Proposed interpretation of complex seismic and radiative signatures associated with the X9.3-class flare of 6 September 2017

Abstract:

We propose the interpretation of multi wavelength observations of the flare of 6 September 2017 with the sunquake with a second bounce. The flare observations in HXR, GR, Lyα, EUV, Hα, and WL emission were obtained with strongly varying spatial resolution and temporal coverage. We propose some likely scenarios for heating of flaring atmospheres in the footpoints with sunquakes, which were supported with EUV and Hα emission by generating hydrodynamic models with the radiative hydrodynamic code HYDRO2GEN. The simulated results can account for the blueshifts derived from the EUV emission and the redshifts observed in the He II line with the EUV Imaging Spectrometer and in Hα line emission by the CRisp Imaging Spectro-Polarimeter in the Swedish Solar Telescope. The parameters of hydrodynamic shocks produced by particle beams in flaring atmospheres were used as the initial conditions for the hydrodynamic models of acoustic wave generation in the solar interior. The Hα line profiles with large redshifts observed in three kernels were interpreted with the full NLTE radiative simulations in all optically thick transitions applied for flaring atmospheres with fast downward motions. We considerthermal and non-thermal excitation and ionisation of hydrogen atoms by energetic power-law electron beams. The observed Hα line profiles in three kernels were fit with the simulate blue wing emission of the Hα line profiles shifted significantly (by 4-6 Å) towards the red wings, because of strong downward motions with velocities about 300 km s^-1 by the shocks generated by powerful beams. The flaring atmosphere associated with the largest sunquake with a second bounce is found consistent with being induced by a strong hydrodynamic shock produced by a mixed beam deposited at an angle of -30° from the local vertical. We explain the occurrence of a second bounce in the largest sunquake by a stronger momentum delivered by the shock generated in the flaring atmosphere by a mixed beam and deeper depths of the interior where this shock was deposited. The wave characteristics of seismic sources 1 and 3 were consistent with those produced by the shocks generated by mixed beams deposited at different angles to the local vertical. The differences of seismic signatures produced in the flares of 6 September 2011 and 2017 are also discussed.