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 Flows in a Helical Flux Rope
Credit: IRIS, LMSAL/NASA, Wei Liu
Solar prominences are cool, chromospheric-temperature material suspended in the million-degree hot corona. They often reside within the so-called coronal cavities of oval-shaped dark regions of lower density than the ambient corona. Coronal cavities are believed to be cross-sections of flux ropes threaded by helical magnetic field lines. In this movie, taken by IRIS at 2796 Angstrom on November 10, 2016, we see such a prominences embedded in the lower portion of a coronal cavity. The most intriguing feature here is the mass flows along circular paths, some in the clockwise direction, while others in the counter-clockwise direction. We believe these flows are channeled by the magnetic field lines on which the ionized plasma is frozen onto. Such flow patterns are consistent with the expectation in helical magnetic flux ropes, which can eventually erupt as coronal mass ejections (CMEs) and impact near-Earth space weather.