Macroscopic quasi-linear theory of electromagnetic electron cyclotron instability associated with core and halo solar wind electrons

Spacecraft observations made near 1 AU show that both core and halo solar wind electrons exhibit temperature anisotropies that appear to be regulated by marginal electromagnetic electron cyclotron instability condition. In the literature, the threshold conditions of this instability, operative for T-perpendicular to > T-||, have been expressed as an inverse correlation between the temperature anisotropy, T-perpendicular to/T-||, and parallel beta, beta(||), but such a relation was deduced on the basis of linear stability analysis combined with empirical fitting. The present paper, on the other hand, employs macroscopic quasi-linear analysis for core-halo two-component model of the solar wind electrons, in order to follow the self-consistent time history of the core and halo temperature development as well as the dynamics of magnetic field perturbation wave energy. In the present analysis, the inverse correlation for core and halo temperature anisotropy and parallel beta naturally emerges from the solutions of self-consistent theory. The present findings indicate that the macroscopic quasi-linear method may be useful for modeling the dynamics of solar wind electrons.