Field-aligned and Magnetic Reconnection Flows in a Magnetohydrodynamic Simulation of Prominence-cavity System

Abstract

Nested ring-shaped line-of-sight (LOS) oriented flows in coronal cavities have been observed in recent years but rarely explained. Using a magnetohydrodynamic simulation of a prominence-cavity system, we investigate the relationship between the simulated field-aligned flows, magnetic reconnection flows, and the LOS-oriented flows observed by the Coronal Multi-Channel Polarimeter. The field-aligned flows are along magnetic field lines toward the dips and driven by the hydrodynamic forces exerted by the prominence condensation. The reconnection flows are driven by the overlying reconnection and tether-cutting reconnection. The velocity of the reconnection flows increases from the quasi-static phase to the fast-rise phase, reaching several kilometers per second, which is similar to the speed of the field-aligned flows. We calculate the synthetic Doppler images by forward modeling and compare them with the observed LOS-oriented flows. The synthetic images show that the LOS-oriented flows of one ring with opposite internal flow driven by the field-aligned flows are identified in the simulation. And the synthetic images integrated along three different LOSs can resemble the observed direction reversal of the LOS-oriented flow in about 20 hr, when the included angle of two adjacent LOSs is about 10°. These results suggest that the observed LOS-oriented flows of one ring with an opposite internal flow may be explained by the LOS integration effect of field-aligned flows along different loops.