This talk will present MHD simulations of a confined filament eruption, which produced a solar flare but no coronal mass ejection. The onset of the event (on 2002 May 27) was modeled in Toeroek & Kliem (2005), using the magnetic flux rope equilibrium by Titov & Demoulin (1999) as the initial condition. The event was found to be a good candidate for the occurrence of the helical kink instability, but a relatively high value for the magnetic twist, 2.5 field line turns, was estimated. Now the eruption is followed into the main flare phase.  This is characterized by a sequence of two reconnection events involving the magnetic flux of the rope (the filament) as well as the ambient, overlying flux. First, the top part of the rope reconnects with the ambient flux. Second, the legs of the resulting split rope approach each other and reconnect. This leads to the reformation of a flux rope, with less twist, and also restores the overlying flux. The shapes of the field lines which reconnect in steps 1 and 2 correspond well to the observed flare loops. These showed considerable brightness, although the eruption remained confined. This appears plausible from the fact that these loops were involved in two phases of reconnection, each of which contributed to the heating of the flare plasma. The reformation of the flux rope may yield a path to homologous flare events; however, the reformed rope is only rather weakly twisted. Overall, the sequence of ideal MHD instability and magnetic reconnection corresponds well to the observations of the eruption. A parametric study is performed, varying all key parameters of the initial equilibrium. This yields a lower and apparently more realistic estimate for the twist at eruption onset of about 1.7 field line turns.

中国科学院天体结构与演化重点实验室