SH22A-05
Sunquake Generation by Coronal Magnetic Restructuring
Tuesday, 15 December 2015: 11:20
2011 (Moscone West)
Alexander J B Russell, University of Dundee, Dundee, United Kingdom, Michaela Mooney, University of St Andrews, St Andrews, United Kingdom, James Edward Leake, US Naval Research Laboratory, Washington, DC, United States and Hugh S Hudson, University of California Berkeley, Berkeley, CA, United States
Abstract:
Solar flares and coronal mass ejections are powered by major restructurings of the coronal magnetic field, which appear to strongly perturb the magnetic field in the photosphere as well. Could the associated Lorentz forces generate sunquakes, as suggested by Hudson et al. 2008? Here, we present the first MHD simulations of sunquake generation by magnetic field perturbations, and explore the details of this mechanism. The downgoing magnetic field change is modelled as an Alfven wave, which propagates into the lower atmosphere. When it reaches the vicinity of the beta=1 layer (where the Alfven and sound speeds are equal), non-linear coupling excites a downgoing acoustic wave, which we interpret as a sunquake. The amplitude of the acoustic wave increases nonlinearly with the amplitude of the magnetic perturbation, reaching a limit where around 35% of the injected Poynting flux is transferred to the seismic wave - enough energy to match sunquake observations.
