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.
Counter-streaming Flows in a Solar Prominence
Credit: IRIS, LMSAL/NASA, Wei Liu
Solar prominences are cool, chromospheric-temperature material suspended in the million-degree hot corona. This prominence, observed by IRIS on 2018-Mar-9 on the northwest solar limb, shows multiple threads mainly in the horizontal direction. There are interesting mass flows in opposite directions on neighboring threads. These are so-called counter-streaming flows that often appear in on-disk filaments as well and have been seen in H-alpha observations. The cause of such flows in opposite directions is still a mystery, but it has to do with the pressure gradient along those prominence threads. Some of these flows also exhibit wavy motions that are likely manifestations of Alfvenic waves present on the magnetic field lines supporting those prominence threads.