The universally growing mode in the solar atmosphere: coronal heating by drift waves

TL;DR

This paper demonstrates that drift waves driven by density gradients in the solar atmosphere can cause significant plasma heating through Landau and stochastic mechanisms, potentially explaining coronal heating.

Contribution

It introduces a comprehensive analysis of drift wave-induced heating in the solar atmosphere using established laboratory plasma theory, highlighting stochastic heating's efficiency.

Findings

Stochastic heating is more effective on ions than electrons.

Heavy ions are heated more efficiently than lighter ions.

Drift wave heating rates can surpass current estimates for coronal heating.

Abstract

The heating of the plasma in the solar atmosphere is discussed within both frameworks of fluid and kinetic drift wave theory. We show that the basic ingredient necessary for the heating is the presence of density gradients in the direction perpendicular to the magnetic field vector. Such density gradients are a source of free energy for the excitation of drift waves. We use only well established basic theory, verified experimentally in laboratory plasmas. Two mechanisms of the energy exchange and heating are shown to take place simultaneously: one due to the Landau effect in the direction parallel to the magnetic field, and another one, stochastic heating, in the perpendicular direction. The stochastic heating i) is due to the electrostatic nature of the waves, ii) is more effective on ions than on electrons, iii) acts predominantly in the perpendicular direction, iv) heats heavy ions more efficiently than lighter ions, and v) may easily provide a drift wave heating rate that is orders of magnitude above the value that is presently believed to be sufficient for the coronal heating, i.e., $\simeq 6 \cdot 10^{-5} $J/(m$^3$s) for active regions and $\simeq 8 \cdot 10^{-6} $J/(m$^3$s) for coronal holes. This heating acts naturally through well known effects that are, however, beyond the current standard models and theories.