Statistical analysis of earthward flow bursts in the inner plasma sheet during substorms

In this article, we study the velocity distribution, density, duration, and energy transport of earthward flow bursts in the inner plasma sheet (IPS) during three substorm phases using the data of Cluster in 2001 and 2002. The mean peak velocity of earthward flow bursts in recovery phases (390 km/s) is smaller than those in growth and expansion phases (490 and 520 km/s). The super earthward flow bursts (V > 1000 km/s) appear more frequently in the expansion phase. The average ion density of earthward flow bursts in the recovery phase is 0.14 cm(-3), much smaller than those in growth and expansion phases (0.28 and 0.21 cm(-3)), indicating that lobe reconnections most likely occur in the recovery phase. The average durations of earthward flow bursts in recovery phase are 48 s, smaller than those in growth and expansion phases (99 and 103 s), suggesting that the reconnections occurring in recovery phase are rather short-lived. The earthward flow bursts in the expansion phase have largest capability of the transport of energy, about 7 times that in the recovery phase. Thus the earthward flow bursts in the expansion phase can produce largest impact effects to the inner magnetosphere.