On the field-aligned Poynting fluxes of plasmaspheric hiss

In this study, we investigate Poynting fluxes of plasmaspheric hiss waves using the Van Allen Probes wave observation. The hiss waves are identified based on the number density of cold plasma, wave frequency, ellipticity, wave normal angle, and planarity. The statistical results show that on the dayside the Poynting flux magnitudes of the hiss waves are stronger than those on the nightside and their field-aligned components are much larger than the perpendicular components. We calculate the net Poynting flux direction R_s of hiss waves along field-aligned direction for different frequency ranges, under different geomagnetic activities, and in different MLT sectors, whose sign can indicate the balance between the growth and damping processes. We find that in the inner plasmasphere R_s is negative while in the outer plasmasphere R_s is positive and their transition locations significantly depend on wave frequency and geomagnetic activity. The results suggest that the local generation of hiss waves may be important in the outer plasmasphere.