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.
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4 Apr 2017
Heading to the solar minimum
Credit: IRIS, LMSAL/NASA, Wei Liu (IRIS Planner of the week)
The Sun has an 11-year activity cycle. At the moment, we are heading toward the solar minimum, with the Sun being progressively quiet. For about a week, there was no sunspot or active region visible on the Sun. This movie, captured by IRIS on 2017-March-19, shows a very minor GOES-A6.5 class flare, which was about 100 times weaker than a moderate C-class flare. Yet, this was the largest flare of the entire week, indicating the Sun is indeed getting very quiet. Meanwhile, it is interesting to note that, even small in magnitude, this flare still exhibits a two-ribbon morphology, often seen in large flares. That said, by the time of the writing (2017-April-03), the Sun has produced some large flares including two > M5 class in the past few days from AR 12644. This indicates that the path to solar minimum is not straight, but will have some episodes with temporarily enhanced activity levels.