M6 flare in NOAA 1967
posted: February 6, 2014

On 27 January, a big, complex region rounded the Sun's east limb and was labelled NOAA 1967. This large sunspot group was the return of NOAA 1944 which appeared early January and was very active at that time, including 7 M- and 1 X-class flare. Using solar eclipse glasses, both groups were easy naked-eye objects.

During the week, NOAA 1967 increased its sunspot area and magnetic complexity. So far, this has resulted in 34 C- and 20 M-class flares. The strongest flare occurred on 30 January (M6.6 peaking at 16:11UT) and was associated with a filament eruption east of NOAA 1967's trailing portion.

Interestingly, this flare did not take place in one of the various strong delta structures of the group (sunspots of opposite magnetic polarity very close to each other: see this STCE news item). Instead, the eruption took place behind the main spots of the group's trailing section.

The mosaic underneath shows the various phases of this flare (15:00-18:00UT). First, there was a small flare just behind the filament resulting in a fan shaped plasma ejection. This event resulted in the filament becoming unstable and being ejected. The brightest phase of the flare took place near the top end of the area where the filament was ejected. Finally, over the location of the blast site, a series of post-flare coronal loops were formed (a so-called "arcade").

This movie first shows the evolution of NOAA 1967 in white light from 30 January till 2 February. Then follow 3 movies in successively higher temperatures (SDO/AIA 304, 171 and 131) showing the evolution of the M6-event from 15:00UT till 18:00UT. In the beginning of each of these 3 movies, the end of a partial lunar eclipse can be seen and the Sun is a little bit shaky. Indeed, the fine guidance systems on AIA and HMI can't work because they need to see the whole Sun to keep the images centered from exposure to exposure. Steady images resumed once the eclipse was over.

The movie ends with LASCO/C2 clips from the associated full halo coronal mass ejection (CME) in white light and difference imagery, first seen in LASCO/C2 (see SOHO) images at 16:12UT. The glancing blow of this CME arrived late on 2 February, but the impact was weak and geomagnetic conditions remained quiet.