Propagation velocities and dimensions of plasmoid structures in the near‐Earth magnetotail

Abstract

Measurements from the High Energy Particle‐Low energy particle Detector experiment (HEP‐LD) and Magnetic Field experiment (MGF) onboard the GEOTAIL spacecraft are used to estimate characteristic flow velocities and scale sizes of plasmoid structures released in the near‐Earth magnetotail during substorm events. Bulk velocities are derived from the azimuthal distribution of energetic ions and typical scale sizes are thereafter calculated from the duration of the plasmoid signatures. The results show great variability from one event to another. Velocities range from 250–700 km/s and scale sizes were in the range 3–9 RE for the events studied. Despite the great variability, the velocities are somewhat lower than earlier observations from the distant tail.