MESSENGER Observations of Multiple Magnetic Energy Releases during Mercury’s Substorm

Abstract Substorms are energy storage and dissipation processes that occur in planetary magnetospheres accompanied by numerous phenomena, such as magnetic dipolarizations, plasma sheet thinning thickening, flux ropes, plasmoid ejections. Recent MESSENGER observations have revealed substorm activity Mercury’s near magnetotail, with average durations of 2–3 minutes for both the growth expansion phases. Herein, we report spacecraft sporadic short-term during phase magnetotail. Three dipolarizations lasting ∼4 were detected manifested step-like enhancements northward component field. The field strength decreased each dipolarization, indicating an intermittent release energy. They arise owing to multiple pileup effects caused planetward bursty bulk flows ejected from distant magnetotail reconnections. Additionally, close proximity observed occurrence pulse-like fluctuations B y component. These new suggest substorm, can be local transient processes, although duration is much shorter than Earth.