Dynamic Current Injection into Magnetic Loops in Active Regions I. Supplies of Energy and Mass to Active-Region Corona in the Form of Dynamic Loop Brightenings

Abstract

One of the discoveries by Yohkoh is that a large part of the soft X-ray emission from the active-region corona comes from hot gas injected dynamically into magnetic loops from below. We propose that the major part of the supply of energy and mass to active region corona may be due to a dynamical leakage of magnetic twists produced in the subphotospheric convection layer. These twists naturally propogate out along the magnetic field to the active region corona as a large-amplitude torsional Alfvén-wave packet (TAWP, equivalent to a coaxially self-closed packet of MHD current), and the active-region corona is a dumping ground for such currents. These TAWP’s, which are passively produced in the dominant gas motion in the convection layer, dynamically influence the lower pressure gas as they propagate out into the chromosphere and the corona. The flux tube in the corona is pinched near the axis and heated. The pinched region propagates dynamically with the Alfvén velocity along the magnetic loop, driving the pinch-heated high-temperature gas into a spinning jet (a sweeping pinch). This may explain the supply of energy and mass to active-region corona in the form of the active-region loop brightenings found by Yohkoh.