Including the Transition Region in Models of the Large‐Scale Solar Corona

2001 ◽  
Vol 546 (1) ◽  
pp. 542-551 ◽  
Author(s):  
Roberto Lionello ◽  
Jon A. Linker ◽  
Zoran Mikić
Keyword(s):  
Solar Corona ◽  
Transition Region ◽  
Large Scale

scholarly journals Propagation of an MHD Shock in the Vicinity of a Magnetic Neutral Sheet

1980 ◽  
Vol 91 ◽  
pp. 323-326
Author(s):  
D. J. Mullan ◽  
R. S. Steinolfson
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Solar Corona ◽  
Large Scale ◽  
Field Structure ◽  
Neutral Sheet ◽  
Solar Cosmic Rays ◽  
Magnetic Field Structure ◽  
Large Scale Magnetic Field ◽  
Highly Correlated

The acceleration of solar cosmic rays in association with certain solar flares is known to be highly correlated with the propagation of an MHD shock through the solar corona (Svestka, 1976). The spatial structure of the sources of solar cosmic rays will be determined by those regions of the corona which are accessible to the flare-induced shock. The regions to which the flare shock is permitted to propagate are determined by the large scale magnetic field structure in the corona. McIntosh (1972, 1979) has demonstrated that quiescent filaments form a single continuous feature (a “baseball stitch”) around the surface of the sun. It is known that helmet streamers overlie quiescent filaments (Pneuman, 1975), and these helmet streamers contain large magnetic neutral sheets which are oriented essentially radially. Hence the magnetic field structure in the low solar corona is characterized by a large-scale radial neutral sheet which weaves around the entire sun following the “baseball stitch”. There is therefore a high probability that as a shock propagates away from a flare, it will eventually encounter this large neutral sheet.

scholarly journals The Magnetized Disk-Halo Transition Region of M51

2018 ◽  
Vol 14 (A30) ◽  
pp. 319-322 ◽  
Author(s):  
M. Kierdorf ◽  
S. A. Mao ◽  
A. Fletcher ◽  
R. Beck ◽  
M. Haverkorn ◽  
...  
Keyword(s):  
Transition Region ◽  
Large Scale ◽  
Model Parameters ◽  
Very Large Array ◽  
X Band ◽  
Model Predictions ◽  
The Galaxy ◽  
Linearly Polarized ◽  
Grand Design ◽  
Different Depths

AbstractAn excellent laboratory for studying large scale magnetic fields is the grand design face-on spiral galaxy M51. Due to wavelength-dependent Faraday depolarization, linearly polarized synchrotron emission at different radio frequencies gives a picture of the galaxy at different depths: Observations at L-band (1 – 2 GHz) probe the halo region while at C- and X-band (4 – 8 GHz) the linearly polarized emission probe the disk region of M51. We present new observations of M51 using the Karl G. Jansky Very Large Array (VLA) at S-band (2 – 4 GHz), where previously no polarization observations existed, to shed new light on the transition region between the disk and the halo. We discuss a model of the depolarization of synchrotron radiation in a multilayer magneto-ionic medium and compare the model predictions to the multi-frequency polarization data of M51 between 1 – 8 GHz. The new S-band data are essential to distinguish between different models. Our study shows that the initial model parameters, i.e. the total regular and turbulent magnetic field strengths in the disk and halo of M51, need to be adjusted to successfully fit the models to the data.

scholarly journals Magnetohydrodynamic calculation of the temperature and wind velocity profile of the solar transition region. Preliminary results.

2018 ◽  
Vol 145 ◽  
pp. 03009 ◽  
Author(s):  
Todor M. Mishonov ◽  
Albert M. Varonov ◽  
Nedeltcho I. Zahariev ◽  
Rositsa V. Topchiyska ◽  
Boian V. Lazov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spectral Density ◽  
Solar Corona ◽  
Temperature Profile ◽  
Transition Region ◽  
Wind Velocity ◽  
Spectral Lines ◽  
Mhd Waves ◽  
Dimensional Approximation ◽  
Height Dependence

The sharp almost step like increase the temperature in the transition region (TR) between chromosphere and solar corona is well-known from decades; for first time we are giving a detailed magnetohydrodynamic (MHD) calculation of the height dependence of the temperature. The width of the transition region is evaluated by maximal value of the logarithmic derivative of the temperature. At fixed heating, only MHD can give such a narrow width and in such sense, even the qualitative agreement with the observational data, gives the final verdict what the heating mechanism of the solar corona is. Static profiles of the temperature and wind velocity are calculated for static frequency dependent spectral density of the incoming MHD waves; no time dependent computer simulations. At fixed spectral density of MHD waves, the MHD calculation predicts height dependence of the non-thermal broadening of spectral lines and its angular dependence. For illustration is used one dimensional approximation of completely ionized hydrogen plasma in weak magnetic field, but it is considered that the width of the TR is weakly dependent with respect of further elaboration. The analyzed MHD calculation is a numerical confirmation of the qualitative concept of self-induced opacity of the plasma with respect to MHD waves. The plasma viscosity strongly increases with the temperature. Heated by MHD waves, plasma increases the wave absorption and this positive feedback leads to further heating. The static temperature profile is a result of a self-consistent calculation of propagation of MHD wave through the static background of wind and temperature profile. The numerical method allows consideration of incoming MHD waves with an arbitrary spectral density. Further elaboration of the method are briefly discussed: influence of second viscosity in the chromospheric part of the TR, influence of the magnetic field on the coronal side of the TR and investigation of such type effects on the width of the TR.

The Large-Scale Density Structure of the Solar Corona and the Heliospheric Current Sheet

1996 ◽  
Vol 458 ◽  
pp. 817 ◽  
Author(s):  
Madhulika Guhathakurta ◽  
Thomas E. Holzer ◽  
R. M. MacQueen
Keyword(s):  
Solar Corona ◽  
Current Sheet ◽  
Large Scale ◽  
Heliospheric Current Sheet ◽  
Density Structure

scholarly journals Coronal global EIT waves as tools for multiple diagnostics

2007 ◽  
Vol 3 (S247) ◽  
pp. 243-250
Author(s):  
I. Ballai ◽  
M. Douglas
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Solar Disk ◽  
Coronal Loop ◽  
Large Scale ◽  
Theoretical Models ◽  
Coronal Loops ◽  
Quiet Sun ◽  
Propagating Waves ◽  
Global Magnetic Field

AbstractObservations in EUV lines of the solar corona revealed large scale propagating waves generated by eruptive events able to travel across the solar disk for large distances. In the low corona, CMEs are known to generate, e.g. EIT waves which can be used to sample the coronal local and global magnetic field. This contribution presents theoretical models for finding values of magnetic field in the quiet Sun and coronal loops based on the interaction of global waves and local coronal loops as well as results on the generation and propagation of EIT waves. The physical connection between local and global solar coronal events (e.g. flares, EIT waves and coronal loop oscillations) will also be explored.

scholarly journals Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Solar Physics ◽  
2017 ◽  
Vol 292 (8) ◽  
Author(s):  
Jaroslav Dudík ◽  
Elena Dzifčáková ◽  
Nicole Meyer-Vernet ◽  
Giulio Del Zanna ◽  
Peter R. Young ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
Transition Region ◽  
Nonequilibrium Processes

scholarly journals The Large-Scale Structure of the Corona

1980 ◽  
Vol 5 ◽  
pp. 549-556
Author(s):  
Jack B. Zirker
Keyword(s):  
Solar Corona ◽  
White Light ◽  
Large Scale ◽  
Dimensional Space ◽  
Coronal Holes ◽  
Solar Limb ◽  
Active Regions ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Fast Wind

The solar corona serves as a prototype of the outer atmospheres of all cool stars. Because of its nearness we can study this prototype in more detail than any other example. Considerable progress has been made recently in understanding how the large scale structure of the solar corona controls the genesis of the solar wind and the distribution of slow and fast wind streams throughout the three-dimensional space surrounding the sun. In this review we will discuss some of the progress made in this field during the last few years. We will emphasize the observational data and the inferences that can be made more or less directly from them. T. Holzer will discuss the theoretical aspects of stellar wind acceleration in another paper in this symposium.The large scale structures of the solar corona consist essentially of three kinds: streamers, active regions and coronal holes. Figure 1 is a familiar photograph of the solar corona, obtained in white light at the total eclipse of 30 June 1973 by the High Altitude Observatory. The streamers are the petal-like structures extending out from the black lunar limb. They taper to narrow radial spikes that have been traced out as far as 10-12 solar radii (Keller, 1979). Daily measurements of the white light corona at the Mauna Loa Observatory (Hundhausen et al. 1979) and the Pic-du-Midi Observatory (Dollfus et al., 1977) since 1965 show that the streamers are fan-shaped structures that may extend 120° in solar longitude. We see them in various perspectives at the solar limb.

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