Trajectory traces of charged particles in the magnetosphere

Abstract

The characteristic enhancements of ring current particles with energies of about 1–100keV, associated with magnetospheric substorms, were observed by Explorer 45 (S³‐A) around the plasmapause in the afternoon to midnight region and showed the characteristic structure called a ‘nose’ in the proton spectrograms. This paper examines the time‐developing characteristics of newly injected particles in the magnetosphere under a recently proposed convection electric field and a dipole magnetic field. Approximate equations of a bounce period, a second adiabatic invariant, and a bounce‐averaged azimuthal velocity are given with an error of less than about 10 −3 for all pitch angles. The complete set of flow patterns of 90° pitch angles is also described by means of inflection lines through which radial and/or azimuthal drifts change their directions and where particle velocities show their local minima, i.e., the flow becomes sluggish. These particle tracings in the magnetosphere, from which time dependent particle fronts can be constructed, give the basic concept and mechanics to explain the complex and dynamical properties of the magnetic storm time particle enhancements.