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Properties of the 15 February 2011 Flare Seismic Sources

Zharkov, S.; Green, L. M.; Matthews, S. A.; Zharkova, V. V.


L. M. Green

S. A. Matthews

V. V. Zharkova


The first near-side X-class flare of Solar Cycle 24 occurred in February 2011 (SOL2011-02-05T01:55) and produced a very strong seismic response in the photosphere. One sunquake was reported by Kosovichev (Astrophys. J. Lett. 734, L15, 2011), followed by the discovery of a second sunquake by Zharkov, Green, Matthews et al. (Astrophys. J. Lett. 741, L35, 2011). The flare had a two-ribbon structure and was associated with a flux-rope eruption and a halo coronal mass ejection (CME) as reported in the CACTus catalogue. Following the discovery of the second sunquake and the spatial association of both sources with the locations of the feet of the erupting flux rope (Zharkov, Green, Matthews et al., Astrophys. J. Lett. 741, L35, 2011), we present here a more detailed analysis of the observed photospheric changes in and around the seismic sources. These sunquakes are quite unusual, taking place early in the impulsive stage of the flare, with the seismic sources showing little hard X-ray (HXR) emission, and strongest X-ray emission sources located in the flare ribbons. We present a directional time–distance diagram computed for the second source, which clearly shows a ridge corresponding to the travelling acoustic-wave packet and find that the sunquake at the second source happened about 45 seconds to one minute earlier than the first source. Using acoustic holography we report different frequency responses of the two sources. We find strong downflows at both seismic locations and a supersonic horizontal motion at the second site of acoustic-wave excitation.

Journal Article Type Article
Publication Date 2013-06
Journal Solar Physics
Print ISSN 0038-0938
Electronic ISSN 1573-093X
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 284
Issue 2
Pages 315-327
APA6 Citation Zharkov, S., Green, L. M., Matthews, S. A., & Zharkova, V. V. (2013). Properties of the 15 February 2011 Flare Seismic Sources. Solar Physics, 284(2), 315-327.
Keywords Sun: helioseismology; Sun: flares; Sun: X-rays; Gamma ray
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Copyright Statement
This is a post-peer-review, pre-copyedit version of an article published in Solar physics. The final authenticated version is available online at:

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