The Thermal Nonequilibrium of Prominences

We present numerical simulations and analytic theory for the thermal nonequilibrium of solar coronal flux tubes that have a stretched-out, dipped geometry, appropriate for a prominence/filament. Our simulations indicate that if the heating in such a flux tube is localized near the chromosphere, then condensations appear which undergo a continuous cycle of formation, motion, and destruction, even though the heating and all other imposed conditions on the loop are purely time independent. We show how this nonsteady evolution can be understood in terms of simple scaling-law theory. The implications of thermal nonequilibrium for observations of the solar corona are discussed. We argue that the model can explain both the formation of prominence condensations and recent observations of their dynamics.