Resonant absorption and damping of hydromagnetic waves in solar corona

Abstract

Although, the hot solar corona was discovered more than sixty years ago, however, the exact dissipation mechanism that heats the corona is still unknown. Resonant absorption and damping of Alfven waves appear to be one of the major candidates in this respect. The corona is highly structured and inhomogeneous medium, containing a large number of discrete magnetic loops. In this paper a cylindrical magnetic flux tube with a specified density profile is considered, and the ideal equation of motion in coronal condition is obtained. The problem is reduced to solving a wave equation for the component of magnetic perturbation along the tube axis. The mathematical formalism is identical with that of the propagation of electromagnetic waves in optical fibers with a varying index of refraction through the cross section of the fiber. The ideal equations of magnetic and velocity fields in the global modes are singular and are solved numerically, using a modified shooting scheme. Resistive and viscous dissipation rates as an exponential time decay of disturbances are obtained. The results show that the amount of energy produced in the resonant layer inside the tube seems to be responsible for heating the corona.

Keywords

• resonant absorption
• Alfven waves
• dissipation
• solar coronal heating