Electron loss and acceleration during storm time: The contribution of wave‐particle interaction, radial diffusion, and transport processes

摘要

During the period 19–22 November 2007, the near‐equatorial satellites THEMIS D (ThD) and E (ThE) traversed the Earth’s morningside magnetosphere once per day and for nearly 2 h the orbits tracked close to each other, providing an excellent opportunity to investigate the evolution of energetic electrons fluxes (EEFs) on two time scales. By analyzing the electrons in the energy range 100–300 keV, we have found that the EEFs undergo different evolutions in the different subregions of Earth’s morningside magnetosphere during a moderate storm. The evolutions at three specific locations, showing, respectively, the features of electron loss, acceleration, and conservation, have been analyzed in detail. Our observations reveal that, during storm time, the evolution of EEFs involves five processes: (1) the resonant interaction between chorus and energetic electrons, which can contribute to both loss and acceleration of electrons depending on the distribution of phase space density, (2) the radial diffusion, which is indicated by the good coherence between ULF waves and EEFs and dominates in the region where the chorus is relatively weak; (3) the adiabatic transport, which affects the EEFs at L > 6 during the recovery phase and prefers to work on large time scale (>1 d); (4) the magnetopause shadowing, which can evacuate electrons at L > 7 during the storm main phase but play minor roles during the recovery phase, when the magnetopause was moving outward; (5) the magnetospheric convection, which can significantly affect the dynamics of the 100 keV electrons. All these five processes couple to each other and determine the EEFs together.