Heating of coronal loops by fast mode MHD waves

Solar Physics ◽  
1979 ◽  
Vol 64 (2) ◽  
pp. 287-301 ◽  
Author(s):  
Shadia Rifai Habbal ◽  
Egil Leer ◽  
Thomas E. Holzer
Keyword(s):  
Mhd Waves ◽  
Coronal Loops ◽  
Fast Mode

Heating of Coronal Loops by Fast-Mode MHD-Waves

1979 ◽  
Vol 44 ◽  
pp. 228-231
Author(s):  
S.R. Habbal ◽  
T.E. Holzer ◽  
E. Leer
Keyword(s):  
Solar Radius ◽  
Mhd Waves ◽  
Coronal Loops ◽  
X Rays ◽  
Fast Mode

Loops in the corona, ranging in size from a few hundredths of a solar radius to a few tenths are observed in X-rays and EUV (Vaiana et al., 1976; Levine and Withbroe, 1977). Their temperatures are in the 2 to 3 million degree range and the densities vary from 108to 1010cm-3(Foukal, 1975; Krieger, 1977).

scholarly journals Galactic Center threads as nuclear magnetohydrodynamic waves

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Mhd Waves ◽  
Fast Mode ◽  
Magnetohydrodynamic Waves ◽  
Compression Waves ◽  
Sgr A ◽  
The Waves ◽  
The Magnetic Field

Abstract Propagation of fast-mode magnetohydrodynamic (MHD) compression waves is traced in the Galactic Center with a poloidal magnetic cylinder. MHD waves ejected from the nucleus are reflected and guided along the magnetic field, exhibiting vertically stretched fronts. The radio threads and non-thermal filaments are explained as due to tangential views of the waves driven by sporadic activity in Sgr A$^*$, or by multiple supernovae. In the latter case, the threads could be extremely deformed relics of old supernova remnants exploded in the nucleus.

scholarly journals The Distinction Between Thermal Nonequilibrium and Thermal Instability

Solar Physics ◽  
2019 ◽  
Vol 294 (12) ◽  
Author(s):  
James A. Klimchuk
Keyword(s):  
Large Amplitude ◽  
Thermal Instability ◽  
Mhd Waves ◽  
Accelerated Cooling ◽  
Coronal Loops ◽  
Thermal Nonequilibrium ◽  
Cold Condensation

AbstractFor some forms of steady heating, coronal loops are in a state of thermal nonequilibrium and evolve in a manner that includes accelerated cooling, often resulting in the formation of a cold condensation. This is frequently confused with thermal instability, but the two are in fact fundamentally different. We explain the distinction and discuss situations where they may be interconnected. Large-amplitude perturbations, perhaps associated with MHD waves, likely play a role in explaining phenomena that have been attributed to thermal nonequilibrium but also seem to require cross-field communication.

Numerical modelling of MHD waves in the solar chromosphere

2005 ◽  
Vol 364 (1839) ◽  
pp. 395-404 ◽  
Author(s):  
Mats Carlsson ◽  
Thomas J Bogdan
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Mode Conversion ◽  
Three Dimensions ◽  
Mhd Waves ◽  
Solar Chromosphere ◽  
Fast Mode ◽  
Reflected Waves ◽  
The Waves ◽  
The Magnetic Field

Acoustic waves are generated by the convective motions in the solar convection zone. When propagating upwards into the chromosphere they reach the height where the sound speed equals the Alfvén speed and they undergo mode conversion, refraction and reflection. We use numerical simulations to study these processes in realistic configurations where the wavelength of the waves is similar to the length scales of the magnetic field. Even though this regime is outside the validity of previous analytic studies or studies using ray-tracing theory, we show that some of their basic results remain valid: the critical quantity for mode conversion is the angle between the magnetic field and the k-vector: the attack angle. At angles smaller than 30° much of the acoustic, fast mode from the photosphere is transmitted as an acoustic, slow mode propagating along the field lines. At larger angles, most of the energy is refracted/reflected and returns as a fast mode creating an interference pattern between the upward and downward propagating waves. In three-dimensions, this interference between waves at small angles creates patterns with large horizontal phase speeds, especially close to magnetic field concentrations. When damping from shock dissipation and radiation is taken into account, the waves in the low–mid chromosphere have mostly the character of upward propagating acoustic waves and it is only close to the reflecting layer we get similar amplitudes for the upward propagating and refracted/reflected waves. The oscillatory power is suppressed in magnetic field concentrations and enhanced in ring-formed patterns around them. The complex interference patterns caused by mode-conversion, refraction and reflection, even with simple incident waves and in simple magnetic field geometries, make direct inversion of observables exceedingly difficult. In a dynamic chromosphere it is doubtful if the determination of mean quantities is even meaningful.

Nonlinear development of MHD waves in coronal loops

1997 ◽  
Vol 19 (12) ◽  
pp. 1891-1894 ◽  
Author(s):  
S. Parhi ◽  
B.P. Pandey ◽  
M. Goossens ◽  
G.S. Lakhina ◽  
P. De Bruyne
Keyword(s):  
Mhd Waves ◽  
Coronal Loops ◽  
Nonlinear Development

scholarly journals Mode Coupling in the Solar Corona. V. Reduction of the Coupled Equations

1977 ◽  
Vol 30 (6) ◽  
pp. 661 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Solar Corona ◽  
Mode Coupling ◽  
Mhd Waves ◽  
Fast Mode ◽  
Coupling Theory ◽  
Mode Coupling Theory ◽  
Coupled Equations

A simplified version of the mode-coupling theory of Clemmow and Heading is developed by reducing the set of coupled equations to two for the magnetoionic theory and three for the MHD theory. The simplified theory reproduces known results for coupling in the neighbourhood of coupling points. It is used to treat coupling between the MHD waves, and it is found that coupling between the fast mode and the Alfven mode for VA ;?; C, is stronger than the coupling between any other pair of modes. The strongest coupling of all is between the Alfven and slow (magnetoacoustic) modes for VA ~ C,.

scholarly journals Mode-Coupled MHD Waves in the Corona and Solar Wind

1980 ◽  
Vol 91 ◽  
pp. 139-141
Author(s):  
M. Heinemann ◽  
S. Olbert
Keyword(s):  
Solar Wind ◽  
Mode Coupling ◽  
Wkb Approximation ◽  
Mhd Waves ◽  
Fast Mode ◽  
Compressional Waves

The purpose of this paper is to outline a model of mode-coupled MHD compressional waves in the corona and solar wind. The eventual aim of this work is to be able to compute how MHD waves propagate through the corona and into the solar wind beginning with a source of Alfven or fast mode waves at the base of the corona. The necessity for consideration of mode coupling arises because of typical scalelengths in the corona. For wave sources, such as supergranulation, with wave periods of about a day, the different modes do no propagate independently, as in the WKB approximation, but are coupled because the ratio of wavelength to scalelength is of the order of one or greater.

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