scholarly journals Damping of non-isothermal hot coronal loops oscillations

2007 ◽  
Vol 3 (S247) ◽  
pp. 316-319
Author(s):  
M. Luna-Cardozo ◽  
R. Erdélyi ◽  
César A. Mendoza-Briceño
Keyword(s):  
Coronal Loop ◽  
Thermal Conduction ◽  
Numerical Experiments ◽  
Initial Temperature ◽  
Standing Waves ◽  
Coronal Loops ◽  
Governing Equations ◽  
Longitudinal Waves ◽  
Decay Times ◽  
Range Of Values

AbstractHere we investigate longitudinal waves in non-isothermal hot (T ≥ 5.0 MK) coronal loops. Motivated by SOHO SUMER and Yohkoh SXT observations and taking into account gravitational stratification, thermal conduction, compressive viscosity, radiative cooling, and heating, the governing equations of 1D hydrodynamics is solved numerically for standing wave oscillations along a magnetic field line. A semicircular shape is chosen to represent a coronal loop. It was found that the decay time of standing waves decreases with the increase of the initial temperature and the periods of oscillations are affected by the different initial velocities and loop lengths studied by the numerical experiments. The predicted decay times are within the range of values inferred from Doppler-shift oscillations observed by SUMER in hot coronal loops.

scholarly journals Damping of standing slow waves in hot coronal loops

2007 ◽  
Vol 3 (S247) ◽  
pp. 303-311
Author(s):  
Leonardo Di G. Sigalotti ◽  
César A. Mendoza-Briceño ◽  
Marialejandra Luna-Cardozo
Keyword(s):  
Energy Dissipation ◽  
Viscous Dissipation ◽  
Thermal Conduction ◽  
Slow Waves ◽  
Coronal Loops ◽  
Slow Mode ◽  
Decay Times ◽  
Crossing Time ◽  
Linear Limit ◽  
Radiative Losses

AbstractThe damping of standing slow mode oscillations in hot (T > 6 MK) coronal loops is described in the linear limit. The effects of energy dissipation by thermal conduction, viscosity, and radiative losses and gains are examined for both stratified and nonstratified loops. We find that thermal conduction acts on the way of increasing the period of the oscillations over the sound crossing time, whereas the decay times are mostly determined by viscous dissipation. Thermal conduction alone results in slower damping of the density and velocity waves compared to the observations. Only when viscosity is added do these waves damp out at the same rate of the observed SUMER loop oscillations. In the linear limit, the periods and decay times are barely affected by gravity.

scholarly journals ANOMALOUS COOLING OF CORONAL LOOPS WITH TURBULENT SUPPRESSION OF THERMAL CONDUCTION

2016 ◽  
Vol 833 (1) ◽  
pp. 76 ◽  
Author(s):  
Nicolas H. Bian ◽  
Jonathan M. Watters ◽  
Eduard P. Kontar ◽  
A. Gordon Emslie
Keyword(s):  
Thermal Conduction ◽  
Coronal Loops

scholarly journals Thermal conduction effects on the kink instability in coronal loops

2010 ◽  
Vol 525 ◽  
pp. A96 ◽  
Author(s):  
G. J. J. Botha ◽  
T. D. Arber ◽  
A. W. Hood
Keyword(s):  
Thermal Conduction ◽  
Coronal Loops ◽  
Kink Instability

scholarly journals Observation and simulation of a filament eruption associated with the contraction of the overlying coronal loops and the filament rotation

2013 ◽  
Vol 8 (S300) ◽  
pp. 504-506
Author(s):  
X. L. Yan ◽  
Z. K. Xue ◽  
Z. X. Mei
Keyword(s):  
Coronal Loop ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Filament Eruption ◽  
Solar Dynamics ◽  
Rotation Motion

AbstractBy using the data of Solar Dynamics Observatory (SDO), we present a case study of the contraction of the overlying coronal loop and the rotation motion of a sigmoid filament on 2012 May 22. At the beginning of the filament eruption, the overlying coronal loop experienced a significant contraction. In the following, the filament started to rotate counterclockwise. We also carried the simulation to investigate the process of the filament eruption.

scholarly journals Excitation and damping of slow magnetosonic standing waves in a solar coronal loop

2005 ◽  
Vol 436 (2) ◽  
pp. 701-709 ◽  
Author(s):  
M. Selwa ◽  
K. Murawski ◽  
S. K. Solanki
Keyword(s):  
Coronal Loop ◽  
Standing Waves ◽  
Solar Coronal

scholarly journals Signatures of red-shifted footpoints in the quiescent coronal loop system

2019 ◽  
Author(s):  
Yamini K. Rao ◽  
Abhishek K. Srivastava ◽  
Pradeep Kayshap ◽  
Bhola N. Dwivedi
Keyword(s):  
Spectral Data ◽  
Coronal Loop ◽  
Doppler Velocity ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Heating Mechanism ◽  
Multi Wavelength ◽  
Solar Dynamics ◽  
Impulsive Heating ◽  
Imaging Spectrograph

Abstract. We observed quiescent coronal loops using multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) on 2016 April 13. The flows at the footpoints of such loop systems are studied using spectral data from Interface Region Imaging Spectrograph (IRIS). The Doppler velocity distributions at the footpoints lying in the moss region show the negligible or small flows at Ni I, Mg II k3 and C II line corresponding to upper photospheric and chromospheric emissions. Significant red-shifts (downflows) ranging from (1 to 7) km s−1 are observed at Si IV (1393.78 Å; log(T/K) = 4.8) which is found to be consistent with the existing results regarding dynamical loop systems and moss regions. Such downflows agree well with the impulsive heating mechanism reported earlier.

Strong and Weak Damping of Slow MHD Standing Waves in Hot Coronal Loops

Solar Physics ◽  
2006 ◽  
Vol 236 (1) ◽  
pp. 127-136 ◽  
Author(s):  
V. S. Pandey ◽  
B. N. Dwivedi
Keyword(s):  
Standing Waves ◽  
Coronal Loops ◽  
Weak Damping

Nonlinear waves in a hot plasma by Lorentz transformation

1975 ◽  
Vol 13 (2) ◽  
pp. 231-247 ◽  
Author(s):  
P. C. Clemmow
Keyword(s):  
Nonlinear Waves ◽  
Cold Plasma ◽  
Electron Plasma ◽  
Temperature Correction ◽  
Governing Equations ◽  
Longitudinal Waves ◽  
Circularly Polarized ◽  
The Third ◽  
Hot Plasma ◽  
Space Dependence

Wave propagation in a hot, collisionless electron plasma (without ambient magnetic field) is analyzed by coisidering the frame of reference in which the field has no space dependence. It is shown that the governing equations are of the same form as those for a cold plasma, and are likely to have corresponding exact (nonlinear, relativistic) solutions. In particular, it is shown that there exists a solution representing a purely transverse, circularly polarized, monochromatic wave. Three approximate forms of the dispersion relation of this wave are obtained explicitly, the first being valid when the temperature correction is small, the second applying to weak waves, and the third to strong waves. Purely longitudinal waves are also discussed.

Nonlinear compressible magnetoconvection. Part 3. Travelling waves in a horizontal field

1995 ◽  
Vol 300 ◽  
pp. 287-309 ◽  
Author(s):  
D. P. Brownjohn ◽  
N. E. Hurlburt ◽  
M. R. E. Proctor ◽  
N. O. Weiss
Keyword(s):  
Magnetic Field ◽  
Numerical Experiments ◽  
Strong Field ◽  
Travelling Waves ◽  
Standing Waves ◽  
Weak Field ◽  
Horizontal Magnetic Field ◽  
Weakly Nonlinear ◽  
Physical Mechanisms ◽  
The Magnetic Field

We present results of numerical experiments on two-dimensional compressible convection in a polytropic layer with an imposed horizontal magnetic field. Our aim is to determine how far this geometry favours the occurrence of travelling waves. We therefore delineate the region of parameter space where travelling waves are stable, explore the ways in which they lose stability and investigate the physical mechanisms that are involved. In the magnetically dominated regime (with the plasma beta, $\hat{\beta}$ = 8), convection sets in at an oscillatory bifurcation and travelling waves are preferred to standing waves. Standing waves are stable in the strong-field regime ($\hat{\beta}$ = 32) but travelling waves are again preferred in the intermediate region ($\hat{\beta}$ = 128), as suggested by weakly nonlinear Boussinesq results. In the weak-field regime ($\hat{\beta}$ ≥ 512) the steady nonlinear solution undergoes symmetry-breaking bifurcations that lead to travelling waves and to pulsating waves as the Rayleigh number, $\circ{R}$, is increased. The numerical experiments are interpreted by reference to the bifurcation structure in the ($\hat{\beta}$, $\circ{R}$)-plane, which is dominated by the presence of two multiple (Takens-Bogdanov) bifurcations. Physically, the travelling waves correspond to slow magnetoacoustic modes, which travel along the magnetic field and are convectively excited. We conclude that they are indeed more prevalent when the field is horizontal than when it is vertical.

scholarly journals Propagation of Plane Waves in a Thermally Conducting Mixture

2011 ◽  
Vol 2011 ◽  
pp. 1-12
Author(s):  
Baljeet Singh
Keyword(s):  
Free Surface ◽  
Longitudinal Wave ◽  
Plane Waves ◽  
Generalized Thermoelasticity ◽  
Elastic Solid ◽  
Reflection Coefficients ◽  
Governing Equations ◽  
Transverse Waves ◽  
Longitudinal Waves ◽  
Thermally Conducting

The governing equations for generalized thermoelasticity of a mixture of an elastic solid and a Newtonian fluid are formulated in the context of Lord-Shulman and Green-Lindsay theories of generalized thermoelasticity. These equations are solved to show the existence of three coupled longitudinal waves and two coupled transverse waves, which are dispersive in nature. Reflection from a thermally insulated stress-free surface is considered for incidence of coupled longitudinal wave. The speeds and reflection coefficients of plane waves are computed numerically for a particular model.

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