The role of soft electron precipitation and ponderomotive force in the generation of ionospheric outflow in the cusp and polar regions

Abstract:

It is well accepted that the ionosphere is a critical source of plasma for the magnetosphere, providing O+, H+, and He+ which can have wide ranging consequences for the space environment system. A myriad of mechanisms are frequently invoked to drive ionospheric outflows, including: effects of superthermal electron populations, resonant and nonresonant wave particle interactions, centrifugal forces, and more. In this study, we focus on the roles of superthermal electrons in the form of photoelectrons, soft electron precipitation, and the associated secondary electrons as well as on the ponderomotive force of waves in generating ionospheric outflows in the cusp and polar cap. The study is carried out using our Kinetic electron Polar Wind Outflow Model (KePWOM) which treats the ions and thermal electrons as a fluid and the superthermal population with an embedded kinetic model of the Landau-Boltzmann equation. Our simulation results examine the competing effects of superthermal electrons and the ponderomotive force of waves for a variety of precipitation and wave inputs that correspond to the cusp and polar cap. We furthermore compare our results to empirical relationships between ion flux and particle and wave input from FAST observations and find that secondary electrons generated as a result of soft electron precipitation play a critical role in the formation of cusp outflows.