The effect of magnetic field on the damping of slow waves in the solar corona

Abstract

Slow magnetoacoustic waves are routinely observed in astrophysical plasma systems such as the solar corona. As a slow wave propagates through a plasma, it modifies the equilibrium quantities of density, temperature, and magnetic field. In the corona and other plasma systems, the thermal equilibrium is comprised of a balance between continuous heating and cooling processes, the magnitudes of which vary with density, temperature and magnetic field. Thus the wave may induce a misbalance between these competing processes. Its back reaction on the wave has been shown to lead to dispersion, and amplification or damping, of the wave. In this work the importance of the effect of magnetic field in the rapid damping of slow waves in the solar corona by heating/cooling misbalance is evaluated and compared to the effects of thermal conduction. The two timescales characterising the effect of misbalance are derived and calculated for plasma systems with a range of typical coronal conditions. The predicted damping times of slow waves from thermal misbalance in the solar corona are found to be of the order of 10-100 minutes, coinciding with the wave periods and damping times observed. Moreover the slow wave damping by thermal misbalance is found to be comparable to the damping by field-aligned thermal conduction. We show that in the infinite field limit, the wave dynamics is insensitive to the dependence of the heating function on the magnetic field, and this approximation is found to be valid in the corona so long as the magnetic field strength is greater than 10G for quiescent loops and plumes and 100G for hot and dense loops. In summary thermal misbalance may damp slow magnetoacoustic waves rapidly in much of the corona, and its inclusion in our understanding of slow mode damping may resolve discrepancies between observations and theory relying on compressive viscosity and thermal conduction alone.

11 pages, 2 figures. Accepted for publication in A&A

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Cited by in corpus (10)

• Dispersion of Slow Magnetoacoustic Waves in the Active Region Fan Loops Introduced by Thermal Misbalance
• Role of Non-Ideal Dissipation with Heating-Cooling Misbalance on the Phase Shifts of Standing Slow Magnetohydrodynamic Waves
• A new look at the frequency-dependent damping of slow-mode waves in the solar corona
• Alfvénic motions arising from asymmetric acoustic wave drivers in solar magnetic structures
• Chromospheric heating and generation of plasma outflows by impulsively generated two-fluid magnetoacoustic waves
• Coronal seismology by slow waves in non-adiabatic conditions
• Magnetohydrodynamic spectroscopy of a non-adiabatic solar atmosphere
• Exact solution to the problem of slow oscillations in coronal loops and its diagnostic applications
• Slow Magnetoacoustic Oscillations in Stellar Coronal Loops
• Generation of solar chromosphere heating and coronal outflows by two-fluid waves