Prominences do the catwalk
posted: July 31, 2013

The month of July saw some really great prominence activity. Prominences are relatively cool and dense structures reaching all the way up into the Sun's hot outer atmosphere. This movie shows nine events picked from a long list.

All events in this movie show the chromospheric dynamics as seen through SDO's AIA 304 filter. With this wavelength, we observe plasma at a temperature of 50,000 degrees. The plasma in the higher chromosphere and lower transition region emits at this wavelength. A temperature of 50,000 degrees is higher than the temperature of the plasma seen in Hydrogen-alpha (H-alpha, 656.3 nm), but much cooler than most of the other extreme ultraviolet (EUV) filters of SDO. Hence, these "cool" prominences seen in 30.4 nm are usually somewhat beefed up compared to H-alpha (left image underneath; 9 May 2013), whereas they are hardly visible in the "hotter" SDO filters such as AIA 193 (near 1 million degrees; right image underneath). There, if visible at all, they are mostly observed as dark features against the brighter coronal background.

Thereís quite a variety in the prominences shown. For example, the first is by far the largest and most solid prominence eruption of the series. Events 2 and 7 are actually the same active area separated by half a solar rotation. They are no real eruptions, but display dynamical chromospheric activity in which plasma (charged particles) condensates in the Sunís atmosphere before it falls towards the surface along the magnetic field lines. Event 5 had material travelling about one seventh of the solar circumference in less than 3 hours. Thatís an apparent speed of about 65 km/s! Events 3 and 9 were just cute little rings, manner of speaking. Surely, these July prominences knew how to show themselves from their best side!