Reconnection and flows in the Jovian magnetotail as inferred from magnetometer observations

摘要

In Jupiter's magnetosphere, events such as flow bursts and changes to the magnetic field are thought to be driven predominantly by internal processes. Analysis of energetic particle data has established that flow bursts are associated with magnetic reconfiguration in the Jovian magnetotail, Here we use magnetometer data throughout the Jovian magnetotail to identify events that we relate to reconnection and flow. Using quantitative criteria, we have identified 249 reconnection events that are characterized by reversals or significant increases in B0, the north-south component of the magnetic field, over background levels. We discuss the distribution of the events, their occurrence rate, and location inside or outside of a putative neutral line, as functions of radial distance and local time. Using the sign of B0 as a proxy for the flow direction, we establish the location of a statistical separatrix and find that its radial distance varies with local time. Where particle signatures of events in our data set have also been analyzed, they generally show increases of anisotropy. However, we have identified scores of additional events that have not been previously identified in the particle data; many of these new events occur in the premidnight local time sector. Finally, we examine our events for the 2-3 day periodicity that has been reported for flow bursts and auroral polar dawn spots and find that this periodicity is present only intermittently and is not statistically significant.