The Role of Magnetic Fields in Transient Seismic Emission Driven by Atmospheric Heating in Flares
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Transient seismic emission in flares remains largely mysterious. Its discoverers proposed that seismic transients are driven by impulsive heating of the flaring chromosphere. Simulations of such heating show strong shocks, but these are damped by heavy radiative losses as they proceed downward. Because compression of the gas the shock enters both heats it and increases its density, the radiative losses increase radically with the strength of the shock, leaving doubt that sufficient energy can penetrate into the solar interior to explain helioseismic signatures. We note that simulations to date have no account for strong, inclined magnetic fields characteristic of transient-seismic-source environments. A strong horizontal magnetic field, for example, greatly increases the compressional modulus of the chromospheric medium, greatly reducing compression of the gas, hence radiative losses. Inclined magnetic fields, then, must be fundamental to the role of impulsive heating in transient seismic emission.
KeywordsFlares, dynamics Helioseismology Magnetic fields
We thank Joel Allred for sharing his most recent simulations of impulsive thick-target heating of the chromosphere, presented at the November 2012 RHESSI workshop. We also greatly appreciate the insight of Valentina Zharkova at the RHESSI workshop. We similarly appreciate consultation with George Fisher. We are most grateful to Kyoko Watanabe (ISIS) for sharing Hinode observations of the flare SOLA2011-02-15 with us. We appreciate the insights of K.D. Leka and Graham Barnes. We finally appreciate support of this research by contracts from the Solar and Heliospheric Physics Program of the National Aeronautics and Space Administration.
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