Statistical analysis of the plasmaspheric plume at the magnetopause

During times of enhanced magnetospheric convection, cold dense plasma from the plasmasphere can form a plume extending sunward toward the dayside magnetopause. A statistical study is presented of cold high-density plasmaspheric plasma at the magnetopause. Observations from the Time History of Events and Macroscale Interactions (THEMIS) spacecraft show the plume to be present at the dayside magnetopause during 12.5% (148 of 1184) of the crossings. Its most common location in magnetic local time when contacting the magnetopause is at 13.6 h. The magnetopause crossings show evidence for reconnection in 68% of events with the plume while only 47% of events without plume. Although the plume is more likely to be observed at the magnetopause when reconnection is occurring, the typical reconnection jet velocity is lower for plume events than nonplume events, indicating the presence of the plume may be slowing the efficiency of the reconnection process.