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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. Observing the Solar Chromosphere

    CERN Document Server

    Rutten, R J

    2007-01-01

    This review is split into two parts: one on chromospheric line formation in answer to the frequent question "where is my line formed", and one presenting state-of-the-art imagery of the chromosphere. In the first part I specifically treat the formation of the Na D lines, Ca II H & K, and Halpha. In the second I show DOT, IBIS, VAULT, and TRACE images as evidence that the chromosphere consists of fibrils of intrinsically different types. The straight-up ones are hottest. The slanted ones are filled by shocks and likely possess thin transition sheaths to coronal plasma. The ones hovering horizontally over "clapotispheric" cell interiors outline magnetic canopies and are buffeted by shocks, most violently in the quietest regions. In the absence of integral-field ultraviolet spectrometry, H$\\alpha$ remains the principal chromosphere diagnostic. The required fast-cadence profile-sampling imaging is an important quest for new telescope technology.

  4. 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...

  5. 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...

  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. 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

  9. 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 ...

  10. 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...

  11. Diagnosis of solar chromospheric magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Hongqi(张洪起)

    2002-01-01

    This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.

  12. Chromospheric seismology above sunspot umbrae

    CERN Document Server

    Snow, B; Regnier, S

    2015-01-01

    The acoustic resonator is an important model for explaining the three-minute oscillations in the chromosphere above sunspot umbrae. The steep temperature gradients at the photosphere and transition region provide the cavity for the acoustic resonator, which allows waves to be both partially transmitted and partially reflected. In this paper, a new method of estimating the size and temperature profile of the chromospheric cavity above a sunspot umbra is developed. The magnetic field above umbrae is modelled numerically in 1.5D with slow magnetoacoustic wave trains travelling along magnetic fieldlines. Resonances are driven by applying the random noise of three different colours---white, pink and brown---as small velocity perturbations to the upper convection zone. Energy escapes the resonating cavity and generates wave trains moving into the corona. Line of sight (LOS) integration is also performed to determine the observable spectra through SDO/AIA. The numerical results show that the gradient of the coronal ...

  13. 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.

  14. 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.

  15. 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...

  16. 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

  17. 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...

  18. Simulations of chromospheric heating by ambipolar diffusion

    CERN Document Server

    Khomenko, Elena

    2012-01-01

    We propose a mechanism for efficient heating of the solar chromosphere, based on non-ideal plasma effects. Three ingredients are needed for the work of this mechanism: (1) presence of neutral atoms; (2) presence of a non-potential magnetic field; (3) decrease of the collisional coupling of the plasma. Due to decrease of collisional coupling, a net relative motion appears between the neutral and ionized components, usually referred to as "ambipolar diffusion". This results in a significant enhancement of current dissipation as compared to the classical MHD case. We propose that the current dissipation in this situation is able to provide enough energy to heat the chromosphere by several kK on the time scale of minutes, or even seconds. In this paper, we show that this energy supply might be sufficient to balance the radiative energy losses of the chromosphere.

  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. Chromospheric diagnosis with forward scattering polarization

    CERN Document Server

    Carlin, E S

    2016-01-01

    Is it physically feasible to perform chromospheric diagnosis using spatial maps of scattering polarization at the solar disk center? To investigate it we synthesized polarization maps (in 8542 Angstroms) resulting from MHD solar models and NLTE radiative transfer calculations that consider Hanle effect and vertical macroscopic motions. After explaining the physical con- text of forward scattering and presenting our results, we arrive at the definition of Hanle polarity inversion lines. We show how such features can give support for a clearer chromospheric diagnosis in which the magnetic and dynamic effects in the scattering polarization could be disentangled.

  1. 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

  2. Are plasma satellites present among chromospheric lines?

    Science.gov (United States)

    Ohman, Y.

    1983-05-01

    Published literature is examined for evidence of the presence of plasma satellites among the solar chromospheric lines. Indications are found that first-order plasma satellites sometimes appear as a pair of faint chromospheric emission lines in places where forbidden lines, mainly of metals, should be located. Evidence is seen that second-order plasma satellites are present among lines for which emission wings show asymmetry with respect to the distances from the line center and with respect to intensity. Indications are found that fourth-order plasma satellites are present as unidentified diffuse lines situated near parent lines of food strength either in emission or in absorption. All three types of satellites show electron densities on the order of a trillion/cu cm. Indications that plasma satellites may sometimes appear as faint absorption lines in the solar spectrum are discussed.

  3. Heating of the magnetized solar chromosphere by partial ionization effects

    CERN Document Server

    Khomenko, Elena

    2011-01-01

    In this paper, we study the heating of the magnetized solar chromosphere induced by the large fraction of neutral atoms present in this layer. The presence of neutrals, together with the decrease with height of the collisional coupling, leads to deviations from the classical MHD behavior of the chromospheric plasma. A relative net motion appears between the neutral and ionized components, usually referred to as ambipolar diffusion. The dissipation of currents in the chromosphere is enhanced orders of magnitude due to the action of ambipolar diffusion, as compared to the standard ohmic diffusion. We propose that a significant amount of magnetic energy can be released to the chromosphere just by existing force-free 10--40 G magnetic fields there. As a consequence, we conclude that ambipolar diffusion is an important process that should be included in chromospheric heating models, as it has the potential to rapidly heat the chromosphere. We perform analytical estimations and numerical simulations to prove this 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. Linear Polarization Measurements of Chromospheric Emission Lines

    Science.gov (United States)

    Sheeley, N. R., Jr.; Keller, C. U.

    2003-01-01

    We have used the Zurich Imaging Stokes Polarimeter (ZIMPOL I) with the McMath-Pierce 1.5 m main telescope on Kitt Peak to obtain linear polarization measurements of the off-limb chromosphere with a sensitivity better than 1 x 10(exp -5). We found that the off-disk observations require a combination of good seeing (to show the emission lines) and a clean heliostat (to avoid contamination by scattered light from the Sun's disk). When these conditions were met, we obtained the following principal results: 1. Sometimes self-reversed emission lines of neutral and singly ionized metals showed linear polarization caused by the transverse Zeeman effect or by instrumental cross talk from the longitudinal Zeeman effect in chromospheric magnetic fields. Otherwise, these lines tended to depolarize the scattered continuum radiation by amounts that ranged up to 0.2%. 2. Lines previously known to show scattering polarization just inside the limb (such as the Na I lambda5889 D2 and the He I lambda5876 D3 lines) showed even more polarization above the Sun's limb, with values approaching 0.7%. 3. The O I triplet at lambda7772, lambda7774, and lambda7775 showed a range of polarizations. The lambda7775 line, whose maximum intrinsic polarizability, P(sub max), is less than 1%, revealed mainly Zeeman contributions from chromospheric magnetic fields. However, the more sensitive lambda7772 (P(sub max) = 19%) and lambda7774 (P(sub max) = 29%) lines had relatively strong scattering polarizations of approximately 0.3% in addition to their Zeeman polarizations. At times of good seeing, the polarization spectra resolve into fine structures that seem to be chromospheric spicules.

  6. The quiet chromosphere. Old wisdom, new insights, future needs

    CERN Document Server

    Rutten, Robert J

    2010-01-01

    The introduction to this review summarizes chromosphere observation in two figures. The first part showcases the historical emphasis on the eclipse chromosphere in the development of NLTE line formation theory and criticizes 1D modeling. The second part advertises recent breakthroughs after many decades of standstill. The third part discusses what may or should come next.

  7. Measurements of Photospheric and Chromospheric Magnetic Fields

    Science.gov (United States)

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

    2015-12-01

    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. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

  8. 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.

  9. Radiating Current Sheets in the Solar Chromosphere

    CERN Document Server

    Goodman, Michael L

    2014-01-01

    An MHD model of a Hydrogen plasma with flow, an energy equation, NLTE ionization and radiative cooling, and an Ohm's law with anisotropic electrical conduction and thermoelectric effects is used to self-consistently generate atmospheric layers over a $50$ km height range. A subset of these solutions contain current sheets, and have properties similar to those of the lower and middle chromosphere. The magnetic field profiles are found to be close to Harris sheet profiles, with maximum field strengths $\\sim 25-150$ G. The radiative flux $F_R$ emitted by individual sheets is $\\sim 4.9 \\times 10^5 - 4.5 \\times 10^6$ ergs-cm$^{-2}$-s$^{-1}$, to be compared with the observed chromospheric emission rate of $\\sim 10^7$ ergs-cm$^{-2}$-s$^{-1}$. Essentially all emission is from regions with thicknesses $\\sim 0.5 - 13$ km containing the neutral sheet. About half of $F_R$ comes from sub-regions with thicknesses 10 times smaller. A resolution $\\lesssim 5-130$ m is needed to resolve the properties of the sheets. The sheets...

  10. Physics of the Solar Chromosphere: Beyond the Ideal MHD Description

    Science.gov (United States)

    Leake, James

    2015-08-01

    The solar chromosphere is the dynamic, physically complex, layer that lies between the visible solar surface and the magnetically dominated corona. Despite being a moderator of the amount of mass, magnetic field, and energy, that is transferred into the solar corona and the heliosphere and beyond, there are still important open questions regarding the chromosphere. Recent advancements in both observation and theoretical descriptions of the chromosphere have created new ideas about how the chromosphere controls the transfer of the above quantities from the Sun's interior into the heliosphere. Open questions still remain, such as, how is the chromosphere heated, and how do chromospheric events such as spicules, jets, reconnection, and wave propagation and dissipation contribute to the mass and energy balance in the solar atmosphere. Central to these questions are extensions to the standard magneto-hydro-dynamic (MHD) model of the Sun, such as non-local-thermodynamic-equilibrium radiation, and multi-fluid physics. In this talk, we summarize the importance of these extensions and look for the necessary developments to answer open questions about the chromosphere.

  11. 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.

  12. 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.

  13. Chromospheric models for Altair (A7 IV-V)

    Science.gov (United States)

    Ferrero, R. Freire; Gouttebroze, P.; Catalano, S.; Marilli, E.; Bruhweiler, F.; Kondo, Y.; Van Der Hucht, K.; Talavera, A.

    1995-01-01

    The star, Altair (A7 IV-V), is clearly shown to have Lyman-alpha emission of chromospheric origin, while no evidence is found for the Mg II emission reported in previous investigations. We present non-Local Thermodymanic Equilibrium (non-LTE) semiempirical models incorporating partial redistribution of the chromosphere of Altair that reproduce the observed Lyman-alpha emission and the Mg II resonance absorption at 2800 A. We unambiguously establihed that chromospheres exist at spectral types as early as A7 on the main sequence, and we also demonstrate that it very unlikely that the observed emission originates in a corotating expanding wind. This result represents a new challenge for chromospheric heating theories. It may indicate that both differential rotation and convection layers, at least near the equator, exist in this fast rotating (v sin i = 220 km/s) star.

  14. 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.

  15. 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...

  16. 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.

  17. 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...

  18. 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.

  19. 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...

  20. Particle Acceleration and Plasma Heating in the Chromosphere

    Science.gov (United States)

    Zaitsev, V. V.; Stepanov, A. V.

    2015-12-01

    We propose a new mechanism of electron acceleration and plasma heating in the solar chromosphere, based on the magnetic Rayleigh-Taylor instability. The instability develops at the chromospheric footpoints of a flare loop and deforms the local magnetic field. As a result, the electric current in the loop varies, and a resulting inductive electric field appears. A pulse of the induced electric field, together with the pulse of the electric current, propagates along the loop with the Alfvén velocity and begins to accelerate electrons up to an energy of about 1 MeV. Accelerated particles are thermalized in the dense layers of the chromosphere with the plasma density n ≈10^{14} - 10^{15} cm^{-3}, heating them to a temperature of about several million degrees. Joule dissipation of the electric current pulse heats the chromosphere at heights that correspond to densities n ≤10^{11} - 10^{13} cm^{-3}. Observations with the New Solar Telescope at Big Bear Solar Observatory indicate that chromospheric footpoints of coronal loops might be heated to coronal temperatures and that hot plasma might be injected upwards, which brightens ultra-fine loops from the photosphere to the base of the corona. Thereby, recent observations of the Sun and the model we propose stimulate a déjà vu - they are reminiscent of the concept of the chromospheric flare.

  1. The solar chromosphere at high resolution with IBIS. IV. Dual-line evidence of heating in chromospheric network

    CERN Document Server

    Cauzzi, G; Rutten, R J; Tritschler, A; Uitenbroek, H

    2009-01-01

    The structure and energy balance of the solar chromosphere remain poorly known. We have used the imaging spectrometer IBIS at the Dunn Solar Telescope to obtain fast-cadence, multi-wavelength profile sampling of Halpha and Ca II 854.2 nm over a sizable two-dimensional field of view encompassing quiet-Sun network. We provide a first inventory of how the quiet chromosphere appears in these two lines by comparing basic profile measurements in the form of image displays, temporal-average displays, time slices, and pixel-by-pixel correlations. We find that the two lines can be markedly dissimilar in their rendering of the chromosphere, but that, nevertheless, both show evidence of chromospheric heating, particularly in and around network: Halpha in its core width, Ca II 854.2 in its brightness. We discuss venues for improved modeling.

  2. The chromospherically active binary CFTuc revisited

    Science.gov (United States)

    Doǧru, D.; Erdem, A.; Doǧru, S. S.; Zola, S.

    2009-08-01

    This paper presents results derived from analysis of new spectroscopic and photometric observations of the chromospherically active binary system CFTuc. New high-resolution spectra, taken at the Mt. John University Observatory in 2007, were analysed using two methods: cross-correlation and Fourier-based disentangling. As a result, new radial velocity curves of both components were obtained. The resulting orbital elements of CFTuc are a1 sini = 0.0254 +/- 0.0001au, a2sini = 0.0228 +/- 0.0001au, M1sini = 0.902 +/- 0.005Msolar and M2sini = 1.008 +/- 0.006Msolar. The cooler component of the system shows Hα and CaII H&K emissions. Using simultaneous spectroscopic and photometric observations, an anticorrelation between the Hα emission and the BV light curve maculation effects was found. This behaviour indicates a close spatial association between photospheric and chromospheric active regions. Our spectroscopic data and recent BV light curves were solved simultaneously using the Wilson-Devinney code. A dark spot on the surface of the cooler component was assumed to explain large asymmetries observed in the light curves. The following absolute parameters of the components were determined: M1 = 1.11 +/- 0.01Msolar, M2 = 1.23 +/- 0.01Msolar, R1 = 1.63 +/- 0.02Rsolar, R2 = 3.60 +/- 0.02Rsolar, L1 = 3.32 +/- 0.51Lsolar and L2 = 3.91 +/- 0.84Lsolar. The primary component has an age of about 5Gyr and is approaching its main-sequence terminal age. The distance to CFTuc was calculated to be 89 +/- 6pc from the dynamic parallax, neglecting interstellar absorption, in agreement with the Hipparcos value. The orbital period of the system was studied using the O-C analysis. The O-C diagram could be interpreted in terms of either two abrupt changes or a quasi-sinusoidal form superimposed on a downward parabola. These variations are discussed by reference to the combined effect of mass transfer and mass loss, the Applegate mechanism and also a light-time effect due to the existence of

  3. Chromospheric oscillations observed with BBSO and TRACE

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We examine chromospheric oscillations in both a coronal hole (CH) and a quiet Sun (QS) region, by employing Transition Region and Coronal Explorer (TRACE) and Big Bear Solar Observatory (BBSO) data on September 14 and 16, 2004. For the CH, the average oscillation periods of network magnetic field and non-magnetic field (NMF) regions are 257 and 222 s, respectively, and the average period of network field is longer than that of NMF region by 15.8%. In the QS, the average oscillation period is the 225 s for network field and 212 s for the NMF region. The average period of the network field is also longer than that of the NMF region by 6.1%. For the network region, we find that the average period in the CH is longer than that in the QS by 14.2%. This difference between CH and QS is possibly caused by different magnetic configurations i.e. the open magnetic field in the CH and the close field in the QS.

  4. 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...

  5. Multi-wavelength analysis from tomography study on solar chromosphere

    Energy Technology Data Exchange (ETDEWEB)

    Mumpuni, Emanuel Sungging; Herdiwijaya, Dhani; Djamal, Mitra [Program Studi Astronomi, Jl. Ganesha No. 10, Labtek III, Lantai IV, Bandung, Jawa Barat, Indonesia 40135 nggieng@students.itb.ac.id (Indonesia)

    2015-04-16

    The Sun as the most important star for scientific laboratory in astrophysics as well as encompassing all living aspect on Earth, still holds scientific mystery. As the established model that the Sun’s energy fueled by the nuclear reaction, along with transport process to the typical Solar surface on around 6000-K temperature, many aspects still left as an open questions, such as how the chromosphere responded to the photospheric dynamics. In this preliminary work, we try to analyze the Solar chromosphere respond to the Photospheric dynamics using tomography study implementing multi-wavelength analysis observation obtained from Dutch Open Telescope. Using the Hydrogen-alpha Doppler signal as the primary diagnostic tool, we try to investigate the inter-relation between the magnetic and gas pressure dynamics that occur in the chromosphere.

  6. Evolution of Chromospheric Activity: M67 Red Giants

    Science.gov (United States)

    Dupree, A. K.; Whitney, B. A.; Pasquini, L.

    1999-08-01

    Echelle spectra of the Ca II H- and K-line region (λ3950) of 15 red giant stars in the open cluster M67 reveal atmospheric dynamics and determine chromospheric radiative losses in order to assess chromospheric heating requirements and to follow the evolution of chromospheric activity. M67 red giants in conjunction with giants in younger clusters create a continuous group of red giants in the color-magnitude diagram, with 0.1mass motions are well established at these luminosities. Radiative losses, as measured by emission strengths from Ca II, decrease smoothly with decreasing stellar effective temperature in M67 and connect well to a combined sample of warmer cluster giants (NGC 2477, IC 4756, and the Hyades) with Mrelated processes. The relative contribution of each heating mechanism changes with temperature in the stellar atmosphere, and these proportions may change during a star's evolution from the main sequence.

  7. 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.

  8. Solar Atmospheric Oscillations and the Chromospheric Magnetic Topology

    CERN Document Server

    Vecchio, A; Reardon, K P; Janssen, K; Rimmele, T

    2006-01-01

    We investigate the oscillatory properties of the quiet solar chromosphere in relation to the underlying photosphere, with particular regard to the effects of the magnetic topology. We perform a Fourier analysis on a sequence of line-of-sight velocities measured simultaneously in a photospheric (Fe I 709.0 nm) and a chromospheric line (Ca II 854.2 nm). The velocities were obtained from full spectroscopic data acquired at high spatial resolution with the Interferometric BIdimensional Spectrometer (IBIS). The field of view encompasses a full supergranular cell, allowing us to discriminate between areas with different magnetic characteristics. We show that waves with frequencies above the acoustic cut-off propagate from the photosphere to upper layers only in restricted areas of the quiet Sun. A large fraction of the quiet chromosphere is in fact occupied by ``magnetic shadows'', surrounding network regions, that we identify as originating from fibril-like structures observed in the core intensity of the Ca II li...

  9. 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.

  10. CHROMOSPHERIC POLARIZATION IN THE PHOTOSPHERIC SOLAR OXYGEN INFRARED TRIPLET

    Energy Technology Data Exchange (ETDEWEB)

    Del Pino Alemán, Tanausú; Trujillo Bueno, Javier [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)

    2015-07-20

    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{sup −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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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...

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

    Science.gov (United States)

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

    2016-08-01

    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 the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.

  18. The solar chromosphere at high resolution with IBIS. IV. Dual-line evidence of heating in chromospheric network

    NARCIS (Netherlands)

    Cauzzi, G.; Reardon, K.; Rutten, R.J.; Tritschler, A.; Uitenbroek, H.

    2009-01-01

    The structure and energy balance of the solar chromosphere remain poorly known.We used the imaging spectrometer IBIS at the Dunn Solar Telescope to obtain fast-cadence, multi-wavelength profile sampling of Hα and Ca II 854.2 nm over a sizable two-dimensional field of view encompassing quiet-Sun netw

  19. Solar Physics at Evergreen: Solar Dynamo and Chromospheric MHD

    Science.gov (United States)

    Zita, E. J.; Maxwell, J.; Song, N.; Dikpati, M.

    2006-12-01

    We describe our five year old solar physics research program at The Evergreen State College. Famed for its cloudy skies, the Pacific Northwest is an ideal location for theoretical and remote solar physics research activities. Why does the Sun's magnetic field flip polarity every 11 years or so? How does this contribute to the magnetic storms Earth experiences when the Sun's field reverses? Why is the temperature in the Sun's upper atmosphere millions of degrees higher than the Sun's surface temperature? How do magnetic waves transport energy in the Sun’s chromosphere and the Earth’s atmosphere? How does solar variability affect climate change? Faculty and undergraduates investigate questions such as these in collaboration with the High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) in Boulder. We will describe successful student research projects, logistics of remote computing, and our current physics investigations into (1) the solar dynamo and (2) chromospheric magnetohydrodynamics.

  20. The galloping chromosphere. [H alpha observation of oscillating velocity fields

    Science.gov (United States)

    Sawyer, C.

    1974-01-01

    Oscillating velocity fields can be observed on H-alpha filtergrams as a shifting pattern of intensity fluctuations known as 'the galloping chromosphere'. The characteristics of this activity are those of horizontal running waves of typical period of about 300 sec and long wavelength (about 20,000 km) that can be interpreted as acoustic-gravity waves propagating in the acoustic domain. Periods are longer in dark, structured regions, and in fibrils, and the change is quantitatively consistent with the reduction of resonance frequency in a magnetic field of 1 to 10 gauss. These easily observed fluctuations thus offer a means of estimating magnetic-field strength at specific locations in the chromosphere. Phase velocities are high, ranging upward from typical values between 50 and 100 km per sec, and tending to be lower in active regions and toward the limb.

  1. 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...

  2. 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.

  3. 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...

  4. 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-...

  5. The non-active stellar chromosphere: Ca II basal flux

    Science.gov (United States)

    Pérez Martínez, M. I.; Schröder, K.-P.; Hauschildt, P.

    2014-11-01

    We analyse high-resolution, high-s/n European Southern Observatories (ESO)-archive spectra (from UVES, the UV echelle spectrograph) of 76 inactive or modestly active stars of spectral type G to M, main sequence and giants. Using PHOENIX model photospheres with Ca II K lines that match the observed line profiles, we (i) revise the effective temperatures, (ii) obtain a precise surface flux scale for each star and (iii) directly determine the exact surface fluxes of each Ca II K chromospheric emission with respect to the photospheric line profile. We find that our stellar sample exhibits a lower boundary to its chromospheric surface flux distribution with an unprecedented definition. From a subsample of the 25 least active stars, we obtain a simple empirical formula for the basal Ca II flux as a function of effective temperature: log {F^basal_{Ca II(H+K)}} = 7.05(± 0.31) log {T_eff} - 20.86(± 1.15). This is in good agreement with the Mg II basal flux. In a direct comparison with the large body of Mt Wilson S-measurements of the chromospheric Ca II emission and its well-defined cut-off, excellent agreement is achieved as well. A new result, however, is the small scatter of the least active star's fluxes about the basal flux. It is about 25 per cent and equals the residual uncertainties of our approach. At the same time, we do not find any evidence for a gravity dependence within these limits. This strongly confirms the basal flux as a well-defined and universal phenomenon, which characterizes every inactive chromosphere.

  6. On the solar chromosphere observed at the limb with Hinode

    CERN Document Server

    Judge, Philip G

    2010-01-01

    Broad-band images in the Ca II H line, from the BFI instrument on the Hinode spacecraft, show emission from spicules emerging from and visible right down to the observed limb. Surprisingly, little absorption of spicule light is seen along their lengths. We present formal solutions to the transfer equation for given (ad-hoc) source functions, including a stratified chromosphere from which spicules emanate. The model parameters are broadly compatible with earlier studies of spicules. The visibility of Ca II spicules down to the limb in Hinode data seems to require that spicule emission be Doppler shifted relative to the stratified atmosphere, either by supersonic turbulent or organized spicular motion. The non-spicule component of the chromosphere is almost invisible in the broad band BFI data, but we predict that it will be clearly visible in high spectral resolution data. Broad band Ca II H limb images give the false impression that the chromosphere is dominated by spicules. Our analysis serves as a reminder ...

  7. 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.

  8. 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...

  9. DOT tomography of the solar atmosphere VII. Chromospheric response to acoustic events

    NARCIS (Netherlands)

    Rutten, R.J.; van Veelen, B.; Sütterlin, P.

    2008-01-01

    We use synchronous movies from the Dutch Open Telescope sampling the G band, Ca ii H, and Hα with five-wavelength profile sampling to study the response of the chromosphere to acoustic events in the underlying photosphere. We first compare the visibility of the chromosphere in Ca ii H and Hα, demons

  10. 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.

  11. 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.

  12. Radiative diagnostics in the solar photosphere and chromosphere

    CERN Document Server

    Rodríguez, Jaime de la Cruz

    2016-01-01

    Magnetic fields on the surface of the Sun and stars in general imprint or modify the polarization state of the electromagnetic radiation that is leaving from the star. The inference of solar/stellar magnetic fields is performed by detecting, studying and modeling polarized light from the target star. In this review we present an overview of techniques that are used to study the atmosphere of the Sun, and particularly those that allow to infer magnetic fields. We have combined a small selection of theory on polarized radiative transfer, inversion techniques and we discuss a number of results from chromospheric inversions.

  13. ALFVÉNIC WAVE HEATING OF THE UPPER CHROMOSPHERE IN FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Reep, J. W. [National Research Council Post-Doc Program, Naval Research Laboratory, Washington, DC 20375 (United States); Russell, A. J. B., E-mail: jeffrey.reep.ctr@nrl.navy.mil, E-mail: arussell@maths.dundee.ac.uk [Division of Mathematics, University of Dundee, Nethergate, Dundee, DD1 4HN (United Kingdom)

    2016-02-10

    We have developed a numerical model of flare heating due to the dissipation of Alfvénic waves propagating from the corona to the chromosphere. With this model, we present an investigation of the key parameters of these waves on the energy transport, heating, and subsequent dynamics. For sufficiently high frequencies and perpendicular wave numbers, the waves dissipate significantly in the upper chromosphere, strongly heating it to flare temperatures. This heating can then drive strong chromospheric evaporation, bringing hot and dense plasma to the corona. We therefore find three important conclusions: (1) Alfvénic waves, propagating from the corona to the chromosphere, are capable of heating the upper chromosphere and the corona, (2) the atmospheric response to heating due to the dissipation of Alfvénic waves can be strikingly similar to heating by an electron beam, and (3) this heating can produce explosive evaporation.

  14. Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphere

    CERN Document Server

    Gogoberidze, G; Poedts, S; De Keyser, J

    2013-01-01

    We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion thermal effect is highly reduced by the Coulomb collisions and can be ignored for the chromospheric FB-type instabilities. On the contrary, the destabilizing electron thermal effect is important and causes a significant reduction of the neutral drag velocity triggering the instability. The resulting threshold velocity is found as function of chromospheric height. Our results indicate that the FB type instabilities are still less efficient in the global chromospheric heating than the Joule dissipation of the currents driving these instabilities. This conclusion does not exclude the possibility that the FB type instabilities develop in the places where the cross-field currents overcome the threshold value and contribute to the heating locally. Typical length-scales...

  15. 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...

  16. The Hβ Chromospheric Magnetic Field in a Quiescent Filament

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We observed the line-of-sight magnetic field in the chromosphereandphotosphere of a large quiescent filament on the solar disk on September 6, 2001using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. Thechromospheric and photospheric magnetograms together with Hβ filtergrams of thefilament were examined. The filament was located on the neutral line of the largescale longitudinal magnetic field in the photosphere and the chromosphere. Thelateral feet of the filament .were found to be related to magnetic structures with op-posite polarities. Two small lateral feet are linked to weak parasitic polarity. Thereis a negative magnetic structure in the photosphere under a break of the filament.At the location corresponding to the filament in the chromospheric magnetograms,the magnetic strength is found to be about 40-70 Gauss (measuring error about 39Gauss). The magnetic signal indicates the amplitude and orientation of the internalmagnetic field in the filament. We discuss several possible causes which may pro-duce such a measured signal. A twisted magnetic configuration inside the filamentis suggested .

  17. CHROMOSPHERIC MODELS AND THE OXYGEN ABUNDANCE IN GIANT STARS

    Energy Technology Data Exchange (ETDEWEB)

    Dupree, A. K.; Avrett, E. H.; Kurucz, R. L., E-mail: dupree@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

    2016-04-10

    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.

  18. 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.

  19. 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...

  20. 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.

  1. The Chromospheric Activity-Age Relation for M Dwarf Stars

    Science.gov (United States)

    Silvestri, N. M.; Oswalt, T. D.; Hawley, S. L.

    2000-12-01

    We present preliminary results from our study in which we use moderate resolution spectroscopy to determine the correlation between the chromospheric activity and age of M dwarf stars in wide binary systems. We have observed ~50 M dwarf stars from our sample with the Apache Point Observatory 3.5-m telescope. We measure the ratio of Hα luminosity to the bolometric luminosity (LHα /Lbol) of the M dwarf---a measure of activity that is proven to correlate well with age. This project is unique in that it will extend the chromospheric activity-age relation of low-mass main sequence stars beyond the ages provided by cluster methods. The ages so determined are also independent of the uncertainties in cluster age determinations. The technique has the potential to improve by at least a factor of two the precision and the range over which ages can currently be determined for main sequence stars. Work on this project is supported by the NASA Graduate Student Researchers Program grant NGT-50290 (N.M.S.).

  2. Formation of Solar Filaments by Steady and Nonsteady Chromospheric Heating

    CERN Document Server

    Xia, C; Keppens, R; van Marle, A J

    2011-01-01

    It has been established that cold plasma condensations can form in a magnetic loop subject to localized heating of the footpoints. In this paper, we use grid-adaptive numerical simulations of the radiative hydrodynamic equations to parametrically investigate the filament formation process in a pre-shaped loop with both steady and finite-time chromospheric heating. Compared to previous works, we consider low-lying loops with shallow dips, and use a more realistic description for the radiative losses. We demonstrate for the first time that the onset of thermal instability satisfies the linear instability criterion. The onset time of the condensation is roughly \\sim 2 hr or more after the localized heating at the footpoint is effective, and the growth rate of the thread length varies from 800 km hr-1 to 4000 km hr-1, depending on the amplitude and the decay length scale characterizing this localized chromospheric heating. We show how single or multiple condensation segments may form in the coronal portion. In th...

  3. The Impact of Chromospheric Activity on Observed Initial Mass Functions

    CERN Document Server

    Stassun, Keivan G; Dupuy, Trent; Kratter, Kaitlin

    2014-01-01

    Using recently established empirical calibrations for the impact of chromospheric activity on the radii, effective temperatures, and estimated masses of active low-mass stars and brown dwarfs, we reassess the shape of the initial mass function (IMF) across the stellar/substellar boundary in the Upper Sco star-forming region (age 5-10 Myr). We adjust the observed effective temperatures to warmer values using the observed strength of the chromospheric H$\\alpha$ emission, and redetermine the estimated masses of objects using pre--main-sequence evolutionary tracks in the H-R diagram. The effect of the activity-adjusted temperatures is to shift the objects to higher masses by 3-100%. While the slope of the resulting IMF at substellar masses is not strongly changed, the peak of the IMF does shift from ~0.06 to ~0.11 Msun. Moreover, for objects with masses ~0.2 Msun, the ratio of brown dwarfs to stars changes from ~80% to ~33%. These results suggest that activity corrections are essential for studies of the substell...

  4. 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...

  5. 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 ...

  6. 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 ...

  7. 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.

  8. 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...

  9. The Chromospheric Solar Millimeter-wave Cavity; a Common Property in the Semi-empirical Models

    CERN Document Server

    Victor, De la Luz; Emanuele, Bertone

    2014-01-01

    The semi-empirical models of the solar chromosphere are useful in the study of the solar radio emission at millimeter - infrared wavelengths. However, current models do not reproduce the observations of the quiet sun. In this work we present a theoretical study of the radiative transfer equation for four semi- empirical models at these wavelengths. We found that the Chromospheric Solar Milimeter-wave Cavity (CSMC), a region where the atmosphere becomes locally optically thin at millimeter wavelengths, is present in the semi-empirical models under study. We conclude that the CSMC is a general property of the solar chromosphere where the semi-empirical models shows temperature minimum.

  10. Evidence for Fine Structure in the Chromospheric Umbral Oscillation

    CERN Document Server

    Centeno, R; Collados, M; Bueno, J T

    2005-01-01

    Novel spectro-polarimetric observations of the \\ion{He}{1} multiplet are used to explore the dynamics of the chromospheric oscillation above sunspot umbrae. The results presented here provide strong evidence in support of the two-component model proposed by Socas-Navarro and co-authors. According to this model, the waves propagate only inside channels of sub-arcsecond width (the ``active'' component), whereas the rest of the umbra remains nearly at rest (the ``quiet'' component). Although the observations support the fundamental elements of that model, there is one particular aspect that is not compatible with our data. We find that, contrary to the scenario as originally proposed, the active component remains through the entire oscillation cycle and harbors both the upflowing and the downflowing phase of the oscillation.

  11. 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 ...

  12. Dynamics of Chromospheric Upflows and Underlying Magnetic Fields

    CERN Document Server

    Yurchyshyn, Vasyl; Goode, Phil

    2013-01-01

    We used \\ha-0.1 nm and magnetic field (at 1.56$\\mu$) data obtained with the New Solar Telescope to study the origin of the disk counterparts to type II spicules, so-called rapid blueshifted excursions (RBEs). The high time cadence of our chromospheric (10 s) and magnetic field (45 s) data allowed us to generate x-t plots using slits parallel to the spines of the RBEs. These plots, along with potential field extrapolation, led us to suggest that the occurrence of RBEs is generally correlated with the appearance of new, mixed or unipolar fields in close proximity to network fields. RBEs show a tendency to occur at the interface between large-scale fields and small-scale dynamic magnetic loops and thus are likely to be associated with existence of a magnetic canopy. Detection of kinked and/or inverse "Y" shaped RBEs further confirm this conclusion.

  13. ACCELERATION OF TYPE II SPICULES IN THE SOLAR CHROMOSPHERE

    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)

    2012-10-01

    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 {approx}150-460 km s{sup -1}, horizontally localized within {approx}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 {approx}20 times smaller than vertical speeds. Terminal velocity is reached {approx}100 s after acceleration begins. The increase in the mechanical and thermal energy of the plasma during acceleration is (2-3) Multiplication-Sign 10{sup 22} ergs. The radial component of the Lorentz force compresses the plasma during the acceleration process by factors as large as {approx}100. The Joule heating flux generated during this process is essentially due to proton Pedersen current dissipation and can be {approx}0.1-3.7 times the heating flux of {approx}10{sup 6} ergs cm{sup -2} s{sup -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.

  14. The Effects of Transients on Photospheric and Chromospheric Power Distributions

    Science.gov (United States)

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

    2016-09-01

    We have observed a quiet-Sun region with the Swedish 1 m Solar Telescope equipped with the CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, Hα 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 whether 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 strongly influence the power maps. The short and finite lifetime of these events strongly affects all power maps, potentially influencing the observed power distribution. We show that Doppler-shifted transients like RBEs and RREs that occur ubiquitously can have a dominant effect on the formation of the power halos in the quiet Sun. For magnetic shadows, transients like mottles do not seem to have a significant effect on the power suppression around 3 minutes, and wave interaction may play a key role here. Our high-cadence observations reveal that flows, waves, and shocks manifest in the presence of magnetic fields to form a nonlinear magnetohydrodynamic system.

  15. Simulations of Alfvén and Kink Wave Driving of the Solar Chromosphere: Efficient Heating and Spicule Launching

    Science.gov (United States)

    Brady, C. S.; Arber, T. D.

    2016-10-01

    Two of the central problems in our understanding of the solar chromosphere are how the upper chromosphere is heated and what drives spicules. Estimates of the required chromospheric heating, based on radiative and conductive losses, suggest a rate of ˜0.1 erg cm-3 s-1 in the lower chromosphere and drops to ˜10-3 erg cm-3 s-1 in the upper chromosphere. The chromosphere is also permeated by spicules, higher density plasma from the lower atmosphere propelled upwards at speeds of ˜10-20 km s-1, for so-called Type I spicules, which reach heights of ˜3000-5000 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 30 years it has been proposed that photospheric driving of MHD waves may be responsible for both heating and spicule formation. This paper presents results from a high-resolution MHD treatment of photospheric driven Alfvén and kink waves propagating upwards into an expanding flux tube embedded in a model chromospheric atmosphere. We show that the ponderomotive coupling from Alfvén and kink waves into slow modes generates shocks, which both heat the upper chromosphere and drive spicules. These simulations show that wave driving of the solar chromosphere can give a local heating rate that matches observations and drive spicules consistent with Type I observations all within a single coherent model.

  16. Possible chromospheric activity cycles in II Peg, UX Ari and V711 Tau

    CERN Document Server

    Buccino, Andrea P

    2008-01-01

    We study the Mount Wilson indices we obtained indirectly from IUE high and low resolution spectra of the RS CVn-type systems II Peg (K2IV), UX Ari (K0IV+G5V) and V711 Tau (K1IV+G5V), extensively observed by IUE from 1978 to 1996. We analyze the activity signatures, which correspond to the primary star, with the Lomb-Scargle periodogram. From the analysis of V711 Tau data, we found a possible chromospheric cycle with a period of 18 years and a shorter near 3-year cycle, which could be associated to a chromospheric flip-flop cycle. The data of II Peg also suggest a chromospheric cycle of near 21 years and a flip-flop cycle of 9 years approximately. Finally, we obtained a possible chromospheric cycle of near 6 years for UX Ari.

  17. 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...

  18. DOT Tomography of the Solar Atmosphere VII. Chromospheric Response to Acoustic Events

    CERN Document Server

    Rutten, Robert J; Suetterlin, Peter

    2008-01-01

    We use synchronous movies from the Dutch Open Telescope sampling the G band, Ca II and Halpha with five-wavelength profile sampling to study the response of the chromosphere to acoustic events in the underlying photosphere. We first compare the visibility of the chromosphere in Ca II H and Halpha, demonstrate that studying the chromosphere requires Halpha data, and summarize recent developments in understanding why this is so. We construct divergence and vorticity maps of the photospheric flow field from the G-band images and locate specific events through the appearance of bright Ca II H grains. The reaction of the Halpha chromosphere is diagnosed in terms of brightness and Doppler shift. We show and discuss three particular cases in detail: a regular acoustic grain marking shock excitation by granular dynamics, a persistent flasher which probably marks magnetic-field concentration, and an exploding granule. All three appear to buffet overlying fibrils, most clearly in Dopplergrams. Although our diagnostic d...

  19. 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...

  20. Possible chromospheric activity cycles in II Peg, UX Ari and V711 Tau

    Science.gov (United States)

    Buccino, Andrea P.; Mauas, Pablo J. D.

    2009-02-01

    We study the Mount Wilson indices we obtained indirectly from IUE high and low resolution spectra of the RS CVn-type systems II Peg (K2IV), UX Ari (K0IV+G5V) and V711 Tau (K1IV+G5V), extensively observed by IUE from 1978 to 1996. We analyze the activity signatures, which correspond to the primary star, with the Lomb-Scargle periodogram. From the analysis of V711 Tau data, we found a possible chromospheric cycle with a period of 18 years and a shorter ~3 year cycle, which could be associated to a chromospheric flip-flop cycle. The data of II Peg also suggest a chromospheric cycle of ~21 years and a flip-flop cycle of ~9 years. Finally, we obtained a possible chromospheric cycle of ~6 years for UX Ari.

  1. 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.

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

    CERN Document Server

    Russell, Alexander J B

    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 transmission from corona to chromosphere can exceed 20% of incident energy for wave periods of one second or less. Damping of waves in the chromosphere depends strongly on wave frequency: waves with periods 10 seconds or longer pass through the chromosphere with relatively little damping, however, for periods of 1 second 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 ch...

  5. EFFECT OF CORONAL TEMPERATURE ON THE SCALE OF SOLAR CHROMOSPHERIC JETS

    Energy Technology Data Exchange (ETDEWEB)

    Iijima; Yokoyama, T.H., E-mail: h.iijima@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-10-20

    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 an 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 chromospheric shock waves. However, when the coronal temperature is low, the gravitational deceleration becomes more important and the chromospheric jets approach ballistic motion.

  6. 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.

  7. 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...

  8. 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).

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

    Science.gov (United States)

    Airapetian, V. S.; Leake, J. E.; Carpenter, Kenneth G.

    2015-01-01

    We present the first magnetohydrodynamic model of the stellar chromospheric heating and acceleration of the outer atmospheres of cool evolved stars, using α 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 Alfvén 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 Alfvé 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 due to resistive (Joule) dissipation of electric currents, induced by upward propagating non-linear Alfvé waves, 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, Alfvé 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 Alfvé waves becomes significant in the outer chromosphere at 1 stellar radius from the photosphere. The calculated terminal velocity and the mass loss rate are consistent with the observationally derived wind properties in α Tau.

  10. 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 ...

  11. The chromospherically--active binary CF Tuc revisited

    CERN Document Server

    Dogru, D; Dogru, S S; Zola, S

    2009-01-01

    New high-resolution spectra, of the chromospherically active binary system CF Tuc, taken at the Mt. John University Observatory in 2007, were analyzed using two methods: cross-correlation and Fourier--based disentangling. As a result, new radial velocity curves of both components were obtained. The resulting orbital elements of CF Tuc are: $a_{1}{\\sin}i$=$0.0254\\pm0.0001$ AU, $a_{2}{\\sin}i$=$0.0228\\pm0.0001$ AU, $M_{1}{\\sin}i$=$0.902\\pm0.005$ $M_{\\odot}$, and $M_{2}{\\sin}i$=$1.008\\pm0.006$ $M_{\\odot}$. The cooler component of the system shows H$\\alpha$ and CaII H & K emissions. Our spectroscopic data and recent $BV$ light curves were solved simultaneously using the Wilson-Devinney code. A dark spot on the surface of the cooler component was assumed to explain large asymmetries observed in the light curves. The following absolute parameters of the components were determined: $M_{1}$=$1.11\\pm0.01$ $M_{\\odot}$, $M_{2}$=$1.23\\pm0.01$ $M_{\\odot}$, $R_{1}$=$1.63\\pm0.02$ $R_{\\odot}$, $R_{2}$=$3.60\\pm0.02$ $R_{\\o...

  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. 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...

  15. Numerical simulations of wave propagation in the solar chromosphere

    CERN Document Server

    Nutto, C; Roth, M

    2010-01-01

    We present two-dimensional simulations of wave propagation in a realistic, non-stationary model of the solar atmosphere. This model shows a granular velocity field and magnetic flux concentrations in the intergranular lanes similar to observed velocity and magnetic structures on the Sun and takes radiative transfer into account. We present three cases of magneto-acoustic wave propagation through the model atmosphere, where we focus on the interaction of different magneto-acoustic wave at the layer of similar sound and Alfv\\'en speeds, which we call the equipartition layer. At this layer the acoustic and magnetic mode can exchange energy depending on the angle between the wave vector and the magnetic field vector. Our results show that above the equipartition layer and in all three cases the fast magnetic mode is refracted back into the solar atmosphere. Thus, the magnetic wave shows an evanescent behavior in the chromosphere. The acoustic mode, which travels along the magnetic field in the low plasma-$\\beta$ ...

  16. Relation between photospheric magnetic field and chromospheric emission

    CERN Document Server

    Rezaei, R; Beck, C A R; Bruls, J H M J; Schmidt, W

    2007-01-01

    We simultaneously observed the Stokes parameters of the photospheric iron line pair at 630.2 nm and the intensity profile of the chromospheric Ca II H line at 396.8 nm in a quiet Sun region at a heliocentric angle of 53 deg. We perform a statistical analysis of network and inter-network properties.The H-index is the integrated emission in a 0.1 nm band around the Ca core. We separate a non-magnetically, H_non, and a magnetically, H_mag, heated component from a non-heated component, H_co in the H-index. The average network and inter-network H-indices are equal to 12 and 10 pm, respectively. The emission in the network is correlated with the magnetic flux density, approaching a value of H 10 pm for vanishing flux. The inter-network magnetic field distribution peaks around 200 G and its mean absolute flux density is 11 Mx cm$^{-2}$. We find that a dominant fraction of the calcium emission caused by the heated atmosphere in the magnetic network, has non-magnetic origin (H_mag 2pm, H_non 3pm). Considering the effe...

  17. 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

  18. Long-term chromospheric activity of non-eclipsing RS CVn-type stars

    Science.gov (United States)

    Buccino, A. P.; Mauas, P. J. D.

    2009-02-01

    Context: The IUE database provides several UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims: Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22 468 (V711 Tau, HR 1099, K1IV+G5V), HD 21 242 (UX Ari, K0IV+G5V), and HD 224 085 (II Peg, K2IV). Methods: We first obtained the Mount Wilson index S from the IUE high and low-resolution spectra. Secondly, we used the Lomb-Scargle periodogram to analyse the mean annual index and the amplitude of the rotational modulation of the index S. Results: For HD 22 468 (V711 Tau, HR 1099), we find a possible chromospheric cycle with a period of ~18 years and a shorter cycle with a period of ~3 years, which could be associated to a chromospheric “flip-flop” cycle. The data of HD 224 085 (II Peg) also suggest a chromospheric cycle of ~21 years and a flip-flop cycle of ~9 years. Finally, we obtained a possible chromospheric cycle of ~7 years for HD 21 242 (UX Ari).

  19. 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...

  20. 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.

  1. Chromospheric activity and rotational modulation of the RS Canum Venaticorum binary V711 Tauri during 1998-2004

    Science.gov (United States)

    Cao, Dongtao; Gu, Shenghong

    2015-05-01

    We present long-term high-resolution spectroscopic observations of the very active RS Canum Venaticorum-type star V711 Tau, obtained during several observing runs from 1998 to 2004, and study its chromospheric activity. Using the spectral subtraction technique, several optical chromospheric activity indicators [including the He I D3, Na I D1, D2, Hα and Ca II infrared triplet (IRT) lines] formed at different atmospheric heights are analysed. Strong chromospheric emission supports earlier results that indicate that V711 Tau is a very active system. Two large optical flares were detected during our observations. The results suggest that the main part of chromospheric emission is attributed to the primary star of the system. The secondary also presents weak emission but is less active. The ratios of EW8542/EW8498 indicate that Ca II IRT emission arises predominantly from plage-like regions. We have found rotational modulation of chromospheric activity in the Hα and Ca II IRT lines, which suggests the presence of the chromospheric active longitudes over the surface of V711 Tau. Two active longitudes separated by about 180° were observed to dominate the activity, and the so-called flip-flop phenomenon was seen during our observations. Moreover, the chromospheric activity level shows a long-term variation that gradually increases from a deep minimum near the year 2002. A close spatial connection of photospheric spots and chromospheric active regions in both short and long timescales was found for V711 Tau.

  2. 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

  3. 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...

  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. Conditions for Photospherically Driven Alfvenic Oscillations to Heat the Solar Chromosphere by Pedersen Current Dissipation

    CERN Document Server

    Goodman, Michael L

    2014-01-01

    A magnetohydrodynamic model that includes a complete electrical conductivity tensor is used to estimate conditions for photospherically driven, linear, non-plane Alfvenic oscillations extending from the photosphere to the lower corona to drive a chromospheric heating rate due to Pedersen current dissipation that is comparable to the net chromospheric net radiative loss of $\\sim 10^7$ ergs-cm$^{-2}$-sec$^{-1}$. The heating rates due to electron current dissipation in the photosphere and corona are also computed. The wave amplitudes are computed self-consistently as functions of an inhomogeneous background (BG) atmosphere. The effects of the conductivity tensor are resolved numerically using a resolution of 3.33 m. The oscillations drive a chromospheric heating flux $F_{Ch} \\sim 10^7 - 10^8$ ergs-cm$^{-2}$-sec$^{-1}$ at frequencies $\

  6. 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 ...

  7. A new approach for modelling chromospheric evaporation in response to enhanced coronal heating: 1 the method

    CERN Document Server

    Johnston, C D; Cargill, P J; De Moortel, I

    2016-01-01

    We present a new computational approach that addresses the difficulty of obtaining the correct interaction between the solar corona and the transition region in response to rapid heating events. In the coupled corona, transition region and chromosphere system, an enhanced downward conductive flux results in an upflow (chromospheric evaporation). However, obtaining the correct upflow generally requires high spatial resolution in order to resolve the transition region. With an unresolved transition region, artificially low coronal densities are obtained because the downward heat flux jumps across the unresolved region to the chromosphere, underestimating the upflows. Here, we treat the lower transition region as a discontinuity that responds to changing coronal conditions through the imposition of a jump condition that is derived from an integrated form of energy conservation. To illustrate and benchmark this approach against a fully resolved one-dimensional model, we present field-aligned simulations of corona...

  8. 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.

  9. 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

  10. 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.

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

    CERN Document Server

    Imada, Shinsuke; Watanabe, Tetsuya

    2015-01-01

    We have studied the chromospheric evaporation flow during the impulsive phase of the flare by using the Hinode/EIS 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 kappa0 = classical value) and the enthalpy flux dominant regime (kappa0 = 0.1 x 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 o...

  12. 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.

  13. Testing Wave Propagation Properties in the Solar Chromosphere with ALMA and IRIS

    Science.gov (United States)

    Fleck, Bernard; Straus, Thomas; Wedemeyer, Sven

    2016-05-01

    Waves and oscillations are interesting not only from the point of view that they can propagate energy into the chromosphere and dissipate that energy to produce non-radiative heating, they also carry information about the structure of the atmosphere in which they propagate. Since the late 80s there is substantial evidence that the chromospheric wave field is dominated by a non-propagating component, presumably resulting from wave reflection at the transition region. Observations of Doppler oscillations measured in the Ca II infrared tripet lines, Ca II K, and He 10830 all show vanishing phase lags (i.e. vanishing travel time differences) between the various lines, in particular also for frequencies above the cut-off frequency. Why is the apparent phase speed of high frequency acoustic waves in the chromosphere so high? Are these results misleading because of complex radiation transfer effects in these optically thick lines? ALMA, which acts as a linear thermometer of the solar chromosphere, will provide measurements of the local plasma conditions that should be, at least in principle, much easier to interpret. Multi-wavelength time series of ALMA observations of the temperature fluctuations of inter-network oscillations should allow travel time measurements between different heights as these disturbances propagate through the chromosphere and thus should finally settle the long-standing question about the propagation characteristics of high frequency acoustic waves in the chromosphere. We plan to combine ALMA mm-observations with high resolution IRIS observations in the Mg II h and k lines, and until ALMA observations are available, will study the expected signals using time series of mm-maps from 3D radiation hydrodynamics simulations that are being prepared within the framework of the Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON).

  14. Chromospheric Observations of a Kink Wave in an On-disk Active Region Fibril

    Science.gov (United States)

    Pietarila, A. M.; Aznar Cuadrado, R.; Hirzberger, J.; Solanki, S.

    2011-12-01

    Most observations of kink and Alfven waves in the chromosphere are made in off-limb spicules. Here we present observations of a kink wave in high spatial and temporal resolution Ca II 8542 data of an active region fibril on the solar disk. The properties of the observed wave are similar to kink waves in spicules. From the inferred wave phase and period we estimate the lower limit for the field strength in the chromospheric fibril to be a few hundred Gauss. The observations indicate that the event may have been triggered by a small-scale reconnection event higher up in the atmosphere.

  15. Rayleigh-Taylor Instability and Excitation of Super-Dreicer Electric Fields in the Solar Chromosphere

    Science.gov (United States)

    Zaitsev, V. V.; Kronshtadtov, P. V.; Stepanov, A. V.

    2016-09-01

    Within the framework of the long-standing so-called "number problem" in the physics of solar flares, we consider the excitation of a super-Dreicer electric field at the leading edge of the electric current pulse that occurs at the chromospheric legs of a coronal magnetic loop as a result of the magnetic Rayleigh-Taylor instability. It is shown that for a sufficiently strong electric current, I0 ≥ 10^{10} A, the current pulse propagates in the non-linear mode and generates a strong longitudinal electric field Ez, which strongly depends on the current ( Ez ∝ I03) and can exceed the Dreicer field ( Ez > ED). In this case, the bulk of electrons in the site of the current pulse is in a runaway mode, and the energy release rate in the chromosphere increases significantly. Super-Dreicer electric fields also provide injection of protons into the regime of acceleration by Langmuir turbulence generated by fast electrons at the leading edge of the electric current pulse. The electric field at the pulse edge can exceed the Dreicer field starting from the chromosphere level with the number density n ≈ 10^{13} cm^{-3}. At a lower current I0 < 10^{10} A, a super-Dreicer mode at the higher levels of the chromosphere with n < 10^{12} cm^{-3} occurs.

  16. Long-term chromospheric activity of non-eclipsing RS CVn-type stars

    CERN Document Server

    Buccino, Andrea P

    2008-01-01

    Context. The IUE database provides a large number of UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims. Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22468 (V711 Tau, HR 1099, K1IV+G5V), HD 21242 (UX Ari, K0IV+G5V) and HD 224085 (II Peg, K2IV). Methods. We first obtain the Mount Wilson index S from the IUE high and low-resolution spectra. Secondly, we analyse with the Lomb-Scargle periodogram the mean annual index S and the amplitude of its rotational modulation. Results. For HD 22468 (V711 Tau, HR 1099), we found a possible chromospheric cycle with a period of 18 years and a shorter cycle with a period of 3 years, which could be associated to a chromospheric "flip-flop" cycle. The data of HD 224085 (II Peg) also suggest a chromospheric cycle of 21 years and a flip-flop cycle of 9 years. Finally, we obtained a p...

  17. 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...

  18. What do iris observations of Mg II k tell us about the solar plage chromosphere?

    CERN Document Server

    Carlsson, Mats; De Pontieu, Bart

    2015-01-01

    We analyze observations from the Interface Region Imaging Spectrograph of the Mg II k line, the Mg II UV subordinate lines, and the O I 135.6 nm line to better understand the solar plage chromosphere. We also make comparisons with observations from the Swedish 1 m Solar Telescope of the H{\\alpha} line, the Ca II 8542 line, and Solar Dynamics Observatory/Atmospheric Imaging Assembly observations of the coronal 19.3 nm line. To understand the observed Mg II profiles, we compare these observations to the results of numerical experiments. The single-peaked or flat-topped Mg II k profiles found in plage imply a transition region at a high column mass and a hot and dense chromosphere of about 6500 K. This scenario is supported by the observed large-scale correlation between moss brightness and filled-in profiles with very little or absent self-reversal. The large wing width found in plage also implies a hot and dense chromosphere with a steep chromospheric temperature rise. The absence of emission in the Mg II subo...

  19. Chromospheric polarimetry through multi-line observations of the 850 nm spectral region

    CERN Document Server

    Noda, C Quintero; Katsukawa, Y; Rodriguez, J de la Cruz; Carlsson, M; Anan, T; Oba, T; Ichimoto, K; Suematsu, Y

    2016-01-01

    Future solar missions and ground-based telescopes aim to understand the magnetism of the solar chromosphere. We performed a supporting study in Quintero Noda et al. (2016) focused on the infrared Ca II 8542 A line and we concluded that is one of the best candidates because it is sensitive to a large range of atmospheric heights, from the photosphere to the middle chromosphere. However, we believe that it is worth to try improving the results produced by this line observing additional spectral lines. In that regard, we examined the neighbour solar spectrum looking for spectral lines that could increase the sensitivity to the atmospheric parameters. Interestingly, we discovered several photospheric lines that greatly improve the photospheric sensitivity to the magnetic field vector. Moreover, they are located close to a second chromospheric line that also belongs to the Ca II infrared triplet, i.e. the Ca II 8498 A line, and enhances the sensitivity to the atmospheric parameters at chromospheric layers. We conc...

  20. 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 ...

  1. 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...

  2. 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...

  3. Spectro-polarimetric observation in UV with CLASP to probe the chromosphere and transition region

    Science.gov (United States)

    Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère, Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi, Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi; Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto; Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca; Carlsson, Mats

    2016-05-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA sounding-rocket experiment that was performed in White Sands in the US on September 3, 2015. During its 5-minute ballistic flight, CLASP successfully made the first spectro-polarimetric observation in the Lyman-alpha line (121.57 nm) originating in the chromosphere and transition region. Since the Lyman-alpha polarization is sensitive to magnetic field of 10-100 G by the Hanle effect, we aim to infer the magnetic field information in such upper solar atmosphere with this experiment.The obtained CLASP data showed that the Lyman-alpha scattering polarization is about a few percent in the wings and the order of 0.1% in the core near the solar limb, as it had been theoretically predicted, and that both polarization signals have a conspicuous spatio-temporal variability. CLASP also observed another upper-chromospheric line, Si III (120.65 nm), whose critical field strength for the Hanle effect is 290 G, and showed a measurable scattering polarization of a few % in this line. The polarization properties of the Si III line could facilitate the interpretation of the scattering polarization observed in the Lyman-alpha line.In this presentation, we would like to show how the upper chromosphere and transition region are seen in the polarization of these UV lines and discuss the possible source of these complicated polarization signals.

  4. 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...

  5. 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...

  6. 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 ...

  7. 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.

  8. MHD Modelling of Coronal Loops: Injection of High-Speed Chromospheric Flows

    Science.gov (United States)

    Petralia, A.; Reale, F.; Orlando, S.; Klimchuk, J. A.

    2014-01-01

    Context. Observations reveal a correspondence between chromospheric type II spicules and bright upward-moving fronts in the corona observed in the extreme-ultraviolet (EUV) band. However, theoretical considerations suggest that these flows are probably not the main source of heating in coronal magnetic loops. Aims. We investigate the propagation of high-speed chromospheric flows into coronal magnetic flux tubes and the possible production of emission in the EUV band. Methods. We simulated the propagation of a dense 104 K chromospheric jet upward along a coronal loop by means of a 2D cylindrical MHD model that includes gravity, radiative losses, thermal conduction, and magnetic induction. The jet propagates in a complete atmosphere including the chromosphere and a tenuous cool (approximately 0.8 MK) corona, linked through a steep transition region. In our reference model, the jet initial speed is 70 km per second, its initial density is 10(exp 11) per cubic centimeter, and the ambient uniform magnetic field is 10 G. We also explored other values of jet speed and density in 1D and different magnetic field values in 2D, as well as the jet propagation in a hotter (approximately 1.5 MK) background loop. Results. While the initial speed of the jet does not allow it to reach the loop apex, a hot shock-front develops ahead of it and travels to the other extreme of the loop. The shock front compresses the coronal plasma and heats it to about 10(exp 6) K. As a result, a bright moving front becomes visible in the 171 Angstrom channel of the SDO/AIA mission. This result generally applies to all the other explored cases, except for the propagation in the hotter loop. Conclusions. For a cool, low-density initial coronal loop, the post-shock plasma ahead of upward chromospheric flows might explain at least part of the observed correspondence between type II spicules and EUV emission excess.

  9. 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.

  10. 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

  11. 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 ...

  12. 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

  13. HEATING OF THE PARTIALLY IONIZED SOLAR CHROMOSPHERE BY WAVES IN MAGNETIC STRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Shelyag, S.; Przybylski, D. [Department of Mathematics and Information Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST (United Kingdom); Khomenko, E.; Vicente, A. de, E-mail: shelyag@gmail.com [Instituto de Astrofísica de Canarias, E-38205, C/Vía Láctea, s/n, La Laguna, Tenerife (Spain)

    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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)

    CERN Document Server

    Carlin, E S

    2014-01-01

    This paper shows the first synthetic tomography of the quiet solar chromosphere formed by spatial maps of scattering polarization. It has been calculated for the CaII 8498, 8542 and 3934 A lines by solving the NLTE (non-local thermodynamical equilibrium) RT (radiative transfer) problem of the second kind in a 3D atmosphere model obtained from realistic MHD (magneto-hydrodynamical) simulations. Maps of circular polarization were calculated neglecting atomic polarization. Our investigation focuses on the linear polarization signals induced by kinematics, radiation field anisotropy and Hanle effect in forward-scattering geometry. Thus, instead of considering slit profiles at the limb as normally done in the study of the second solar spectrum, we synthetize and analyze spatial maps of polarization at disk center. It allows us to understand the spatial signatures of dynamics and magnetic field in the linear polarization for discriminating them observationally. Our results suggest new ideas for chromospheric diagno...

  19. 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...

  20. 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.

  1. The Hanle and Zeeman Effects in Solar Spicules: A Novel Diagnostic Window on Chromospheric Magnetism

    CERN Document Server

    Bueno, J T; Centeno, R; Collados, M; Landi degl'Innocenti, E

    2005-01-01

    An attractive diagnostic tool for investigating the magnetism of the solar chromosphere is the observation and theoretical modeling of the Hanle and Zeeman effects in spicules, as shown in this letter for the first time. Here we report on spectropolarimetric observations of solar chromospheric spicules in the He I 10830 \\AA multiplet and on their theoretical modeling accounting for radiative transfer effects. We find that the magnetic field in the observed (quiet Sun) spicular material at a height of about 2000 km above the visible solar surface has a strength of the order of 10 G and is inclined by approximately $35^{\\circ}$ with respect to the local vertical direction. Our empirical finding based on full Stokes-vector spectropolarimetry should be taken into account in future magnetohydrodynamical simulations of spicules.

  2. 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.

  3. Solar Hard X-ray Source Sizes in a Beam-Heated and Ionised Chromosphere

    CERN Document Server

    O'Flannagain, A; Gallagher, P T

    2014-01-01

    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 using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) have shown that HXR source sizes are 3-6 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 ionisation (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionised 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 ionised region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to...

  4. 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...

  5. 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...

  6. 2D Radiative MHD Simulations of the Importance of Partial Ionization in the Chromosphere

    CERN Document Server

    Martinez-Sykora, Juan; Hansteen, Viggo

    2012-01-01

    The solar chromosphere is weakly ionized and interactions between ionized particles and neutral particles likely have significant consequences for the thermodynamics of the plasma. We investigate the importance of introducing neutral particles using numerical 2.5D radiative MHD simulations obtained with the Bifrost code. The models span from the upper layers of the convection zone to the low corona, and solve the full MHD equations with non-grey and NLTE radiative transfer, and thermal conduction. The effects of partial ionization are implemented using the generalized Ohm's law. The approximations required in going from three fluids to the generalized Ohm's law are tested in our simulations. The Ohmic diffusion, the Hall term, and ambipolar diffusion show strong variations in the chromosphere. These strong variations of the various magnetic diffusivities are absent or significantly underestimated when, as has been common for these types of studies, using the VAL-C model as a basis for estimates. In addition, ...

  7. 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.

  8. An Automated Algorithm to Distinguish and Characterize Solar Flares and Associated Sequential Chromospheric Brightenings

    CERN Document Server

    Kirk, M S; Jackiewicz, J; McNamara, B J; McAteer, R T J

    2011-01-01

    We present a new automated algorithm to identify, track, and characterize small-scale brightening associated with solar eruptive phenomena observed in H{\\alpha}. The temporal spatially-localized changes in chromospheric intensities can be separated into two categories: flare ribbons and sequential chromospheric brightenings (SCBs). Within each category of brightening we determine the smallest resolvable locus of pixels, a kernel, and track the temporal evolution of the position and intensity of each kernel. This tracking is accomplished by isolating the eruptive features, identifying kernels, and linking detections between frames into trajectories of kernels. We fully characterize the evolving intensity and morphology of the flare ribbons by observing the tracked flare kernels in aggregate. With the location of SCB and flare kernels identified, they can easily be overlaid on top of complementary data sets to extract Doppler velocities and magnetic field intensities underlying the kernels. This algorithm is ad...

  9. Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks

    CERN Document Server

    Brannon, Sean

    2014-01-01

    Magnetic reconnection in the corona results in contracting flare loops, releasing energy into plasma heating and shocks. The hydrodynamic shocks so produced drive thermal conduction fronts (TCFs) which transport energy into the chromosphere and drive upflows (evaporation) and downflows (condensation) in the cooler, denser footpoint plasma. Observations have revealed that certain properties of the transition point between evaporation and condensation (the "flow reversal point" or FRP), such as temperature and velocity-temperature derivative at the FRP, vary between different flares. These properties may provide a diagnostic tool to determine parameters of the coronal energy release mechanism and the loop atmosphere. In this study, we develop a 1-D hydrodynamical flare loop model with a simplified three-region atmosphere (chromosphere/transition region/corona), with TCFs initiated by shocks introduced in the corona. We investigate the effect of two different flare loop parameters (post-shock temperature and tra...

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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...

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

    Science.gov (United States)

    Imada, Shinsuke; Murakami, Izumi; Watanabe, Tetsuya

    2015-10-01

    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 κ0 = classical value) and the enthalpy flux dominant regime (κ0 = 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.

  16. 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...

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. Challenges to Understand Stellar Chromospheres and Stellar Activity: The Limit Case of Late-A and Early-F Stars

    Science.gov (United States)

    Freire Ferrero, R.; Gouttebroze, P.

    The onset of chromospheric activity appears at late-A and early-F stars where theories predict atmospheres in radiative equilibrium and shallow or non-existent convective zones. The detection of Ly-α emission cores in several A and F stars, first with the IUE satellite and then with the HST, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0. ^m19 (Catalano et al. [CITE]). Semiempirical chromospheric models for Altair allowed us (Freire et al. [CITE]) to explain the observed emission profiles taking into account normal HI IS absorption. However, due to the very high rotational velocity we analyzed alternative hypotheses like the formation of Ly-α emissions into a corotating expanding wind, but we ruled out this alternative because we obtained inconsistent results. In addition, X-ray emission (originated surely in a corona) strengthen the presence of a chromosphere. Here we place the problem of chromospheric activity of late-A and early-F stars in the general context of the formation of over-photospheric stellar layers, comparing them with late-type star and solar cases.

  4. 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.

  5. 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.

  6. 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...

  7. 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

  8. 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.

  9. 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.

  10. MHS sunspot model from deep sub-photospheric to chromospheric layers

    CERN Document Server

    Khomenko, E

    2008-01-01

    In order to understand the influence of magnetic fields on the propagation properties of waves, as derived from different local helioseismology techniques, forward modeling of waves is required. Such calculations need a model in magnetohydrostatic equilibrium as initial atmosphere to propagate oscillations through it. We provide a method to construct such a model in equilibrium for a wide range of parameters to be used for simulations of artificial helioseismologic data. The method combine the advantages of self-similar solutions and current-distributed models. A set of models is developed by numerical integration of magnetohydrostatic equations from the sub-photospheric to chromospheric layers.

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

    OpenAIRE

    Imada, Shinsuke; MURAKAMI, Izumi; Watanabe, Tetsuya

    2015-01-01

    We have studied the chromospheric evaporation flow during the impulsive phase of the flare by using the Hinode/EIS 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 therma...

  12. Limits of shock heating for the chromospheres of low-gravity stars

    Science.gov (United States)

    Gadelmavla, Diaa

    2016-07-01

    This work discusses theoretical limits of chromospheric heating by shock waves in stars with low surface gravity. The computations are self consistent, and based on waves generated in stellar convection zones. We employ the new finding of the mixing length parameter α = 1.8. The Ca~II~H+K and Mg~II~h+k fluxes are computed assuming partial redistribution (PRD). The results show the strong dependence of the number of formed shocks and their transmission through the atmosphere on the value of the surface gravity. For stars with solar gravity, heating by shock waves is very efficient, this efficiency decreases with decreasing the value of G. For fixed effective temperature and solar metallicity, the temperature of the chromosphere increase with increasing the stellar surface gravity. A linear correlation is found between the surface gravity and the number of transmitted shocks. The emitted Mg~II and Ca~II fluxes show also a linear dependance on G. It has been found that there is a clear threshold value of G where no shocks are formed. The theoretically computed basal Ca~II and Mg~II fluxes follow simple formulae as a function of stellar surface gravity.

  13. 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...

  14. 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.

  15. 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.

  16. 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...

  17. 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...

  18. 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...

  19. Photospheric and chromospheric activity on the young solar-type star HD 171488

    CERN Document Server

    Frasca, A; Kovari, Zs; Marilli, E; Cakirli, O

    2010-01-01

    We present the results of contemporaneous spectroscopic and photometric monitoring of the young solar-type star HD171488 (Prot~1.337 d) aimed at studying surface inhomogeneities at photospheric/chromospheric levels. Echelle FOCES spectra (R~40000) and Johnson photometry have been performed in 2006. Spectral type, rotational velocity, metallicity, and gravity were determined using a code developed by us. The metallicity was measured from the analysis of iron lines. The spectral subtraction technique was applied to the most relevant chromospheric diagnostics included in the FOCES spectral range (CaII IRT, Halpha, HeI-D3, Hbeta, CaII H&K). A model with two large high-latitude spots is sufficient to reproduce the B/V light curves and the radial velocity modulation, if a temperature difference between photosphere and spots of 1500 K is used. A Doppler imaging analysis of photospheric lines confirms a similar spot distribution. With the help of an analogous geometric two-spot model, we are able to reproduce the...

  20. 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...

  1. 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.

  2. 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.

  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. 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...

  5. 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.

  6. 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...

  7. Ca II H and K Chromospheric Emission Lines in Late K and M Dwarfs

    CERN Document Server

    Rauscher, E; Marcy, Geoffrey W.; Rauscher, Emily

    2006-01-01

    We have measured the profiles of the Ca II H and K chromospheric emission lines in 147 main sequence stars of spectral type M5-K7 (0.30-0.55 solar masses) using multiple high resolution spectra obtained during six years with the HIRES spectrometer on the Keck 1 telescope. Remarkably, the average FWHM, equivalent widths, and line luminosities of Ca II H and K increase by a factor of 3 with increasing stellar mass over this small range of stellar masses. We fit the H and K lines with a double Gaussian model to represent both the chromospheric emission and the non-LTE central absorption. Most of the sample stars display a central absorption that is typically redshifted by ~0.1 km/s relative to the emission, but the nature of this velocity gradient remains unknown. The FWHM of the H and K lines increase with stellar luminosity, reminiscent of the Wilson-Bappu effect in FGK-type stars. Both the equivalent widths and FWHM exhibit modest temporal variability in individual stars. At a given value of M_v, stars exhibi...

  8. 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...

  9. 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

  10. 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.

  11. 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.

  12. 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...

  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. 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.

  16. 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.

  17. Time-dependent hydrogen ionisation in 3D simulations of the solar chromosphere. Methods and first results

    NARCIS (Netherlands)

    Leenaarts, J.; Wedemeyer-Bohm, S.

    2006-01-01

    Context. The hydrogen ionisation degree deviates substantially from statistical equilibrium under the conditions of the solar chromosphere. A realistic description of this atmospheric layer thus must account for time-dependent non-equilibrium effects. Aims. Advancing the realism of numerical simulat

  18. 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.

  19. 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...

  20. 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

  1. 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

  2. Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere

    CERN Document Server

    Tian, H; Cranmer, S R; De Pontieu, B; Peter, H; Martínez-Sykora, J; Golub, L; McKillop, S; Reeves, K K; Miralles, M P; McCauley, P; Saar, S; Testa, P; Weber, M; Murphy, N; Lemen, J; Title, A; Boerner, P; Hurlburt, N; Tarbell, T D; Wuelser, J P; Kleint, L; Kankelborg, C; Jaeggli, S; Carlsson, M; Hansteen, V; McIntosh, S W

    2014-01-01

    As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80-250 km/s from the narrow bright network lanes of this interface region. These jets have lifetimes of 20-80 seconds and widths of 300 km or less. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with ~20 km/s amplitudes. Many jets reach temperatures of at least ~100000 K and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.

  3. The key role of solar dynamics in the chromospheric Hanle polarization

    CERN Document Server

    Carlin, E S

    2016-01-01

    The quantum theory of polarized light allows one to model scattering in the solar atmosphere for inferring its properties. This powerful approach has revealed two key long-standing problems in solar physics: the puzzling dilemmas between theory and observations in several anomalously polarized spectral lines and the need for inferring the ubiquitous weak chromospheric magnetic fields, which requires discriminating the Hanle effect in dynamic optically thick plasmas. However, the ever-present dynamics, i.e., the temporal evolution of heatings and macroscopic motions, has been widely disregarded when modeling and interpreting the scattering polarization. This has hindered a consistent theoretical solution to the puzzle while falsifying the Hanle diagnosis. Here, we show that the dynamical evolution is a keystone for solving both problems because its systematic impact allows an explanation of the observations from 'anomalous' instantaneous polarization signals. Evolution accounted for, we reproduce amplitudes an...

  4. Slender Ca II H fibrils mapping magnetic fields in the low solar chromosphere

    CERN Document Server

    Jafarzadeh, Shahin; Solanki, S K; Wiegelmann, T; Riethmueller, T; van Noort, M; Szydlarski, M; Rodriguez, J Blanco; Barthol, P; Iniesta, J C del Toro; Gandorfer, A; Gizon, L; Hirzberger, J; Knoelker, M; Pillet, V Martinez; Suarez, D Orozco; Schmidt, W

    2016-01-01

    A dense forest of slender bright fibrils near a small solar active region is seen in high-quality narrow-band Ca II H images from the SuFI instrument onboard the Sunrise balloon-borne solar observatory. The orientation of these slender Ca II H fibrils (SCF) overlaps with the magnetic field configuration in the low solar chromosphere derived by magnetostatic extrapolation of the photospheric field observed with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are qualitatively aligned with small-scale loops computed from a novel inversion approach based on best-fit numerical MHD simulation. Such loops are organized in canopy-like arches over quiet areas that differ in height depending on the field strength near their roots.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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...

  12. 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.

  13. The Key Role of Solar Dynamics in the Chromospheric Hanle Polarization

    Science.gov (United States)

    Carlin, E. S.; Bianda, M.

    2016-11-01

    The quantum theory of polarized light allows one to model scattering in the solar atmosphere for inferring its properties. This powerful approach has revealed two key long-standing problems in solar physics: the puzzling dilemmas between theory and observations in several anomalously polarized spectral lines and the need for inferring the ubiquitous weak chromospheric magnetic fields, which requires discriminating the Hanle effect in dynamic optically thick plasmas. However, the ever-present dynamics, i.e., the temporal evolution of heatings and macroscopic motions, has been widely disregarded when modeling and interpreting the scattering polarization. This has hindered a consistent theoretical solution to the puzzle while falsifying the Hanle diagnosis. Here, we show that the dynamical evolution is a keystone for solving both problems because its systematic impact allows an explanation of the observations from “anomalous” instantaneous polarization signals. Evolution accounted for, we reproduce amplitudes and (spectral and spatial) shapes of the Ca i 4227 Å polarization at solar disk center, identifying a restrictive arrangement of magnetic fields, kinematics, heatings, and spatio-temporal resolution. We find that the joint action of dynamics, Hanle effect, and low temporal resolutions mimics Zeeman linear polarization profiles, the true weak-field Zeeman signals being negligible. Our results allow reinterpretation of many polarization signals of the solar spectra and support time-dependent scattering polarization as a powerful tool for deciphering the spatio-temporal distribution of chromospheric heatings and fields. This approach may be a key aid in developing the Hanle diagnosis for the solar atmosphere.

  14. 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...

  15. The solar chromosphere at high resolution with IBIS. II. Acoustic shocks in the quiet internetwork and the role of magnetic fields

    CERN Document Server

    Vecchio, A; Reardon, K P

    2008-01-01

    (Abridged) Aims: We characterize the dynamics of the quiet inter-network chromosphere by studying the occurrence of acoustic shocks and their relation with the concomitant photospheric structure and dynamics. Methods: We analyze a comprehensive data set that includes high resolution chromospheric and photospheric spectra obtained with the IBIS imaging spectrometer in two quiet-Sun regions. This is complemented by high-resolution sequences of MDI magnetograms of the same targets. From the chromospheric spectra we identify the spatio-temporal occurrence of the acoustic shocks. We compare it with the photospheric dynamics by means of both Fourier and wavelet analysis, and study the influence of magnetic structures. Results: Mid-chromospheric shocks occur as a response to underlying powerful photospheric motions at periodicities nearing the acoustic cut-off, consistent with 1-D hydrodynamical modeling. However, their spatial distribution within the supergranular cells is highly dependent on the local magnetic top...

  16. 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

  17. Simulations of the Mg II k and Ca II 8542 lines from an AlfvÉn Wave-heated Flare Chromosphere

    Science.gov (United States)

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

    2016-08-01

    We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfvén 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 8542 Å profiles that 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 Interface Region Imaging Spectrograph observations. The predicted differences between the Ca ii 8542 Å 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.

  18. 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 ...

  19. Evidence for collisional depolarization of the \\ion{Ba}{ii} ${\\lambda}4554$ line in the low chromosphere

    CERN Document Server

    Derouich, M

    2008-01-01

    Context. Rigorous modeling of the \\ion{Ba}{ii} ${\\lambda}4554$ formation is potentially interesting since this strongly polarized line forms in the solar chromosphere where the magnetic field is rather poorly known. Aims. To investigate the role of isotropic collisions with neutral hydrogen in the formation of the polarized \\ion{Ba}{ii} ${\\lambda}4554$ line and, thus, in the determination of the magnetic field. Methods. Multipole relaxation and transfer rates of the $d$ and p-states of \\ion{Ba}{ii} by isotropic collisions with neutral hydrogen are calculated. We consider a plane parallel layer of \\ion{Ba}{ii} situated at the low chromosphere and anisotropically illuminated from below which produces linear polarization in the ${\\lambda}4554$ line by scattering processes. To compute that polarization, we solve the statistical equilibrium equations for \\ion{Ba}{ii} levels including collisions, radiation and magnetic field effects. Results. Variation laws of the relaxation and transfer rates with hydrogen number ...

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

    Science.gov (United States)

    Shimanovskaya, Elena; Bruevich, Vasiliy; Bruevich, Elena

    2016-09-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the 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 cycle, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.

  1. 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.

  2. 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.

  3. RESOLVING THE FAN-SPINE RECONNECTION GEOMETRY OF A SMALL-SCALE CHROMOSPHERIC JET EVENT WITH THE NEW SOLAR TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Zhicheng; Chen, Bin; Goode, Philip R.; Cao, Wenda [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102 (United States); Ji, Haisheng [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    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.

  4. 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.

  5. X-Shooter spectroscopy of young stellar objects III. Photospheric and chromospheric properties of Class III objects

    CERN Document Server

    Stelzer, B; Alcala, J M; Manara, C F; Biazzo, K; Covino, E; Rigliaco, E; Testi, L; Covino, S; D'Elia, V

    2013-01-01

    We analyzed X-Shooter/VLT spectra of 24 ClassIII sources from three nearby star-forming regions (sigmaOrionis, LupusIII, and TWHya). We determined the effective temperature, surface gravity, rotational velocity, and radial velocity by comparing the observed spectra with synthetic BT-Settl model spectra. We investigated in detail the emission lines emerging from the stellar chromospheres and combined these data with archival X-ray data to allow for a comparison between chromospheric and coronal emissions. Both X-ray and Halpha luminosity as measured in terms of the bolometric luminosity are independent of the effective temperature for early-M stars but decline toward the end of the spectral M sequence. For the saturated early-M stars the average emission level is almost one dex higher for X-rays than for Halpha: log(L_x/L_bol) = -2.85 +- 0.36 vs. log(L_Halpha/L_bol) = -3.72 +- 0.21. When all chromospheric emission lines (including the Balmer series up to H11, CaII HK, the CaII infrared triplet, and several HeI...

  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. 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...

  9. 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...

  10. On the Connection between Propagating Solar Coronal Disturbances and Chromospheric Footpoints

    Science.gov (United States)

    Bryans, P.; McIntosh, S. W.; De Moortel, I.; De Pontieu, B.

    2016-09-01

    The Interface Region Imaging Spectrograph (IRIS) provides an unparalleled opportunity to explore the (thermal) interface between the chromosphere, transition region, and the coronal plasma observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). The SDO/AIA observations of coronal loop footpoints show strong recurring upward propagating signals—“propagating coronal disturbances” (PCDs) with apparent speeds of the order of 100-120 km s-1. That signal has a clear signature in the slit-jaw images of IRIS in addition to identifiable spectral signatures and diagnostics in the Mg iih (2803 Å) line. In analyzing the Mg iih line, we are able to observe the presence of magnetoacoustic shock waves that are also present in the vicinity of the coronal loop footpoints. We see there is enough of a correspondence between the shock propagation in Mg iih, the evolution of the Si iv line profiles, and the PCD evolution to indicate that these waves are an important ingredient for PCDs. In addition, the strong flows in the jet-like features in the IRIS Si iv slit-jaw images are also associated with PCDs, such that waves and flows both appear to be contributing to the signals observed at the footpoints of PCDs.

  11. 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 ...

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

    Science.gov (United States)

    Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Simões, Paulo J. A.

    2016-09-01

    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 the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (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 Å, C ii 1334.535 Å, Mg ii 2796.354 Å, and O i 1355.598 Å emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si iv, C ii, and Mg ii during the impulsive phase. Mg ii shows redshifts during the bursts and stationary emission at other times. The Si iv and C ii profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates.

  13. 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.

  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. 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...

  16. 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...

  17. 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 ...

  18. 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...

  19. 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.

  20. The energy of waves in the photosphere and lower chromosphere: 1. Velocity statistics

    CERN Document Server

    Beck, C; Rezaei, R; Collados, M

    2009-01-01

    Acoustic waves are one of the primary suspects besides magnetic fields for the chromospheric heating process to temperatures above radiative equilibrium (RE). We derived the mechanical wave energy as seen in line-core velocities to obtain a measure of mechanical energy flux with height for a comparison with the energy requirements in a semi-empirical atmosphere model. We analyzed a 1-hour time series and a large-area map of Ca II H spectra on the traces of propagating waves. We analyzed the velocity statistics of several spectral lines in the wing of Ca II H, and the line-core velocity of Ca II H. We converted the velocity amplitudes into volume and mass energy densities. For comparison, we used the increase of internal energy necessary to lift a RE atmosphere to the HSRA temperature stratification. We find that the velocity amplitude grows in agreement with linear wave theory and thus slower with height than predicted from energy conservation. The mechanical energy of the waves above around z~500 km is insuf...

  1. 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 ...

  2. 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 ...

  3. Diagnosis of Magnetic and Electric Fields of Chromospheric Jets through Spectropolarimetric Observations of HI Paschen Lines

    CERN Document Server

    Anan, Tetsu; Ichimoto, Kiyoshi

    2014-01-01

    Magnetic fields govern the plasma dynamics in the outer layers of the solar atmosphere, and electric fields acting on neutral atoms that move across the magnetic field enable us to study the dynamical coupling between neutrals and ions in the plasma. In order to measure the magnetic and electric fields of chromospheric jets, the full Stokes spectra of the Paschen series of neutral hydrogen in a surge and in some active region jets that took place at the solar limb were observed on May 5, 2012, using the spectropolarimeter of the Domeless Solar Telescope at Hida observatory, Japan. First, we inverted the Stokes spectra taking into account only the effect of magnetic fields on the energy structure and polarization of the hydrogen levels. Having found no definitive evidence of the effects of electric fields in the observed Stokes profiles, we then estimated an upper bound for these fields by calculating the polarization degree under the magnetic field configuration derived in the first step, with the additional ...

  4. 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...

  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. 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...

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

    CERN Document Server

    Lipartito, Isabel; Reardon, Kevin; Cauzzi, Gianna

    2014-01-01

    We recently reported extremely rapid changes in chromospheric fine structure observed using the IBIS instrument in the red wing of H alpha. Here, we examine data obtained during the same observing run (August 7 2010), 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 vs. sheet-like structures. Principal Component Analysis shows that the very rapid H alpha 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 ...

  8. Temporal Evolution of Chromospheric Oscillations in Flaring Regions: A Pilot Study

    Science.gov (United States)

    Monsue, T.; Hill, F.; Stassun, K. G.

    2016-10-01

    We have analyzed Hα intensity images obtained at a 1 minute cadence with the Global Oscillation Network Group (GONG) system to investigate the properties of oscillations in the 0-8 mHz frequency band at the location and time of strong M- and X-class flares. For each of three subregions within two flaring active regions, we extracted time series from multiple distinct positions, including the flare core and quieter surrounding areas. The time series were analyzed with a moving power-map analysis to examine power as a function of frequency and time. We find that, in the flare core of all three subregions, the low-frequency power (˜1-2 mHz) is substantially enhanced immediately prior to and after the flare, and that power at all frequencies up to 8 mHz is depleted at flare maximum. This depletion is both frequency- and time-dependent, which probably reflects the changing depths visible during the flare in the bandpass of the filter. These variations are not observed outside the flare cores. The depletion may indicate that acoustic energy is being converted into thermal energy at flare maximum, while the low-frequency enhancement may arise from an instability in the chromosphere and provide an early warning of the flare onset. Dark lanes of reduced wave power are also visible in the power maps, which may arise from the interaction of the acoustic waves and the magnetic field.

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

    Science.gov (United States)

    Lorenzo-Oliveira, D.; Porto de Mello, G. F.; Dutra-Ferreira, L.; Ribas, I.

    2016-10-01

    Context. 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. Aims: The Ca II infrared triplet (IRT lines, λλ 8498, 8542, and 8662) 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. Methods: We obtain the Ca II IRT absolute fluxes for 113 FGK stars from high signal-to-noise ratio (S/N) 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 (Teff), metallicity ([Fe/H]), and gravities (log g) avoiding the degeneracy usually present in photometric continuum calibrations based solely on color indices. Results: The internal uncertainties achieved for continuum absolute flux calculations are ≈2% of the solar chromospheric flux, one order of magnitude lower than for photometric calibrations. Using Monte Carlo simulations, we gauge the impact of observational errors on the final chromospheric fluxes due to the absolute continuum flux calibration and find that Teffuncertainties are properly mitigated by the photospheric correction leaving [Fe/H] as the dominating factor in the chromospheric flux uncertainty. Conclusions: Across the FGK spectral types, the Ca II IRT lines are sensitive to chromospheric activity. The reduced internal uncertainties reported here enable us to build a new chromospheric absolute flux scale and explore the age-activity relation from the active regime down to very low activity levels and

  10. NEAR-ULTRAVIOLET EXCESS IN SLOWLY ACCRETING T TAURI STARS: LIMITS IMPOSED BY CHROMOSPHERIC EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Ingleby, Laura; Calvet, Nuria; Bergin, Edwin; McClure, Melissa [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Herczeg, Gregory [Max-Planck-Institut fuer Extraterrestriche Physik, Postfach 1312, D-85741 Garching (Germany); Brown, Alexander; France, Kevin [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Alexander, Richard [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Edwards, Suzan [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); Espaillat, Catherine; Brown, Joanna [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Gregory, Scott G.; Hillenbrand, Lynne [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Roueff, Evelyne; Abgrall, Herve [LUTH and UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, Place J. Janssen, F-92195 Meudon (France); Valenti, Jeff [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Walter, Frederick [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Johns-Krull, Christopher [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Linsky, Jeffrey [JILA, University of Colorado and NIST, 440 UCB Boulder, CO 80309-0440 (United States); Ardila, David, E-mail: lingleby@umich.edu, E-mail: ncalvet@umich.edu, E-mail: gregoryh@mpe.mpg.de [NASA Herschel Science Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125 (United States); and others

    2011-12-20

    Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations of the {approx}5-9 Myr old stars RECX-1 and RECX-11, obtained with the Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph on the Hubble Space Telescope, as well as optical and near-infrared spectroscopic observations. The two stars have similar levels of near-UV emission, although spectroscopic evidence indicates that RECX-11 is accreting and RECX-1 is not. The line profiles of H{alpha} and He I {lambda}10830 in RECX-11 show both broad and narrow redshifted absorption components that vary with time, revealing the complexity of the accretion flows. We show that accretion indicators commonly used to measure mass accretion rates, e.g., U-band excess luminosity or the Ca II triplet line luminosity, are unreliable for low accretors, at least in the middle K spectral range. Using RECX-1 as a template for the intrinsic level of photospheric and chromospheric emission, we determine an upper limit of 3 Multiplication-Sign 10{sup -10} M{sub Sun} yr{sup -1} for RECX-11. At this low accretion rate, recent photoevaporation models predict that an inner hole should have developed in the disk. However, the spectral energy distribution of RECX-11 shows fluxes comparable to the median of Taurus in the near-infrared, indicating that substantial dust remains. Fluorescent H{sub 2} emission lines formed in the innermost disk are observed in RECX-11, showing that gas is present in the inner disk, along with the dust.

  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 behaviour of the excess CaII H & K and H$\\varepsilon$ emissions in chromospherically active binaries

    CERN Document Server

    Montes, D; Cornide, M; De Castro, E

    1995-01-01

    In this work we analyze the behaviour of the excess Ca~{\\sc ii} H \\& K and H\\epsilon emissions in a sample of 73 chromospherically active binary systems (RS~CVn and BY~Dra classes), of different activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fern\\'andez-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995c). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active-chromosphere contribution to the Ca~{\\sc ii} H \\& K lines in these 73 systems. We have determined the excess Ca~{\\sc ii} H \\& K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. We have found that the components of active binaries are generally stronger emitters than s...

  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. 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}...

  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 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.

  17. 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.

  18. 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

  19. The solar chromosphere at high resolution with IBIS. I. New insights from the Ca II 854.2 nm line

    CERN Document Server

    Cauzzi, G; Uitenbroek, H; Cavallini, F; Falchi, A; Falciani, R; Janssen, K; Rimmele, T; Vecchio, A; Woeger, F

    2007-01-01

    (Abridged) Aims: In this paper, we seek to establish the suitability of imaging spectroscopy performed in the Ca II 854.2 nm line as a means to investigate the solar chromosphere at high resolution. Methods: We utilize monochromatic images obtained with the Interferometric BIdimensional Spectrometer (IBIS) at multiple wavelengths within the Ca II 854.2 nm line and over several quiet areas. We analyze both the morphological properties derived from narrow-band monochromatic images and the average spectral properties of distinct solar features such as network points, internetwork areas and fibrils. Results: The spectral properties derived over quiet-Sun targets are in full agreement with earlier results obtained with fixed-slit spectrographic observations, highlighting the reliability of the spectral information obtained with IBIS. Furthermore, the very narrowband IBIS imaging reveals with much clarity the dual nature of the Ca II 854.2 nm line: its outer wings gradually sample the solar photosphere, while the c...

  20. Chromospheric activity on the late-type star V1355 Ori using Lijiang 1.8-m and 2.4-m telescopes

    Science.gov (United States)

    Pi, Qing-Feng; Zhang, Li-Yun; Chang, Liang; Han, Xian-Ming; Lu, Hong-Peng; Zhang, Xi-Liang; Wang, Dai-Mei

    2016-10-01

    We obtained new high-resolution spectra using the Lijiang 1.8-m and 2.4-m telescopes to investigate the chromospheric activities of V1355 Ori as indicated in the behaviors of Ca ii H&K, Hδ, Hγ, Hβ, Na i D1, D2, Hα and Ca ii infrared triplet (IRT) lines. The observed spectra show obvious emissions above the continuum in Ca ii H&K lines, absorptions in the Hδ, Hγ, Hβ and Na i D1, D2 lines, variable behavior (filled-in absorption, partial emission with a core absorption component or emission above the continuum) in the Hα line, and weak self-reversal emissions in the strong filled-in absorptions of the Ca ii IRT lines. We used a spectral subtraction technique to analyze our data. The results show no excess emission in the Hδ and Hγ lines, very weak excess emissions in the Na i D1, D2 lines, excess emission in the Hβ line, clear excess emission in the Hα line, and excess emissions in the Ca ii IRT lines. The value of the ratio of EW8542/EW8498 is in the range 0.9 to 1.7, which implies that chromospheric activity might have been caused by plage events. The value of the ratio E Hα/E Hβ is above 3, indicating that the Balmer lines would arise from prominence-like material. We also found time variations in light curves associated with equivalent widths of chromospheric activity lines in the Na i D1, D2, Ca ii IRT and Hα lines in particular. These phenomena can be explained by plage events, which are consistent with the behavior of chromospheric activity indicators.

  1. 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

  2. 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.

  3. 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

  4. 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...

  5. New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation

    CERN Document Server

    Kowalski, Adam F; Carlsson, Mats; Allred, Joel C; Uitenbroek, Han; Osten, Rachel A; Holman, Gordon

    2015-01-01

    (abridged) The heating mechanism at high densities during M dwarf flares is poorly understood. Spectra of M dwarf flares in the optical and near-ultraviolet wavelength regimes have revealed three continuum components during the impulsive phase: 1) an energetically dominant blackbody component with a color temperature of T $\\sim$ 10,000 K in the blue-optical, 2) a smaller amount of Balmer continuum emission in the near-ultraviolet at lambda $<$ 3646 Angstroms and 3) an apparent pseudo-continuum of blended high-order Balmer lines. These properties are not reproduced by models that employ a typical "solar-type" flare heating level in nonthermal electrons, and therefore our understanding of these spectra is limited to a phenomenological interpretation. We present a new 1D radiative-hydrodynamic model of an M dwarf flare from precipitating nonthermal electrons with a large energy flux of $10^{13}$ erg cm$^{-2}$ s$^{-1}$. The simulation produces bright continuum emission from a dense, hot chromospheric condensat...

  6. From CoRoT 102899501 to the Sun. A time evolution model of chromospheric activity on the main sequence

    CERN Document Server

    Gondoin, P; Fridlund, M; Frasca, A; Guenther, E W; Hatzes, A; Deeg, H J; Parviainen, H; Eigmueller, P; Deleuil, M

    2012-01-01

    Using a model based on the rotational modulation of the visibility of active regions, we analyse the high-accuracy CoRoT lightcurve of the active young star CoRoT102899501. Spectroscopic follow-up observations are used to derive its fundamental parameters. We compare its chromospheric activity level with a model of chrosmospheric activity evolution established by combining relationships between the R'HK index and the Rossby number with a recent model of stellar rotation evolution on the main sequence. We measure the spot coverage of the stellar surface as a function of time, and find evidence for a tentative increase from 5-14% at the beginning of the observing run to 13-29% 35 days later. A high level of magnetic activity on CoRoT102899501 is corroborated by a strong emission in the Balmer and Ca II HK lines (logR'HK ~ -4). The starspots used as tracers of the star rotation constrain the rotation period to 1.625+/-0.002 days and do not show evidence for differential rotation. The effective temperature (Teff=...

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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...

  12. 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.

  13. 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...

  14. 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...

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

    Science.gov (United States)

    Fontenla, J. M.; Linsky, Jeffrey L.; Witbrod, Jesse; France, Kevin; Buccino, A.; Mauas, Pablo; Vieytes, Mariela; Walkowicz, Lucianne M.

    2016-10-01

    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 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. We construct a one-dimensional simple model for the physical structure of the star’s chromosphere, chromosphere-corona transition region, and corona using non-LTE radiative transfer techniques and many molecular lines. The synthesized spectrum for this model fits the continuum and lines across the UV-to-optical spectrum. Particular emphasis is given to the emission lines at wavelengths that are shorter than 300 nm observed with the Hubble Space Telescope, which have important effects on the photochemistry of the exoplanet atmospheres. The FUV line ratios indicate that the transition region of GJ 832 is more biased to hotter material than that of the quiet Sun. The excellent agreement of our computed EUV luminosity with that obtained by two other techniques indicates that our model predicts reliable EUV emission from GJ 832. We find that the unobserved EUV flux of GJ 832, which heats the outer atmospheres of exoplanets and drives their mass loss, is comparable to the active Sun. Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations

  16. 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

  17. Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly$\\alpha$ line in a MHD model of the chromosphere-corona transition region

    CERN Document Server

    Stepan, Jiri; Leenaarts, Jorrit; Carlsson, Mats

    2015-01-01

    Probing the magnetism of the upper solar chromosphere requires measuring and modeling the scattering polarization produced by anisotropic radiation pumping in UV spectral lines. Here we apply PORTA (a novel radiative transfer code) to investigate the hydrogen Ly$\\alpha$ line in a 3D model of the solar atmosphere resulting from a state of the art MHD simulation. At full spatial resolution the linear polarization signals are very significant all over the solar disk, with a large fraction of the field of view showing line-center amplitudes well above the 1% level. Via the Hanle effect the line-center polarization signals are sensitive to the magnetic field of the model's transition region, even when its mean field strength is only 15 G. The breaking of the axial symmetry of the radiation field produces significant forward-scattering polarization in Ly$\\alpha$, without the need of an inclined magnetic field. Interestingly, the Hanle effect tends to decrease such forward-scattering polarization signals in most of ...

  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. 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...

  20. 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...

  1. 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...

  2. 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.

  3. 双色球中奖号码随机性检验%Random Test of the Double Chromospheres Lottery Number

    Institute of Scientific and Technical Information of China (English)

    张利凤

    2014-01-01

    随着彩票的不断推广,市面上出现了各种各样预测号码的书籍以及软件,吸引了众多彩民的目光,而这些预测的号码究竟是否有其科学合理性呢?这里就从双色球为例,来检验随机号码的随机性,看双色球的中奖号码是否是随机的,最终通过SPSS软件运用游程检验的方法得到双色球中奖号码是随机出现的,因此建议彩民不要轻信各种预测号码的软件及书籍,而是应该做到理性博彩。%With the continuous promotion of the lottery, a lot of books and software about predicting the winning number have attracted eyes, and whether these numbers predict are scientific rationality? The paper takes the double chromospheres as a example to test the random of the ball's number. Eventually, run test proves that the winning number is random by using SPSS. It is recommended that lottery buyer do not believe the various forecasts number software and books, and should be rational betting.

  4. The solar chromosphere at high resolution with IBIS: III. Comparison of Ca II K and Ca II 854.2 nm imaging

    CERN Document Server

    Reardon, K P; Cauzzi, G

    2008-01-01

    Filtergrams obtained in Ca II H, Ca II K and H-alpha are often employed as diagnostics of the solar chromosphere. However, the vastly disparate appearance between the typical filtergrams in these different lines calls into question the nature of what is actually being observed. We investigate the lack of obvious structures of magnetic origin such as fibrils and mottles in on-disk Ca II H and K images by directly comparing a temporal sequence of classical Ca II K filtergrams with a co-spatial and co-temporal sequence of spectrally resolved Ca II 854.2 images obtained with the Interferometric Bidimensional Spectrometer (IBIS), considering the effect of both the spectral and spatial smearing. We find that the lack of fine magnetic structuring in Ca II K filtergrams, even with the narrowest available filters, is due to observational effects. Signatures of fibrils remain however in the temporal evolution of the filtergrams, in particular with the evidence of magnetic shadows around the network elements. The Ca II ...

  5. Starspot evolution, differential rotation, and magnetic cycles in the chromospherically active binaries lambda andromedae, sigma Geminorum, II Pegasi, and V711 Tauri

    Science.gov (United States)

    Henry, Gregory W.; Eaton, Joel A.; Hamer, Jamesia; Hall, Douglas S.

    1995-01-01

    We have analyzed 15-19 yr of photoelectric photometry, obtained manually and with automated telescopes, of the chromospherically active binaries lambda And, sigma Gem, II Peg, and V711 Tau. These observations let us identify individual dark starspots on the stellar surfaces from periodic dimming of the starlight, follow the evolution of these spots, and search for long-term cyclic changes in the properties of these starspots that might reveal magnetic cycles analogous to the Sun's 11 yr sunspot cycle. We developed a computer code to fit a simple two-spot model to our observed light curves that allows us to extract the most easily determinable and most reliable spot parameters from the light curves, i.e., spot longitudes and radii. We then used these measured properties to identify individual spots and to chart their life histories by constructing migration and amplitude curves. We identified and followed 11 spots in lambda And, 16 in sigma Gem, 12 in II Peg, and 15 in V711 Tau. Lifetimes of individual spots ranged from a few months to longer than 6 yr. Differential rotation coefficients, estimated from the observed range of spot rotation periods for each star and defined by equation (2), were 0.04 for lambda And, 0.038 for sigma Gem, 0.005 for II Peg, and 0.006 for V711 Tau, versus 0.19 for the Sun. We searched for cyclic changes in mean brightness, B-V color index, and spot rotation period as evidence for long-term cycles. Of these, long-term variability in mean brightness appears to offer the best evidence for such cycles in these four stars. Cycles of 11.1 yr for lambda And, 8.5 yr for sigma Gem, 11 yr for II Peg, and 16 yr V711 Tau are implied by these mean brightness changes. Cyclic changes in spot rotation period were found in lambda And and possibly II Peg. Errors in B-V were too large for any long-term changes to be detectable.

  6. The HADES RV Programme with HARPS-N@TNG IV. Time resolved analysis of the Ca ii H&K and H{\\alpha} chromospheric emission of low-activity early-type M dwarfs

    CERN Document Server

    Scandariato, G; Biazzo, K; Leto, G; Stelzer, B; Sanchez, R Zanmar; Claudi, R; Cosentino, R; Damasso, M; Desidera, S; Álvarez, E González; Hernández, J I González; Gratton, R; Lanza, A F; Maggio, A; Messina, S; Micela, G; Pagano, I; Perger, M; Piotto, G; Rebolo, R; Ribas, I; Rosich, A; Sozzetti, A; Mascareño, A Suárez

    2016-01-01

    M dwarfs are prime targets for planet search programs, particularly of those focused on the detection and characterization of rocky planets in the habitable zone. Understanding their magnetic activity is important because it affects our ability to detect small planets, and it plays a key role in the characterization of the stellar environment. We analyze observations of the Ca II H&K and H{\\alpha} lines as diagnostics of chromospheric activity for low-activity early-type M dwarfs. We analyze the time series of spectra of 71 early-type M dwarfs collected for the HADES project for planet search purposes. The HARPS-N spectra provide simultaneously the H&K doublet and the H{\\alpha} line. We develop a reduction scheme able to correct the HARPS-N spectra for instrumental and atmospheric effects, and to provide flux-calibrated spectra in units of flux at the stellar surface. The H&K and H{\\alpha} fluxes are compared with each other, and their variability is analyzed. We find that the H and K flux excesse...

  7. 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

  8. 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...

  9. 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

  10. 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...

  11. 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.

  12. Transverse Motions of Chromospheric Type II Spicules Observed by the New Solar Telescope

    CERN Document Server

    Yurchyshyn, V; Abramenko, V

    2012-01-01

    Using high resolution off-band \\ha\\ data from the New Solar Telescope and Morlet wavelet analysis technique, we analyzed transverse motions of type II spicules observed near the North Pole of the Sun. Our new findings are that i) some of the observed type II spicules display kink or an inverse "Y" features, suggesting that their origin may be due to magnetic reconnection, and ii) type II spicules tend to display coherent transverse motions/oscillations. Also, the wavelet analysis detected significant presence of high frequency oscillations in type II spicules, ranging from 30 to 180 s with the the average period of 90 s. We conclude that at least some of type II spicules and their coherent transverse motions may be caused by reconnection between large scale fields rooted in the intergranular lanes and and small-scale emerging dipoles, a process that is know to generate high frequency kink mode MHD waves propagating along the magnetic field lines.

  13. 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...

  14. 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 ...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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.

  20. The Connection between the Corona and Chromosphere during a Multiple Event Observation

    Science.gov (United States)

    Cirtain, Jonathan

    2008-01-01

    NOAA AR 10940 (Jan 25 2007 - Feb 09 2007) rotated into view producing a CME and EIT wave, and followed by at least 27 B and C class flares as rotated across the disk. As it reached the west limb it proceeded to produce a sequence of jets and filament eruptions that were observed in unprecedented detail. I present observations from TRACE, EIT, HINODE XRT / SOT / EIS, RHESSI, GOES 12 and STEREO-A COR 1 to investigate part of the sequence of events that lead to a filament eruption and sympathetic jet at 02:30 - 03:00 02/09/07. I concentrate on the topology changes and infer that external breakout reconnection was the mechanism that lead to the removal of overlying field and subsequent filament eruption I will also discuss the instrument development activities at MSFC.

  1. 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...

  2. 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.

  3. 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.

  4. 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...

  5. 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.

  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. 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.

  8. NUV Excess in Slowly Accreting T Tauri Stars: Limits Imposed by Chromospheric Emission

    CERN Document Server

    Ingleby, Laura; Bergin, Edwin; Herczeg, Gregory; Brown, Alexander; Alexander, Richard; Edwards, Suzan; Espaillat, Catherine; France, Kevin; Gregory, Scott G; Hillenbrand, Lynne; Roueff, Evelyne; Valenti, Jeff; Walter, Frederick; Johns-Krull, Christopher; Brown, Joanna; Linsky, Jeffrey; McClure, Melissa; Ardila, David; Abgrall, Herve; Bethell, Thomas; Hussain, Gaitee; Yang, Hao

    2011-01-01

    Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations of the ~5-9 Myr old stars RECX-1 and RECX-11, obtained with the Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), as well as optical and near infrared spectroscopic observations. The two stars have similar levels of near UV emission, although spectroscopic evidence indicates that RECX-11 is accreting and RECX-1 is not. The line profiles of Halpha and He I 10830 in RECX-11 show both broad and narrow redshifted absorption components that vary with time, revealing the complexity of the accretion flows. We show that accretion indicators commonly used to measure mass accretion rates, e.g. U band excess luminosity or the Ca II triplet line luminosity are unreliable for low accretors, at least in the middle K spectral range. Using RECX-1 as...

  9. 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.

  10. 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

  11. 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...

  12. 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 ...

  13. 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...

  14. 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...

  15. 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.

  16. Patterns of X-ray, Chromospheric, and Radio Emission in Low-mass Stars: Fast and Slow Magnetic Reconnection

    Science.gov (United States)

    Mullan, D. J.

    2010-10-01

    Magnetic reconnection events in the atmospheres of low-mass dwarf stars can be classified as either slow or fast, depending on whether ohmic diffusion or Hall currents dominate in the reconnection process. We suggest that the separation of reconnection into slow and fast categories can help to explain some systematics of low-mass dwarfs as regards their emissions in X-rays, Hα, and radio. On the one hand, in the warmer dwarfs (M7) are inefficient emitters in Hα and X-rays but strong emitters in radio, may be understood in the context that only slow reconnection is permitted to occur in those stars, as a result of high electrical resistivity. However, even though only slow reconnection is permitted in the latter stars, the speed of the outflow jets from reconnection sites can serve as efficient sources of radio emission as a result of the electron cyclotron maser instability.

  17. 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...

  18. 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...

  19. 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.

  20. 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...

  1. 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...

  2. 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

  3. 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.

  4. Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes

    CERN Document Server

    Khomenko, E; Collados, M; Bueno, J Trujillo

    2008-01-01

    We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at 10830 A. We conclude that the efficiency of energy exchange by radiation in the solar photosphere can lead to a significant reduction of the cut-off frequency and may allow for the propagation of the 5 minutes waves vertically into the chromosphere.

  5. 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.

  6. 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.

  7. Spectropolarimetric investigation of the propagation of magnetoacoustic waves and shock formation in sunspot atmospheres

    CERN Document Server

    Centeno, R; Collados, M; Bueno, Javier Trujillo; Centeno, Rebecca; Collados, Manuel

    2006-01-01

    Velocity oscillations in sunspot umbrae have been measured simultaneously in two spectral lines: the photospheric Silicon I 10827 A line and the chromospheric Helium I 10830 A multiplet. From the full Stokes inversion of temporal series of spectropolarimetric observations we retrieved, among other parameters, the line of sight velocity temporal variations at photospheric and chromospheric heights. Chromospheric velocity oscillations show a three minute period with a clear sawtooth shape typical of propagating shock wave fronts. Photospheric velocity oscillations have basically a five minute period, although the power spectrum also shows a secondary peak in the three minute band which has proven to be predecessor for its chromospheric counterpart. The derived phase spectra yield a value of the atmospheric cut-off frequency around 4 mHz and give evidence for the upward propagation of higher frequency oscillation modes. The phase spectrum has been reproduced with a simple model of linear vertical propagation of ...

  8. 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.

  9. 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.

  10. 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.

  11. 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...

  12. 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...

  13. 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.

  14. 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.

  15. New Insights on Late-A and Early-F Star Activity

    Science.gov (United States)

    Freire Ferrero, R.; Catalano, S.; Marilli, E.; Gouttebroze, P.; Talavera, A.; Bruhweiler, F.

    The onset of chromospheric activity in late-A and early-F stars is here discussed. The detection of Ly- emission core in several A and F atars with the IUE satellite, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0m.19 (Marilli et al., 1996). Semiempirical chromospheric models for Altair allowed us (Freire Ferrero et al., 1995) to explain the observed emission profiles taking into account normal H I interstellar (IS) absorption. However, due to the very high rotational velocity, we analysed alternative hypotheses to explain the observed emissions: (1) circumstellar or shell matter; (2) co-rotating expanding optically thin wind. We ruled out these hypotheses because their effects are negligible and as a consequence, this result reinforces the chromospheric origin of the observed Ly- core in Altair. The stars of our sample, having observed Ly- profilies similar to Altair's and similar stellar and IS properties, should reproduce similar chromospheric behaviour. Here we discuss several important questions that are raised by these results.

  16. BIDIRECTIONAL OUTFLOWS AS EVIDENCE OF MAGNETIC RECONNECTION LEADING TO A SOLAR MICROFLARE

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jie; Ding, M. D.; Li, Ying; Yang, Kai; Cheng, Xin; Fang, Cheng [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China); Chen, Feng [Max-Plank-Institut für Sonnensystemforschung, D-37077, Göttingen (Germany); Cao, Wenda, E-mail: dmd@nju.edu.cn [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)

    2016-03-20

    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 ±(70–80) km s{sup −1}, comparable with the local Alfvén 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 Å images. The instability of the flux rope may initiate the flare-related reconnection. These observations provide clear evidence of magnetic reconnection in the chromosphere and show the similar mechanisms of a microflare to those of major flares.

  17. 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.

  18. 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...

  19. 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...

  20. Clasp/SJ Observation of Time Variations of Lyman-Alpha Emissions in a Solar Active Region

    Science.gov (United States)

    Ishikawa, S.; Kubo, M.; Katsukawa, Y.; Kano, R.; Narukage, N.; Ishikawa, R.; Bando, T.; Winebarger, A.; Kobayashi, K.; Trujillo Bueno, J.; Auchere, F.

    2016-01-01

    The Chromospheric Lyman-alpha SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on September 3, 2015 to investigate the solar chromosphere, and the slit-jaw (SJ) optical system took Lya images with the high time cadence of 0.6 s. By the CLASP/SJ observation, many time variations in the solar chromosphere with the time scale of time variations and relation to the coronal structure observed by SDO/AIA. We compared the Ly(alpha) time variations at footpoints of coronal magnetic fields observed by AIA 211 Å (approx.2 MK) and AIA 171 Å (0.6 MK), and non-loop regions. As the result, we found the time variations had more in the footpoint regions. On the other hand, the time variations had no dependency on the temperature of the loop.

  1. A Correlation Between Stellar Activity and the Surface Gravity of Hot Jupiters

    CERN Document Server

    Hartman, Joel D

    2010-01-01

    Recently Knutson et al. (2010) have demonstrated a correlation between the presence of temperature inversions in the atmospheres of hot Jupiters, and the chromospheric activity levels of the host stars. Here we show that there is also a correlation, with greater than 99.5% confidence, between the surface gravity of hot Jupiters and the activity levels of the host stars, such that high surface gravity planets tend be found around high activity stars. We also find a less significant positive correlation between planet mass and chromospheric activity, but no significant correlation is seen between planet radius and chromospheric activity. We consider the possibility that this may be due to an observational bias against detecting lower mass planets around higher activity stars, but conclude that this bias is only likely to affect the detection of planets much smaller than those considered here. Finally, we speculate on physical origins for the correlation, including the possibility that the effect of stellar inso...

  2. 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...

  3. ALMA observations of alpha Centauri: First detection of main-sequence stars at 3mm wavelength

    CERN Document Server

    Liseau, R; Bayo, A; Bertone, E; Black, J H; del Burgo, C; Chavez, M; Danchi, W; De la Luz, V; Eiroa, C; Ertel, S; Fridlund, M C W; Justtanont, K; Krivov, A; Marshall, J P; Mora, A; Montesinos, B; Nyman, L -A; Olofsson, G; Sanz-Forcada, J; Thebault, P; White, G J

    2014-01-01

    The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and those of other stars constitute an active field of research. By studying stellar chromospheres one aims at identifying the relevant physical processes. Defining the permittable extent of the parameter space can also serve as a template for the Sun-as-a-star. Earlier observations with Herschel and APEX have revealed the temperature minimum of alpha Cen, but these were unable to spatially resolve the binary into individual components. With the data reported here, we aim at remedying this shortcoming. Furthermore, these earlier data were limited to the wavelength region between 100 and 870mu. In the present context, we intend to extend the spectral mapping to longer wavelengths, where the contrast between stellar photospheric and chromospheric emission becomes increasingly evident. ALMA is particularly suited to point sources, such as unresolved stars. ALMA provides the means to achieve our obj...

  4. 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...

  5. 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.

  6. 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.

  7. 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...

  8. 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

  9. 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.

  10. Spectro-Polarimetric Properties of Small-Scale Plasma Eruptions Driven by Magnetic Vortex Tubes

    CERN Document Server

    Kitiashvili, Irina N

    2014-01-01

    Highly turbulent nature of convection on the Sun causes strong multi-scale interaction of subsurface layers with the photosphere and chromosphere. According to realistic 3D radiative MHD numerical simulations ubiquitous small-scale vortex tubes are generated by turbulent flows below the visible surface and concentrated in the intergranular lanes. The vortex tubes can capture and amplify magnetic field, penetrate into chromospheric layers and initiate quasi-periodic flow eruptions that generates Alfv\\'enic waves, transport mass and energy into the solar atmosphere. The simulations revealed high-speed flow patterns, and complicated thermodynamic and magnetic structures in the erupting vortex tubes. The spontaneous eruptions are initiated and driven by strong pressure gradients in the near-surface layers, and accelerated by the Lorentz force in the low chromosphere. In this paper, the simulation data are used to further investigate the dynamics of the eruptions, their spectro-polarimetric characteristics for the...

  11. 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 ...

  12. 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.

  13. Sequential Chomospheric Brightening: An Automated Approach to Extracting Physics from Ephemeral Brightening

    CERN Document Server

    Kirk, Michael S; Jackiewicz, Jason; McAteer, R T James; McNamara, Bernie J

    2012-01-01

    We make a comparison between small scale chromospheric brightenings and energy release processes through examining the temporal evolution of sequential chromospheric brightenings (SCBs), derive propagation velocities, and propose a connection of the small-scale features to solar flares. Our automated routine detects and distinguishes three separate types of brightening regularly observed in the chromosphere: plage, flare ribbon, and point brightenings. By studying their distinct dynamics, we separate out the flare-associated bright points commonly known as SCBs and identify a propagating Moreton wave. Superimposing our detections on complementary off-band images, we extract a Doppler velocity measurement beneath the point brightening locations. Using these dynamic measurements, we put forward a connection between point brightenings, the erupting flare, and overarching magnetic loops. A destabilization of the pre-flare loop topology by the erupting flare directly leads to the SCBs observed.

  14. 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.

  15. Small-scale dynamo magnetism as the driver for heating the solar atmosphere.

    Science.gov (United States)

    Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques

    2015-06-11

    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.

  16. 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.

  17. A Quasi-One-Dimensional Model for a Solar Flux Tube

    Institute of Scientific and Technical Information of China (English)

    杨志良; 张洪起; 张枚; 冯学尚

    2002-01-01

    We develop the quasi-one-dimensional flux tube model with magnetohydrodynamical equations. In order to know whether the magnetic field can maintain their similar structurefrom photosphere to chromosphere, we suppose that the flux tube is thin in radius relative to the length, and that the quantities in the cross section are averaged.The radii of the flux tube and the magnetic field are numerically simulated. One of the important results shows that the flux tube does not expand as quickly as the existing model when it is out of the photosphere with high velocity. This is consistent with observations of the magnetic field in the photosphere and chromosphere.

  18. 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.

  19. Kink Waves in an Active Region Dynamic Fibril

    Science.gov (United States)

    Pietarila, A.; Aznar Cuadrado, R.; Hirzberger, J.; Solanki, S. K.

    2011-10-01

    We present high spatial and temporal resolution Ca II 8542 Å 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.

  20. 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)

  1. Mode transformation and frequency change with height in 3D numerical simulations of magneto-acoustic wave propagation in sunspots

    CERN Document Server

    Felipe, T; Collados, M

    2010-01-01

    Three-dimensional numerical simulations of magnetoacoustic wave propagation are performed in a sunspot atmosphere with a computational domain covering from the photosphere to the chromosphere. The wave source, with properties resembling the solar spectrum, is located at different distances from the axis of the sunspot for each simulation. These results are compared with the theory of mode transformation and also with observational features. Simulations show that the dominant oscillation frequency in the chromosphere decreases with the radial distance from the sunspot axis. The energy flux of the different wave modes involved, including de Alfv\\'en mode, is evaluated and discussed.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. 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

  8. Comportamiento de la cromósfera solar en la línea H-alfa durante el período enero/05-agosto/06

    Science.gov (United States)

    Missio, H.; Davoli, D.; Aquilano, R.

    Using the instrument at Observatorio Astronómico Municipal de Rosario (OAMR), we analyze the solar chromospheric activity during the period January/05-August/06. The instrument is a Carl Zeiss refractor telescope of 150 mm aperture and 2250 mm of focal distance with a monochromatic filter in the H-alpha line. We take as proxy for the solar activity the area covered by chromospheric ``plages''. The measurements are done using photographic registers. We describe our technique and the results obtained. We observe a decrease of solar activity that corresponds to the end of cycle 23. FULL TEXT IN SPANISH

  9. Comportamiento de la cromosfera solar en la línea Hα durante el período enero-diciembre de 1998

    Science.gov (United States)

    Davoli, D.; Missio, H.; Olivero, J.; Acero, S.

    Using the instrumental of the O.A.M.R., consistent in a refractor elbowed telescope Carl Zeiss, of 150 mm. of aperture and focal distance of 2250 mm., provided with a monochromatic filter to the Hα line. We have followed the solar chromospherical activity during the period January-December 1998, taking as indicator the area occupied for the chromospherical flares. The measurements were realized over photograpics registers. We describe the technique used and the results obtained. We can see a noted increase of the solar activity corresponding with the course of the cycle 23.

  10. Comportamiento de la cromósfera solar en la línea Hα durante el período enero de 1993 - diciembre de 1996

    Science.gov (United States)

    Acero, S.; Davoli, D.; Missio, H.

    Using the instrumental of the O.A.M.R., consistent in a refractor elbowed telescope mark Carl Zeiss, of 150 mm. of aperture and 2250 mm. of focal distance, provided of a monochromatic filter to the line Hα we surveyed the solar chromospherical activity during the period January 1993 - December 1996, taking as indicator the area occupied for the chromospherical flares. The measurements were realized over photograpic registers. We describe the technique used and the results obtained. We can see a diminution of the solar activity corresponding with the end of the cycle 22.

  11. 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.

  12. 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

  13. 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.)

  14. 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.

  15. Solar Atmospheric Dynamics

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This review focuses on acoustic oscillations n the solar at- mosphere.There s much debate on photospheric p stons to chromo- spher c oscillations,on the penetration height of acoustic shocks,and on the r contr but on to chromospheric heat ng,w th new nput coming from space observations and from nume

  16. 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 ...

  17. 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.

  18. 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.

  19. 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.)

  20. 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

  1. 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, $\

  2. 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.

  3. The lower solar atmosphere

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    This "rapporteur" report discusses the solar photosphere and low chromosphere in the context of chemical composition studies. The highly dynamical nature of the photosphere does not seem to jeopardize precise determination of solar abundances in classical fashion. It is still an open question how th

  4. 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.

  5. 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...

  6. 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...

  7. TEMPORAL EVOLUTION OF MULTIPLE EVAPORATING RIBBON SOURCES IN A SOLAR FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Graham, D. R.; Cauzzi, G., E-mail: dgraham@arcetri.astro.it [INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)

    2015-07-10

    We present new results from the Interface Region Imaging Spectrograph (IRIS) 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 s 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 upflows of up to ∼300 km s{sup −1} and chromospheric downflows up to 40 km s{sup −1}. 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 considered a prototypical, “elementary” flare kernel.

  8. Basic Properties of Plasma-Neutral Coupling in the Solar Atmosphere

    Science.gov (United States)

    Goodman, Michael

    2015-04-01

    Plasma-neutral coupling (PNC) in the solar atmosphere concerns the effects of collisions between charged and neutral species’. It is most important in the chromosphere, which is the weakly ionized, strongly magnetized region between the weakly ionized, weakly magnetized photosphere and the strongly ionized, strongly magnetized corona. The charged species’ are mainly electrons, protons, and singly charged heavy ions. The neutral species’ are mainly hydrogen and helium. The resistivity due to PNC can be several orders of magnitude larger than the Spitzer resistivity. This enhanced resistivity is confined to the chromosphere, and provides a highly efficient dissipation mechanism unique to the chromosphere. PNC may play an important role in many processes such as heating and acceleration of plasma; wave generation, propagation, and dissipation; magnetic reconnection; maintaining the near force-free state of the corona; and limiting mass flux into the corona. It might play a major role in chromospheric heating, and be responsible for the existence of the chromosphere as a relatively thin layer of plasma that emits a net radiative flux 10-100 times greater than that of the overlying corona. The required heating rate might be generated by Pedersen current dissipation triggered by the rapid increase of magnetization with height in the lower chromosphere, where most of the net radiative flux is emitted. Relatively cool regions of the chromosphere might be regions of minimal Pedersen current dissipation due to smaller magnetic field strength or perpendicular current density. This talk will discuss PNC from an MHD point of view, and focus on the basic parameters that determine its effectiveness. These parameters are ionization fraction, magnetization, and the electric field that drives current perpendicular to the magnetic field. By influencing this current and the electric field that drives it, PNC directly influences the rate at which energy is exchanged between the

  9. Simulating the Formation and Evolution of Solar Prominences in Coronal Cavities

    Science.gov (United States)

    Xia, C.; Keppens, R.

    2015-12-01

    The physical mechanism responsible for the formation and the mass cycling of solar prominences has been uncertain for decades, because of the difficulty of knowing the three-dimensional (3D) magnetic field hosting prominences and the mass supply from chromosphere to prominences. Here we report comprehensive 3D simulations which demonstrate that the chromospheric evaporation and the coronal condensation in a magnetic flux rope lead to the formation of a quiescent prominence with complex internal fluid dynamics. First, we simulate the formation of a stable magnetic flux rope in the corona starting from a sheared magnetic bipolar arcade driven by shearing and converging flows at the bottom, using isothermal magnetohydrodynamics (MHD) modeling including gravity. Second, we fill the magnetic flux rope with hydrostatic plasma from chromosphere to corona and simulate a quiet sun in an equilibrium using full thermodynamic MHD with anisotropic thermal conduction, optically thin radiative losses, and parameterized heating. Then, we add extra strong heating localized in two circular regions covering chromospheric foot points of the flux rope. As the plasma is evaporated into corona, the lower part of the flux rope evolve into thermally unstable situation due to dominative radiative losses, where multiple blobs and threads of condensations form and move continuously mainly along local magnetic field. Some of the condensations fall down to chromosphere without support of magnetic dips near the foot region of the flux rope. Others linger in magnetic dips and descend slowly. Synthetic images of Solar Dynamics Observatory views with the Atmospheric Imaging Assembly shows many properties of quiescent prominences from real observations, such as, dynamics dark threads under elliptical coronal cavity.

  10. 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

  11. The cause of spatial structure in solar He i 1083 nm multiplet images

    Science.gov (United States)

    Leenaarts, Jorrit; Golding, Thomas; Carlsson, Mats; Libbrecht, Tine; Joshi, Jayant

    2016-10-01

    Context. The He i 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, but the influence of the complex three-dimensional structure of the chromosphere and corona has however never been investigated. This structure must play an essential role because images taken in He i 1083 nm show structures with widths down to 100 km. Aims: We aim to understand the effect of the three-dimensional temperature and density structure in the solar atmosphere on the formation of the He i 1083 nm line. Methods: We solved the non-LTE radiative transfer problem assuming statistical equilibrium for a simple nine-level helium atom that nevertheless captures all essential physics. As a model atmosphere we used a snapshot from a 3D radiation-MHD simulation computed with the Bifrost code. Ionising radiation from the corona was self-consistently taken into account. Results: The emergent intensity in the He i 1083 nm is set by the source function and the opacity in the upper chromosphere. The former is dominated by scattering of photospheric radiation and does not vary much with spatial location. The latter is determined by the photonionisation rate in the He i ground state continuum, as well as the electron density in the chromosphere. The spatial variation of the flux of ionising radiation is caused by the spatially-structured emissivity of the ionising photons from material at T ≈ 100 kK in the transition region. The hotter coronal material produces more ionising photons, but the resulting radiation field is smooth and does not lead to small-scale variation of the UV flux. The corrugation of the transition region further increases the spatial variation of the amount of UV radiation in the chromosphere. Finally we find that variations in the chromospheric electron density also cause strong variation in He i 1083 nm opacity. We compare our

  12. 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.

  13. 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...

  14. 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.

  15. A regularization method for extrapolation of solar potential magnetic fields

    Science.gov (United States)

    Gary, G. A.; Musielak, Z. E.

    1992-01-01

    The mathematical basis of a Tikhonov regularization method for extrapolating the chromospheric-coronal magnetic field using photospheric vector magnetograms is discussed. The basic techniques show that the Cauchy initial value problem can be formulated for potential magnetic fields. The potential field analysis considers a set of linear, elliptic partial differential equations. It is found that, by introducing an appropriate smoothing of the initial data of the Cauchy potential problem, an approximate Fourier integral solution is found, and an upper bound to the error in the solution is derived. This specific regularization technique, which is a function of magnetograph measurement sensitivities, provides a method to extrapolate the potential magnetic field above an active region into the chromosphere and low corona.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Solar Polarimetry - from Turbulent Magnetic Fields to Sunspots

    Science.gov (United States)

    Kleint, Lucia

    2016-07-01

    Polarimetric measurements are essential to investigate the solar magnetic field. Scattering polarization and the Hanle effect allow us to probe the turbulent magnetic field and the still open questions of its strength and variability. Directed magnetic fields can be detected via the Zeeman effect. To derive their orientation and strength, so-called inversion codes are used, which iteratively modify a model atmosphere and calculate the resulting polarization profiles that are then compared to the observations. While photospheric polarimetry is well-established, chromospheric polarimetry is still in its infancy, especially because it requires a treatment in non-LTE, making it a complex non-linear problem. But some of the most important open questions concern the strength and geometry of the chromospheric magnetic field. In this talk, I will review different polarimetric analysis techniques and recent advances in magnetic field measurements going from the small scales of turbulent magnetic fields to changes of magnetic fields in an active region during flares.

  1. 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.

  2. 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.

  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. 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...

  5. 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.

  6. 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.

  7. Non-equilibrium calcium ionisation in the solar atmosphere

    CERN Document Server

    Wedemeyer-Böhm, Sven

    2011-01-01

    Our aim is to determine the dominant processes and timescales for the ionisation equilibrium of calcium under solar chromospheric conditions. The study is based on numerical simulations with the RADYN code, which includes hydrodynamics, radiative transfer, and a detailed non-equilibrium treatment of hydrogen, calcium, and helium. The simulations are characterised by upwards propagating shock waves, which cause strong temperature fluctuations and variations of the ionisation degree of calcium. The passage of a hot shock front leads to a strong net ionisation of Ca II, rapidly followed by net recombination. The relaxation timescale of the Ca ionisation state is found to be of the order of a few seconds at the top of the photosphere and 10 to 30 s in the upper chromosphere. Generally, the timescales are significantly reduced in the wakes of hot shock fronts. The timescales can be reliably determined from a simple analysis of the eigenvalues of the transition rate matrix. The timescales are dominated by the radia...

  8. 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

    2016-03-24

    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.

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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.

  14. 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.

  15. 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...

  16. 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.)

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. Suprathermal electron distributions in the solar transition region

    CERN Document Server

    Vocks, C; Mann, G

    2016-01-01

    Suprathermal tails are a common feature of solar wind electron velocity distributions, and are expected in the solar corona. From the corona, suprathermal electrons can propagate through the steep temperature gradient of the transition region towards the chromosphere, and lead to non-Maxwellian electron velocity distribution functions (VDFs) with pronounced suprathermal tails. We calculate the evolution of a coronal electron distribution through the transition region in order to quantify the suprathermal electron population there. A kinetic model for electrons is used which is based on solving the Boltzmann-Vlasov equation for electrons including Coulomb collisions with both ions and electrons. Initial and chromospheric boundary conditions are Maxwellian VDFs with densities and temperatures based on a background fluid model. The coronal boundary condition has been adopted from earlier studies of suprathermal electron formation in coronal loops. The model results show the presence of strong suprathermal tails ...

  2. 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.

  3. 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...

  4. Analysis of time dependent phenomena observed with the LPSP OSO-8 instrument

    Science.gov (United States)

    Leibacher, J. W.

    1979-01-01

    The dynamics of the solar photosphere and chromosphere are studied. Observations obtained by the Laboratorie de Physique Stellaire et Planetaire's (LPSP) ultraviolet spectrometer onboard the OSO-8 spacecraft are analyzed, and dynamic models of the chromosphere and the emitted resonance line spectrum are calculated. Some of the unpublished data analysis and theoretical modeling which are being prepared for publication are discussed. A discussion of the state of the theory of velocity fields in the solar atmosphere is also presented. An invited review presented at the OSO-8 Workshop on the topic of oscillatory motions in the quiet sun is included. The results of the OSO-8 data analysis prepared in close collaboration with LPSP scientists are presented. Material for two articles is also presented.

  5. 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...

  6. Observations and modelling of Helium lines in solar flares

    CERN Document Server

    Simões, Paulo J A; Labrosse, Nicolas; Kerr, Graham S

    2015-01-01

    We explore the response of the He II 304 {\\AA} and He I 584 {\\AA} line intensities to electron beam heating in solar flares using radiative hydrodynamic simulations. Comparing different electron beams parameters, we found that the intensities of both He lines are very sensitive to the energy flux deposited in the chromosphere, or more specifically to the heating rate, with He II 304 {\\AA} being more sensitive to the heating than He I 584 {\\AA}. Therefore, the He line ratio increases for larger heating rates in the chromosphere. A similar trend is found in observations, using SDO/EVE He irradiance ratios and estimates of the electron beam energy rate obtained from hard X-ray data. From the simulations, we also found that spectral index of the electrons can affect the He ratio but a similar effect was not found in the observations.

  7. 3D simulations of Magnetohydrodynamic (MHD) waves in the magnetized solar atmosphere

    CERN Document Server

    Vigeesh, G; Hasan, S S; Erdelyi, R

    2011-01-01

    We present results of three-dimensional numerical simulation of magnetohydrodynamic (MHD) wave propagation in a magnetic flux tube. Our study aims at understanding the properties of various MHD wave modes generated by different nature of photospheric motions. We consider two scenarios observed in the solar photosphere, namely, granular buffeting and vortex-like motion, among the simplest mechanism for generation of waves within strong magnetic flux concentration. We show that, granular buffeting is likely to produce strong slow (acoustic) waves as compared to vortical motions, which mainly are a source of stronger fast waves. Correspondingly, the acoustic flux transported by these waves vary. We show that the waves generated by granular buffeting are likely to produce stronger emission in the chromospheric network. We argue that different mechanisms of wave generation are active during the evolution of a magnetic element in the intergranular lane resulting in temporally varying emission at chromospheric heigh...

  8. 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...

  9. Synthetic activity indicators for M-type dwarf stars

    CERN Document Server

    Wedemeyer, Sven

    2015-01-01

    Here, we present a set of time-dependent 3D RMHD simulations of a M-dwarf star representative of AD Leo, which extend from the upper convection zone into the chromosphere. The 3D model atmospheres are characterized by a very dynamic and intermittent structure on small spatial and temporal scales and a wealth of physical processes, which by nature cannot be described by means of 1D static model atmospheres. Artificial observations of these models imply that a combination of complementary diagnostics such as Ca II lines and the continuum intensity from UV to millimeter wavelengths, probe various properties of the dynamics, thermal and magnetic structure of the photosphere and the chromosphere and thus provide measures of stellar activity, which can be compared to observations. The complicated magnetic field structure and its imprint in synthetic diagnostics may have important implications for the understanding and characterization of stellar activity and with it possibly for the evaluation of planetary habitabi...

  10. 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...

  11. 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...

  12. Comportamiento de la cromósfera solar en la línea H-alpha durante el ciclo 23

    Science.gov (United States)

    Davoli, D.; Aquilano, R.; Missio, H.

    Using the instrumental of the Observatorio Astronómico Municipal de Rosario (OAMR), we analyze the solar chromospheric activity during an approximate period of 11 years. The instrument is a Carl Zeiss refractor telescope of 150 mm aperture and 2250 mm of focal distance with monochromatic filter in the H-alpha line. We take as proxy for the solar activity the area covered by chromospheric plages. Simultaneously, we determine the relative wolf number from observations of the solar photosphere. We describe our technique and the results obtained. We observe 2 maxima of solar activity in the years 2000 and 2001 respectively, and a later decrease of this activity with low average values starting around 2006 that corresponds to the end of cycle 23. FULL TEXT IN SPANISH

  13. LEMUR: Large European Module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission

    CERN Document Server

    Teriaca, Luca; Auchère, Frédéric; Brown, Charles M; Buchlin, Eric; Cauzzi, Gianna; Culhane, J Len; Curdt, Werner; Davila, Joseph M; Del Zanna, Giulio; Doschek, George A; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T; Green, Lucie; Harra, Louise K; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Rob; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P; Wiegelmann, Thomas; Winter, Berend; Young, Peter

    2011-01-01

    Understanding the solar outer atmosphere requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1" and 0.3"), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research...

  14. 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...

  15. 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.

  16. 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...

  17. 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. ...

  18. Dislocations in magnetohydrodynamic waves in a stellar atmosphere.

    Science.gov (United States)

    López Ariste, A; Collados, M; Khomenko, E

    2013-08-23

    We describe the presence of wave front dislocations in magnetohydrodynamic waves in stratified stellar atmospheres. Scalar dislocations such as edges and vortices can appear in Alfvén waves, as well as in general magnetoacoustic waves. We detect those dislocations in observations of magnetohydrodynamic waves in sunspots in the solar chromosphere. Through the measured charge of all the dislocations observed, we can give for the first time estimates of the modal contribution in the waves propagating along magnetic fields in solar sunspots.

  19. 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.

  20. 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)

  1. 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).

  2. 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.

  3. Dislocations in magnetohydrodynamic waves in a stellar atmosphere

    CERN Document Server

    Ariste, A López; Khomenko, E

    2013-01-01

    We describe the presence of wavefront dislocations in magnetohydrodynamic waves in stratified stellar atmospheres. Scalar dislocations such as edges and vortices can appear in Alfv\\'en waves, as well as in general magneto-acoustic waves. We detect those dislocations in observations of magnetohydrodynamic waves in sunspots in the solar chromosphere. Through the measured charge of all the dislocations observed, we can give for the first time estimates of the modal contribution in the waves propagating along magnetic fields in solar sunspots.

  4. 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...

  5. 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).

  6. 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.

  7. 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...

  8. 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...

  9. Plage

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    A region of intensified emission in the solar chromosphere. Plages are revealed in monochromatic images obtained in the light of various emission lines, for example, the hydrogen-α line and the `H' and `K' lines of ionized calcium. The name derives from the French word for `beach', an allusion to the fact that these features stand out like bright sandy beaches against the fainter background of th...

  10. 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.

  11. 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...

  12. 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.

  13. 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.

  14. 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...

  15. 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 ...

  16. 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...

  17. 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.

  18. 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.

  19. 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...

  20. 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...

  1. 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...

  2. Photometric Observations of Two Cool Stars: HD 17025 and HD 38392

    Science.gov (United States)

    Stȩpień, K.

    1995-07-01

    UBV(RI)c observations of a G6/G8IV star HD17025 suggest a variation period of about 9 days. The light curve has a marginal amplitude of about 0.015 of a magnitude but is poorly defined and needs an independent confirmation. No prominent chromospheric emission is visible in a spectrum of this star. The other observed star, a K2 dwarf HD38392, did not show measurable light variations over a two weeks period of observations.

  3. 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.

  4. 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.

  5. 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...

  6. 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...

  7. 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.

  8. 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...

  9. 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...

  10. 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...

  11. The connection between stellar activity cycles and magnetic field topology

    Science.gov (United States)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C. P.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Waite, I. A.

    2016-08-01

    Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained form ZDI and activity cycles.

  12. A semi-empirical model for the M star GJ832 using modeling tools developed for computing semi-empirical solar models

    Science.gov (United States)

    Linsky, Jeffrey; Fontenla, Juan; France, Kevin

    2016-05-01

    We present a semi-empirical model of the photosphere, chromosphere, transition region, and corona for the M2 dwarf star GJ832, which hosts two exoplanets. The atmospheric model uses a modification of the Solar Radiation Physical Modeling tools developed by Fontenla and collaborators. These computer codes model non-LTE spectral line formation for 52 atoms and ions and include a large number of lines from 20 abundant diatomic molecules that are present in the much cooler photosphere and chromosphere of this star. We constructed the temperature distribution to fit Hubble Space Telescope observations of chromospheric lines (e.g., MgII), transition region lines (CII, CIV, SiIV, and NV), and the UV continuum. Temperatures in the coronal portion of the model are consistent with ROSAT and XMM-Newton X-ray observations and the FeXII 124.2 nm line. The excellent fit of the model to the data demonstrates that the highly developed model atmosphere code developed to explain regions of the solar atmosphere with different activity levels has wide applicability to stars, including this M star with an effective temperature 2200 K cooler than the Sun. We describe similarities and differences between the M star model and models of the quiet and active Sun.

  13. 12 Years of Stellar Activity Observations in Argentina

    CERN Document Server

    Mauas, Pablo J D; Diaz, R; Vieytes, M; Petrucci, R; Jofre, E; Abrevaya, X; Luoni, M L; Valenzuela, P

    2012-01-01

    We present an observational program we started in 1999, to systematically obtain mid-resolution spectra of late-type stars, to study in particular chromospheric activity. In particular, we found cyclic activity in four dM stars, including Prox-Cen. We directly derived the conversion factor that translates the known S index to flux in the Ca II cores, and extend its calibration to a wider spectral range. We investigated the relation between the activity measurements in the calcium and hydrogen lines, and found that the usual correlation observed is the product of the dependence of each flux on stellar color, and it is not always preserved when simultaneous observations of a particular star are considered. We also used our observations to model the chromospheres of stars of different spectral types and activity levels, and found that the integrated chromospheric radiative losses, normalized to the surface luminosity, show a unique trend for G and K dwarfs when plotted against the S index.

  14. Spectropolarimetric capabilities of Ca II 8542 A line

    CERN Document Server

    Noda, C Quintero; Rodríguez, J de la Cruz; Katsukawa, Y; Ichimoto, K; Anan, T; Suematsu, Y

    2016-01-01

    The next generation of space and ground-based solar missions aim to study the magnetic properties of the solar chromosphere using the infrared Ca II lines and the He I 10830 {\\AA} line. The former seem to be the best candidates to study the stratification of magnetic fields in the solar chromosphere and their relation to the other thermodynamical properties underlying the chromospheric plasma. The purpose of this work is to provide a detailed analysis of the diagnostic capabilities of the Ca II 8542 {\\AA} line, anticipating forthcoming observational facilities. We study the sensitivity of the Ca II 8542 {\\AA} line to perturbations applied to the physical parameters of reference semi-empirical 1D model atmospheres using response functions and we make use of 3D MHD simulations to examine the expected polarization signals for moderate magnetic field strengths. Our results indicate that the Ca II 8542 {\\AA} line is mostly sensitive to the layers enclosed between $\\log$ $\\tau=[0,-5.5]$, under the physical conditio...

  15. Strong Blue Asymmetry in H α Line as a Preflare Activity

    Science.gov (United States)

    Cho, Kyuhyoun; Lee, Jeongwoo; Chae, Jongchul; Wang, Haimin; Ahn, Kwangsu; Yang, Heesu; Lim, Eun-kyung; Maurya, Ram Ajor

    2016-08-01

    Chromospheric activities before solar flares provide important clues to the mechanisms that initiate solar flares, but are as yet poorly understood. We report a significant and rapid H α line broadening before the solar flare SOL2011-09-29T18:08 that was detected using the unprecedented high-resolution H α imaging spectroscopy with the Fast Imaging Solar Spectrograph (FISS) installed on the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The strong H α broadening extends as a blue excursion up to -4.5 Å and as a red excursion up to 2.0 Å, which implies a mixture of velocities in the range of -130 km s^{-1} to 38 km s-1 derived by applying the cloud model, comparable to the highest chromospheric motions reported before. The H α blueshifted broadening lasts for about six minutes and is temporally and spatially correlated with the start of a rising filament, which is later associated with the main phase of the flare as detected by the Atmosphere Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The potential importance of this H α blueshifted broadening as a preflare chromospheric activity is briefly discussed within the context of the two-step eruption model.

  16. Driving Solar Spicules and Jets with Magnetohydrodynamic Turbulence: Testing a Persistent Idea

    Science.gov (United States)

    Cranmer, Steven R.; Woolsey, Lauren N.

    2015-10-01

    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 Alfvén waves. These forces involve the conversion of transverse Alfvén 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 (TR). 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 turbulence. The resulting mode-converted compressive waves are strongly variable in time, with a higher TR occurring when the amplitudes are large and a lower TR when the amplitudes are small. In this picture, the TR bobs up and down by several Mm on timescales less than a minute. These motions produce narrow, intermittent extensions of the chromosphere that have similar properties as the observed jets and Type II spicules.

  17. Pederson Current Dissipation In Emerging Active Regions

    Science.gov (United States)

    Leake, James E.; Linton, M. G.

    2011-05-01

    Pederson current dissipation in emerging active regions. Certain regions of the solar atmosphere, such as the photosphere and chromosphere, as well as prominences, contain a significant amount of neutral atoms, and a complete description of the plasma requires including the effects of partial ionization. In the chromosphere the dissipation of Pederson currents is important for the evolution of emerging magnetic fields. Due to the relatively high number density in the chromosphere, the ion-neutral collision time-scale is much smaller than timescales associated with flux emergence. Hence we use a single-fluid approach to model the partially ionized plasma. Looking at both the emergence of large-scale sub-surface structures, and the emergence and reconnection of undulatory fields, we investigate the effect of Pederson current dissipation on the state of the emerging field, on magnetic reconnection and on dissipative heating of the atmosphere. Specifically we examine the effect of motions across fieldlines in the partially ionized regions, and how this can increase the free energy supplied to the corona by flux emergence. We also look at reconnection associated with flux emergence in the partially ionized atmosphere, and how this can account for observed small-scale brightenings (Ellerman Bombs).

  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. The Coronal Solar Magnetism Observatory

    Science.gov (United States)

    Tomczyk, S.; Landi, E.; Zhang, J.; Lin, H.; DeLuca, E. E.

    2015-12-01

    Measurements of coronal and chromospheric magnetic fields are arguably the most important observables required for advances in our understanding of the processes responsible for coronal heating, coronal dynamics and the generation of space weather that affects communications, GPS systems, space flight, and power transmission. The Coronal Solar Magnetism Observatory (COSMO) is a proposed ground-based suite of instruments designed for routine study of coronal and chromospheric magnetic fields and their environment, and to understand the formation of coronal mass ejections (CME) and their relation to other forms of solar activity. This new facility will be operated by the High Altitude Observatory of the National Center for Atmospheric Research (HAO/NCAR) with partners at the University of Michigan, the University of Hawaii and George Mason University in support of the solar and heliospheric community. It will replace the current NCAR Mauna Loa Solar Observatory (http://mlso.hao.ucar.edu). COSMO will enhance the value of existing and new observatories on the ground and in space by providing unique and crucial observations of the global coronal and chromospheric magnetic field and its evolution. The design and current status of the COSMO will be reviewed.

  20. Strong Blue Asymmetry in Hα Line as a Preflare Activity

    Science.gov (United States)

    Cho, Kyuhyoun; Lee, Jeongwoo; Chae, Jongchul; Wang, Haimin; Ahn, Kwangsu; Yang, Heesu; Lim, Eun-kyung; Maurya, Ram Ajor

    2016-10-01

    Chromospheric activities before solar flares provide important clues to the mechanisms that initiate solar flares, but are as yet poorly understood. We report a significant and rapid Hα line broadening before the solar flare SOL2011-09-29T18:08 that was detected using the unprecedented high-resolution Hα imaging spectroscopy with the Fast Imaging Solar Spectrograph (FISS) installed on the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The strong Hα broadening extends as a blue excursion up to -4.5 Å and as a red excursion up to 2.0 Å, which implies a mixture of velocities in the range of -130 km s^{-1} to 38 km s-1 derived by applying the cloud model, comparable to the highest chromospheric motions reported before. The Hα blueshifted broadening lasts for about six minutes and is temporally and spatially correlated with the start of a rising filament, which is later associated with the main phase of the flare as detected by the Atmosphere Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The potential importance of this Hα blueshifted broadening as a preflare chromospheric activity is briefly discussed within the context of the two-step eruption model.