MHS model of an active region associated to a flare

LÓPEZ FUENTES, M.C.; MANDRINI, C.H.; ROVIRA, M.G.; DÉMOULIN, P.

Villa Elisa

Congreso; 42 Reunión Anual de la Asociación Argentina de Astronomía; 1998

Asociación Argentina de Astronomía

Using observations obtained by different instruments, we have analyzed the active region (AR) NOAA 7070 associated to an X3/B3 flare. The intense UV emission has been an outstanding characteristic of this event, 17 times larges than that of the whole solar disk. This is similar to the emission observed in stars in which flares are produced. We have modelled the atmospheric magnetic field, using a magnetohydrostatic approach using photospheric magnetograms as boundary conditions. The magnetic field presents a high shear close to the AR inversion line. This is seen not only in the transverse component of the photospheric, but also in the coronal loops observed in X-rays. The high shear of the coronal loops disappears after the flare, and they show a topology closer to that of a potential field. This is in agreement with what is expected when the field relaxes after the stored energy has been released. Using the magnetic virial theorem, and after the computed model, we estimate that the energy variation is enough to account for the observed flare.