Abstract:
Using multiwavelength observations from the Solar Dynamics Observatory
(SDO) and the Solar Terrestrial Relations Observatory (STEREO), we investigate the mechanism of two successive eruptions (F1 and F2) of a filament in active region NOAA 11444
on 27 March 2012. The filament was inverse J-shaped and lay along a quasi-circular polarity
inversion line (PIL). The first part of the filament erupted at ∼ 2:30 UT on 27 March 2012
(F1), the second part at around 4:20 UT on the same day (F2). A precursor or preflare brightening was observed below the filament main axis about 30 min before F1. The brightening
was followed by a jet-like ejection below the filament, which triggered its eruption. Before
the eruption of F2, the filament seemed to be trapped within the overlying arcade loops
for almost 1.5 h before it successfully erupted. Interestingly, we observe simultaneously
contraction (∼ 12 km s−1) and expansion (∼ 20 km s−1) of arcade loops in the active region
before F2. Magnetograms obtained with the Helioseismic and Magnetic Imager (HMI) show
converging motion of the opposite polarities, which result in flux cancellation near the PIL.
We suggest that flux cancellation at the PIL resulted in a jet-like ejection below the filament
main axis, which triggered F1, similar to the tether-cutting process. F2 was triggered by
removal of the overlying arcade loops via reconnection. Both filament eruptions produced
high-speed (∼ 1000 km s−1) coronal mass ejections.
