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Lost and found sunquake in the 6 September 2011 flare caused by beam electrons
摘要： The active region NOAA 11283 produced two X-class ?ares on 6 and 7 September 2011 that have been well studied by many authors. The X2.1 class ?are occurred on September 6, 2011 and was associated with the ?rst of two homologous white light ?ares produced by this region, but no sunquake was found with it despite the one being detected in the second ?are of 7 September 2011. In this paper we present the ?rst observation of a sunquake for the 6 September 2011 ?are detected via statistical signi?cance analysis of egression power and veri?ed via directional holography and time–distance diagram. The surface wavefront exhibits directional preference in the north-west direction We interpret this sunquake and the associated ?are emission with a combination of a radiative hydrodynamic model of a ?aring atmosphere heated by electron beam and a hydrodynamic model of acoustic wave generation in the solar interior generated by a supersonic shock. The hydrodynamic model of the ?aring atmosphere produces a hydrodynamic shock travelling with supersonic velocities toward the photosphere and beneath. For the ?rst time we derive velocities (up to 140 km s?1) and onset time (about 50 s after ?are onset) of the shock deposition at given depths of the interior. The shock parameters are con?rmed by the radiative signatures in hard X-rays and white light emission observed from this ?are. The shock propagation in the interior beneath the ?are is found to generate acoustic waves elongated in the direction of shock propagation, that results in an anisotropic wavefront seen on the solar surface. Matching the detected seismic signatures on the solar surface with the acoustic wave front model derived for the simulated shock velocities, we infer that the shock has to be deposited under an angle of about 30? to the local solar vertical. Hence, the improved seismic detection technique combined with the double hydrodynamic model reported in this study opens new perspectives for observation and interpretation of seismic signatures in solar ?ares.
关键词： Sun: X-rays, gamma rays,radiative transfer,Sun: ?ares,Sun: helioseismology,hydrodynamics
更新于2025-09-23 15:21:21
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Large-scale photospheric motions determined from granule tracking and helioseismology from SDO/HMI data
摘要： Context. Large-scale ?ows in the Sun play an important role in the dynamo process linked to the solar cycle. The important large-scale ?ows are the differential rotation and the meridional circulation with an amplitude of km s?1 and few m s?1, respectively. These ?ows also have a cycle-related components, namely the torsional oscillations. Aims. Our attempt is to determine large-scale plasma ?ows on the solar surface by deriving horizontal ?ow velocities using the techniques of solar granule tracking, dopplergrams, and time–distance helioseismology. Methods. Coherent structure tracking (CST) and time-distance helioseismology were used to investigate the solar differential rotation and meridional circulation at the solar surface on a 30-day HMI/SDO sequence. The in?uence of a large sunspot on these large-scale ?ows with a speci?c 7-day HMI/SDO sequence has been also studied. Results. The large-scale ?ows measured by the CST on the solar surface and the same ?ow determined from the same data with the helioseismology in the ?rst 1 Mm below the surface are in good agreement in amplitude and direction. The torsional waves are also located at the same latitudes with amplitude of the same order. We are able to measure the meridional circulation correctly using the CST method with only 3 days of data and after averaging between ±15? in longitude. Conclusions. We conclude that the combination of CST and Doppler velocities allows us to detect properly the differential solar rotation and also smaller amplitude ?ows such as the meridional circulation and torsional waves. The results of our methods are in good agreement with helioseismic measurements.
关键词： Sun: helioseismology,Sun: granulation,Sun: atmosphere,Sun: rotation
更新于2025-09-09 09:28:46