N 87 - 20939 HEATING OF life SOLAR CORONA

It has been suggested that resonance absorption of low frequency magnetohydrodynamic waves could be responsible for heating the solar corona (lonson, 1982; Hollweg, 1984). In this paper an improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. To accomplish this, the wave equation for a mildly dissipative, compressible plasma is derived from the linearized magnetohydrodynamic equations for a plasma with transverse Alfven speed gradients. For parameters representative of the solar corona, it is found that a two scale description of the wave motion is appropriate. The large scale motion, which can be approximated as nearly ideal, Pms a scale which is on the order of the width of the loop. The small scale wave, however, has a transverse scale much smaller than the width of the loop, 0.3-250 km, and is highly dissipative. These two wave motions are coupled in a narrow resonance region in the loop where the global wave frequency equals the local Alfven wave frequency. Formally this coupling comes about from using the method of matched asymptotic expansions to match the inner and outer (small and large scale) solutions. The resultant heating rate can be calculated from either of these solutions. A formula derived using the outer (ideal) solution is presented, and shown to be consistent with observations of heating and line broadening in the solar corona.