Probing the solar coronal heating function with slow magnetoacoustic waves

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Nugget
Number: 393
1st Author: Dmitrii Y. Kolotkov
2nd Author: et al.
Published: 16 November 2020
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Contents

Introduction

The solar corona contains waves of many types, and their great significance follows immediately from the simple fact that the corona consists mainly of fields, not matter - the energy and its sometimes violent conversions come from the electromagnetic field directly, although we detect the dynamics only via the properties of the visible gas content.

For compressive waves, the coronal plasma that appears to be in an apparent thermal equilibrium formed by the balance of energy losses and gains acts as an active medium. In other words, the wave experiences a back-reaction of the modification of the cooling and heating rates by the density and temperature perturbations, either losing or gaining energy from the energy supply that heats the plasma. This natural mechanism of the energy exchange between a thermodynamically active plasma and its wave population is known as a wave-induced heating/cooling misbalance.

In Ref. [1] we have presented a novel seismological method allowing us to determine empirical constraints on the unknown coronal heating function by combining the theory of perturbed thermal equilibrium and the observed behaviour of slow magnetoacoustic waves.

Stability of acoustic and thermal modes in the corona for varying heating models

In the continuously heated and cooled coronal plasma with thermal conduction and plasma-β -> 0, the dynamics of coupled linear slow magnetoacoustic and thermal (entropy-related) modes, perturbing both heating and cooling processes, strongly depends on the ratio between the wave period and the characteristic timescales of the parallel thermal conduction and thermal misbalance [1,2]:

393fa.png

Acknowlegements

The co-authors of this Nugget are Timothy J. Duckenfield and Valery M. Nakariakov.

Bibliography

[1] In press in Astron. Astrophys., doi: 10.1051/0004-6361/202039095.

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