Followup to last week's Nugget -- The Sigmoid That Wouldn't Quit

Science nugget: June 19, 1998

Last week we reported on a beautiful S-shaped active region, which blasted a CME towards the Earth. This week's short Science Nugget is a followup: after the coronal mass ejection of 11-Jun-98, it was noted that the region was still "sigmoidal", though it didn't describe such a perfect S-shape. Since it seems that sigmoidal active regions are more likely to spawn coronal mass ejections, this might have been interpreted as meaning the region was still capable of eruption, even after 11-jun-98.

The region did in fact erupt again, after rotating behind the southwest limb of the Sun. On 16-jun-98, the region spawned a beautiful CME that was captured in images by SXT and LASCO. The event registered as an M-class flare (see the GOES plot above).

An SXT movie is available at URL:

http://www.solar.isas.ac.jp/~freeland/movies/98jun16_oldsigmoid_small.html (smaller version) http://www.solar.isas.ac.jp/~freeland/movies/98jun16_oldsigmoid.html (larger version)

LASCO movies are available at URL:

http://lasco-www.nrl.navy.mil/daily_mpg/1998_06/980616_c2.mpg (C2 movie) http://lasco-www.nrl.navy.mil/daily_mpg/1998_06/980616_c3.mpg (C3 movie) The LASCO movies show a number of CMEs. The very fast one at the end of the movie corresponds to this event.

D. McKenzie (mckenzie@isass0.solar.isas.ac.jp) and G. Simnett : June 19, 1998