Abstract
Abstract. We report an attenuation of hiss wave intensity in the duskside of the outer plasmasphere in response to enhanced convection and a substorm based on Van Allen Probe observations. Using test particle codes, we simulate the dynamics of energetic electron fluxes based on a realistic magnetospheric electric field model driven by solar wind and subauroral polarization stream. We suggest that the enhanced magnetospheric electric field causes the outward and sunward motion of energetic electrons, corresponding to the decrease of energetic electron fluxes on the duskside, leading to the subsequent attenuation of hiss wave intensity. The results indicate that the enhanced electric field can significantly change the energetic electron distributions, which provide free energy for hiss wave amplification. This new finding is critical for understanding the generation of plasmaspheric hiss and its response to solar wind and substorm activity.
Highlights
Plasmaspheric hiss is a structureless, extremely lowfrequency (ELF) whistler-mode wave that is found primarily in the plasmasphere (Russell et al, 1969; Thorne et al, 1973) and plasmaspheric plumes (Chan and Holzer, 1976; Shi et al, 2019; Yuan et al, 2012; Hayakawa et al, 1986)
The Poynting flux of hiss waves observed at higher L shells (> ∼ 4.67) before the enhanced convection and substorm was directed away from the Equator, and the trend of the calculated linear wave growth rates is consistent with the observed hiss wave intensification, both of which suggest that these hiss waves in the outer plasmasphere are mainly locally amplified
The reduction of hiss wave intensity in the outer plasmasphere after the enhanced convection and substorm may be mainly caused by the reduced fluxes of energetic electrons, which provide a source of free energy for hiss amplification
Summary
Plasmaspheric hiss is a structureless, extremely lowfrequency (ELF) whistler-mode wave that is found primarily in the plasmasphere (Russell et al, 1969; Thorne et al, 1973) and plasmaspheric plumes (Chan and Holzer, 1976; Shi et al, 2019; Yuan et al, 2012; Hayakawa et al, 1986). H. Li et al.: Attenuation of plasmaspheric hiss associated with the enhanced magnetospheric electric field. Besides the global contribution of ESW, the ionospheric subauroral polarization stream (SAPS) is potentially an important contributor to the magnetospheric electric field near the duskside (Goldstein et al, 2003, 2005b, a). It has been known that the dawn–dusk convection electric field plays an important role in the motions of charged particles through the E × B drift, especially during strong geomagnetic activity (Burch, 1977; Ejiri, 1978; Frank, 1975). Using test particle simulations based on the realistic electric field model, we provide direct evidence that the enhanced magnetospheric electric field can contribute to the attenuation of hiss wave intensity on the duskside
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