Quantitative tests of a steady state theory of solar wind electrons

Abstract

IMP electron data are compared to several predictions of a steady state theory of solar wind electrons which assumes that transport is controlled by the macroscopic interplanetary electric and magnetic fields and elastic Coulomb collisions with the solar wind protons and thermal electrons. One of the predictions based on these assumptions is that the ratio of forward to backward phase space density of field‐aligned extrathermal electrons should be 6∶1. In contrast, measurements of electron distributions within the only steady state solar wind flow identified to date, the high‐speed solar wind, show this ratio to be typically about an order of magnitude larger. Based on a larger set of assumptions, the theory further predicts an anticorrelation between the solar wind bulk speed and (1) the fractional density of extrathermal electrons, (2) the component of the temperature of the extrathermal electrons parallel to the interplanetary magnetic field, and (3) the total heat flux. These anticorrelations are not found in the IMP electron data set. Good agreement between the predictions and the observations may require modification of a number of assumptions of the theory. Most important may be the need to include inelastic Coulomb and/or wave‐electron collisions.