Structure and statistical properties of plasmoids in Jupiter's magnetotail

摘要

Plasmoids and other reconnection-related signatures have been observed in Jupiter's magnetotail through analysis of magnetic field and energetic particle data. Previous studies have established the spatial distribution and recurrence period of tail reconnection events, and identified the location of a statistical X-line separating inward and outward flow. Here we present new analysis focusing specifically on 43 plasmoid signatures observed in magnetometer data in order to establish the average properties and internal structure of Jovian plasmoids. We present statistics on the observed plasmoid length scale, duration, radial position, and local time distribution. On average, the observed plasmoids have a similar to 3 R-J radial extent and similar to 7min duration and result in the closure of similar to 4-8 GWb of open flux from reconnection of open field lines in the postplasmoid plasma sheet. We also determine the amount of mass released and the magnetic flux closed in order to understand the role of tail reconnection in the transport of mass and flux in Jupiter's magnetosphere. The observed plasmoid properties are consistent with a mass loss rate of similar to 0.7-120kg/s and a flux closure rate of similar to 7-70 GWb/d. We conclude that tail reconnection and plasmoid release is an important method of flux transport at Jupiter but likely cannot account for the mass input from Io, suggesting that additional mass loss mechanisms may be significant. Finally, we examine the plasmoid interior structure through minimum variance analysis and find that most plasmoids lack a core field and are better described by magnetic loops rather than flux ropes.