Stability and mode analysis of solar coronal loops using thermodynamic irreversible energy principles: II. Modes in twisted non-isothermal magnetic field configurations

Authors
Costa, A.; <div class="autor_fcen" id="3892">González, R.</div>
Publication Year
2008
Language
English
Format
article
Status
Published version
Description
Aims. We study the stability and modes of non - isothermal coronal loop models with different intensity values of equilibrium twisted magnetic field.Methods. We use an energy principle obtained by means of non - equilibrium thermodynamic arguments. The principle is expressed in terms of Hermitian operators and enables us to consider the coupled system of equations, the balance of energy equation and the equation of motion, to obtain modes and eigenmodes in a spectrum ranging from short to long-wavelength disturbances without using weak varying approximations of the equilibrium parameters. Long-wavelength perturbations introduce additional difficulties because the inhomogeneous nature of the medium produce disturbances corresponding to continuous intervals of eigenfrequencies, which cannot be considered as purely sinusoidal.Results. We analyze the modification of periods, modes structure, and stability when the helicity, the magnetic field strength, and the radius of the fluxtube are varied. The efficiency of the damping due to the resonant absorption mechanism is analyzed in terms of modes that can either impulsively release or store magnetic energy.Conclusions. We find that the onset of the instability is associated with a critical value of the helicity and the magnetic energy content has a determinant role on the instability of the system with respect to the stabilizing effect of the resonant absorption mechanism. © 2008 ESO.
Fil:González, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Source
Astron. Astrophys. 2008;489(2):755-762
Subject
Sun: corona
Sun: magnetic fields
Sun: oscillations
Absorption
Energy efficiency
Equations of motion
Magnetic field measurement
Magnetic fields
Magnetic materials
Mathematical operators
Mechanisms
Solar energy
Thermodynamic stability
Thermodynamics
Coronal loops
Coupled systems
Critical values
Eigen-frequencies
Eigen-modes
Energy equation
Energy principles
Equation of motion
Equilibrium parameters
Helicity
Hermitian operators
Intensity values
Irreversible energy
Long wavelengths
Magnetic energies
Magnetic field configurations
Magnetic field strengths
Mode analysis
Non-equilibrium
Non-isothermal
Resonant absorption
Solar coronal loops
Stabilizing effects
Sun: corona
Sun: magnetic fields
Sun: oscillations
System stability
Access level
Open access
License
http://creativecommons.org/licenses/by/2.5/ar
Repository
Biblioteca Digital (UBA-FCEN)
Institution
Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
OAI Identifier
snrd:HASH0134708f257ee72c1fcb8c61