Nonlinear Landau resonance between EMIC waves and cold electrons in the inner magnetosphere

It has been suggested previously that electromagnetic ion cyclotron (EMIC) waves can heat cold electrons (1–10 eV) via Landau resonance, these electrons being a source of energy for stable auroral red arc emissions. To investigate the energy transfer between cold electrons and EMIC waves in the present study, test-particle simulations were conducted to examine the interaction process at the microscopic level, with a particular focus on the nonlinearity. The nonlinear Landau resonance between cold electrons and EMIC waves was found to occur easily at normal EMIC wave amplitudes. Parametric studies were also conducted to determine how the nonlinearity depends on the electron pitch angle, energy, wave frequency, normal angle, and background plasma density. The simulation results suggest that the nonlinear resonance between EMIC waves and cold electrons is universal and probably plays an important role in damping EMIC waves in the equatorial region.