3 research outputs found
Alternating bursts of low energy ions and electrons near the substorm onset
The substorm associated behavior of the low energy particles (30&nbsp;eV&ndash;28.5&nbsp;keV) near the earthward edge of the plasma sheet is examined using data from CRRES during the late growth and early expansion phases of a substorm on 12 March 1991 and their significance for the substorm onset mechanism is discussed. In this substorm, the CRRES was located on <i>L</i> ~6.3 and ~20&deg; westward of the substorm onset and observed the sequence of the alternating bursts of the low energy ions and electrons. The bursts of the 0.633&ndash;9.6&nbsp;keV ions occurred 1&ndash;2&nbsp;min before the (7.31&ndash;21.7&nbsp;keV) electron bursts. The first ion burst happened 2min before the substorm onset, at the moment of weak brightening of the most equatorial pre-breakup arc near the latitude ~62&deg;. The alternation of the ion and electron bursts may be a signature of a drift-Alfv&#233;n ballooning instability on the inner edge of the plasma sheet near substorm onset
Studies of the substorm on March 12, 1991: 1. Structure of substorm activity and auroral ions
The substorm on March 12, 1991 is studied using the data of ground-based network of magnetometers, all-sky cameras and TV recordings of aurora, and measurements of particle fluxes and magnetic field onboard a satellite in the equatorial plane. The structure of substorm activity and the dynamics of auroral ions of the central plasma sheet (CPS) and energetic quasi-trapped ions related to the substorm are considered in the first part. It is shown that several sharp changes in the fluxes and pitch-angle distribution of the ions which form the substorm ion injection precede a dipolarization of the magnetic field and increases of energetic electrons, and coincide with the activation of aurora registered 20 degrees eastward from the satellite. A conclusion is drawn about different mechanisms of the substorm acceleration (injection) of electrons and ions