Generation of Sunquakes and Coronal Waves from Proton Beam Heating in an Acoustic Simulation

How sunquakes and coronal waves are generated in solar flares and whether there is a single mechanism for their generation remains an open-ended question. While heating by electron beams has often been suggested as a potential means of excitation, electrons are strongly affected by collisions. It is generally difficult for electron beams to penetrate deeply enough into the atmosphere to elicit a seismic response. Protons of comparable energy, however, are able to penetrate more deeply due to their higher mass. In this work, we explore the possibility of proton beams as a means of exciting sunquakes. Bulk acceleration profiles are derived from RADYN simulations of proton beam heating and are used as input to an acoustic model to examine the resulting amplitude of the generated sunquake wavefront. For fixed energy flux and two power-law indices, the low-energy cut-off for the non-thermal particle energy distribution function is varied between 50 keV and 3000 keV. We find that the proton beams with smaller low-energy cut-offs are far more effective at generating sunquakes of realistic amplitude and that the power-law index does not strongly affect these results. In addition to the expected sunquake wavefront, the proton beam heating causes strong coronal waves leading to a chromospheric wavefront which appears to be traveling at supersonic speeds in time-distance diagrams. The connection between the coronal and chromospheric wavefronts provides an acoustic analog for the relationship between the coronal (EIT) and Moreton waves.