Characteristics of Plasmaspheric Hiss Wave Spectrum and Their Effects on Energetic Electron Dynamics
Thursday, 18 December 2014
Plasmaspheric hiss emissions are known to play a fundamental role in scattering energetic electrons, and thus create the slot region between the inner and outer radiation belts. Using newly available Van Allen Probes wave data, which provide extensive coverage in the entire inner magnetosphere, we evaluate the global distribution of hiss wave frequency spectrum and wave intensity categorized by various levels of geomagnetic activity. Our statistical results show that observed hiss peak wave frequencies are generally significantly lower than the previously adopted value (~550 Hz) and hiss wave intensity frequently extends below 100 Hz, which is the previously adopted lower-cutoff frequency, particularly at larger L-shells (> 4) on the dayside. We also evaluate the electron lifetime caused by hiss-driven pitch angle scattering based on the new hiss frequency spectrum observed by Van Allen Probes and the previously adopted hiss wave model, and find that the difference in electron lifetime is energy dependent and could be up to a factor of ~5. Finally, we discuss the importance of incorporating a realistic hiss wave spectrum into quantification of hiss-driven electron precipitation loss.