Statistical Relationship Between Exohiss Waves and Plasmaspheric Hiss

Abstract

Based on the Van Allen Probe A observations from 2013 to 2015, we show the statistical relationship between exohiss waves and plasmaspheric hiss. Both hiss and exohiss waves have higher occurrence rates on the dayside (MLT = 8–20) and are positively correlated. The appearance of exohiss waves is nearly independent of the plasmapause density gradient at magnetic latitudes below 21°. Most exohiss waves (~ 68–88%) are propagating equatorward, and their amplitudes are generally smaller than those of hiss waves. This is consistent with the hiss leakage at high latitudes and associated energy dissipation. Less than 32% of exohiss waves are propagating poleward, probably due to multiple reflections of leaked hiss or excitation by equatorial instability. Although the inward reflection of chorus waves at high latitudes could produce equatorward propagating exohiss and hiss waves, this can explain only 10% of exohiss waves with larger amplitudes than hiss.

Non‐Adiabatic Acceleration of Injected Electrons in the Inner Magnetosphere: Joint Observations by the Van Allen Probe and the BeiDa Imaging Electron Spectrometer

“…Particularly, the higher frequency waves (shown in Figures 5a–5c) could directly disturb the electron's gyro motion, thereby causing the violation of the first adiabatic invariant. Particularly, the waves observed in the WFR channels were likely exohiss waves, as they were circularly polarized and propagated at small wave normal angle, consistent with the characteristic features of exohiss (e.g., Wang et al., 2020; Zhu et al., 2019). (See Figure S3 in Supporting Information for more details).…”

Competitive Influences of Different Plasma Waves on the Pitch Angle Distribution of Energetic Electrons Inside and Outside Plasmasphere

“…Under different solar or geomagnetic activities, the spatial variation of hiss intensity modifies effectively the spatial range of slot region (L. Y. Li, Yu, et al., 2017; L. Y. Li, Yang, et al., 2019). Plasmaspheric hiss sometimes leaks out the plasmapause and becomes whistler‐mode exohiss waves (Wang et al., 2020; Zhu et al., 2015). Some exohiss waves may be amplified by substorm electron injection (Gao et al., 2018).…”

Complementary and Catalytic Roles of Man‐Made VLF Waves and Natural Plasma Waves in the Loss of Radiation Belt Electrons

“…Plasmaspheric hiss (f ∼ 20–4000 Hz) may be excited by the anisotropic instability of hot electrons (Chen et al., 2012) or originates from the inward penetration of whistler‐mode chorus waves (Bortnik et al., 2009). The hiss intensity depends on solar wind dynamic pressure, plasma flow velocity, orientation of interplanetary magnetic field (IMF) (L. Y. Li et al., 2019) and geomagnetic conditions (Meredith et al., 2018; Wang et al., 2020; Yu et al., 2017).…”