Solar Prominence Formation by Thermal Nonequilibrium

Judy Karpen (NRL)

Solar prominences (called filaments when seen on the disk) have been observed for centuries, yet their structure and origin remain enigmatic. They consist of predominantly dynamic, cool, dense, material suspended in the corona above filament channels, which are regions of highly stressed magnetic fields narrowly surrounding polarity inversion lines. The thermal nonequilibrium model for prominence formation provides an explanation for the well-observed presence of predominantly dynamic, cool, dense, material suspended in the corona above filament channels. According to this model, condensations form readily along long, low-lying magnetic field lines when heating is localized near the chromosphere. Often this process yields a dynamic cycle in which condensations repetitively form, stream along the field, and ultimately disappear by falling onto the nearest footpoint. I will briefly review the characteristics of solar prominences, summarize the thermal nonequilibrium model, present our recent results of a numerical investigation of impulsive (nanoflare) heating in a model prominence flux tube, and compare the outcome with steady-heating simulations and prominence observations. These results place important constraints on coronal heating in filament channels, and strengthen the case for thermal nonequilibrium as the process responsible for the plasma structure in prominences.