Mirror instability and L-mode electromagnetic ion cyclotron instability: Competition in the Earth's magnetosheath

We performed both two- and three-dimensional hybrid simulations of the competing processes between the L-mode electromagnetic ion cyclotron (EMIC) and mirror instabilities, assuming anisotropic energetic ions with T ⊥ /T ∥ = 4.0. In the two-dimensional model, the energy of the EMIC waves is higher at the linear growth phase because its growth rate is larger than that of the mirror mode. In the three-dimensional model, however, the energy of the mirror mode waves is larger than that of the EMIC waves for all times because the wave number spectra of mirror mode waves form torus-like structures. We also theoretically derived a necessary condition for the dominance of the mirror instability