Controlling Effect of Wave Models and Plasma Boundaries on the Dynamic Evolution of Relativistic Radiation Belt Electrons

Modeling and observations have shown that energy diffusion by chorus waves is an important source of acceleration of electrons to relativistic energies. By performing long term simulations using the three dimensional Versatile Electron Radiation Belt code, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modelling of MeV electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they can not only produce a net acceleration but also a net loss of MeV electrons. Decrease in high latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high latitude waves can result in a net loss of MeV electrons.

Apart from the magnetosphere of the Earth, chorus waves at high latitudes on the other planets also need further investigation. Shprits et al (2012) showed that depending on the latitudinal extent of waves, chorus waves may produce net acceleration or loss on both Jupiter and Saturn. Chorus wave measurements at high latitudes in the magnetospheres of Jupiter from satellites such as Juno will help us to improve our understanding of the effects of chorus waves at high latitudes. In particular, the presence of strong waves at high latitudes may indicate that chorus waves are incapable of producing a net acceleration of electrons.

Our simulation results also show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. The magnetopause shadowing effect is included by using last closed drift shell, and it is shown to significantly contribute to the dropouts of relativistic electrons at high L*.

References:

1. Wang, D., and Shprits, Y. Y. (2019). On how high-latitude chorus waves tip the balance between acceleration and loss of relativistic electrons. GRL.

2. Wang, D. et al. (2020). The effect of plasma boundaries on the dynamic evolution of relativistic radiation belt electrons. JGR.