Seismological constraints on the solar coronal heating function
Published: 12/2020
Characteristic thermal misbalance time τM (11) for typical coronal densities and temperatures and a fixed heating model a = 0.5 and b = −3.5, for which both acoustic and thermal modes are stable over the entire intervals of plasma densities and temperatures considered. The colour scheme is adjusted so that the values of τM from about 10 min to 100 min are shown in green. The blue symbols illustrate typical combinations of coronal plasma density and temperature in hot and dense loops in active regions (star), warm and less dense quiescent loops (circle), and polar plumes (box).
Astronomy & Astrophysics, Volume 644, id.A33, 6 pp.
Kolotkov D. Y., Duckenfield T. J., Nakariakov, V. M.
Aims: The hot solar corona exists because of the balance between radiative and conductive cooling and some counteracting heating mechanism that remains one of the major puzzles in solar physics.
Methods: The coronal thermal equilibrium is perturbed by magnetoacoustic waves, which are abundantly present in the corona, causing a misbalance between the heating and cooling rates. As a consequence of this misbalance, the wave experiences a back-reaction, either losing or gaining energy from the energy supply that heats the plasma, at timescales comparable to the wave period.
Results: In particular, the plasma can be subject to wave-induced instability or over-stability, depending on the specific choice of the coronal heating function. In the unstable case, the coronal thermal equilibrium would be violently destroyed, which does not allow for the existence of long-lived plasma structures typical for the corona. Based on this, we constrained the coronal heating function using observations of slow magnetoacoustic waves in various coronal plasma structures.
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