Multi-Spacecraft Analysis of Dipolarization Events With Inductive, Radial Electric Fields in the Inner Magnetosphere

Abstract

Dipolarization events with inductive, radial electric fields are investigated with multi-spacecraft analysis techniques. Observations by Magnetospheric Multiscale with separations around ion scales are used to study spatial and temporal variations of these events in the inner magnetosphere. $J\times B$ force, magnetic pressure force, and tension force are compared based on the Taylor expansion method, which includes the curlometer technique. The magnetic pressure force, possibly related to energetic particles and magnetic flux transported from the magnetotail, tends to contribute to the $J\times B$ force for the background components near the equator, while the tension force, related to Alfvén waves, contributes to the fluctuating components or outside the equator. The scale length is thousands of km for the background components, probably related to meso-scale structures, while that length is tens to a thousand km for fluctuating components. The small-scale fluctuations would be related to particle acceleration. The fluctuations are inferred to be Alfvén waves with quasi-perpendicular propagation directions and with finite temperature or kinetic effects. These fluctuations could be intermittent and not self-similar between different inter-spacecraft distances. Some energy transfer from fluctuations to particles would occur.