A Comparative Study on the Distributions of Incoherent and Coherent Plasmaspheric Hiss

Abstract We perform a comparative study on the distributions of incoherent and coherent plasmaspheric hiss, based on the Van Allen Probe data. The statistics show that incoherent hiss (∼10–20 pT) is widely distributed in dayside plasmasphere, with peak frequencies below 500 Hz; intense coherent hiss (amplitudes up to 80 pT) occurs in outer plasmasphere of L > 4 (L denotes the L‐shell.), whose frequency increases with ambient magnetic field significantly. The Poynting flux analysis indicates that incoherent hiss generally propagates omni‐directionally inside the plasmasphere, with features of external sources; the coherent hiss propagates away from the equatorial region in outer plasmasphere and has a reversed direction in inner plasmasphere, indicating two different wave sources by local generation and ducted lightning generated whistler, respectively. This comparative study helps us to better understand the origination of plasmaspheric hiss.