Transport of ions in presence of induced electric field and electrostatic turbulence: Source of ions injected into ring current

Abstract

The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O + flux of 2.8 × 10 8 cm −2 s −1 (w > 10 eV) and an H + flux of 5.5 × 10 8 cm −2 s −1 (w > .63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O + flux and a large part of the H + flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.