Earthward transport of energetic protons in the Earth's plasma sheet

Abstract

The transport of magnetospheric energetic protons (Ep ∼ 0.29‐0.50 MeV) in the earth’s plasma sheet at downstream distances of ∼ 30‐45 Re is studied on a statistical basis with 5.5 min average data from the APL/JHU Charged Particle Measurement Experiment on the IMP 7 and IMP 8 spacecraft. The analysis shows that there is a net earthward transport of these particles, although tailward streaming is observed as frequently as earthward streaming. The net transport is earthward for all Kp conditions and for low as well as high flux thresholds. The averaged net particle flux is ∼ 2 × 10²cm−2sec−1, which translates into averaged particle and energy fluxes over the plasma sheet region of ∼ 4 × 1022sec−1 and ∼ 2 × 1016ergs sec−1, respectively. It is suggested that this particle influx could be a possible source of protons for the earth’s outer radiation belt.