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 d 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 delta-spot region, where the plasma heats up to 1.9 . 10(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 delta 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, highresolution (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.
|Titolo:||A MULTI-INSTRUMENT ANALYSIS OF A C4.1 FLARE OCCURRING IN A delta SUNSPOT|
|Data di pubblicazione:||2016|
|Appare nelle tipologie:||1.1 Articolo in rivista|