Sunquake with a second bounce, other sunquakes, and emission associated with the X9.3 flare of 6 September 2017. I. Observations |
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Valentina Zharkova Submitted: 2020-05-12 14:26
The 6 September 2017 X9.3 solar flare produced very unique observations of magnetic field transients and a few
seismic responses, or sunquakes, detected by the Helioseismic and Magnetic Imager (HMI) instrument aboard Solar Dynamic
Observatory (SDO) spacecraft, including the strongest sunquake ever reported. This flare was one of a few flares occurring
within a few days or hours in the same active region. Despite numerous reports of the fast variations of magnetic field, and
seismic and white light emission, no attempts were made to interpret the flare features using multi-wavelength observations.
In this study, we attempt to produce the summary of available observations of the most powerful flare of the 6 September
2017 obtained using instruments with different spatial resolutions (Paper 1) and to provide possible interpretation of the flaring
events, which occurred in the locations of some seismic sources (paper 2). We employed non-linear force-free field (NLFFF)
extrapolations followed by magnetohydrodynamic simulations in order to identify the presence of several magnetic flux ropes
prior to the initiation of this X9.3 flare. Sunquakes were observed using the directional holography and time–distance diagram
detection techniques. The high-resolution method to detect the Hα line kernels in the CRISP instrument at the diffraction level
limit was also applied. We explore the available gamma-ray (GR), hard X-ray (HXR), Lyman-α, and extreme ultra-violet (EUV)
emission for this flare comprising two flaring events observed by space- and ground-based instruments with different spatial
resolutions. For each flaring event we detect a few seismic sources, or sunquakes, using Dopplergrams from the HMI/SDO
instrument coinciding with the kernels of Hα line emission with strong redshifts and white light sources. The properties of
sunquakes were explored simultaneously with the observations of HXR (with KONUS/WIND and the Reuven Ramaty High
Energy Solar Spectroscopic Imager (RHESSI) payload), EUV (with the Atmospheric Imaging Assembly (AIA/SDO and the
EUV Imaging Spectrometer (EIS) aboard Hinode payload), Hα line emission (with the CRisp Imaging Spectro-Polarimeter
(CRISP) in the Swedish Solar Telescope (SST)), and white light emission (with HMI/SDO). The locations of sunquake and
Hα kernels are associated with the footpoints of magnetic flux ropes formed immediately before the X9.3 flare onset. For the
first time we present the detection of the largest sunquake ever recorded with the first and second bounces of acoustic waves
generated in the solar interior, the ripples of which appear at a short distance of 5-8 Mm from the initial flare location. Four
other sunquakes were also detected, one of which is likely to have occurred 10 minutes later in the same location as the largest
sunquake. Possible parameters of flaring atmospheres in the locations with sunquakes are discussed using available temporal
and spatial coverage of hard X-ray, gamma-ray, EUV, hydrogen Hα-line, and white light emission in preparation for their use
in an interpretation to be given in Paper 2.
Authors: S. Zharkov, S. Matthews, V. Zharkova, M. Druett, S. Inoue, I. E. Dammasch, C. Macrae
Projects:
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Publication Status: AStronomy and Astrophysics, in press
Last Modified: 2020-05-14 08:57
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