ENERGY-TRANSPORT TO THE SOLAR CORONA BY MAGNETIC KINK WAVES

We show that the magnetic kink waves generated by the motions of photospheric footpoints of the coronal flux tubes can supply adequate energy for heating the quiet corona, provided there are occasional rapid motions of these footpoints as found in recent observations (Vigneau et al. 1992). Choudhuri, Auffret, & Priest (1992) modeled the solar corona as isothermal atmosphere and showed that these rapid motions are much more efficient for transporting energy compared to the slow footpoint motions taking place most of the time. We extend these calculations for a two-layer atmosphere, with the lower layer having chromospheric thickness and temperature, and the upper layer having coronal temperature. Even in the presence of such a temperature jump, we find that the rapid footpoint motions are still much more efficient for transporting energy to the corona and the estimated energy flux is sufficient for quiet coronal heating, i.e., we reinforce the conclusions of Choudhuri, Auffret, & Priest (1992). In addition to presenting results for the solar corona, we discuss the general problem of the propagation of kink pulses in a two-layer atmosphere for different possible values of the basic parameters. We find a fairly complicated behavior which could not be anticipated from the analysis of a pure Fourier mode. For pulses generated by rapid footpoint motions, the energy flux decreases due to reflection at the transition layer. For pulses generated by slow footpoint motions, however, the behavior of the system is governed by modes, which are evanescent in the lower layer, but can tunnel through it. The energy flux carried by such pulses can actually increase when there is a temperature jump in the atmosphere.