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Spectroscopic signatures related to a sunquake

Matthews, S. A.; Harra, L. K.; Zharkov, S.; Green, L. M.

Authors

S. A. Matthews

L. K. Harra

L. M. Green

Abstract

© 2015. The American Astronomical Society. All rights reserved.. The presence of flare-related acoustic emission (sunquakes (SQs)) in some flares, and only in specific locations within the flaring environment, represents a severe challenge to our current understanding of flare energy transport processes. In an attempt to contribute to understanding the origins of SQs we present a comparison of new spectral observations from Hinode's EUV imaging Spectrometer (EIS) and the Interface Region Imaging Spectrograph (IRIS) of the chromosphere, transition region, and corona above an SQ, and compare them to the spectra observed in a part of the flaring region with no acoustic signature. Evidence for the SQ is determined using both time-distance and acoustic holography methods, and we find that unlike many previous SQ detections, the signal is rather dispersed, but that the time-distance and 6 and 7 mHz sources converge at the same spatial location. We also see some evidence for different evolution at different frequencies, with an earlier peak at 7 mHz than at 6 mHz. Using EIS and IRIS spectroscopic measurements we find that in this location, at the time of the 7 mHz peak the spectral emission is significantly more intense, shows larger velocity shifts and substantially broader profiles than in the location with no SQ, and there is a good correlation between blueshifted, hot coronal, hard X-ray (HXR), and redshifted chromospheric emission, consistent with the idea of a strong downward motion driven by rapid heating by nonthermal electrons and the formation of chromospheric shocks. Exploiting the diagnostic potential of the Mg ii triplet lines, we also find evidence for a single large temperature increase deep in the atmosphere, which is consistent with this scenario. The time of the 6 mHz and time-distance peak signal coincides with a secondary peak in the energy release process, but in this case we find no evidence of HXR emission in the quake location, instead finding very broad spectral lines, strongly shifted to the red, indicating the possible presence of a significant flux of downward propagating Alfvén waves.

Publication Date Oct 10, 2015
Journal Astrophysical journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 812
Issue 1
Article Number ARTN 35
Pages 35
Institution Citation Matthews, S. A., Harra, L. K., Zharkov, S., & Green, L. M. (2015). Spectroscopic signatures related to a sunquake. The Astrophysical journal, 812(1), 35. https://doi.org/10.1088/0004-637x/812/1/35
DOI https://doi.org/10.1088/0004-637x/812/1/35
Keywords Sun: atmosphere; Sun: flares; Sun: helioseismology; Sun: UV radiation
Publisher URL http://iopscience.iop.org/article/10.1088/0004-637X/812/1/35/meta
Copyright Statement © 2015. The American Astronomical Society. All rights reserved.
Additional Information Copy of article published in: Astrophysical journal, 2015, v.812, issue 35

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Copyright Statement
© 2015. The American Astronomical Society. All rights reserved.



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