Nonlinear Gyrokinetic Simulation of the Magnetosphere‐Ionosphere Feedback Coupling

Abstract A nonlinear gyrokinetic simulation is applied to the magnetosphere‐ionosphere (M‐I) coupling system to investigate spontaneous growth of auroral structures and electron acceleration self‐consistently. Perturbations of electron density, potential and field‐aligned current in the auroral ionosphere develop through the feedback instability, resulting in nonlinear deformations of the auroral structures. The linear and nonlinear developments of the M‐I feedback coupling system are well captured by the gyrokinetic simulation. Simultaneously, a part of the electromagnetic field energy amplified through the M‐I coupling is transferred to electrons through wave‐particle interactions, providing field‐aligned acceleration by the parallel electric field. While the estimated electron acceleration does not quantitatively account for the Alfvénic aurora, further extensions of the present simulation will lead to a self‐consistent model which simultaneously explains enhancement of the broad‐band electromagnetic fluctuations and the electron acceleration.