Estimation of radial gradients of phase space density from POLAR observations during a quiet period prior to a sudden solar wind dynamic pressure enhancement

Abstract

We have analyzed POLAR electron flux data to estimate the radial gradients of electron phase space density (PSD) immediately prior to a sudden solar wind dynamic pressure enhancement at ∼1135 UT on 12 August 2001. In this event, the instantaneous flux changes from the magnetospheric compression at L ∼ 7.6 in the postmidnight magnetic local time sector are observed to be both energy and pitch angle (PA) dependent: a substantial flux increase for lower energies ( < L < 8.5 using the constructed electron flux model and Tsyganenko magnetospheric model for quiet times. The estimates show a positive PSD gradient for low energies (