Plasmaspheric hiss plays a key role in shaping the radiation belt environment, whose origin remains under active debate. Using the wave and particle data of Van Allen Probes, Geostationary Operational Environmental Satellites, and Time History of Events and Macroscale Interactions during Substorm spacecraft, we here examine the nightside plasmaspheric hiss generation during a substorm. The substorm‐electron injection caused the plasmapause to shrink promptly from L_pp=6.6 to 5.1. Corresponding to the azimuthal drift of the injected electrons, the plasmaspheric hiss was intensified gradually from nightside to dayside. Particularly, in the inner postmidnight plasmasphere free from the substorm injection, the instantaneous peak amplitude of hiss reached 0.9 nT. The enhanced hiss within the locally unchanged plasma must originate from other spatial regions. Our data and modeling demonstrate that the large‐amplitude hiss was generated by the substorm‐injected electrons drifting into the outer postmidnight plasmasphere, rather than linked to the nightside chorus suffering strong Landau damping or the dayside chorus/hiss propagating azimuthally to the nightside plasmasphere.

Magnetospheric whistler mode waves are of great importance in the radiation belt electron dynamics. Here on the basis of the analysis of a rare event with the simultaneous disappearances of whistler mode plasmaspheric hiss, exohiss, and chorus triggered by a sudden decrease in the solar wind dynamic pressure, we provide evidences for the following physical scenarios: (1) nonlinear generation of chorus controlled by the geomagnetic field inhomogeneity, (2) origination of plasmaspheric hiss from chorus, and (3) leakage of plasmaspheric hiss into exohiss. Following the reduction of the solar wind dynamic pressure, the dayside geomagnetic field configuration with the enhanced inhomogeneity became unfavorable for the generation of chorus, and the quenching of chorus directly caused the disappearances of plasmaspheric hiss and then exohiss.

Magnetosonic waves play a potentially important role in the complex evolution of the radiation belt electrons. These waves typically appear as discrete emission lines along the proton gyrofrequency harmonics, consistent with the prediction of the local Bernstein mode instability of hot proton ring distributions. Magnetosonic waves are nearly dispersionless particularly at low harmonics and therefore have the roughly unchanged frequency time structures during the propagation. On the basis of Van Allen Probes observations, we here present the first report of magnetosonic harmonic falling and rising frequency emissions. They lasted for up to 2 hr and occurred primarily in the dayside plasmatrough following intense substorms. These harmonic emission lines were well spaced by the proton gyrofrequency but exhibited a clear falling (rising) frequency characteristic in a regime with the temporal increase (decrease) of the proton gyrofrequency harmonics. Such unexpected structures might be produced by the nonlinear interactions between the locally generated magnetosonic waves at the proton gyrofrequency harmonics and a constant frequency magnetosonic wave propagating away from the Earth.