Characteristics of Coronal Inflows

Abstract

This paper describes coronal inflows observed with the Large Angle Spectrometric Coronagraph (LASCO). The inflows are not seen above 5.5 R_solar, which appears to be a ``point of no return'' for the Sun's plasmas and fields. Below this height, most inflows seem to indicate magnetic flux that is returning to the Sun after its reconnection at sector boundaries. Some inflows have characteristics (like fast, oppositely directed ejections of material) that are easily interpreted in terms of conventional models of field line reconnection. However, the overwhelming majority of coronal inflows have a more complex behavior that typically includes the following characteristics:1. The birth of a very weak, localized density enhancement about 4-5 R_solar from Sun center and its initially slow downward motion along a coronal ray;2. Acceleration to a maximum speed of 50-100 km s^-1, and the formation of a sinking column;3. Deceleration and the appearance of a dark depletion tail, visible against the bright background structures in the lower corona;4. The formation of a stretched loop below about 2.5 R_solar.We suppose that the initial downward motion is a preparatory stage for reconnection, which occurs in the depleted region in the wake of the sinking column and is later revealed by the formation of a stretched loop in the lower corona.