A New Approach to the Coronal Heating Problem

Abstract

The heating of the solar corona is discussed within both frameworks of kinetic and fluid drift wave theory. It is shown that the basic ingredient necessary for the heating is the presence of the background density gradients in the direction perpendicular to the magnetic field vector These gradients are a source of free energy for the electrostatic instabilities. Strongly growing modes are found for some typical coronal plasma parameters. The instabilities a) imply the presence of electric fields that can accelerate the plasma particles in both the perpendicular and the parallel direction with respect to the magnetic field vector, and b) can stochastically heat ions. 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 perpendicidar direction, iv) heats heavier 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 heating the solar corona.

Solar nanoflares and other smaller energy release events as growing drift waves

“…The wavelength parallel to the magnetic field vector is taken as λ z = s • 10 4 m. We have introduced a parameter s that we can vary within the range 10 −1 − 10 3 in order to demonstrate that the mode behavior remains unchanged at various density scale lengths L n , provided that we keep the ratio λ z /L n constant. It can easily be shown that in this case the ratio γ/ω r also remains constant [19,20], while both quantities are shifted either to lower or higher values. As example, the mode frequency for s = 1, L n = 100 m, and λ y = 1 m is ω r = 231 Hz, and it changes as 231/s when the other parameters are fixed.…”