Seismic emission from the solar flares of 2003 October 28 and 29

We report the detection of seismic waves emitted from powerful solar flares that occurred in NOAA Active Region 10486 on 2003 October 28 and 29. We used helioseismic holography to image the seismic sources of the waves. This technique was previously used to image the source of seismic emission from the large solar flare of 1996 July 9. Egression power maps at 6 mHz with a 2 mHz bandwidth reveal multiple compact acoustic sources strongly associated with the footpoints of a coronal loop that hosted the flares. The total acoustic energy in the flare signatures is a very small fraction of the total energy radiated by the flares. The acoustic signatures are co-aligned with hard X-ray signatures, suggesting a direct link between energetic particles accelerated during the flare and the acoustic waves as a hydrodynamic response of the chromosphere, or possibly the underlying photosphere, to these particles at the footpoints of the loop. There is also evidence of high-energy protons impinging onto the chromosphere in the neighborhoods of the acoustic sources. Observations of emission in the D1 line of neutral sodium at the onset of the October 29 flare show evidence of a downward-propagating shock/condensation at the onset of the flare. Concurrent Global Oscillation Network Group ( GONG) intensity observations show significant radiative emission with a sudden onset in the compact region encompassing the acoustic signature. Most flares appear to be acoustically inactive. Photospheric heating by high-energy protons is likely to be a major factor in seismic emission from acoustically active flares.