Team-building activity for sunspot groups
posted: November 6, 2013

Every year, many companies organize activities for their personnel in order to have some fun and to strengthen the team spirit. Late October, some sunspot groups got the same idea. However, their idea of a fun team-building activity was quite different: Together, they wanted to destroy a nearly million km long solar filament. This spectacular movie reveals how they did it.

The team of sunspot groups consisted of NOAA 1875, 1877 and 1882. These complex groups (see the previous STCE Newsletter) produced several strong flares and were certainly up for the job. The unsuspecting victim was a collection of filamentary bits and pieces around two big blobs of "cold" plasma on the southern hemisphere (see annotated H-alpha image above). The small filamentary pieces were better visible in EUV filters such as AIA 304, indicating that they consisted of slightly hotter material than the two H-alpha blobs (see image below).

The westward (trailing) part of the filament erupted during the morning hours of 25 October, following the X1.7 flare in NOAA 1882. See the previous STCE Newsletter for more details on this eruption. Image underneath shows the fading flare in NOAA 1882 simultaneously with the already rising westward part of the filament. Interestingly, this filament eruption did not seem to have produced a (substantial) coronal mass ejection (CME).

NOAA 1875 was more subtle. Instead of brute force, it used several small C-flares to induce a major magnetic restructuring between NOAA 1875 and 1877, including a material ejection and a transient coronal hole. This resulted in the eastern (rightmost) plasma blob to become unstable and erupt starting around 09:00UT on 26 October. It produced a very nice CME with core filament. The magnetic restructuring is best visible in EUV filters showing the million degree hot corona.

Following spectacular X- and M-class flaring activity in sunspot region NOAA1875 early on 28 October, the magnetic fields around NOAA1877 became unstable and an M1.4-flare occurred peaking at 11:53UT. The restructuring magnetic fields caused a violent ejection of the remaining filament. Here too, a not-Earth-directed CME could be observed.

Mission accomplished: great teamwork by the sunspot groups resulted in the annihilation of a million km long solar filament!

Credits - Images were taken from the GONG H-alpha Network, SDO, SOHO and Helioviewer.