Effects of Electron Temperature Anisotropy on Mirror Instability Evolution in the Magnetosheath

Abstract:

Mirror modes are large amplitudes non-propagating structures frequently observed in the magnetosheath. It is suggested that electron temperature anisotropy can enhance the mirror instability growth rate while leaving the proton cyclotron instability unaffected, therefore it can help mirror instability to dominate the proton cyclotron instability in the Earth's magnetosheath. We used particle in cell expanding box simulations to investigate the electron temperature anisotropy effects on mirror instability evolution. Electron temperature anisotropy leads to generation of electron whistler instability. Our results show that the electron whistler instability grows much faster than the proton mirror instability and consumes all the electron free energy so there is no electron temperature anisotropy left for mirror instability to take advantage to grow faster than the proton cyclotron instability.