Generation of realistic short chorus wave packets

Abstract Most lower-band chorus waves observed in the inner magnetosphere propagate under the form of moderately intense short wave packets with fast frequency and phase variations. Therefore, understanding the formation mechanism of such short wave packets is crucial for accurately modelling electron nonlinear acceleration or precipitation into the atmosphere by these waves. We compare chorus wave statistics from the Van Allen Probes with predictions from a simple model of short wave packet generation by wave superposition with resonance non-overlap, as well as with results from Vlasov Hybrid Simulations of chorus wave generation in an inhomogeneous magnetic field in the presence of one or two simultaneous triggering waves. We show that the observed moderate amplitude short chorus wave packets can be formed by a superposition of two or more waves generated near the magnetic equator with a sufficiently large frequency difference.