Energetic oxygen ion bursts in the distant magnetotail

This paper reports on the characteristics of Of beam sequences detected in GEOTAIL/HEP-LD observations in the distant tail (X=-60 and -90 Re). The relationship to concurrent plasma and magnetic field data is also discussed. The energetic O+ burst usually last only 20 to 30 minutes, exhibit strong beam-like structures, appear after substorm onset are located in the post plasmoid plasma sheet (PPPS), and are embedded in plasma flowing tailward at very high speeds (exceeding 1000Km/s). The bulk speed of the oxygen beam indicate that these ions were accelerated to the same velocity as the plasma. The energy dispersion in the oxygen bursts allows us to estimate the position of the acceleration source (presumably the acceleration region position) as lying between X=-15 and -20 Re. The distant tail is a unique location for monitoring substorm dynamic processes; details are smoothed out during the downtail propagation and only principal features are conserved.