Simultaneous observation of the plasma sheet in the near Earth and distant magnetotail: ISEE‐1 and ISEE‐3

Abstract

We present particle data from the spacecraft 1981‐025 and 1982‐019 at geosynchronous orbit (6.6 RE), from ISEE‐1 in the near‐earth geomagnetic tail and from ISEE‐3 in the distant geomagnetic tail at ∼ 130 RE obtained during the first half of March 22, 1983. The spacecraft observations are supplemented by ground‐based magnetograms from near local‐midnight stations. Two substorm particle injections were detected at ∼ 0715 and 0806 UT at geosynchronous orbit. At the same time suprathermal plasma sheet protons are observed at ISEE‐1. Multiple entries and exits into and out of the plasma sheet are recorded at ISEE‐3 in the distant tail. A substorm recovery is indicated by a poleward leap of the substorm electrojet at 0900 UT. After 0900 UT ISEE‐1 and ISEE‐3 entered the plasma sheet simultaneously within a few minutes. At the boundary of the recovering plasma sheet strong earthward streaming (ISEE‐1) and tailward streaming (ISEE‐3) suprathermal protons are observed, indicating that the two spacecraft were on opposite sides of the particle source. This represents the first measurement of ion beams at the plasma sheet boundary occurring simultaneously in the near‐earth region and in the deep tail flowing in opposite directions.