On the quality of resonant absorption as a coronal loop heating mechanism

Abstract

The qualityQ of a resonance is defined as the ratio of the total energy contained in the system to the dissipation per driving cycle. Hence, a ‘good quality’ resonance is one with little losses, i.e., little dissipation per driving cycle. However, for heating coronal plasmas by means of resonant absorption of waves, ‘bad’ quality resonances are required. Here, the quality of the MHD resonances that occur when an inhomogeneous coronal loop is excited by incident waves is investigated for typical coronal loop parameter values in the frame work of linear, resistive MHD. It is shown that the resonances in coronal loops have bad quality and, hence, yield a lot of Ohmic heating per driving cycle compared to the total energy stored in the loop. As a consequence, the time scales of the heating process are relatively short and resonant absorption turns out to be a viable candidate for the heating of the magnetic loops observed in the solar corona.