A multi-instrument analysis of a C4.1 flare occurring in a δ sunspot
- Dipartimento di Fisica e Astronomia—Sezione Astrofisica, Università di Catania, via S. Sofia 78, I-95123 Catania (Italy)
- INAF—Osservatorio Astrofisico di Catania, via S. Sofia 78, I-95123 Catania (Italy)
- Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, I-00133 Rome (Italy)
- INAF—Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monte Porzio Catone (Italy)
- NSO—National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States)
- LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon (France)
We present an analysis of multi-instrument space- and ground-based observations relevant to a C4.1 solar flare that occurred in the active region (AR) NOAA 11267 on 2011 August 6. Solar Dynamics Observatory observations indicate that at the flare’s beginning, it was localized in the preceding sunspot of the AR, which exhibits a δ configuration. Along the polarity inversion line between its opposite polarities we find a large shear angle of about 80°. The helicity accumulation shows that the AR does not obey the general hemispheric helicity rule. At the flare peak, unique observations taken with the X-Ray Telescope aboard Hinode reveal that the bulk of the X-ray emission takes place in the δ-spot region, where the plasma heats up to ≈1.9⋅10{sup 7} K. During the gradual phase, we observe the development of a Y-shaped structure in the corona and in the high chromosphere. An extruding structure forms, being directed from the emitting region above the δ spot toward the following sunspot. This structure cools down in a few tens of minutes while moving eastward along a direction opposite to the flare ribbon expansion. Finally, remote brightenings are found at the easternmost footpoint of this structure, appearing as a third flare ribbon in the chromosphere. After some minutes, RHESSI measurements show that the X-ray emission is localized in the region close to the crossing point of the coronal Y-shaped structure. Simultaneously, high-resolution (0.″15) observations performed at the Swedish 1 m Solar Telescope indicate a decreasing trend of the Ca ii H intensity in the flare ribbons with some transient enhancements. All these findings suggest that this event is a manifestation of magnetic reconnection, likely induced by an asymmetric magnetic configuration in a highly sheared region.
- OSTI ID:
- 22886946
- Journal Information:
- Astrophysical Journal, Vol. 819, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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