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Description
Variation of plasma density and magnetic field in space plasma drives the development of temperature anisotropies in the component species. A sufficiently large anisotropy of electrons in the direction perpendicular to the ambient magnetic field causes whistler and mirror instabilities to grow. It has been suggested that the anisotropy of the electron species can affect the growth of instabilities in the proton species (Ahmadi et. al., 2016), which may help to explain why observations of proton instabilities in Earth’s Magnetosheath show the growth of unstable mirror modes (Kaufmann et al., 1970) in regions where linear theory predicts cyclotron instabilities will dominate. Given the potential for cross-species interplay, a thorough understanding of the behaviour of the electron whistler instability, which typically dominates the electron species, is crucial. By leveraging multidimensional kinetic simulations with the Energy Conserving Semi-Implicit Method (Gonzalez-Herrero et al., 2018), this work examines the behaviour of the electron whistler instability in parameter space typical of Earth’s Magnetosheath. Recent work has shown that the effect of high-energy tails found in kappa distributions on reducing the growth rate of the whistler instability is insufficient to counteract the consumption of electron temperature anisotropy. Thus the suitability of a low-electron beta parameter space, where the whistler instability is stable but electron temperature anisotropy is sufficient to enhance the proton mirror instability, is being investigated for its suitability to explain observations in the Magnetosheath.
References:
Ahmadi, N., Germaschewski, K., and Raeder, J., "Effects of Electron Temperature Anisotropy on Proton Mirror Instability Evolution", Journal of Geophysical Research 121 (2016): 5350-365.
Kaufmann, R, L., Horng, J., and Wolfe, A., "Large-amplitude Hydromagnetic Waves in the Inner Magnetosheath", Journal of Geophysical Research 75 (1970): 4666-676.
Gonzalez-Herrero, D., Boella, E., and Lapenta, G., "Performance Analysis and Implementation Details of the Energy Conserving Semi-Implicit Method Code (ECsim)", Computer Physics Communications 229 (2018): 162-69.
