What with all the surprise activity of the Sun at solar minimum of late, I’ve found myself looking around the solar observation sites an awful lot more than I used to. During all the commotion back in 2003 when the Sun was blasting out record breaking X-ray flares one after another, I really didn’t think I could be surprised with anything else the Sun would do. That was until, very much unannounced, three sunspots rotated into view, blasting another X-ray flare into space… at solar minimum. The strange thing was, that these sunspots weren’t even from this solar cycle, they were from the previous one that ended some time around December 2007! And now we get a stunning, detailed view of more unexpected solar activity from the Solar Terrestrial Relations Observatory (STEREO), a hi-res video of dynamic coronal loops…
On April 18th-19th, the “Behind” STEREO probe (there are two probes, one “Ahead” and one “Behind” the Earth’s orbit) observed a region of heightened coronal loop activity. Looking at the images, and the latitudes, I’m fairly certain the loops are anchored in the old sunspots left over from the previous cycle. Again, the long duration of these spots have surprised me, especially considering how energetic the region is. Regardless, STEREO is continuing to improve our understanding of the dynamic magnetic flux and highly radiating coronal loops. Take a look at this video of the long EUV coronal loops as observed at 171A (plasma at approximately 1 million Kelvin).
What I most enjoyed in this video are the flashes of EUV microflares across the solar disk. In the 40 hours of observation time, the surface appears to sparkle as magnetic flux twists and reconnects, flaring. It is obvious that huge quantities of hot plasma are being heated as it travels along the coronal loops, the extent of which is pretty surprising.
It is solar missions such as STEREO that give solar physicists the perfect opportunity to observe the Sun at high resolution and high cadence (each frame in the video is taken 2.5 minutes apart) so small-scale and short-period features can be observed to propagate.
Thanks Susan Martin at the Mars Foundation for the heads up!
Source: SOHO Pick of the Week