On the use of positrons as tracers to study the motions of electrons trapped in the Earth's magnetosphere

Instruments carried on earth satellites continue to reveal the distribution and time behavior of the earth's trapped radiation environment in increasing detail, yet remarkably little is known of the sources of the energetic particles that make up this environment. The vast majority of the particles probably derive their energy from dynamic processes (i.e., electric fields, time-varying magnetic fields, hydromagnetic waves, etc.) in the magnetosphere, but there is, at present, practically no firm knowledge about the nature of these processes. It is likely that the acceleration processes are associated in some way with gross motions of the low-energy (cold) plasma, such as those induced by the flow of the solar wind around the boundary of the magnetosphere cavity [Axford and Hines, 1961] or by the rotation of the earth [Hones, 1963a]. Therefore the inability, in measurements of the natural trapped radiation, to identify specific particles or groups of particles, to follow them as they move through the magnetosphere, or to measure the changes in their energy is a serious handicap in the effort to develop an understanding of magnetosphere dynamics.