UCLA

Plasmaspheric hiss is known to play an important role in controlling the overall structure and dynamics of radiation belt electrons inside the plasmasphere. Using newly available Van Allen Probes wave data, which provide excellent coverage in the entire inner magnetosphere, we evaluate the global distribution of the hiss wave frequency spectrum and wave intensity for different levels of substorm activity. Our statistical results show that observed hiss peak frequencies are generally lower than the commonly adopted value (~550-Hz), which was in frequent use, and that the hiss wave power frequently extends below 100-Hz, particularly at larger L shells (>-~3) on the dayside during enhanced levels of substorm activity. We also compare electron pitch angle scattering rates caused by hiss using the new statistical frequency spectrum and the previously adopted Gaussian spectrum and find that the differences are up to a factor of ~5 and are dependent on energy and L shell. Moreover, the new statistical hiss wave frequency spectrum including wave power below 100-Hz leads to increased pitch angle scattering rates by a factor of ~1.5 for electrons above ~100-keV at L~5, although their effect is negligible at L-≤-3. Consequently, we suggest that the new realistic hiss wave frequency spectrum should be incorporated into future modeling of radiation belt electron dynamics. Key Points Hiss wave power is activity dependent and frequently extends below 100-Hz Hiss peak frequency is dependent on L and lower than the previous value 550-Hz Difference in hiss diffusion rate is up to 5, and realistic spectra should be used