Effect of Local Thermal Equilibrium Misbalance on Long-wavelength Slow Magnetoacoustic Waves

Journal Article · Wed Nov 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA8EA3· OSTI ID:22679705

Nakariakov, V. M. ^[1]; Afanasyev, A. N. ^[2]; Kumar, S.

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1. Centre for Fusion, Space and Astrophysics, Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom)
2. Institute of Solar-Terrestrial Physics SB RAS, P.O. Box 291, Lermontov St. 126A, Irkutsk 664033 (Russian Federation)

Evolution of slow magnetoacoustic waves guided by a cylindrical magnetic flux tube that represents a coronal loop or plume, is modeled accounting for the effects of finite gas pressure, weak nonlinearity, dissipation by thermal conduction and viscosity, and the misbalance between the cooling by optically thin radiation and unspecified heating of the plasma. An evolutionary equation of the Burgers–Malthus type is derived. It is shown that the cooling/heating misbalance, determined by the derivatives of the combined radiative cooling and heating function, with respect to the density, temperature, and magnetic field at the thermal equilibrium affect the wave rather strongly. This effect may either cause additional damping, or counteract it, or lead to the gradual amplification of the wave. In the latter case, the coronal plasma acts as an active medium for the slow magnetoacoustic waves. The effect of the cooling/heating misbalance could be important for coronal slow waves, and could be responsible for certain discrepancies between theoretical results and observations, in particular, the increased or decreased damping lengths and times, detection of the waves at certain heights only, and excitation of compressive oscillations. The results obtained open up a possibility for the diagnostics of the coronal heating function by slow magnetoacoustic waves.

• OSTI ID: 22679705
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 849; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMPLIFICATION
DENSITY
DETECTION
EXCITATION
HEATING
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOACOUSTIC WAVES
MAGNETOACOUSTICS
MAGNETOHYDRODYNAMICS
NONLINEAR PROBLEMS
OSCILLATIONS
PLASMA
RADIATIVE COOLING
STAR EVOLUTION
SUN
THERMAL CONDUCTION
THERMAL EQUILIBRIUM
WAVELENGTHS