IRIS Movie of the Day
At least once a week a movie of the Sun taken by NASA's Interface Region Imaging Spectrograph (IRIS) is posted by one of the scientists operating the instrument.
Prominence bubble formation
Credit: IRIS, LMSAL/NASA, Milan Gosic
On 01-October-2018 IRIS captured quite a rare phenomenon, formation of a prominence bubble. Prominences represent cool gas at coronal heights. Compared to the surrounding million Kelvin hot coronal plasma, prominences are about 100 times cooler, and also about 100 times denser. Prominence bubbles are large, dark voids or cavities pushing up into quiescent prominences from below. They are induced by emerging flux beneath the preexisting prominences. These bubbles are typically ~10 Mm large and cease to move at heights of 5-10 Mm. Eventually, prominence bubbles become unstable when they transform into one large plume or a series of smaller ones.