Author:

Keywords:

instabilities, Sun: corona, waves, Science & Technology, Physical Sciences, Astronomy & Astrophysics, RESONANT ABSORPTION, ALFVEN WAVES, SOLAR, PLASMA, MODE, ATMOSPHERE, LOOPS, physics.plasm-ph, 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0306 Physical Chemistry (incl. Structural), 5101 Astronomical sciences, 5107 Particle and high energy physics, 5109 Space sciences

Abstract:

A mechanism for self-heating of the solar corona is discussed. It is shown that the free energy available in the form of sheared flows gives rise to unstable electrostatic perturbations which accelerate and heat particles. The electrostatic perturbations can occur through two processes, viz., by a purely growing sheared flow-driven instability and/or by a sheared flow-driven drift wave. These processes can occur throughout the corona and, hence, this self-heating mechanism could be very important for coronal heating. These instabilities can give rise to local perturbed electrostatic potentials φ 1 of up to 100 volts within 3 × 10 -2 to a few seconds time, if the (dimensionless) initial perturbation is assumed to be about 1%, that is, eφ 1 /T e ≃ 10 -2 . The wavelengths in the direction perpendicular to the external magnetic field B 0 vary from about 10m to 1m in our model. The purely growing instability creates electrostatic fields by sheared flows even if there is no density gradient, whereas a density gradient is crucial for the occurrence of the drift wave instability. The purely growing instability develops a small real frequency as well in the two-ion coronal plasma. In the solar corona, very low frequency (of the order of 1Hz) drift dissipative waves can also occur due to electron-ion collisions. © 2012. The American Astronomical Society. All rights reserved..