Modeling the properties of plasmaspheric hiss: 2. Dependence on the plasma density distribution

Wave propagation plays an important role in linking the chorus source in the plasma trough region and the hiss emission in the plasmasphere. We investigate the dependence of plasmaspheric hiss on the background plasma density, which essentially controls the evolution of chorus after its generation at MLT = 10. The variation of plasma density under study includes variation of the location and width of the plasmapause, and the variation of the density distribution in the trough. We demonstrate that the plasmapause shape does not affect the peak hiss intensity significantly, but it does regulate the hiss intensity near the field-aligned direction. As the plasmasphere contracts or the plasmapause width increases, the field-aligned component of plasmaspheric hiss become relatively more intense, as does the intensity of hiss in the inner region, although the peak hiss intensity remains about the same. The trough density distribution, on the other hand, directly influences the accessibility of chorus rays into plasmasphere, and therefore plays an important role in the peak hiss intensity. As the density gradient in the plasma trough increases toward the plasmasphere, the resulting peak in the hiss intensity can increase by up to 10 dB.