science.gov (United States)

    Deng, Na; Denker, C.; Verma, M.; Shimizu, T.; Liu, C.; Wang, H.

    2011-05-01

    A coordinated observing campaign was carried out during 2010 November 16-30 using German Vacuum Tower Telescope (VTT) and Hinode to investigate properties of small-scale spicules on the solar disk. The high-spectral resolution Echelle spectrograph at the VTT on Tenerife acquired spectra of the chromospheric halpha (656.28 nm) and photospheric Fe I (656.92 nm) lines in a region centered on a small pore. Hinode mission provides high-cadence vector magnetograms, G-band and Ca II H images, EIS and XRT observations of the same region. We present statistical properties of spicules (type I and II), such as spectral characteristics, velocities, spatial distribution and temporal evolution, paying particular attention to type II spicules or chromospheric jets. We investigate the photospheric magnetic structure, flow field and their evolution attempting to find the origin of chromospheric jets. The vertical extent of identified chromospheric jets in the transition region and corona will be studied using EIS and XRT observations in conjunction with SDO observations.

  20. Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere

    Czech Academy of Sciences Publication Activity Database

    Piantschitsch, I.; Amerstorfer, U.; Thalmann, J.; Utz, D.; Hanslmeier, A.; Bárta, Miroslav; Thonhofer, S.; Lemmerer, B.

    2014-01-01

    Roč. 38, č. 1 (2014), s. 59-66. ISSN 1845-8319 R&D Projects: GA MŠk(CZ) 7AMB14AT022 Institutional support: RVO:67985815 Keywords : MHD simulation * chromosphere * reconnection Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  1. Mining the Advanced Spectral Library (ASTRAL): Characterizing Winds of Evolved M-Stars

    Science.gov (United States)

    Nielsen, Krister E.; Carpenter, K. G.; Kober, G. V.; Cheng, K.; Ayres, T. R.; Harper, G.

    2013-01-01

    The HST/STIS treasury program Advanced Spectral Library (ASTRAL) enables investigations of the character and dynamics of the wind and chromosphere of cool stars, using high quality spectral data. This paper present the analysis of the outflowing winds of the M3.4 giant Gamma Cru and the M2Iab supergiant Alpha Ori. The outer atmospheres of these objects show strong evidence for significant inhomogeneity in their thermal and kinematic structure, and are in general not well understood. The wind features are characterized by a strong chromospheric emission suppressed by a overlying wind absorption, for many transitions producing a double peak feature. The relative strengths and wavelength shifts between the absorption and emission components of the lines reflect the acceleration of the wind from the base of the chromosphere, as the self-absorption is due to the overlying wind absorption, whose velocity relative to the chromosphere varies with height and thus line opacity. The wind profiles are sensitive to the wind opacity, turbulence and flow velocity, and hence favorable to analyze with the Sobolev source function with Exact Integration of the transfer equation (SEI) code. This paper will show a velocity and intensity analysis of the wind profiles and modeling with the SEI code to derive an improved set of wind parameters, primarily, for Gamma Cru.

  2. Physical Parameters of Dark Mottles Derived from High Resolution Optical Spectra

    Czech Academy of Sciences Publication Activity Database

    Tsiropoula, G.; Tziotziou, K.; Schwartz, Pavol; Kotrč, Pavel; Heinzel, Petr

    Nizozemí: ESA Publications Division, 2005 - (Danesy, D.), ---. (SP. 600). ISBN 92-9092-911-1. [European Solar Physics Meeting /11/. Leuven (BE), 11.09.2005-16.09.2005] R&D Projects: GA AV ČR IAA3003203 Institutional research plan: CEZ:AV0Z10030501 Keywords : chromosphere * fine structure Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  3. Temporal evolution of multiple evaporating ribbon sources in a solar flare

    CERN Document Server

    Graham, D R

    2015-01-01

    We present new results from the Interface Region Imaging Spectrograph showing the dynamic evolution of chromospheric evaporation and condensation in a flare ribbon, with the highest temporal and spatial resolution to date. IRIS observed the entire impulsive phase of the X-class flare SOL2014-09-10T17:45 using a 9.4 second cadence `sit-and-stare' mode. As the ribbon brightened successively at new positions along the slit, a unique impulsive phase evolution was observed for many tens of individual pixels in both coronal and chromospheric lines. Each activation of a new footpoint displays the same initial coronal up-flows of up to ~300 km/s, and chromospheric downflows up to 40 km/s. Although the coronal flows can be delayed by over 1 minute with respect to those in the chromosphere, the temporal evolution of flows is strikingly similar between all pixels, and consistent with predictions from hydrodynamic flare models. Given the large sample of independent footpoints, we conclude that each flaring pixel can be c...

  4. Magneto-static Modeling of the Mixed Plasma Beta Solar Atmosphere Based on Sunrise/IMaX Data

    Czech Academy of Sciences Publication Activity Database

    Wiegelmann, T.; Neukirch, A.J.; Nickeler, Dieter Horst; Solanki, S.K.; Martinez Pillet, V.; Borrero, J.M.

    2015-01-01

    Roč. 815, č. 1 (2015), 10/1-10/6. ISSN 0004-637X R&D Projects: GA ČR GA13-24782S Institutional support: RVO:67985815 Keywords : numerical methods * Sun chromosphere * Sun corona Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.993, year: 2014

  5. Evidence of relentless reconnections at boundaries of supergranular network lanes in quiet sun and coronal hole

    NARCIS (Netherlands)

    Aiouaz, T.

    2008-01-01

    Doppler-shift properties of the solar transition region (TR) and low corona are investigated in relation to the underlying chromospheric supergranular network, with particular regard to the role of the magnetic field. EUV line properties were obtained from a large raster scan of the solar chromosphe

  6. SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network

    Czech Academy of Sciences Publication Activity Database

    Wedemeyer, S.; Bastian, T.S.; Brajsa, R.; Bárta, Miroslav; Hudson, H. S.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; de Pontieu, B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J.H.; Antolin, P.; Gunár, Stanislav; Labrosse, N.; Benz, A. O.; Nindos, A.; Steffen, M.; Scullion, E.; Doyle, J.E.; Zaqarashvili, T.; Hanslmeier, A.; Nakariakov, V. M.; Heinzel, Petr; Ayres, T.; Karlický, Marian

    2015-01-01

    Roč. 56, č. 12 (2015), s. 2679-2692. ISSN 0273-1177 R&D Projects: GA ČR GA13-24782S EU Projects: European Commission(XE) 312495 Institutional support: RVO:67985815 Keywords : solar atmosphere * chromosphere * millimeter radiation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.358, year: 2014

  7. Formation and Plasma Circulation of Solar Prominences

    Science.gov (United States)

    Xia, C.; Keppens, R.

    2016-05-01

    Solar prominences are long-lived cool and dense plasma curtains in the hot and rarefied outer solar atmosphere or corona. The physical mechanism responsible for their formation and especially for their internal plasma circulation has been uncertain for decades. The observed ubiquitous downflows in quiescent prominences are difficult to interpret because plasma with high conductivity seems to move across horizontal magnetic field lines. Here we present three-dimensional numerical simulations of prominence formation and evolution in an elongated magnetic flux rope as a result of in situ plasma condensations fueled by continuous plasma evaporation from the solar chromosphere. The prominence is born and maintained in a fragmented, highly dynamic state with continuous reappearance of multiple blobs and thread structures that move mainly downward, dragging along mass-loaded field lines. The circulation of prominence plasma is characterized by the dynamic balance between the drainage of prominence plasma back to the chromosphere and the formation of prominence plasma via continuous condensation. Plasma evaporates from the chromosphere, condenses into the prominence in the corona, and drains back to the chromosphere, establishing a stable chromosphere–corona plasma cycle. Synthetic images of the modeled prominence with the Solar Dynamics Observatory Atmospheric Imaging Assembly closely resemble actual observations, with many dynamical threads underlying an elliptical coronal cavity.

  8. Multiwavelength analysis of a solar quiet region

    Czech Academy of Sciences Publication Activity Database

    Tsiropoula, G.; Tziotziou, K.; Schwartz, Pavol; Heinzel, Petr

    2009-01-01

    Roč. 493, č. 1 (2009), s. 217-225. ISSN 0004-6361 Grant ostatní: EU(XE) ESA-PECS project No. 98030 Institutional research plan: CEZ:AV0Z10030501 Keywords : Sun * chromosphere * transition region Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.179, year: 2009

  9. Bidirectional outflows as evidence of magnetic reconnection leading to a solar microflare

    CERN Document Server

    Hong, Jie; Li, Ying; Yang, Kai; Cheng, Xin; Chen, Feng; Fang, Cheng; Cao, Wenda

    2016-01-01

    Magnetic reconnection is a rapid energy release process that is believed to be responsible for flares on the Sun and stars. Nevertheless, such flare-related reconnection is mostly detected to occur in the corona, while there have been few studies concerning the reconnection in the chromosphere or photosphere. Here we present both spectroscopic and imaging observations of magnetic reconnection in the chromosphere leading to a microflare. During the flare peak time, chromospheric line profiles show significant blueshifted/redshifted components on the two sides of the flaring site, corresponding to upflows and downflows with velocities of $\\pm$(70--80) km s$^{-1}$, comparable with the local Alfv\\'{e}n speed as expected by the reconnection in the chromosphere. The three-dimensional nonlinear force-free field configuration further discloses twisted field lines (a flux rope) at a low altitude, cospatial with the dark threads in He I 10830 \\r{A} images. The instability of the flux rope may initiate the flare-related...

  10. Generation of Electrojets in Weakly Ionized Plasmas through a Collisional Dynamo

    CERN Document Server

    Dimant, Yakov S; Fletcher, Alex C

    2016-01-01

    Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earth's ionosphere near the magnetic equator where neutral winds drive the plasma across the geomagnetic field. Similar processes take place in the Solar chromosphere and MHD generators. This letter argues that not all convective neutral flows generate electrojets and it introduces the corresponding universal criterion for electrojet formation, $\

  11. Giants of eclipse the ζ [Zeta] Aurigae stars and other binary systems

    CERN Document Server

    Griffin, Elizabeth

    2015-01-01

    The zeta Aurigae stars are the rare but illustrious sub-group of binary stars that undergo the dramatic phenomenon of "chromospheric eclipse". This book provides detailed descriptions of the ten known systems, illustrates them richly with examples of new spectra, and places them in the context of stellar structure and evolution. Comprised of a large cool giant plus a small hot dwarf, these key eclipsing binaries reveal fascinating changes in their spectra very close to total eclipse, when the hot star shines through differing heights of the "chromosphere", or outer atmosphere, of the giant star. The phenomenon provides astrophysics with the means of analyzing the outer atmosphere of a giant star and how that material is shed into space. The physics of these critical events can be explained qualitatively, but it is more challenging to extract hard facts from the observations, and tough to model the chromosphere in any detail. The book offers current thinking on mechanisms for heating a star's chromosphere an...

  12. Observations and NLTE modeling of Ellerman bombs

    Czech Academy of Sciences Publication Activity Database

    Berlicki, Arkadiusz; Heinzel, Petr

    2014-01-01

    Roč. 567, July (2014), A110/1-A110/10. ISSN 0004-6361 R&D Projects: GA ČR(CZ) GAP209/11/2463 Institutional support: RVO:67985815 Keywords : Sun: chromosphere * line: profiles * imaging spectroscopy Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  13. Report on the Dutch expedition to observe the 1973 June 30 solar eclipse. II

    International Nuclear Information System (INIS)

    This paper continues to report the Dutch expedition to Atar, Mauritania, to observe the total solar eclipse of June 30, 1973. The purpose of this expedition was to obtain spectra from the transition region photosphere-chromosphere with high spectral and time resolution. (Auth.)

  14. iota Horologi, the first coronal activity cycle in a young solar-like star

    CERN Document Server

    Sanz-Forcada, J; Metcalfe, T S; 10.1051/0004-6361/201321388

    2013-01-01

    Context: The shortest chromospheric (Ca II H&K) activity cycle (1.6 yr) has been recently discovered in the young (~600 Myr) solar-like star iota Hor. Coronal X-ray activity cycles have only been discovered in a few stars other than the Sun, all of them with an older age and a lower activity level than iota Hor. Aims: We intended to find the X-ray coronal counterpart of the chromospheric cycle for i Hor. This represents the first X-ray cycle observed in an active star, as well as the paradigm of the first coronal cycles in the life of a solar-like star. Methods: We monitored i Hor with XMM-Newton observations spanning almost two years. The spectra of each observation are fit with two-temperature coronal models to study the long-term variability of the star. Results: We find a cyclic behavior in X-rays very similar to the contemporaneous chromospheric cycle. The continuous chromospheric monitoring for more than three cycle lengths shows a trend toward decreasing amplitude, apparently modulated by a longer ...

  15. Internetwork dynamics

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This review places current research in quiet-Sun chromospheric dynamics in the context of past and future work, concentrating on observational aspects of three-minute oscillations and Ca II K2V grains. The subject is of interest at present because observations and simulations come together to permit

  16. Dynamics of the solar atmosphere above a pore with a light bridge

    Czech Academy of Sciences Publication Activity Database

    Sobotka, Michal; Švanda, Michal; Jurčák, Jan; Heinzel, Petr; Del Moro, D.; Berrilli, F.

    2013-01-01

    Roč. 560, December (2013), A84/1-A84/14. ISSN 0004-6361 R&D Projects: GA ČR GAP209/12/0287; GA ČR GPP209/12/P568 Institutional support: RVO:67985815 Keywords : sunspots * chromosphere * photosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.479, year: 2013

  17. Spectral response of the solar atmosphere to an X-class flare event

    Science.gov (United States)

    Lacatus, Daniela Adriana; Donea, Alina

    2016-05-01

    The only X-class flare of 2015 observed by IRIS occurred at 16:22 UT on 11 March 2015, in AR 12297. This flare generated significant seismic transients in the photosphere at the eastern location of the flare. IRIS observations of the chromosphere and transition region help us understand the physics of the sunquake. In this work we will analyse this event using data from IRIS, SDO, and RHESSI. The IRIS rasters scanned the area between the main footpoints of the solar flare, and a wealth of chromospheric information has been inferred about the dynamics of the event. The main X-ray emission dominates the eastern flare footpoint, being missed by the IRIS slit. Significant enhancements in the chromospheric and TR lines intensities were identified. The forbidden line of Fe XXI 1354.1 Å is detected after the flare peak revealing the coronal responses to the flare. Plasma downflows of up to 300 km/s were identified in the majority of the observed lines, consistent with magnetic field local reconfiguration. We have also analysed an erupting filament developing at an earlier time, which moved rapidly towards the eastern part of the active region. We discuss the possibility that this filament might have pre-conditioned the chromosphere for the flare process.

  18. Characteristics of the Fe II and C II emission in high-resolution IUE spectra (2300-3000 A) of Alpha Orionis

    Science.gov (United States)

    Carpenter, K. G.

    1984-01-01

    A study is presented of Fe II and C II emission features in the 2300-3000 A region of four high-resolution IUE spectra of Alpha Ori obtained during the period 1978 April-1982 November. A set of 42 unmutilated, unblended Fe II lines of multiplets UV 1-3, 32-33, 35-36, and 60-64 and the C II (UV 0.01) intercombination lines have been identified and measured to determine their velocities, fluxes, and asymmetries. A correlation of Fe II line asymmetry with intrinsic line strength indicates a velocity field which is initially constant, then algebraically increases with radius to a maximum value and then decreases significantly before reaching an asymptotic flow speed far from the star. The mean velocity of the chromospheric regions emitting Fe II does not appear to differ substantially from the time-average of the photospheric velocity, but there is evidence that the two regions are not strongly coupled and thus that the chromosphere does not strictly follow the semiperiodic 6 year pulsations of the photosphere. An analysis of the C II line fluxes produces estimates of the electron density in the chromosphere in the range 3.2 x 10 to the 7th-1.3 x 10 to the 8th per sq cm and indicates that the region emitting C II is geometrically thick, extending at least one-tenth, and perhaps as far as 1.2, photospheric radii from the base of the chromosphere.

  19. Are there double layers in solar coronal transition region that accelerate ions originating solar wind?

    Science.gov (United States)

    Singh, N.

    2013-12-01

    Drawing from the physics of laser plasma expansion, laboratory experiments, magnetospheric observations on double layers (DLs), theory and simulations, we suggest that solar coronal transition region may contain randomly distributed numerous patches of double layers, which accelerate the ions from the upper chromosphere into the low corona. We expect the DLs to be distributed in a vertically thin layer while horizontally they are distributed widely. Such DLs provide a novel mechanism for the origin of the solar wind. The DL-based mechanism is based on expansion of dense cold chromospheric plasma consisting of cold ions, cold electrons with temperature Tc and a minor hot electron population with temperature Teh. Such plasma expansion naturally involves electric double layers, which are thin structures with vertical widths L much less than, say, about 100 plasma Debye lengths d. We envision that such double layers form in the upper chromosphere where charged particles collisions with neutral particles become rare at heights h > 1500 km above the photosphere and where ion-electron collision mean-free-path length S > L~ 10d. Such DLs are likely to form in magnetic flux tubes (coronal funnels) undergoing magnetic reconnection with magnetic fields in the chromospheric magnetic networks. Such reconnections produce the prerequisite hot electron population in the flux tube. The apparent vertical width of the coronal transition region (CTR) of the order of a few hundred kilometers is the consequence of the DLs vertically displaced in the plasma volume where the condition S > L ~ 10d is met. Since the magnetic reconnection and the DLs are dynamically evolving events, the CTR must be a highly dynamic region giving the observed zigzag boundary. The existence of the DLs in the CTR can be inferred from the outflow of ions from the chromosphere as beams, consisting of heavy and light ions, having the same energy before they are affected by other plasma processes and the solar

  20. NST and IRIS multi-wavelength observations of an M1.0 class solar flare

    Science.gov (United States)

    Vargas Domínguez, Santiago; Sadykov, Viacheslav; Kosovichev, Alexander; Sharykin, Ivan; Struminsky, Alexei; Zimovets, Ivan

    2015-08-01

    Although solar flares are the most energetic events in the Solar System and have direct impact in the interplanetary space and ultimately in our planet, there are still many unresolved issues concerning their generation, the underlying processes of particle acceleration involved, the effect at different layer in the solar atmosphere, among others. This work presents new coordinated observations from the New Solar Telescope (NST) and the space telescope IRIS that acquired simultaneous observations of an M1.0 class flare occurred on 12 June, 2014 in active region NOAA 12087. NST filtergrams using the TiO filter, together with chromospheric data from the Halpha line allow us to study the evolution of the event from the first signs of the intensification of the intensity in the region. We focused on a small portion where the intensity enhancement in Halpha (blue and red wings) seems to be triggered, and discovered a rapid expansion of a flux-rope structure near the magnetic neutral line, in the sequence of high-resolution photospheric images. IRIS observations evidenced strong emission of the chromospheric and transition region lines during the flare. Jet-like structures are detected before the initiation of the flare in chromospheric lines and strong non-thermal emission in the transition region at the beginning of the impulsive phase. Evaporation flows with velocities up to 50 km/s occurred in the hot chromospheric plasma. We interpreted the result in terms of the “gentle” evaporation that occurs after accelerated particles heat the chromosphere.

  1. The Solar-Stellar Connection (NAG5-6124: SOHO Guest Investigator Program)

    Science.gov (United States)

    Ayres, Thomas R.

    1997-01-01

    The following is a final report from the SOHO Guest Investigator program to use the SUMER far-UV spectrometer to obtain imaging spectroscopy in support of the goals of the so-called "solar-stellar connection." In particular, a major emphasis was utilization of the long-slit time-resolved maps of the solar surface in bright far-UV emission lines to deduce how particular aspects of the temporally and spatially averaged line profiles trace back to individual structural features of the magnetically disturbed outer atmosphere; to help interpret the unresolved line profiles from high quality stellar observations (say, with the Space Telescope Imaging Spectrograph). The researchers served two tours of duty in the SOHO Operations Center as SUMER planners, during which time we conducted an extensive series of observing programs. These can be divided into three general categories: surface mapping, translimb spectroscopy, and active region diagnostics. We have analyzed some of the large volumes of data to the point where we have presented them in poster papers, and in invited papers at national and international meetings. Listed below are the titles of the preliminary publications we have written, including brief abstracts to indicate the main results. (1) Chromospheric structure and Dynamics-- Observations -- The chromosphere is a highly structured dynamic 'layer' of the solar outer atmosphere. Here, not only are the effects of mechanical heating first evident (moving upward in altitude from the deep photosphere), but also the amount of nonradiative energy deposited is far greater than in the albeit much hotter overlying transition region and corona. Further, the chromosphere is by far the thickest zone of the solar atmosphere with respect to the pressure scale height. A major goal of stellar astrophysics is to understand how the chromosphere is heated and why it adopts its peculiar structure. A cursory examination of solar filtergrams and high-resolution movies demonstrates

  2. Recent progresses in the simulation of small-scale magnetic fields

    CERN Document Server

    Steiner, Oskar

    2007-01-01

    New high-resolution observations reveal that small-scale magnetic flux concentrations have a delicate substructure on a spatial scale of 0.1''. Its basic structure can be interpreted in terms of a magnetic flux sheet or tube that vertically extends through the ambient weak-field or field-free atmosphere with which it is in mechanical equilibrium. A more refined interpretation comes from new three-dimensional magnetohydrodynamic simulations that are capable of reproducing the corrugated shape of magnetic flux concentrations and their signature in the visible continuum. Furthermore it is shown that the characteristic asymmetric shape of the contrast profile of facular granules is an effect of radiative transfer across the rarefied atmosphere of the magnetic flux concentration. I also discuss three-dimensional radiation magnetohydrodynamic simulations of the integral layers from the top of the convection zone to the mid-chromosphere. They show a highly dynamic chromospheric magnetic field, marked by rapidly movi...

  3. An Open Source, Massively Parallel Code for Non-LTE Synthesis and Inversion of Spectral Lines and Zeeman-induced Stokes Profiles

    CERN Document Server

    Socas-Navarro, H; Ramos, A Asensio; Bueno, J Trujillo; Cobo, B Ruiz

    2014-01-01

    With the advent of a new generation of solar telescopes and instrumentation, the interpretation of chromospheric observations (in particular, spectro-polarimetry) requires new, suitable diagnostic tools. This paper describes a new code, NICOLE, that has been designed for Stokes non-LTE radiative transfer, both for synthesis and inversion of spectral lines and Zeeman-induced polarization profiles, spanning a wide range of atmospheric heights, from the photosphere to the chromosphere. The code fosters a number of unique features and capabilities and has been built from scratch with a powerful parallelization scheme that makes it suitable for application on massive datasets using large supercomputers. The source code is being publicly released, with the idea of facilitating future branching by other groups to augment its capabilities.

  4. Solar prominences: 'double, double ... boil and bubble'

    CERN Document Server

    Keppens, Rony

    2015-01-01

    Observations revealed rich dynamics within prominences, the cool 10,000 K, macroscopic (sizes of order 100 Mm) "clouds" in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to Rayleigh-Taylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting a magnetohydrodynamic description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully non-linear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh-Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence mater...

  5. Spatially Resolved Images and Solar Irradiance Variability

    Indian Academy of Sciences (India)

    R. Kariyappa

    2008-03-01

    The Sun is the primary source of energy that governs both the terrestrial climate and near-earth space environment. Variations in UV irradiances seen at earth are the sum of global (solar dynamo) to regional (active region, plage, network, bright points and background) solar magnetic activities that can be identified through spatially resolved photospheric, chromospheric and coronal features. In this research, the images of CaII K-line (NSO/Sac Peak) have been analysed to segregate the various chromospheric features.We derived the different indices and estimated their contribution from the time series data to total CaII K emission flux and UV irradiance variability. A part of the important results from this research is discussed in this paper.

  6. A Bcool spectropolarimetric survey of over 150 solar-type stars

    Science.gov (United States)

    Marsden, Stephen; Petit, Pascal; Jeffers, Sandra; do Nascimento, Jose-Dias; Carter, Bradley; Brown, Carolyn

    2014-08-01

    As part of the Bcool project, over 150 solar-type stars chosen mainly from planet search databases have been observed between 2006 and 2013 using the NARVAL and ESPaDOnS spectropolarimeters on the Telescope Bernard Lyot (Pic du Midi, France) and the Canada France Hawaii Telescope (Mauna Kea, USA), respectively. These single ``snapshot'' observations have been used to detect the presence of magnetic fields on 40% of our sample, with the highest detection rates occurring for the youngest stars. From our observations we have determined the mean surface longitudinal field (or an upper limit for stars without detections) and the chromospheric surface fluxes, and find that the upper envelope of the absolute value of the mean surface longitudinal field is directly correlated to the chromospheric emission from the star and increases with rotation rate and decreases with age.

  7. A Bcool spectropolarimetric survey of over 150 solar-type stars

    CERN Document Server

    Marsden, Stephen; Jeffers, Sandra; Nascimento, Jose-Dias do; Carter, Bradley; Brown, Carolyn

    2013-01-01

    As part of the Bcool project, over 150 solar-type stars chosen mainly from planet search databases have been observed between 2006 and 2013 using the NARVAL and ESPaDOnS spectropolarimeters on the Telescope Bernard Lyot (Pic du Midi, France) and the Canada France Hawaii Telescope (Mauna Kea, USA), respectively. These single 'snapshot' observations have been used to detect the presence of magnetic fields on 40% of our sample, with the highest detection rates occurring for the youngest stars. From our observations we have determined the mean surface longitudinal field (or an upper limit for stars without detections) and the chromospheric surface fluxes, and find that the upper envelope of the absolute value of the mean surface longitudinal field is directly correlated to the chromospheric emission from the star and increases with rotation rate and decreases with age.

  8. Stochastic transients as a source of quasi-periodic processes in the solar atmosphere

    CERN Document Server

    Yuan, Ding; Jiao, Fangran; Walsh, Robert W

    2016-01-01

    Solar dynamics and turbulence occur at all heights of the solar atmosphere and could be described as stochastic processes. We propose that finite lifetime transients recurring at a certain place could trigger quasi-periodic processes in the associated structures. In this study, we developed a mathematical model for finite lifetime and randomly occurring transients, and found that quasi-periodic processes, with period longer than the time scale of the transients, are detectable intrinsically in form of trains. We simulate their propagation in an empirical solar atmospheric model with chromosphere, transition region and corona. We found that, due to the filtering effect of the chromospheric cavity, only the resonance period of the acoustic resonator is able to propagate to the upper atmosphere, such a scenario is applicable to slow magnetoacoustic waves in sunspots and active regions. If the thermal structure of the atmosphere is less wild and acoustic resonance does not take effect, the long period oscillation...

  9. Rapidly Rotating, X-ray Bright Stars in the Kepler Field

    CERN Document Server

    Howell, Steve B; Boyd, Padi; Smith, Krista Lynne; Gelino, Dawn

    2016-01-01

    We present Kepler light curves and optical spectroscopy of twenty X-ray bright stars located in the Kepler field of view. The stars, spectral type FK, show evidence for rapid rotation including chromospheric activity 100 times or more above the Sun at maximum and flaring behavior in their light curves. Eighteen of our objects appear to be (sub)giants and may belong to the class of FK Com variables, that is evolved rapidly spinning single stars with no excretion disk and high levels of chromospheric activity. Such stars are rare and are likely the result of W UMa binary mergers, a process believed to produce the FK Com class of variable and their descendants. The FK Com stage, including the presence of an excretion disk, is short-lived but leads to longer-lived stages consisting of single, rapidly rotating evolved (sub)giants with high levels of stellar activity.

  10. Simulated interaction of magnetohydrodynamic shock waves with a complex network-like region

    Science.gov (United States)

    Santamaria, I. C.; Khomenko, E.; Collados, M.; de Vicente, A.

    2016-05-01

    We provide estimates of the wave energy reaching the solar chromosphere and corona in a network-like magnetic field topology, including a coronal null point. The waves are excited by an instantaneous strong subphotospheric source and propagate through the subphotosphere, photosphere, chromosphere, transition region, and corona with the plasma beta and other atmospheric parameters varying by several orders of magnitude. We compare two regimes of the wave propagation: a linear and nonlinear regime. While the amount of energy reaching the corona is similar in both regimes, this energy is transmitted at different frequencies. In both cases the dominant periods of waves at each height strongly depend on the local magnetic field topology, but this distribution is only in accordance with observations in the nonlinear case. Movies are available in electronic form at http://www.aanda.org

  11. Solar Spicules: Prospects for Breakthroughs in Understanding with Solar-B

    Science.gov (United States)

    Sterling, A.

    Spicules densely populate the lower solar atmosphere; any image or movie of the chromosphere shows a plethora of them or their "cousins," such as mottles or fibrils. Yet despite several decades of effort we still do not know the mechanism that generates them, or how important their contribution is to the material and energy balance of the overall solar atmosphere. Solar-B will provide exciting new chromospheric observations at high time- and spatial-resolution, along with associated quality magnetic field data, that promise to open doors to revolutionary breakthroughs in spicule research. In this presentation we will review the current observational and theoretical status of spicule studies, and discuss prospects for advances in spicule understanding during the Solar-B era.

  12. Cool stars, stellar systems, and the sun; Proceedings of the 6th Cambridge Workshop, Seattle, WA, Sept. 18-21, 1989

    Science.gov (United States)

    Wallerstein, George (Editor)

    1990-01-01

    The present conference on cool stars, stellar systems, and the sun encompasses stellar chromospheres and coronae, binary stars, the stellar evolution of contracting stars and red giants, stellar evolution abundances of the elements, mass loss and envelopes, and stellar pulsation. Specific issues addressed include theories regarding the acoustic and magnetic heating of stellar chromospheres and coronae, stellar granulation, wave heating in magnetic flux tubes, observations of the solar Ca-II lines, longitudinal-transverse magnetic tube waves in the solar atmosphere, radio emission from rapidly rotating cool giant stars, and spot temperatures and area coverages on active dwarf stars. Also addressed are the optical and UV spectra of RS-CVn stars, emission lines from T-Tauri stars, the spectroscopy of HR1614 group stars, red giants in external galaxies, the rotation of evolved stars, the transition from red giant to planetary nebula, and radiative transfer in the dynamic atmospheres of variable stars.

  13. H$\\alpha$ and EUV observations of a partial CME

    CERN Document Server

    Christian, Damian J; Antolin, Patrick; Mathioudakis, Mihalis

    2015-01-01

    We have obtained H$\\alpha$ high spatial and time resolution observations of the upper solar chromosphere and supplemented these with multi-wavelength observations from the Solar Dynamic Observatory (SDO) and the {\\it Hinode} ExtremeUltraviolet Imaging Spectrometer (EIS). The H$\\alpha$ observations were conducted on 11 February 2012 with the Hydrogen-Alpha Rapid Dynamics Camera (HARDcam) instrument at the National Solar Observatory's Dunn Solar Telescope. Our H$\\alpha$ observations found large downflows of chromospheric material returning from coronal heights following a failed prominence eruption. We have detected several large condensations ("blobs") returning to the solar surface at velocities of $\\approx$200 km s$^{-1}$ in both H$\\alpha$ and several SDO AIA band passes. The average derived size of these "blobs" in H$\\alpha$ is 500 by 3000 km$^2$ in the directions perpendicular and parallel to the direction of travel, respectively. A comparison of our "blob" widths to those found from coronal rain, indicate...

  14. Magnetic, Thermal and Dynamical Evolution of AN M3.2 Two-Ribbon Flare

    Science.gov (United States)

    Collados, Manuel; Kuckein, Christoph; Manso Sainz, Rafael; Asensio Ramos, Andres

    On 2013, 17th May, a two-ribbon M3.2 flare took place in the solar atmosphere on the active region AR 11748. The flare evolution was observed at the German VTT of the Observatorio del Teide using the instrument TIP-II, with spectropolarimetric measurements of the photosphere (Si I at 1082.7 nm) and the chromosphere (Helium triplet at 1083 nm). Simultaneous spectroscopic data of the chromospheric spectral line of Ca II at 854.2 nm and filtergrams at Halpha were also obtained. The flare evolution as observed from the ground can be compared with the changes observed by AIA@SDO at different ultraviolet wavelengths. The ground observations covered several hours, including the pre-flare, impulsive, gradual and post-flare phases. We present maps of the magnetic field, thermal and dynamical properties of the region during its evolution from pre- to post-flare phase.

  15. Driving Solar Spicules and Jets with Magnetohydrodynamic Turbulence: Testing a Persistent Idea

    CERN Document Server

    Cranmer, Steven R

    2015-01-01

    The solar chromosphere contains thin, highly dynamic strands of plasma known as spicules. Recently, it has been suggested that the smallest and fastest (Type II) spicules are identical to intermittent jets observed by the Interface Region Imaging Spectrograph. These jets appear to expand out along open magnetic field lines rooted in unipolar network regions of coronal holes. In this paper we revisit a thirty-year-old idea that spicules may be caused by upward forces associated with Alfven waves. These forces involve the conversion of transverse Alfven waves into compressive acoustic-like waves that steepen into shocks. The repeated buffeting due to upward shock propagation causes nonthermal expansion of the chromosphere and a transient levitation of the transition region. Some older models of wave-driven spicules assumed sinusoidal wave inputs, but the solar atmosphere is highly turbulent and stochastic. Thus, we model this process using the output of a time-dependent simulation of reduced magnetohydrodynamic...

  16. Relation between the Sunrise photospheric magnetic field and the Ca II H bright features

    Science.gov (United States)

    Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.; Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A.

    Recent observations from the Sunrise balloon-borne solar telescope have enabled us to reach an unprecedented high spatial resolution on the solar surface with the near-ultraviolet photo-spheric and chromospheric images as well as the magnetograms. We use these high resolution observations to investigate the structure of the solar upper photosphere and lower chromosphere as well as their temporal evolutions. We study the relation between the inter-granular Ca II 397 nm bright structures in images obtained by the Sunrise Filter Imager (SuFI) and their corresponding photospheric vector magnetic field computed from the Imaging Magnetogram eXperiment (IMaX) observations. The targets under study are in a quiet Sun region and close to disc-centre.

  17. Combined ultraviolet studies of astronomical source

    Science.gov (United States)

    Dupress, A. K.; Baliunas, S. L.; Blair, W. P.; Hartmann, L. W.; Huchra, J. P.; Raymond, J. C.; Smith, G. H.; Soderblom, D. R.

    1985-01-01

    As part of its Ultraviolet Studies of Astronomical Sources the Smithsonian Astrophysical Observatory for the period 1 Feb. 1985 to 31 July 1985 observed the following: the Cygnus Loop; oxygen-rich supernova remnants in 1E0102-72; the Large Magellanic Cloud supernova remnants; P Cygni profiles in dwarf novae; soft X-ray photoionization of interstellar gas; spectral variations in AM Her stars; the mass of Feige 24; atmospheric inhomogeneities in Lambda Andromedae and FF Aquarii; photometric and spectroscopic observation of Capella; Alpha Orionis; metal deficient giant stars; M 67 giants; high-velocity winds from giant stars; accretion disk parameters in cataclysmic variables; chromospheric emission of late-type dwarfs in visual binaries; chromospheres and transient regions of stars in the Ursa Major group; and low-metallicity blue galaxies.

  18. Optické návrhy několika přístrojů sluneční fyziky

    Czech Academy of Sciences Publication Activity Database

    Rail, Zdeněk; Jareš, Daniel; Tomka, David; Doleček, Roman

    Úpice : Hvězdárna v Úpici, 2013 - (Marková, E.), s. 40-45 ISBN 978-80-86303-35-2. [Člověk ve svém pozemském a kosmickém prostředí. Úpice (CZ), 15.05.2012-17.05.2012] R&D Projects: GA MŠk(CZ) ED2.1.00/03.0079 Institutional support: RVO:61389021 Keywords : The optical designs of chromospheric telescope s and coronograph * spektrographs with birefringent and Fabry-Perot filters * minimization of number of optical members and scattered light * high quality and contrast images of solar chromosphere and corona Subject RIV: BH - Optics, Masers, Lasers http://www.cbks.cz/Upice2012/40.pdf

  19. SUMER: Solar Ultraviolet Measurements of Emitted Radiation

    Science.gov (United States)

    Wilhelm, K.; Axford, W. I.; Curdt, W.; Gabriel, A. H.; Grewing, M.; Huber, M. C. E.; Jordan, S. D.; Kuehne, M.; Lemaire, P.; Marsch, E.

    1992-01-01

    The experiment Solar Ultraviolet Measurements of Emitted Radiation (SUMER) is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. Specifically, SUMER will measure profiles and intensities of Extreme Ultraviolet (EUV) lines emitted in the solar atmosphere ranging from the upper chromosphere to the lower corona; determine line broadenings, spectral positions and Doppler shifts with high accuracy, provide stigmatic images of selected areas of the Sun in the EUV with high spatial, temporal and spectral resolution and obtain full images of the Sun and the inner corona in selectable EUV lines, corresponding to a temperature from 10,000 to more than 1,800,000 K.

  20. Calculated Sunspot and Quiet-Sun Mg II Profiles Compared With IRIS DataEugene Avrett and Hui TianHarvard-Smithsonian Center for Astrophysics60 Garden Street, Cambridge, MA 02138

    Science.gov (United States)

    Avrett, Eugene H.

    2014-06-01

    A new sunpsot model has been derived, consistent with the SUMER atlas data of Curdt, et al. and Mg II profile data from IRIS. Comparisons are made with Quiet-Sun results from both sources. It is necessary to include molecules in the sunspot model not only account for the low brightness temperatures near 1850 /AA but also for the density variations higher in the atmosphere. The minimum temperature is roughly 2500 K in the sunspot model and 4500 K for the quiet Sun. The Mg II H line profile is centrally reversed in both cases, with the peak intensity originating where the temperature rises abruptly from the minimum value. The line center is formed at the top of the chromosphere where the temperature rises abruptly from 10,000 K into the chromosphere-corona transition region. The calculated Mg II line center intensity is much smaller than observed, for models constrained by the EUV continuum data.

  1. Modelling of Reflective Propagating Slow-mode Wave in a Flaring Loop

    CERN Document Server

    Fang, X; Van Doorsselaere, T; Keppens, R; Xia, C

    2015-01-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by the synthesized \\textit{Solar Dynamics Observatory}/Atmospheric Imaging Assembly (AIA) 131, 94~\\AA~emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km/s in an 80 Mm length loop with an average temperatu...

  2. The seven components of Hα and the 9873 MHz line

    International Nuclear Information System (INIS)

    Under conditions pertaining to the middle chromosphere, the nlj-substates of the n = 2 and n = 3 states of hydrogen are found to be populated proportionally to their degree of degeneracy. Thus, the non-LTE formation of the Hα line is not expected to be influenced by some exotic excitation conditions in one of its seven components. The overpopulation of the 2Ssub(1/2) substate relative to the 2Psub(3/2) substate does not depend upon details of the radiative transfer in Hα, so that it rests wholly on the transfer in Lα (Milkey and Mihalas, 1973). One-component plane parallel models of the chromosphere thus further predict that the 2Ssub(1/2)-2Psub(3/2), 9873 MHz (3.04 cm) line will not be observeable in the radio-spectrum of the quiet Sun. (Auth.)

  3. Fine structures in the atmosphere above a sunspot umbra

    CERN Document Server

    Bharti, L; Solanki, S K

    2013-01-01

    We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904, obtained with the Swedish Solar Telescope (SST) La Palma, Canary Islands. Time series of high resolution \\ion{Ca}{ii}\\,$H$ images show transient jet-like structures in sunspot umbrae are elongated, which we call umbral microjets. These jets are directed roughly parallel to nearby penumbral microjets, suggesting that they are aligned with the background magnetic field. In general, first a bright dot-like structure appears, from which a jet later emerges, although some jets appear without an associated chromospheric dot. Bright photospheric umbral dots are associated with umbral microjets arising in the outer umbra. Nevertheless, a one-to-one correspondence between jet-like events and underlying umbral dots is not seen. They are typically less than 1\\arcsec ~long and less than 0\\farcs3 wide. The typical lifetime of umbral microjets is around one minute. The brightness of these structures increases from the...

  4. Beyond MHD: modeling and observation of partially ionized solar plasma processes

    CERN Document Server

    Khomenko, Elena

    2015-01-01

    The temperature and density conditions in the magnetized photosphere and chromosphere of the Sun lead to a very small degree of atomic ionization. In addition, at particular height, the magnetic field may be strong enough to give rise to a cyclotron frequency larger than the collisional frequency for some species, while for others the opposite may happen. These circumstances influence the collective behavior of the particles and some of the hypotheses of magnetohydrodynamics may be relaxed, giving rise to non-ideal MHD effects. In this paper we discuss our recent developments in modeling non-ideal plasma effects derived from the presence of a large amount of neutrals in the solar photosphere and the chromosphere, as well as observational consequences of these effects.

  5. Coronal Magnetic Fields Derived from Simultaneous Microwave and EUV Observations and Comparison with the Potential Field Model

    CERN Document Server

    Miyawaki, Shun; Shibasaki, Kiyoto; Shiota, Daikou; Nozawa, Satoshi

    2015-01-01

    We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the DEM measurements using EUV observations. We derived line of sight component of the coronal magnetic field from polarization observations of the thermal bremsstrahlung in the NOAA active region 11150, observed around 3:00 UT on February 3, 2011 using the Nobeyama Radioheliograph at 17 GHz. Because the thermal bremsstrahlung intensity at 17 GHz includes both chromospheric and coronal components, we extracted only the coronal component by measuring the coronal emission measure in EUV observations. In addition, we derived only the radio polarization component of the corona by selecting the region of coronal loops and weak magnetic field strength in the chromosphere along the line of sight. The upper limit of the coronal longitudinal magnetic fields were determined as 100 - 210 G. We also calculated the coronal longitudinal magnetic fields from the potential field extrapola...

  6. The Dynamics of Funnel Prominences

    CERN Document Server

    Keppens, Rony

    2014-01-01

    We present numerical simulations in 2.5D settings where large scale prominences form in situ out of coronal condensation in magnetic dips, in close agreement with early as well as recent reporting of `funnel prominences'. Our simulation uses full thermodynamic MHD with anisotropic thermal conduction, optically thin radiative losses, and parametrized heating as main ingredients to establish a realistic arcade configuration from chromosphere to corona. The chromospheric evaporation from especially transition region heights ultimately causes thermal instability and we witness the growth of a prominence suspended well above the transition region, continuously gaining mass and cross-sectional area. Several hours later, the condensation has grown into a structure connecting the prominence-corona transition region with the underlying transition region, and a continuous downward motion from the accumulated mass represents a drainage that matches observational findings. A more dynamic phase is found as well, with coro...

  7. Discovery of three new RS Canum Venaticorum-like counterparts to HEAO I X-ray sources

    Science.gov (United States)

    Buckley, D. A. H.; Tuohy, I. R.; Remillard, R. A.; Bradt, H. V.; Schwartz, D. A.

    1987-01-01

    The identification of three high-latitude HEAO I Scanning Modulation Collimator X-ray sources with the chromospherically active RS CVn-like stars HD 113816, HD 146413, and HD 39576 is reported. Optical observations, including coude spectroscopy and broad-band and narrow band photoelectric photometry are presented. The Ca II emission strength of all three stars shows that they are chromospherically active. HD 146413 and HD 39576 exhibit variable X-ray emission in the 1-13 keV energy range, while HD 113816 is a softer and steadier source. The level of X-ray flux detected from these three stars is some one to two orders of magnitude higher than predicted empirically from the Ca II emission fluxes. It is proposed that this emission results from flarelike activity.

  8. New Eyes on the Sun — Solar Science with ALMA

    Science.gov (United States)

    Wedemeyer, S.

    2016-03-01

    In Cycle 4, which starts in October 2016, the Atacama Large Millimeter/submillimeter Array (ALMA) will be open for regular observations of the Sun for the first time. ALMA’s impressive capabilities have the potential to revolutionise our understanding of our host star, with far-reaching implications for our knowledge about stars in general. The radiation emitted at ALMA wavelengths originates mostly from the chromosphere — a complex and dynamic layer between the photosphere and the corona that is prominent during solar eclipses. Despite decades of intensive research, the chromosphere is still elusive due to its complex nature and the resulting challenges to its observation. ALMA will change the scene substantially by opening up a new window on the Sun, promising answers to long-standing questions.

  9. Viscosity effects on waves in partially and fully ionized plasma in magnetic field

    CERN Document Server

    Vranjes, J

    2014-01-01

    Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on two very different waves (Alfven and Langmuir) in solar atmosphere. A full set of viscosity coefficients is presented which includes coefficients for electrons, protons and hydrogen atoms. These are applied to layers with mostly magnetized protons in solar chromosphere where the Alfven wave could in principle be expected. The viscosity coefficients are calculated and presented graphically for the altitudes between 700 and 2200 km, and required corresponding cross sections for various types of collisions are given in terms of altitude. It is shown that in chromosphere the viscosity plays no role for the Alfven wave, which is only strongly affected by ion friction with neutrals. In corona, assuming the magnetic field of a few Gauss, the Alfven wave is more affected by ion viscosity than by ion-electron friction only for wavelengths shorter that 1-30 km, dependent on parameters and assuming the perturbed magnetic fiel...

  10. Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares

    CERN Document Server

    Testa, Paola; Allred, Joel; Carlsson, Mats; Reale, Fabio; Daw, Adrian; Hansteen, Viggo; Martinez-Sykora, Juan; Liu, Wei; DeLuca, Ed; Golub, Leon; McKillop, Sean; Reeves, Kathy; Saar, Steve; Tian, Hui; Lemen, Jim; Title, Alan; Boerner, Paul; Hurlburt, Neal; Tarbell, Ted; Wuelser, J P; Kleint, Lucia; Kankelborg, Charles; Jaeggli, Sarah

    2014-01-01

    The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (about 20 to 60 seconds) of intensity and velocity on small spatial scales at the footpoints of hot dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of non-thermal electrons, which are generated in small impulsive heating events called "coronal nanoflares". The accelerated electrons deposit a sizable fraction of their energy in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.

  11. Atmospheric activity in red dwarf stars

    International Nuclear Information System (INIS)

    Active and inactive stars of similar mass and luminosity have similar physical conditions in their photospheres, outside of magnetically disturbed regions. Such field structures give rise to stellar activity, which manifests itself at all heights of the atmosphere. Observations of uneven distributions of flux across the stellar disc have led to the disovery of photospheric starspots, chromospheric plage areas, and coronal holes. Localized transient behavior has been identified in both thermal and non-thermal sources, such as flares, shock waves and particle acceleration. The common element to all active regions is the presence of strong magnetic field structures connecting the violently turbulent deep layers in the convection zones of stars with the tenuous outer atmospheres. Transport and dissipation of energy into the chromospheric and coronal regions are still much debated topics

  12. Ellerman Bombs, Type II White-light Flares and Magnetic Reconnection in the Solar Lower Atmosphere

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ellerman bombs and Type II white-light flares share many common features despite the large energy gap between them. Both are considered to result from local heating in the solar lower atmosphere. This paper presents numerical simulations of magnetic reconnection occurring in such a deep atmosphere, with the aim to account for the common features of the two phenomena. Our numerical results manifest the following two typical characteristics of the assumed reconnection process: (1) magnetic reconnection saturates in ~600-900 s, which is just the lifetime of the two phenomena; (2) ionization in the upper chromosphere consumes quite a large part of the energy released through reconnection, making the heating effect most significant in the lower chromosphere. The application of the reconnection model to the two phenomena is discussed in detail.

  13. Measurements of Ca II Infrared Triplet Lines of Young Stellar Objects

    CERN Document Server

    Moto'oka, Keiko

    2015-01-01

    Equivalent widths and line widths of Ca II infrared triplet emission lines were measured in high-resolution optical spectra of 39 young stellar objects.We found that the equivalent widths of the emission lines decrease with stellar evolution. It has been often claimed that strong chromospheric activity is generated by a dynamo process caused by fast rotation of the photosphere. However, we found no clear correlation between the strength of the Ca II lines and the stellar rotation velocity. Instead, we found that the objects with high mass accretion rates had stronger Ca II emission lines. This correlation supports the turbulent chromosphere model or the magnetic accretion theory for classical T Tauri stars. We also noticed that the equivalent widths of Ca II lines of transitional disk objects are one-tenth of those of classical T Tauri stars, even if the masses of the circumstellar disks are comparable.

  14. Observational evidence for enhanced magnetic activity of superflare stars.

    Science.gov (United States)

    Karoff, Christoffer; Knudsen, Mads Faurschou; De Cat, Peter; Bonanno, Alfio; Fogtmann-Schulz, Alexandra; Fu, Jianning; Frasca, Antonio; Inceoglu, Fadil; Olsen, Jesper; Zhang, Yong; Hou, Yonghui; Wang, Yuefei; Shi, Jianrong; Zhang, Wei

    2016-01-01

    Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares. PMID:27009381

  15. Chemical Composition of the RS CVn-type Star 29 Draconis

    CERN Document Server

    Barisevi\\vcius, G; Berdyugina, S; Chorniy, Y; Ilyin, I

    2011-01-01

    Photospheric parameters and chemical composition are determined for the single-lined chromospherically active RS CVn-type star 29 Draconis (HD 160538). From the high resolution spectra obtained on the Nordic Optical Telescope, abundances of 22 chemical elements, including the key elements such as 12C, 13C, N and O, were investigated. The differential line analysis with the MARCS model atmospheres gives Teff=4720 K, log g=2.5, Fe/H]=-0.20, [C/Fe]=-0.14, [N/Fe]=0.08, [O/Fe]=-0.04, C/N=2.40, 12C/13C=16. The low value of the 12C/13C ratio gives a hint that extra mixing processes in low-mass chromospherically active stars may start earlier than the theory of stellar evolution predicts.

  16. Resonant energy conversion of 3-minute intensity oscillations into Alfven waves in the solar atmosphere

    CERN Document Server

    Kuridze, D

    2007-01-01

    Nonlinear coupling between 3-minute oscillations and Alfven waves in the solar lower atmosphere is studied. 3-minute oscillations are considered as acoustic waves trapped in a chromospheric cavity and oscillating along transversally inhomogeneous vertical magnetic field. It is shown that under the action of the oscillations the temporal dynamics of Alfven waves is governed by Mathieu equation. Consequently, the harmonics of Alfven waves with twice period and wavelength of 3-minute oscillations grow exponentially in time near the layer where the sound and Alfven speeds equal. Thus the 3-minute oscillations are resonantly absorbed by pure Alfven waves near this resonant layer. The resonant Alfven waves may penetrate into the solar corona taking energy from the chromosphere. Therefore the layer c_s=v_A may play a role of energy channel for otherwise trapped acoustic oscillations.

  17. The histeresis of the indices of solar activity and of the ionospheric indices in 11-yr cycles. The histeresis of the stellar activity indices in the cyclic activity similar to the Sun

    CERN Document Server

    Bruevich, E A; Kazachevskaya, T V; Katyushina, V V; Nusinov, A A

    2016-01-01

    The analysis of the effect of the hysteresis, which manifests itself in an ambiguous relationship of radiation from the photosphere, chromosphere and corona on the rise and decline phases of the solar and stellar activity cycles have done. Some indices of solar activity: the flux of the hydrogen Lyman-alpha emission, the 10.7 cm flux, the sunspot number SSN, the flux in the coronal green line 530.3 nm, the solar constant TSI and the 280 nm Mg II flux were studied. The stars with the well-determined cycles were examined to detect the effect of hysteresis between the chromosphere's S-index CaII fluxes versus the photosphere's fluxes Fphotosphere.

  18. ALMA's high-cadence imaging capabilities for solar observations

    CERN Document Server

    Wedemeyer, Sven

    2015-01-01

    The Atacama Large Millimeter/submillimeter Array offers an unprecedented view of our Sun at sub-/millimeter wavelengths. The high spatial, temporal, and spectral resolution facilitates the measurement of gas temperatures and magnetic fields in the solar chromosphere with high precision. The anticipated results will revolutionize our understanding of the solar atmosphere and may in particular result in major steps towards solving the coronal heating problem. Based on state-of-the-art 3D radiation magnetohydrodynamic simulations, we calculate the emergent continuum intensity (and thus brightness temperature maps) in the wavelength range accessed by ALMA and simulate instrumental effects for different array configurations. First results show that the local gas temperature can be closely mapped with ALMA and that much of the complex small-scale chromospheric pattern can be resolved.

  19. Effect of cross-redistribution on the resonance scattering polarization of O I line at 1302 Å

    International Nuclear Information System (INIS)

    Oxygen is the most abundant element on the Sun after hydrogen and helium. The intensity spectrum of resonance lines of neutral oxygen, namely, O I (1302, 1305, and 1306 Å), has been studied in the literature for chromospheric diagnostics. In this paper, we study the resonance scattering polarization in the O I line at 1302 Å using two-dimensional (2D) radiative transfer in a composite atmosphere constructed using a 2D magneto-hydrodynamical snapshot in the photosphere and columns of the one-dimensional FALC atmosphere in the chromosphere. The methods developed by us recently in a series of papers to solve multi-dimensional polarized radiative transfer have been incorporated in our new code POLY2D, which we use for our analysis. We find that multi-dimensional radiative transfer including XRD effects is important in reproducing the amplitude and shape of scattering polarization signals of the O I line at 1302 Å.

  20. An open-source, massively parallel code for non-LTE synthesis and inversion of spectral lines and Zeeman-induced Stokes profiles

    Science.gov (United States)

    Socas-Navarro, H.; de la Cruz Rodríguez, J.; Asensio Ramos, A.; Trujillo Bueno, J.; Ruiz Cobo, B.

    2015-05-01

    With the advent of a new generation of solar telescopes and instrumentation, interpreting chromospheric observations (in particular, spectropolarimetry) requires new, suitable diagnostic tools. This paper describes a new code, NICOLE, that has been designed for Stokes non-LTE radiative transfer, for synthesis and inversion of spectral lines and Zeeman-induced polarization profiles, spanning a wide range of atmospheric heights from the photosphere to the chromosphere. The code features a number of unique features and capabilities and has been built from scratch with a powerful parallelization scheme that makes it suitable for application on massive datasets using large supercomputers. The source code is written entirely in Fortran 90/2003 and complies strictly with the ANSI standards to ensure maximum compatibility and portability. It is being publicly released, with the idea of facilitating future branching by other groups to augment its capabilities. The source code is currently hosted at the following repository: http://https://github.com/hsocasnavarro/NICOLE

  1. Detection of large acoustic energy flux in the solar atmosphere

    CERN Document Server

    González, N Bello; Pillet, V Martínez; Bonet, J A; Solanki, S K; Iniesta, J C del Toro; Schmidt, W; Gandorfer, A; Domingo, V; Barthol, P; Berkefeld, T; Knölker, M

    2010-01-01

    We study the energy flux carried by acoustic waves excited by convective motions at sub-photospheric levels. The analysis of high-resolution spectropolarimetric data taken with IMaX/Sunrise provides a total energy flux of ~ 6400--7700 Wm$^{-2}$ at a height of ~ 250 km in the 5.2-10 mHz range, i.e. at least twice the largest energy flux found in previous works. Our estimate lies within a factor of 2 of the energy flux needed to balance radiative losses from the chromosphere according to Anderson & Athay (1989) and revives interest in acoustic waves for transporting energy to the chromosphere. The acoustic flux is mainly found in the intergranular lanes but also in small rapidly-evolving granules and at the bright borders, forming dark dots and lanes of splitting granules.

  2. Simulating coronal condensation dynamics in 3D

    CERN Document Server

    Moschou, S P; Xia, C; Fang, X

    2015-01-01

    We present numerical simulations in 3D settings where coronal rain phenomena take place in a magnetic configuration of a quadrupolar arcade system. Our simulation is a magnetohydrodynamic simulation including anisotropic thermal conduction, optically thin radiative losses, and parametrised heating as main thermodynamical features to construct a realistic arcade configuration from chromospheric to coronal heights. The plasma evaporation from chromospheric and transition region heights eventually causes localised runaway condensation events and we witness the formation of plasma blobs due to thermal instability, that evolve dynamically in the heated arcade part and move gradually downwards due to interchange type dynamics. Unlike earlier 2.5D simulations, in this case there is no large scale prominence formation observed, but a continuous coronal rain develops which shows clear indications of Rayleigh-Taylor or interchange instability, that causes the denser plasma located above the transition region to fall do...

  3. Stellar Evidence of a Solar Dynamo in Transition

    CERN Document Server

    Metcalfe, Travis S; van Saders, Jennifer

    2016-01-01

    Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation-age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro~2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation-age relations. We use these data along with a sample of well characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun is in a transitional ...

  4. Non-equilibrium CO chemistry in the solar atmosphere

    CERN Document Server

    Ramos, A A; Carlsson, M; Cernicharo, J

    2003-01-01

    Investigating the reliability of the assumption of instantaneous chemical equilibrium (ICE) for calculating the CO number density in the solar atmosphere is of crucial importance for the resolution of the long-standing controversy over the existence of `cool clouds' in the chromosphere, and for determining whether the cool gas owes its existence to CO radiative cooling or to a hydrodynamical process. Here we report the first results of such an investigation in which we have carried out time-dependent gas-phase chemistry calculations in radiation hydrodynamical simulations of solar chromospheric dynamics. We show that while the ICE approximation turns out to be suitable for modeling the observed infrared CO lines at the solar disk center, it may substantially overestimate the `heights of formation' of strong CO lines synthesized close to the edge of the solar disk, especially concerning vigorous dynamic cases resulting from relatively strong photospheric disturbances. This happens because during the cool phase...

  5. Simulated interaction of MHD shock waves with a complex network-like region

    CERN Document Server

    Santamaria, Irantzu C; Collados, Manuel; de Vicente, Angel

    2016-01-01

    We provide estimates of the wave energy reaching the solar chromosphere and corona in a network-like magnetic field topology, including a coronal null point. The waves are excited by an instantaneous strong subphotospheric source and propagate through the subphotosphere, photosphere, chromosphere, transition region, and corona with the plasma beta and other atmospheric parameters varying by several orders of magnitude. We compare two regimes of the wave propagation: a linear and nonlinear regime. While the amount of energy reaching the corona is similar in both regimes, this energy is transmitted at different frequencies. In both cases the dominant periods of waves at each height strongly depend on the local magnetic field topology, but this distribution is only in accordance with observations in the nonlinear case.

  6. A Multi-wavelength study of the M dwarf binary YY Geminorum

    CERN Document Server

    Butler, C J; Budding, E; Doyle, J G; Foing, B; Bromage, G E; Kellett, B J; Frueh, M; Huovelin, J; Brown, A; Neff, J E

    2015-01-01

    We review the results of the 1988 multi-wavelength campaign on the late-type eclipsing binary YY Geminorum. Observations include: broad-band optical and near infra-red photometry, simultaneous optical and ultraviolet (IUE) spectroscopy, X-ray (Ginga) and radio (VLA) data. From models fitted to the optical light curves, fundamental physical parameters have been determined together with evidence for transient maculations (spots) located near quadrature longitudes and intermediate latitudes. Eclipses were observed at optical, ultraviolet and radio wavelengths. Significant drops in 6cm radio emission near the phases of both primary and secondary eclipse indicate relatively compact radio emitting volumes that may lie between the binary components. IUE observations during secondary eclipse are indicative of a uniform chromosphere saturated with MgII plage-type emission and an extended volume of Ly$\\alpha$ emission. Profile fitting of high-dispersion H alpha spectra confirms the chromospheric saturation and indicate...

  7. Surface imaging of late-type contact binaries II: Halpha 6563 A emission in AE Phoenicis and YY Eridani

    CERN Document Server

    Vilhu, O

    2005-01-01

    We present and discuss the Halpha (6563 A) observations of the contact (W UMa type) binaries AE Phoenicis and YY Eridani, obtaineded in 1989, 1990 and 1995 with the CAT/CES telescope of the Southern European Observatory (ESO). In particular, we compare the intrinsic equivalent widths of both components with the NextGen theoretical models and the saturation limit. We find that the average Halpha equivalent widths are close to the saturation border and that the primary components have excess Halpha-emission, indicating enhanced chromospheric activity. This is compatible with both theoretical and observational suggestions that the primary is the more magnetically active component and is filled with (mostly unresolvable) dark spots and associated chromospheric plages.

  8. The Quiet Sun Network at Subarcsecond Resolution: VAULT Observations and Radiative Transfer Modeling of Cool Loops

    Science.gov (United States)

    Patsourakos, S.; Gouttebroze, P.; Vourlidas, A.

    2007-08-01

    One of the most enigmatic regions of the solar atmosphere is the transition region (TR), corresponding to plasmas with temperatures intermediate of the cool, few thousand K, chromosphere and the hot, few million K, corona. The traditional view is that the TR emission originates from a thin thermal interface in hot coronal structures, connecting their chromosphere with their corona. This paradigm fails badly for cool plasmas (~Tstructures seen in the Lyα line made by the Very High Angular Resolution Ultraviolet Telescope (VAULT). The subarcsecond (~0.3") resolution of VAULT allows us to directly view and resolve looplike structures in the quiet Sun network. We compare the observed intensities of these structures with simplified radiative transfer models of cool loops. The reasonable agreement between the models and the observations indicates that an explanation of the observed fine structure in terms of cool loops is plausible.

  9. Potential Studies of Physical and Chemical Properties of Neuro-protective Walnut and Turmeric Oil - An Analytical Approach

    OpenAIRE

    Joseph Francis PJ; Mullaicharam; Arun KJ; Ramesan MT

    2015-01-01

    This project deals with the extraction and analysis of essential oils from walnut and turmeric. The oil samples were extracted by cold extraction, hot extraction and steam distillation methods using organic solvents such as petroleum ether, chloroform, acetone and methanol. The extracted oils were subjected to thin layer chromatographic studies to understand the nature and number of components present. They were also analysed in UV-VIS spectrophotometer for the presence of chromospheres & tes...

  10. Nature of Quiet Sun Oscillations Using Data from the Hinode, TRACE, and SOHO Spacecraft

    OpenAIRE

    Gupta, G. R.; Subramanian, S.; Banerjee, D.; Madjarska, M. S.; Doyle, J. G.

    2012-01-01

    We study the nature of quiet-Sun oscillations using multi-wavelength observations from TRACE, Hinode, and SOHO. The aim is to investigate the existence of propagating waves in the solar chromosphere and the transition region via analyzing the statistical distribution of power in different locations, e.g. in bright magnetic (network), bright non-magnetic and dark non-magnetic (inter-network) regions, separately. We use Fourier power and phase-difference techniques combined with a wavelet analy...

  11. Emergence of Granular-sized Magnetic Bubbles Through the Solar Atmosphere. III. The Path to the Transition Region

    Science.gov (United States)

    Ortiz, Ada; Hansteen, Viggo H.; Ramón Bellot Rubio, Luis; de la Cruz Rodríguez, Jaime; De Pontieu, Bart; Carlsson, Mats; Rouppe van der Voort, Luc

    2016-07-01

    We study, for the first time, the ascent of granular-sized magnetic bubbles from the solar photosphere through the chromosphere into the transition region and above. Such events occurred in a flux emerging region in NOAA 11850 on 2013 September 25. During that time, the first co-observing campaign between the Swedish 1-m Solar Telescope (SST) and the Interface Region Imaging Spectrograph (IRIS) spacecraft was carried out. Simultaneous observations of the chromospheric Hα 656.28 nm and Ca ii 854.2 nm lines, plus the photospheric Fe i 630.25 nm line, were made with the CRISP spectropolarimeter at the Spitzer Space Telescope (SST) reaching a spatial resolution of 0.″14. At the same time, IRIS was performing a four-step dense raster of the emerging flux region, taking slit jaw images at 133 (C ii, transition region), 140 (Si iv, transition region), 279.6 (Mg ii k, core, upper chromosphere), and 283.2 nm (Mg ii k, wing, photosphere). Spectroscopy of several lines was performed by the IRIS spectrograph in the far- and near-ultraviolet, of which we have used the Si iv 140.3 and the Mg ii k 279.6 nm lines. Coronal images from the Atmospheric Imaging Assembly of the Solar Dynamics Observatory were used to investigate the possible coronal signatures of the flux emergence events. The photospheric and chromospheric properties of small-scale emerging magnetic bubbles have been described in detail in Ortiz et al. Here we are able to follow such structures up to the transition region. We describe the properties, including temporal delays, of the observed flux emergence in all layers. We believe this may be an important mechanism of transporting energy and magnetic flux from subsurface layers to the transition region and corona.

  12. The Multithermal and Multi-stranded Nature of Coronal Rain

    Science.gov (United States)

    Antolin, P.; Vissers, G.; Pereira, T. M. D.; Rouppe van der Voort, L.; Scullion, E.

    2015-06-01

    We analyze coordinated observations of coronal rain in loops, spanning chromospheric, transition region (TR), and coronal temperatures with sub-arcsecond spatial resolution. Coronal rain is found to be a highly multithermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated with coronal rain showers. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. A fast-slow two-step catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, mainly due to a funnel effect from the observed expansion of the magnetic field. Strong density inhomogeneities of 0\\buildrel{\\prime\\prime}\\over{.} 2-0\\buildrel{\\prime\\prime}\\over{.} 5 are found, in which a transition from temperatures of 105 to 104 K occurs. The 0\\buildrel{\\prime\\prime}\\over{.} 2-0\\buildrel{\\prime\\prime}\\over{.} 8 width of the distribution of coronal rain is found to be independent of temperature. The sharp increase in the number of clumps at the coolest temperatures, especially at higher resolution, suggests that the bulk distribution of the rain remains undetected. Rain clumps appear organized in strands in both chromospheric and TR temperatures. We further find structure reminiscent of the magnetohydrodynamic (MHD) thermal mode (also known as entropy mode), thereby suggesting an important role of thermal instability in shaping the basic loop substructure. Rain core densities are estimated to vary between 2 × 1010 and 2.5× {{10}11} cm-3, leading to significant downward mass fluxes per loop of 1-5 × 109 g s-1, thus suggesting a major role in the chromosphere-corona mass cycle.

  13. First measurement of the magnetic field on FK Com and its relation to the contemporaneous starspot locations

    OpenAIRE

    Korhonen, H.; Hubrig, S.; Berdyugina, S. V.; Granzer, Th.; Hackman, T.; Schoeller, M.; Strassmeier, K. G.; M. Weber

    2008-01-01

    In this study we present simultaneous low-resolution longitudinal magnetic field measurements and high-resolution spectroscopic observations of the cool single giant FK Com. The variation of the magnetic field over the rotational period of 2.4 days is compared with the starspot location obtained using Doppler imaging techniques, V-band photometry and V-I colours. The chromospheric activity is studied simultaneously with the photospheric activity using high resolution observations of the Halph...

  14. VizieR Online Data Catalog: High-precision abundances for stars with planets (Ramirez+, 2014)

    Science.gov (United States)

    Ramirez, I.; Melendez, J.; Asplund, M.

    2013-11-01

    High-precision stellar parameters and chemical abundances are presented for 111 stars; 52 of them are late-F type dwarfs and 59 are metal-rich solar analogs. The atomic linelist employed in the derivation of chemical abundances is also given. This linelist includes hyperfine structure parameters for some species. The stars' isochrone masses and ages are also reported, along with estimates of chromospheric activity. (5 data files).

  15. Variability of Active Galactic Nuclei from the Optical to X-ray Regions

    OpenAIRE

    Gaskell, C. Martin; Klimek, Elizabeth S.

    2009-01-01

    Some progress in understanding AGN variability is reviewed. Reprocessing of X-ray radiation to produce significant amounts of longer-wavelength continua seems to be ruled out. In some objects where there has been correlated X-ray and optical variability, the amplitude of the optical variability has exceeded the amplitude of X-ray variability. We suggest that accelerated particles striking material could be linking X-ray and optical variability (as in activity in the solar chromosphere). Beami...

  16. DYNAMICS IN SUNSPOT UMBRA AS SEEN IN NEW SOLAR TELESCOPE AND INTERFACE REGION IMAGING SPECTROGRAPH DATA

    Energy Technology Data Exchange (ETDEWEB)

    Yurchyshyn, V.; Abramenko, V. [Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA 92314 (United States); Kilcik, A. [Department of Space Science and Technologies, Akdeniz University, 07058 Antalya (Turkey)

    2015-01-10

    We analyze sunspot oscillations using Interface Region Imaging Spectrograph (IRIS) slit-jaw and spectral data and narrow-band chromospheric images from the New Solar Telescope (NST) for the main sunspot in NOAA AR 11836. We report that the difference between the shock arrival times as measured by the Mg II k 2796.35 Å and Si IV 1393.76 Å line formation levels changes during the observed period, and peak-to-peak delays may range from 40 s to zero. The intensity of chromospheric shocks also displays long-term (about 20 min) variations. NST's high spatial resolution Hα data allowed us to conclude that, in this sunspot, umbral flashes (UFs) appeared in the form of narrow bright lanes stretched along the light bridges and around clusters of umbral bright points. The time series also suggested that UFs preferred to appear on the sunspot-center side of light bridges, which may indicate the existence of a compact sub-photospheric driver of sunspot oscillations. The sunspot's umbra as seen in the IRIS chromospheric and transition region data appears bright above the locations of light bridges and the areas where the dark umbra is dotted with clusters of umbral dots. Co-spatial and co-temporal data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory showed that the same locations were associated with bright footpoints of coronal loops suggesting that the light bridges may play an important role in heating the coronal sunspot loops. Finally, the power spectra analysis showed that the intensity of chromospheric and transition region oscillations significantly vary across the umbra and with height, suggesting that umbral non-uniformities and the structure of sunspot magnetic fields may play a role in wave propagation and heating of umbral loops.

  17. Constraining magnetic-activity modulations in three solar-like stars observed by CoRoT and NARVAL

    OpenAIRE

    Mathur, S; García, R. A.; Morgenthaler, A.; Salabert, D.; Petit, P.; Ballot, J.; Régulo, C.; Catala, C.

    2013-01-01

    International audience Context. Stellar activity cycles are the manifestation of dynamo process running in the stellar interiors. They have been observed from years to decades thanks to the measurement of stellar magnetic proxies on the surface of the stars, such as the chromospheric and X-ray emissions, and to the measurement of the magnetic field with spectropolarimetry. However, all of these measurements rely on external features that cannot be visible during, for example, a Maunder-typ...

  18. New upper limit to the coronal line emission from the T Tauri star RU Lupi

    International Nuclear Information System (INIS)

    A high dispersion AAT spectrogram sets an upper limit on the [Fe x] emission line lambda 6374.5 A in the T Tauri star RU Lupi. The intensity of any 106 K corona in this star is less than 600 times that of the Sun compared to a chromosphere and transition region of 3 x 103 to 2 x 105 K gas 106 times stronger than the Sun's. The important theoretical implications are noted. (author)

  19. An Interface Region Imaging Spectrograph first view on Solar Spicules

    OpenAIRE

    Pereira, T. M. D.; de Pontieu, B.; Carlsson, M; Hansteen, V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.

    2014-01-01

    Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere remains unknown. Here we give a first glimpse of what quiet Sun spicules look like when observed with NASA's recently launched Interface Region Imaging Spectrograph (IRIS). Using IRIS spectra and filtergrams that sample the chromosphere and transition region we compare the ...

  20. Hard X-ray imaging from the solar probe. [X ray telescope and mission planning

    Science.gov (United States)

    Hudson, H. S.

    1978-01-01

    The solar probe offers a platform with particular advantages for studying solar nonthermal plasma processes via the observations of hard X-radiation from energetic electrons in the chromosphere and corona, these include (1) high sensitivity, (2) a second line of sign (in addition to the earth's) that can aid in three dimensional reconstruction of the source distribution, and, (3) the possibility of correlation with direct measurements of the nonthermal particles from the probe itself.

  1. Activity indicators and stellar parameters of the Kepler targets. An application of the ROTFIT pipeline to LAMOST-Kepler stellar spectra

    OpenAIRE

    Frasca, A.; Molenda-Zakowicz, J.; De Cat, P.; Catanzaro, G; Fu, J. N.; Ren, A. B.; Luo, A. L.; Shi, J. R.; Wu, Y.; Zhang, H. T.

    2016-01-01

    The LAMOST-Kepler survey, whose spectra are analyzed in the present paper, is the first large spectroscopic project aimed at characterizing these sources. Our work is focused at selecting emission-line objects and chromospherically active stars and on the evaluation of the atmospheric parameters. We have used a version of the code ROTFIT that exploits a wide and homogeneous collection of real star spectra, i.e. the Indo US library. We provide a catalog with the atmospheric parameters (Teff, l...

  2. The quiet Sun average Doppler shift of coronal lines up to 2 MK

    OpenAIRE

    Dadashi, Neda; Teriaca, Luca; Solanki, Sami K.

    2011-01-01

    The average Doppler shift shown by spectral lines formed from the chromosphere to the corona reveals important information on the mass and energy balance of the solar atmosphere, providing an important observational constraint to any models of the solar corona. Previous spectroscopic observations of vacuum ultra-violet (VUV) lines have revealed a persistent average wavelength shift of lines formed at temperatures up to 1 MK. At higher temperatures, the behaviour is still essentially unknown. ...

  3. Damping of Alfven waves in solar partially ionized plasmas: effect of neutral helium in multi-fluid approach

    OpenAIRE

    Zaqarashvili, T. V.; Khodachenko, M. L.; Rucker, H.O.

    2011-01-01

    Chromospheric and prominence plasmas contain neutral atoms, which may change the plasma dynamics through collision with ions. Most of the atoms are neutral hydrogen, but a significant amount of neutral helium may also be present in the plasma with a particular temperature. Damping of MHD waves due to ion collision with neutral hydrogen is well studied, but the effects of neutral helium are largely unknown. We aim to study the effect of neutral helium in the damping of Alfven waves in solar pa...

  4. Solar Simulations for the Atacama Large Millimeter Observatory Network

    OpenAIRE

    Wedemeyer, Sven; Bastian, Tim; Brajsa, Roman; Barta, Miroslav; Shimojo, Masumi

    2015-01-01

    The Atacama Large Millimeter/submillimeter Array (ALMA) will be a valuable tool for observing the chromosphere of our Sun at (sub-)millimeter wavelengths at high spatial, temporal and spectral resolution and as such has great potential to address long-standing scientific questions in solar physics. In order to make the best use of this scientific opportunity, the Solar Simulations for the Atacama Large Millimeter Observatory Network has been initiated. A key goal of this international collabo...

  5. Mechanisms of Coronal Heating

    Indian Academy of Sciences (India)

    S. R. Verma

    2006-06-01

    The Sun is a mysterious star. The high temperature of the chromosphere and corona present one of the most puzzling problems of solar physics. Observations show that the solar coronal heating problem is highly complex with many different facts. It is likely that different heating mechanisms are at work in solar corona. Recent observations show that Magnetic Carpet is a potential candidate for solar coronal heating.

  6. DYNAMICS IN SUNSPOT UMBRA AS SEEN IN NEW SOLAR TELESCOPE AND INTERFACE REGION IMAGING SPECTROGRAPH DATA

    International Nuclear Information System (INIS)

    We analyze sunspot oscillations using Interface Region Imaging Spectrograph (IRIS) slit-jaw and spectral data and narrow-band chromospheric images from the New Solar Telescope (NST) for the main sunspot in NOAA AR 11836. We report that the difference between the shock arrival times as measured by the Mg II k 2796.35 Å and Si IV 1393.76 Å line formation levels changes during the observed period, and peak-to-peak delays may range from 40 s to zero. The intensity of chromospheric shocks also displays long-term (about 20 min) variations. NST's high spatial resolution Hα data allowed us to conclude that, in this sunspot, umbral flashes (UFs) appeared in the form of narrow bright lanes stretched along the light bridges and around clusters of umbral bright points. The time series also suggested that UFs preferred to appear on the sunspot-center side of light bridges, which may indicate the existence of a compact sub-photospheric driver of sunspot oscillations. The sunspot's umbra as seen in the IRIS chromospheric and transition region data appears bright above the locations of light bridges and the areas where the dark umbra is dotted with clusters of umbral dots. Co-spatial and co-temporal data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory showed that the same locations were associated with bright footpoints of coronal loops suggesting that the light bridges may play an important role in heating the coronal sunspot loops. Finally, the power spectra analysis showed that the intensity of chromospheric and transition region oscillations significantly vary across the umbra and with height, suggesting that umbral non-uniformities and the structure of sunspot magnetic fields may play a role in wave propagation and heating of umbral loops

  7. Translimb Spectroscopy with SOHO/SUMER

    Science.gov (United States)

    Ayer, Thomas R.

    1997-01-01

    We have used SUMER to obtain deep exposures of the 1300-1400 A spectrum, at the extreme limb and off-limb. Previous "translimb" studies in the thermal infrared had revealed remarkable extensions of cold material (T approximately 3000 K)--traced by carbon monoxide emission lines--into the heart of the hot chromosphere. A main objective of our program was to search for corresponding far-UV signatures of the "thermally-bifurcated" low chromosphere; for example, radiatively fluoresced emissions of the CO A-X 4th-positive system (collisional excitation would be negligible in cold gas). We conducted two separate observing programs with SUMER. Both made use of the 1"-diameter circular aperture, translated across the limb in the minimum motor step increments of 0.375", along the central meridian in the Northern polar coronal hole. The first program executed for nine hours beginning 19UT 25 Oct 1996. The full wavelength range was 1340-1400 A. It was recorded in two overlapping segments, placing key regions of the spectrum alternately on the KBr and bare parts of the detector, to help isolate 2nd-order features. Each segment was integrated for 500 s, and 32 pairs were obtained to span a 12" swath centered on the optical limb. The second program was conducted 00-09UT 01 Dec 1996. It consisted of a single wavelength setting (1300-1340 A) with exposure time 500 s, but twice the spatial coverage of the earlier series: 64 steps, for a total displacement of 24". The strong chromospheric resonance lines of atomic oxygen (1302-1305 A) and ionized carbon (1334-1335 A) were observed on the bare part of the MCP camera. We report our progress in cataloging the rich, diverse translimb emission spectrum; and our efforts to deduce fundamental properties of the thermally heterogeneous chromosphere.

  8. Structures in the outer solar atmosphere

    OpenAIRE

    Fletcher, Lyndsay; Cargill, Peter J.; Antiochos, Spiro K.; Gudiksen, Boris V.

    2014-01-01

    The structure and dynamics of the outer solar atmosphere are reviewed with emphasis on the role played by the magnetic field. Contemporary observations that focus on high resolution imaging over a range of temperatures, as well as UV, EUV and hard X-ray spectroscopy, demonstrate the presence of a vast range of temporal and spatial scales, mass motions, and particle energies present. By focussing on recent developments in the chromosphere, corona and solar wind, it is shown that small scale pr...

  9. Solar ALMA Observations - A new view of our host star

    CERN Document Server

    Wedemeyer, Sven; Brajsa, Roman; Barta, Miroslav; Shimojo, Masumi; Hales, Antonio; Yagoubov, Pavel; Hudson, Hugh

    2015-01-01

    ALMA provides the necessary spatial, temporal and spectral resolution to explore central questions in contemporary solar physics with potentially far-reaching implications for stellar atmospheres and plasma physics. It can uniquely constraint the thermal and magnetic field structure in the solar chromosphere with measurements that are highly complementary to simultaneous observations with other ground-based and space-borne instruments. Here, we highlight selected science cases.

  10. The Young Solar Analogs Project: I. Spectroscopic and Photometric Methods and Multi-year Timescale Spectroscopic Results

    OpenAIRE

    Gray, R. O.; Saken, J. M.; Corbally, C. J.; Briley, M. M.; Lambert, R. A.; Fuller, V. A.; Newsome, I. M.; Seeds, M. F.; Kahvaz, Y.

    2015-01-01

    This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300 - 1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson $S$ chromospheric activity index ($S_{\\rm MW}$), and describe the meth...

  11. Torsional Alfv\\'en waves in solar partially ionized plasma: effects of neutral helium and stratification

    OpenAIRE

    Zaqarashvili, T. V.; Khodachenko, M. L.; Soler, R.

    2012-01-01

    Ion-neutral collisions may lead to the damping of Alfven waves in chromospheric and prominence plasmas. Neutral helium atoms enhance the damping in certain temperature interval, where the ratio of neutral helium and neutral hydrogen atoms is increased. Therefore, the height-dependence of ionization degrees of hydrogen and helium may influence the damping rate of Alfven waves. We aim to study the effect of neutral helium in the damping of Alfven waves in stratified partially ionized plasma of ...

  12. Echelle-MEPSICRON time-resolved spectroscopy of the dwarf nova SS Cygni

    International Nuclear Information System (INIS)

    High-dispersion time-resolved spectroscopy of the dwarf nova SS Cygni was obtained during two consecutive days at the end of an outburst. The emission lines present a double-peaked profile with a peak-to-peak separation of 526±14 km s-1. The lines have a complex structure which includes a narrow asymmetric component coming from a hot spot in the accretion disc or from the chromosphere of the red dwarf. (author)

  13. Echelle-MEPSICRON time-resolved spectroscopy of the dwarf nova SS Cygni

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria, J.; Tapia, M. (Universidad Nacional Autonoma de Mexico, Baja California (Mexico). Inst. de Astronomia); Diego, F. (Institute of Oceanographic Sciences, Godalming (UK)); Costero, R.; Ruiz, E.; Salas, L.; Gutierrez, L.; Enriquez, R. (Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Astronomia)

    1989-10-15

    High-dispersion time-resolved spectroscopy of the dwarf nova SS Cygni was obtained during two consecutive days at the end of an outburst. The emission lines present a double-peaked profile with a peak-to-peak separation of 526{plus minus}14 km s{sup -1}. The lines have a complex structure which includes a narrow asymmetric component coming from a hot spot in the accretion disc or from the chromosphere of the red dwarf. (author).

  14. Phenomena Associated With EIT Waves

    Science.gov (United States)

    Thompson, B. J.; Biesecker, D. A.; Gopalswamy, N.

    2003-01-01

    We discuss phenomena associated with "EIT Wave" transients. These phenomena include coronal mass ejections, flares, EUV/SXR dimmings, chromospheric waves, Moreton waves, solar energetic particle events, energetic electron events, and radio signatures. Although the occurrence of many phenomena correlate with the appearance of EIT waves, it is difficult to mfer which associations are causal. The presentation will include a discussion of correlation surveys of these phenomena.

  15. Stellar coronal magnetic fields and star-planet interaction

    OpenAIRE

    Lanza, A. F.

    2009-01-01

    Evidence of magnetic interaction between late-type stars and close-in giant planets is provided by the observations of stellar hot spots rotating synchronously with the planets and showing an enhancement of chromospheric and X-ray fluxes. We investigate star-planet interaction in the framework of a magnetic field model of a stellar corona, considering the interaction between the coronal field and that of a planetary magnetosphere moving through the corona. The energy budget of the star-planet...

  16. A New Multi-wavelength Solar Telescope: Optical and Near-infrared Solar Eruption Tracer (ONSET)

    OpenAIRE

    Fang, C.; Chen, P. F.; Li, Z.; Ding, M. D.; Dai, Y.; X. Y. Zhang; Mao, W. J.; J. P. Zhang; T. Li; Liang, Y J; Lu, H T

    2013-01-01

    A new multi-wavelength solar telescope, Optical and Near-infrared Solar Eruption Tracer (ONSET) of Nanjing University, was constructed, being fabricated by Nanjing Institute of Astronomical Optics & Technology and run in cooperation with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows: He {\\small I} 10830 \\AA, H$\\alpha$, and white-light at 3600 \\AA and 4250 \\AA, which are selected in order to obtain the dynamics in the corona, chromosphere, and th...

  17. Temporal variations of the CaXIX spectra in solar flares

    OpenAIRE

    Falewicz, R.; Rudawy, P.; Siarkowski, M.

    2009-01-01

    Standard model of solar flares comprises a bulk expansion and rise of abruptly heated plasma (the chromospheric evaporation). Emission from plasma ascending along loops rooted on the visible solar disk should be often dominated, at least temporally, by a blue-shifted emission. However, there is only a very limited number of published observations of solar flares having spectra in which the blue-shifted component dominates the stationary one. In this work we compare observed X-ray spectra of t...

  18. Řetězový filtr pro více astronomicky zajímavých spektrálních čar

    Czech Academy of Sciences Publication Activity Database

    Melich, Radek; Melich, Zbyněk; Šolc, Ivan; Klimeš st., Jan; Klimeš, J.

    Hurbanovo: Slovenska ustredna hvezdaren, 2006, s. 1-5. [Celoštátny slnečný seminár/18./. Modrá (SK), 22.05.2006-26.05.2006] R&D Projects: GA AV ČR 1QS100820502 Institutional research plan: CEZ:AV0Z20430508 Keywords : chain Solc filter * multiwavelength * birefringence * dispersion relation * chromosphere * telescope Subject RIV: BH - Optics, Masers, Lasers http://www.suh.sk/obs/slnsem/melich.pdf

  19. The FIP and Inverse FIP Effects in Solar and Stellar Coronae

    Directory of Open Access Journals (Sweden)

    J. Martin Laming

    2015-09-01

    Full Text Available We review our state of knowledge of coronal element abundance anomalies in the Sun and stars. We concentrate on the first ionization potential (FIP effect observed in the solar corona and slow-speed wind, and in the coronae of solar-like dwarf stars, and the “inverse FIP” effect seen in the corona of stars of later spectral type; specifically M dwarfs. These effects relate to the enhancement or depletion, respectively, in coronal abundance with respect to photospheric values of elements with FIP below about 10 eV. They are interpreted in terms of the ponderomotive force due to the propagation and/or reflection of magnetohydrodynamic waves in the chromosphere. This acts on chromospheric ions, but not neutrals, and so can lead to ion-neutral fractionation. A detailed description of the model applied to closed magnetic loops, and to open field regions is given, accounting for the observed difference in solar FIP fractionation between the slow and fast wind. It is shown that such a model can also account for the observed depletion of helium in the solar wind. The helium depletion is sensitive to the chromospheric altitude where ion-neutral separation occurs, and the behavior of the helium abundance in the closed magnetic loop strongly suggests that the waves have a coronal origin. This, and other similar inferences may be expected to have a strong bearing on theories of solar coronal heating. Chromospheric waves originating from below as acoustic waves mode convert, mainly to fast-mode waves, can also give rise to ion-neutral separation. Depending on the geometry of the magnetic field, this can result in FIP or Inverse FIP effects. We argue that such configurations are more likely to occur in later-type stars (known to have stronger field in any case, and that this explains the occurrence of the Inverse FIP effect in M dwarfs. We conclude with a discussion of possible directions for future work.

  20. Progress on Solar Physics in China During 2004 - 2006

    Institute of Scientific and Technical Information of China (English)

    YAN Yihua; AI Guoxiang

    2006-01-01

    The solar physics studies in China during 2004-2006 from solar interior to solar atmospheres and solar-interplanetary space are summarized. These researches are arranged under the topics of solar interior, photosphere, chromosphere and transition region, corona, flares and CMEs (and the associated radio bursts, X-ray/γ-ray bursts and particle acceleration), solar wind, solar cycle, and ground-based instrumentation.

  1. The Sun-like activity of the solar twin 18 Scorpii

    CERN Document Server

    Hall, J C; Lockwood, G W; Hall, Jeffrey C.; Henry, Gregory W.

    2007-01-01

    We present the results of 10 yr of complementary spectroscopic and photometric observations of the solar twin 18 Scorpii. We show that over the course of its ~7 year chromospheric activity cycle, 18 Sco's brightness varies in the same manner as the Sun's and with a likely brightness variation of 0.09%, similar to the 0.1% decadal variation in the total solar irradiance.

  2. Astrobiologically Interesting Stars within 10 parsecs of the Sun

    OpenAIRE

    de Mello, G. F. Porto; del Peloso, E. F.; Ghezzi, L.

    2005-01-01

    The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity and Galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We...

  3. An Improved Virial Estimate of Solar Active Region Energy

    OpenAIRE

    Wheatland, M. S.; Metcalf, T. R.

    2005-01-01

    The MHD virial theorem may be used to estimate the magnetic energy of active regions based on vector magnetic fields measured at the photosphere or chromosphere. However, the virial estimate depends on the measured vector magnetic field being force-free. Departure from force-freeness leads to an unknown systematic error in the virial energy estimate, and an origin dependence of the result. We present a method for estimating the systematic error by assuming that magnetic forces are confined to...

  4. Atmosphere above a large solar pore

    Czech Academy of Sciences Publication Activity Database

    Sobotka, Michal; Švanda, Michal; Jurčák, Jan; Heinzel, Petr; Del Moro, D.

    Bristol : Institute of Physics, 2013, 012049/1-012049/7. ISSN 1742-6588. - (Journal of Physics Conference Series. 440). [Eclipse on the Coral Sea: Cycle 24 Ascending. Palm Cove (AU), 12.11.2012-16.11.2012] R&D Projects: GA ČR GAP209/12/0287; GA ČR GPP209/12/P568 Institutional support: RVO:67985815 Keywords : high-spatial-resolution * sunspots * chromosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  5. H$\\mathbf{\\alpha}$ Intensity Oscillations in Large Flares

    Indian Academy of Sciences (India)

    Ram Ajor Maurya; Ashok Ambastha

    2008-03-01

    We reinvestigate the problem of Hα intensity oscillations in large flares, particularly those classified as X-class flares. We have used high spatial and temporal resolution digital observations obtained from Udaipur Solar Observatory during the period 1998–2006 and selected several events. Normalized Lomb–Scargle periodogram method for spectral analysis was used to study the oscillatory power in quiet and active chromospheric locations, including the flare ribbons.

  6. Multiwavelength observations of a giant flare on CN Leonis III. Temporal evolution of coronal properties

    OpenAIRE

    Liefke, Carolin; Fuhrmeister, Birgit; Schmitt, Juergen H. M. M.

    2010-01-01

    Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental conditions and the physical processes going on during different phases of the flare. We investigate the properties of the coronal plasma during a giant flare on the active M dwarf CN Leo observed simultaneously with the UVES spectrograph at the VLT and XMM...

  7. Physical Parameter Eclipse Mapping of the quiescent disc in V2051 Ophiuchi

    CERN Document Server

    Vrielmann, S; Offutt, W; Stiening, Rae F.; Offutt, Warren

    2002-01-01

    We analyse simultaneous UBVR quiescent light curves of the cataclysmic variable V2051 Oph using the Physical Parameter Eclipse Mapping method in order to map the gas temperature and surface density of the disc for the first time. The disc appears optically thick in the central regions and gradually becomes optically thin towards the disc edge or shows a more and more dominating temperature inversion in the disc chromosphere. The gas temperatures in the disc range from about 13500 K near the white dwarf to about 6000 K at the disc edge. The intermediate part of the disc has temperatures of 9000 K to 6500 K. The quiescent disc (chromosphere) shows a prominent bright region with temperatures of 10500 K around the impact region of the stream from the secondary with an extension towards smaller azimuths. The disc has a size of 0.53 +- 0.03 R_L1 and a mass accretion rate of between dM/dt = 10^15 g/s to 10^17g/s. The light curves must include an uneclipsed component, a hot chromosphere and/or a disc wind. The PPEM m...

  8. On the plasma flow inside magnetic tornadoes on the Sun

    CERN Document Server

    Wedemeyer, Sven

    2014-01-01

    High-resolution observations with the Swedish 1-m Solar Telescope (SST) and the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures that extend from the solar surface into the chromosphere and the corona. These so-called magnetic tornadoes are primarily detected as rings or spirals of rotating plasma in the Ca II 854.2 nm line core (also known as chromospheric swirls). Detailed numerical simulations show that the observed chromospheric plasma motion is caused by the rotation of magnetic field structures, which again are driven by photospheric vortex flows at their footpoints. Under the right conditions, two vortex flow systems are stacked on top of each other. We refer to the lower vortex, which extends from the low photosphere into the convection zone, as intergranular vortex flow (IVF). Once a magnetic field structure is co-located with an IVF, the rotation is mediated into the upper atmospheric layers and an atmospheric vortex flow (AVF, or magnetic tornado) is generated. In contrast...

  9. On the plasma flow inside magnetic tornadoes on the Sun

    Science.gov (United States)

    Wedemeyer, Sven; Steiner, Oskar

    2014-12-01

    High-resolution observations with the Swedish 1-m Solar Telescope (SST) and the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures that extend from the solar surface into the chromosphere and the corona. These so-called magnetic tornadoes are primarily detected as rings or spirals of rotating plasma in the Ca II 854.2 nm line core (also known as chromospheric swirls). Detailed numerical simulations show that the observed chromospheric plasma motion is caused by the rotation of magnetic field structures, which again are driven by photospheric vortex flows at their footpoints. Under the right conditions, two vortex flow systems are stacked on top of each other. We refer to the lower vortex, which extends from the low photosphere into the convection zone, as intergranular vortex flow (IVF). Once a magnetic field structure is co-located with an IVF, the rotation is mediated into the upper atmospheric layers and an atmospheric vortex flow (AVF, or magnetic tornado) is generated. In contrast to the recent work by Shelyag et al. (2013, ApJ, 776, L4), we demonstrate that particle trajectories in a simulated magnetic tornado indeed follow spirals and argue that the properties of the trajectories decisively depend on the location in the atmosphere and the strength of the magnetic field.

  10. Solar ALMA: Observation-Based Simulations of the mm and sub-mm Emissions from Active Regions

    CERN Document Server

    Fleishman, Gregory; Nita, Gelu

    2015-01-01

    We developed an efficient algorithm integrated in our 3D modeling tool, GX Simulator (Nita et al. 2015), allowing quick computation of the synthetic intensity and polarization maps of solar active regions (AR) in the ALMA spectral range. The algorithm analyzes the photospheric input (white light and magnetogram) to classify a given photospheric pixel to belong to a given photospheric structure. Then, a 1D chromospheric model (Fontenla et al. 2009) is added on top of each pixel, which forms a chromospheric model of the AR. Next step is computation of the mm and sub-mm emission produced from this chromosphere model. A huge advantage of this approach is that emission from any given AR can be synthesized very fast, on the order of a few minutes after the AR selection. Using the GX Simulator tool it is also possible to produce synthetic maps of the microwave (gyroresonance) and EUV emission from the same AR model and compare them with the ALMA synthetic maps and with the corresponding observed microwave and/or EUV...

  11. Height variation of supergranular velocity fields determined from simultaneous OSO 8 satellite and ground-based observations

    International Nuclear Information System (INIS)

    Simultaneous satellite and ground-based observations of supergranular velocities in the Sun were made using the University of Colorado UV Spectrometer on OSO 8 and the Sacramento Peak Observatory diode array instrument. We compare our observations of the steady Doppler velocities seen toward the limb in the middle chromosphere and the photosphere: the observed Si II lambda1817 and Fe I lambda5576 spectral lines differ in height of formation by about 1400 km.The striking results of these observations are that supergranular motions are able to penetrate at leas 11 density scale heights and that, in doing so, the motion increases from about 800 m s-1 in the photosphere to at least 3000 m s-1 in the middle chromosphere. Further, a distinct change appears to occur in the flow structure: whereas the horizontal component of the velocity predominates in low photosphere, suggesting strong braking of vertical momentum, the motions higher in the atmosphere are more isotropic. These observations imply that supergranular velocities should be evident in the transition region.The strong horizontal shear layers in supergranulation must produce turbulence and internal gravity waves. These smaller scale motions have bearing on chromospheric heating and nonthermal line broadening

  12. Emergence of granular-sized magnetic bubbles through the solar atmosphere. III. The path to the transition region

    CERN Document Server

    Ortiz, Ada; Rubio, Luis Ramon Bellot; Rodriguez, Jaime de la Cruz; De Pontieu, Bart; Carlsson, Mats; van der Voort, Luc Rouppe

    2016-01-01

    We study the ascent of granular-sized magnetic bubbles from the solar photosphere through the chromosphere into the transition region and above, for the first time. Such events occurred in a flux emerging region in NOAA 11850 on September 25, 2013. During that time, the first co-observing campaign between the Swedish 1-m Solar Telescope and the IRIS spacecraft was carried out. Simultaneous observations of the chromospheric H$\\alpha$ 656.28 nm and \\ion{Ca}{2} 854.2 nm lines, plus the photospheric \\ion{Fe}{1} 630.25 nm line, were made with the CRISP spectropolarimeter at the SST reaching a spatial resolution of 0."14. At the same time, IRIS was performing a four-step dense raster of the said emerging flux region, taking slit-jaw images at 133 (C~{\\sc ii}, transition region), 140 (\\ion{Si}{4}, transition region), 279.6 (\\ion{Mg}{2} k, core, upper chromosphere), and 283.2 nm (\\ion{Mg}{2} k, wing, photosphere). Spectroscopy of several lines was performed by the IRIS spectrograph in the far and near ultraviolet, of...

  13. Unresolved fine-scale structure in solar coronal loop-tops

    CERN Document Server

    Scullion, Eamon; Wedemeyer, Sven; Antolin, Patrick

    2014-01-01

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer sub-structures within coronal loop cross sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop sub-structures, through taking advantage of the resolving power of the Swedish 1- m Solar Telescope (SST) / CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory (SDO) / Atmospheric Image Assembly (AIA). High resolution imaging of the chromospheric H-alpha 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in H-alpha...

  14. 3D MHD modeling of twisted coronal loops

    CERN Document Server

    Reale, F; Guarrasi, M; Mignone, A; Peres, G; Hood, A W; Priest, E R

    2016-01-01

    We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-beta corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active region temperatures (~3 MK) after ~2/3 hr. Upflows from the chromosphere up to ~100 km/s fill the core of the flux tube to densities above 10^9 cm^-3. More heating is released in the low corona than the high corona and is finely ...

  15. Photometric and spectroscopic observations of three rapidly rotating late-type stars: EY Dra, V374 Peg and GSC 02038-00293

    CERN Document Server

    Korhonen, H; Husarik, M; Mahajan, S; Szczygiel, D; Olah, K

    2010-01-01

    Here, BV(RI)c broad band photometry and intermediate resolution spectroscopy in Halpha region are presented for two rapidly rotating late-type stars: EY Dra and V374 Peg. For a third rapid rotator, GSC 02038-00293, intermediate resolution Halpha spectroscopy and low resolution spectroscopy are used for spectral classification and stellar parameter investigation of this poorly known object. The low resolution spectrum of GSC 02038-00293 clearly indicates that it is a K-type star. Its intermediate resolution spectrum can be best fitted with a model with Teff=4750K and vsini=90km/s, indicating a very rapidly rotating mid-K star. The Halpha line strength is variable, indicating changing chromospheric emission on GSC 02038-00293. In the case of EY Dra and V374 Peg, the stellar activity in the photosphere is investigated from the photometric observations, and in the chromosphere from the Halpha line. The enhanced chromospheric emission in EY Dra correlates well with the location of the photospheric active regions, ...

  16. First detection of thermal radio emission from solar-type stars with the Karl G. Jansky very large array

    International Nuclear Information System (INIS)

    We present the first detections of thermal radio emission from the atmospheres of solar-type stars τ Cet, η Cas A, and 40 Eri A. These stars all resemble the Sun in age and level of magnetic activity, as indicated by X-ray luminosity and chromospheric emission in Ca II H and K lines. We observed these stars with the Karl G. Jansky Very Large Array with sensitivities of a few μJy at combinations of 10.0, 15.0, and 34.5 GHz. τ Cet, η Cas A, and 40 Eri A are all detected at 34.5 GHz with signal-to-noise ratios of 6.5, 5.2, and 4.5, respectively. 15.0 GHz upper limits imply a rising spectral index greater than 1.0 for τ Cet and 1.6 for η Cas A, at the 95% confidence level. The measured 34.5 GHz flux densities correspond to stellar disk-averaged brightness temperatures of roughly 10,000 K, similar to the solar brightness temperature at the same frequency. We explain this emission as optically thick thermal free-free emission from the chromosphere, with possible contributions from coronal gyroresonance emission above active regions and coronal free-free emission. These and similar quality data on other nearby solar-type stars, when combined with Atacama Large Millimeter/Submillimeter Array observations, will enable the construction of temperature profiles of their chromospheres and lower transition regions.

  17. THE INFLUENCE OF NUMERICAL RESOLUTION ON CORONAL DENSITY IN HYDRODYNAMIC MODELS OF IMPULSIVE HEATING

    International Nuclear Information System (INIS)

    The effect of the numerical spatial resolution in models of the solar corona and corona/chromosphere interface is examined for impulsive heating over a range of magnitudes using one-dimensional hydrodynamic simulations. It is demonstrated that the principal effect of inadequate resolution is on the coronal density. An underresolved loop typically has a peak density of at least a factor of two lower than a resolved loop subject to the same heating, with larger discrepancies in the decay phase. The temperature for underresolved loops is also lower indicating that lack of resolution does not 'bottle up' the heat flux in the corona. Energy is conserved in the models to under 1% in all cases, indicating that this is not responsible for the low density. Instead, we argue that in underresolved loops the heat flux 'jumps across' the transition region to the dense chromosphere from which it is radiated rather than heating and ablating transition region plasma. This emphasizes the point that the interaction between corona and chromosphere occurs only through the medium of the transition region. Implications for three-dimensional magnetohydrodynamic coronal models are discussed.

  18. Magnetic fields of an active region filament from full Stokes analysis of Si I 1082.7 nm and He I 1083.0 nm

    CERN Document Server

    Xu, Z; Solanki, S; Liu, Y

    2012-01-01

    Vector magnetic fields of an active region filament in the photosphere and upper chromosphere are obtained from spectro-polarimetric observations recorded with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). We apply Milne-Eddington inversions on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper chromospheric He I triplet at 1083.0 nm to obtain magnetic field vector and velocity maps in two atmosphere layers. We find that: (1)A complete filament was already present in H$\\alpha$ at the beginning of the TIP II data acquisition. Only a partially formed one, composed of multiple small threads, was present in He I. (2) The AR filament comprises two sections. One shows strong magnetic field intensities, about 600 - 800 G in the upper chromosphere and 800 - 1000 G in the photosphere. The other exhibits only comparatively weak magnetic field strengths in both layers. (3) The Stokes V signal is indicative of a dip in the magnetic field strength close to the chr...

  19. Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data

    CERN Document Server

    Yurchyshyn, Vasyl; Kilcik, Ali

    2014-01-01

    We analyse sunspot oscillations using Interface Region Imaging Spectrograph (IRIS) slit-jaw and spectral data and narrow-band chromospheric images from the New Solar Telescope (NST) for the main sunspot in NOAA AR 11836. We report that the difference between the shock arrival times as measured the Mg II k 2796.35\\AA\\ and Si IV 1393.76\\AA\\ line formation levels changes during the observed period and peak-to-peak delays may range from 40~s to zero. The intensity of chromospheric shocks also displays a long term (about 20~min) variations. NST's high spatial resolution \\ha\\ data allowed us to conclude that in this sunspot umbral flashes (UFs) appeared in the form of narrow bright lanes stretched along the light bridges and around clusters of umbral bright points. Time series also suggested that UFs preferred to appear on the sunspot-center side of light bridges, which may indicate the existence of a compact sub-photospheric driver of sunspot oscillations. The sunspot's umbra as seen in the IRIS chromospheric and ...

  20. Spectral signatures of penumbral transients

    Energy Technology Data Exchange (ETDEWEB)

    Reardon, K. [INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy); Tritschler, A. [National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349 (United States); Katsukawa, Y. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2013-12-20

    In this work we investigate the properties of penumbral transients observed in the upper photospheric and chromospheric region above a sunspot penumbra using two-dimensional spectroscopic observations of the Ca II 854.21 nm line with a 5 s cadence. In our 30 minutes of observations, we identify several penumbral-micro jets (PMJs) with cotemporal observations from Dunn Solar Telescope/IBIS and Hinode/SOT. We find that the line profiles of these PMJ events show emission in the two wings of the line (±0.05 nm), but little modification of the line core. These are reminiscent of the line profiles of Ellerman bombs observed in plage and network regions. Furthermore, we find evidence that some PMJ events have a precursor phase starting 1 minute prior to the main brightening that might indicate initial heating of the plasma prior to an acoustic or bow shock event. With the IBIS data, we also find several other types of transient brightenings with timescales of less than 1 minute that are not clearly seen in the Hinode/SOT data. The spectral profiles and other characteristics of these events are significantly different from those of PMJs. The different appearances of all these transients are an indicator of the general complexity of the chromospheric magnetic field and underscore the highly dynamic behavior above sunspots. It also highlights the care that is needed in interpreting broadband filter images of chromospheric lines, which may conceal very different spectral profiles, and the underlying physical mechanisms at work.