The physics of transient seismic emission in flares remains largely mysterious. Its discoverers proposed that these sunquakes are the signature of a shock driven by thick-target heating of the flaring chromosphere. H-{alpha} observations show evidenc
e for such a shock. However, simulations of shocks driven by impulsive chromospheric heating show withering radiative losses as the shock proceeds downward. The compression of the shocked gas heats and increases its density, making it more radiative. So, radiative losses increase radically with the strength of the shock. This has introduced doubt that sufficient energy from such a shock can penetrate into the solar interior to match that indicated by the helioseismic signatures. We point out that simulations of acoustic transients driven by impulsive heating have no account for magnetic fields characteristic of transient-seismic-source environments. These must have a major impact on the seismic flux conducted into the solar interior. A strong horizontal magnetic field, for example, greatly increases the compressional modulus of the chromospheric medium. This greatly reduces compression of the gas, hence the radiative losses as the transient passes through it. This could explain the strong affinity of seismic sources to regions of strong, highly inclined penumbral magnetic fields. The role of inclined magnetic fields, then, is fundamental to our understanding of the role of impulsive heating in transient seismic emission.
Dynamical changes in the solar corona have proven to be very important in inducing seismic waves into the photosphere. Different mechanisms for their generation have been proposed. In this work, we explore the magnetic field forces as plausible mecha
nisms to generate sunquakes as proposed by Hudson, Fisher and Welsch. We present a spatial and temporal analysis of the line-of-sight magnetic field variations induced by the seismically active 2003 October 29 and 2005 January 15 solar flares and compare these results with other supporting observations.
On 2005 January 15, the active region AR10720 produced an X1.2 solar flare that induced high levels of seismicity into the photospheric layers. The seismic source was detected using helioseismic holography and analysed in detail in Paper I. Egression
power maps at 6 mHz with a 2 mHz bandwidth revealed a compact acoustic source strongly correlated with the footpoints of the coronal loop that hosted the flare. We present a magneto-seismic study of this active region in order to understand, for the first time, the magnetic topological structure of a coronal field that hosts an acoustically active solar flare. The accompanying analysis attempts to answer questions such as: Can the magnetic field act as a barrier and prevent seismic waves from spreading away from the focus of the sunquake? And, what is the most efficient magnetic structure that would facilitate the development of a strong seismic source in the photosphere?
