Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017

Abstract

The X9.3 flare of September 6, 2017, was the most powerful flare of Solar Cycle 24. It generated strong white-light emission and multiple helioseismic waves (sunquakes). By using data from Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) as well as hard X-ray data from KONUS instrument onboard WIND spacecraft, and Anti-Coincidence System (ACS) onboard the INTERGRAL space observatory, we investigate spatio-temporal dynamics of photospheric emission sources, identify sources of helioseismic waves and compare the flare photospheric dynamics with the hard X-ray (HXR) temporal profiles. The results show that the photospheric flare impacts started to develop in compact regions in close vicinity of the magnetic polarity inversion line (PIL) in the pre-impulsive phase before detection of the HXR emission. The initial photospheric disturbances were localized in the region of strong horizontal magnetic field of the PIL, and, thus, are likely associated with a compact sheared magnetic structure elongated along the PIL. The acoustic egression power maps revealed two primary sources of generation of sunquakes, which were associated with places of the strongest photospheric impacts in the pre-impulsive phase and the early impulsive phase. This can explain the two types of helioseismic waves observed in this flare. Analysis of the high-cadence HMI filtergrams suggests that the flare energy release developed in the form of sequential involvement of compact low-lying magnetic loops that were sheared along the PIL.

24 pages, 8 figures, submitted to ApJ

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Cited by in corpus (8)

• Spectral Analysis of the September 2017 Solar Energetic Particle Events
• Gamma-ray emission from the impulsive phase of the 2017 September 06 X9.3 flare
• Sunquakes of Solar Cycle 24
• The Chromospheric Response to the Sunquake generated by the X9.3 Flare of NOAA 12673
• Response of SDO/HMI observables to heating of the solar atmosphere by precipitating high-energy electrons
• The 2017 September 6 Flare: Radio Bursts and Pulsations in the 22-5000 MHz Range and Associated Phenomena
• The magnetic field environment of active region 12673 that produced the energetic particle events of September 2017
• Flare Induced Sunquake Signatures in the Ultraviolet as Observed by the Atmospheric Imaging Assembly