Speaker
Description
Early high-cadence chromospheric image sequences recorded with the recently commissioned Daniel K. Inouye Solar Telescope (DKIST) have revealed propagating arc-shaped bright fronts seen to originate from chromospheric bright grains. Prior to the appearance of the bright fronts, we observe vortical flows in the photosphere located underneath the chromospheric bright grains.
Corresponding image sequences synthesized from realistic three-dimensional magnetohydrodynamic simulations show a striking similarity with the observed phenomenon, and reveal that the arc-shaped structures are weak shock fronts triggered by the vortex dynamics of the underlying magnetic flux concentration. The latter are Alfénic pulses propagating along the small-scale magnetic flux concentrations that root in the photosphere. Here, we propose a serendipitous mechanism by which the torsional Alfvén wave excites a predominantly acoustic weak shock front in the ambient medium, capable of dissipating the torsional Alfvén wave.
