Magnetic reconnection: a common origin for flares and AR interconnecting arcs

BAGALÁ. L.G.; MANDRINI, C.H.; ROVIRA, M.G.; DÉMOULIN, P.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2000 vol. 363 p. 779 - 788

0004-6361

We present a study of active region (AR) 7031, where several flares occurred throughout the last week of January, 1992. We analyze in detail the three largest flares, both in Halpha and soft X-rays. During its transit across the disk this region interacted with another one (AR 7038), as indicated by the recurrent brightening in soft X-rays of an interconnecting loop, accompanied by sympathetic flaring. Using a linear force free extrapolation of the photospheric magnetic field, we compute the locations of Quasi-Separatrix Layers (QSLs), which are the likely places where the magnetic field can reconnect. We find that flare brightenings can be linked by field lines having footpoints at the QSLs. Furthermore, field lines connecting AR 7031 and AR 7038 belong to the QSLs computed when magnetograms from both ARs are combined. We conclude that both soft X-ray flare loops and interconnecting loops result from magnetic reconnection at the QSLs. Which of the many QSLs found in the computations are the site of magnetic reconnection depends on the magnetic field evolution. In the studied ARs we can identify three different drivers for energy release: flux emergence, photospheric displacements of the polarities and nearby magnetic reconnection. This last process leads to sympathetic flaring and to the brightness enhancement of the interconnecting arc.