Multiple X-line reconnection in the earth's magnetosphere

A comprehensive review of the multiple X-line reconnection process is made. It is found that magnetic reconnection occurs either with single or multiple X-lines, depending on several conditions. The multiple X-line reconnection process tends to occur when the system length is long, the reconnection rate is high, or the resistivity is small. The multiple X-line reconnection is a time-dependent process and may lead to the repeated formation and convection of plasmoids (or magnetic flux tubes). The multiple X-line reconnection may lead to the occurrence of flux transfer events observed at the earth's dayside magnetopause and the formation of substorms and plasmoids observed in the magnetotail. It appears that multiple X-line reconnection occurs more frequently than the classical single X-line reconnection. A criterion for the transition from a single X-line to a multiple X-line reconnection is obtained.