Local Generation of Plasmaspheric Plume Hiss

The statistical analysis of hiss waves observed in the plasmaspheric plume (Wu et al., 2026, https://doi.org/10.1029/2026gl121667 ) is significant for identifying nonlinear wave growth processes in the equatorial region. Because nonlinear growth rates greatly exceed linear growth rates, they enable the local generation of new wave packets in the equatorial region. These nonlinear growth rates are governed by the background magnetic field gradient and the frequency sweep rates of the growing waves. The spatial extent of the nonlinear generation zone responsible for the local generation of hiss is derived theoretically under an assumption that the increasing gradient of the dipole magnetic field gives a limitation of nonlinear wave growth. The resulting theoretical predictions show reasonable agreement with the statistical distributions of hiss‐wave propagation directions observed in the plasmaspheric plume.