The temperature structure and pressure balance of magnetic loops in active regions

Solar Physics ◽  
1975 ◽  
Vol 43 (2) ◽  
pp. 327-336 ◽  
Author(s):  
P. Foukal
Keyword(s):  
Active Regions ◽  
Temperature Structure ◽  
Pressure Balance

scholarly journals Interpretation of the X-Ray Spectra of Solar Active Regions

1975 ◽  
Vol 68 ◽  
pp. 73-100 ◽  
Author(s):  
Arthur B. C. Walker
Keyword(s):  
Transition Region ◽  
Rate Constant ◽  
Active Regions ◽  
Temperature Structure ◽  
Spectroscopic Techniques ◽  
Density Structure ◽  
Coronal Temperature ◽  
X Ray ◽  
Euv Spectrum

This paper presents a review of recent analytical studies of the coronal X-ray spectrum below 25 Å. The techniques used to compute the theoretical coronal spectrum, and the currently available atomic rate constant data are reviewed first. Spectroscopic techniques which have been proposed for the determination of coronal temperature and density structure, and the results derived from their application to coronal spectra are also reviewed.A number of coronal models based on X-ray observations have been developed recently, and the coronal temperature structure and composition predicted by these models is discussed, and compared with models of the corona and transition region derived from studies of the solar EUV spectrum.

scholarly journals High-temperature solar flare plasma behaviour from crystal spectrometer observations

2015 ◽  
Vol 11 (S320) ◽  
pp. 80-85
Author(s):  
Barbara Sylwester ◽  
Janusz Sylwester ◽  
Kenneth J.H. Phillips ◽  
Anna Kepa ◽  
Tomasz Mrozek
Keyword(s):  
Emission Measure ◽  
Active Regions ◽  
Temperature Structure ◽  
Crystal Spectrometer ◽  
Evolutionary Patterns ◽  
Bent Crystal ◽  
Long Duration ◽  
Class B ◽  
Time Changes ◽  
Spectral Intensities

AbstractWe present results of analysis of the spectra collected with Polish instrument RESIK flown on CORONAS-F satellite. RESIK was the bent crystal spectrometer, measuring spectra in the spectral range 3.3 - 6.1 Å with a high cadence during flares. The emission lines as well as the continuum observed by RESIK are formed in hotter (T > 3 MK) plasmas of active regions and flares. RESIK observed various types of flares: from X-ray class B and C up to strongest flares of X-class, for both, short and long duration events. The analysis of absolute and relative spectral intensities of the lines and continuum observed for 33 events allowed for determining the plasma elemental composition with subsequent detailed study of time changes of the temperature structure of the sources described in terms of the differential emission measure (DEM). As an example we present the typical DEM evolutionary patterns for the C1.9 flare (SOL2002-12-26T08:35) and discuss its thermodynamics.

Temperature structure of active regions deduced from the helium-like sulphur lines

Solar Physics ◽  
1995 ◽  
Vol 157 (1-2) ◽  
pp. 169-184 ◽  
Author(s):  
Tetsuya Watanabe ◽  
Hirohisa Haka ◽  
Toshifumi Shimizu ◽  
Eijiro Hiei ◽  
Robert D. Bentley ◽  
...  
Keyword(s):  
Active Regions ◽  
Temperature Structure

scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 623 ◽  
pp. A136 ◽  
Author(s):  
D. Hintz ◽  
B. Fuhrmeister ◽  
S. Czesla ◽  
J. H. M. M. Schmitt ◽  
E. N. Johnson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Active Regions ◽  
Variable Stars ◽  
Temperature Structure ◽  
M Dwarfs ◽  
Linear Combinations ◽  
One Dimensional ◽  
Best Fit ◽  
Calar Alto ◽  
Infrared Triplet

Chromospheric modeling of observed differences in stellar activity lines is imperative to fully understand the upper atmospheres of late-type stars. We present one-dimensional parametrized chromosphere models computed with the atmosphere code PHOENIX using an underlying photosphere of 3500 K. The aim of this work is to model chromospheric lines of a sample of 50 M2–3 dwarfs observed in the framework of the CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, exoplanet survey. The spectral comparison between observed data and models is performed in the chromospheric lines of Na I D2, Hα, and the bluest Ca II infrared triplet line to obtain best-fit models for each star in the sample. We find that for inactive stars a single model with a VAL C-like temperature structure is sufficient to describe simultaneously all three lines adequately. Active stars are rather modeled by a combination of an inactive and an active model, also giving the filling factors of inactive and active regions. Moreover, the fitting of linear combinations on variable stars yields relationships between filling factors and activity states, indicating that more active phases are coupled to a larger portion of active regions on the surface of the star.

Temperature Structure of Solar Active Regions

1996 ◽  
Vol 459 ◽  
pp. 342 ◽  
Author(s):  
Tsuyoshi Yoshida ◽  
Saku Tsuneta
Keyword(s):  
Active Regions ◽  
Temperature Structure ◽  
Solar Active Regions

scholarly journals A Dynamic Dextral-Sinistral Model for the Structure and Evolution of Prominence Magnetic Fields

1998 ◽  
Vol 167 ◽  
pp. 453-462
Author(s):  
E.R. Priest
Keyword(s):  
Large Scale ◽  
Active Regions ◽  
Pressure Balance ◽  
Natural Rate ◽  
Low Latitude ◽  
Flux Tubes ◽  
Subsurface Flows ◽  
Cool Plasma ◽  
Polarity Inversion Line ◽  
Heating Up

AbstractWe propose the following coherent model for prominences.(i)They are composed of many fine threads whose mass we suggest has two kinds of origin. Some of the mass may be lifted from the upper photosphere in response to cancellation of magnetic flux in small flux tubes. If this rate of mass supply is slow then the mass needs to be supported, but if the mass supply rate is as large as the natural rate of draining then no support is necessary. However, much of the mass may not need to be supplied or supported at all, if it comprises dynamic threads of cool plasma that are in pressure balance with their hot surroundings and are continually forming from the corona and heating up again in response to a localised heating mechanism.(ii)The overall structure is of a large-scale flux tube along the polarity inversion line with an overlying arcade that links the network on either side of the filament channel. The structure of the channel and of barbs is explained by the distribution of flux sources along the channels, with majority polarity producing plagettes and minority polarity the barbs.(iii)The chirality of polar-crown prominences is suggested to be caused by a combination of subsurface flows, flux emergence and reconnection. By contrast, two generic types of low-latitude filament, namely those associated with unipolar flux tongues and with the emergence of new active regions near to remnant regions, are a natural consequence of nonuniform flux distribution and converging flux.

Synoptic Charts of the Solar Eclipses of 1990 and 1991

1994 ◽  
Vol 144 ◽  
pp. 517-521
Author(s):  
Z. Mouradian ◽  
G. Buchholtz ◽  
G. Zlicaric
Keyword(s):  
Solar Limb ◽  
Active Regions ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractThe synoptic charts of solar rotations 1831 and 1844 have been drawn up, corresponding to the eclipses of 22 July 1990 and 11 July 1991. These charts contain the active regions and the filaments, and show the position of the solar limb, at the time of the eclipse. They are for use in studying the coronal structures observed during these eclipses. The variation of these structures is given in the table. The last section of the article contains a formula for identifying the structures out of the limb.

Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

1994 ◽  
Vol 144 ◽  
pp. 431-434
Author(s):  
M. Minarovjech ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
Time Resolution ◽  
Active Regions ◽  
High Time ◽  
High Time Resolution ◽  
List Type ◽  
Type Number ◽  
Coronal Line ◽  
Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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