LONGITUDINAL MAGNETOHYDRODYNAMICS OSCILLATIONS IN DISSIPATIVE, COOLING CORONAL LOOPS

This paper investigates the effect of cooling on standing slow magnetosonic waves in coronal magnetic loops. The damping mechanism taken into account is thermal conduction that is a viable candidate for dissipation of slow magnetosonic waves in coronal loops. In contrast to earlier studies, here we...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2014-05, Vol.786 (1), p.1-8
Main Authors: Al-Ghafri, K S, Ruderman, M S, Williamson, A, Erdelyi, R
Format: Article
Language:English
Subjects:
AMPLITUDES
APPROXIMATIONS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Cooling
Coronal loops
DAMPING
DECAY
Dissipation
DISTURBANCES
ELECTRON TEMPERATURE
EQUATIONS
EVOLUTION
ION TEMPERATURE
LOW-BETA PLASMA
MAGNETIC FIELDS
MAGNETOACOUSTIC WAVES
MAGNETOHYDRODYNAMICS
Mathematical analysis
Mathematical models
ONE-DIMENSIONAL CALCULATIONS
OSCILLATIONS
PERTURBATION THEORY
SEISMOLOGY
SUN
THERMAL CONDUCTION
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:This paper investigates the effect of cooling on standing slow magnetosonic waves in coronal magnetic loops. The damping mechanism taken into account is thermal conduction that is a viable candidate for dissipation of slow magnetosonic waves in coronal loops. In contrast to earlier studies, here we assume that the characteristic damping time due to thermal conduction is not small, but arbitrary, and can be of the order of the oscillation period, i.e., a temporally varying plasma is considered. The approximation of low-beta plasma enables us to neglect the magnetic field perturbation when studying longitudinal waves and consider, instead, a one-dimensional motion that allows a reliable first insight into the problem. The background plasma temperature is assumed to be decaying exponentially with time, with the characteristic cooling timescale much larger than the oscillation period. This assumption enables us to use the WKB method to study the evolution of the oscillation amplitude analytically. Using this method we obtain the equation governing the oscillation amplitude. The analytical expressions determining the wave properties are evaluated numerically to investigate the evolution of the oscillation frequency and amplitude with time. The results show that the oscillation period increases with time due to the effect of plasma cooling. The plasma cooling also amplifies the amplitude of oscillations in relatively cool coronal loops, whereas, for very hot coronal loop oscillations the damping rate is enhanced by the cooling. We find that the critical point for which the amplification becomes dominant over the damping is in the region of 4 MK. These theoretical results may serve as impetus for developing the tools of solar magneto-seismology in dynamic plasmas.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/786/1/36