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Abstract The lower hybrid (LH) waves are electrostatic emissions near the LH resonant frequency. They propagate perpendicularly with a small wavelength comparable to Larmor radius of thermal particles and can be capable of heating both ions and electrons. In this study, we statistically study the global distribution of LH waves in the inner magnetosphere by using Van Allen Probes observation from 2012 to 2018. We find that (a) LH waves are commonly observed in the inner magnetosphere. Most LH waves are confined near the magnetic equator with typical amplitudes of 0.02–0.2 mV/m and occurrence rates up to 10%. (b) LH waves extend to innerLregions with increasing wave amplitudes as AE* increases. (c) Weak LH waves occur at the nightside inside the plasmapause. Moderate and strong LH waves occur at the nightside and noon inside the plasmapause. As AE* increases, they extend to all magnetic local times inside the plasmapause and dawnside outside the plasmapause. 

Abstract Recent observations have reported that magnetosonic waves can exhibit rising‐tone structures in the frequency‐time spectrogram. However, the generation mechanism has not been identified yet. In this paper, we investigate the generation of rising‐tone magnetosonic waves in the terrestrial magnetosphere using 1‐D particle‐in‐cell (PIC) simulations, in which the plasma consists of three components: cool electrons, cool protons and ring distribution protons. We find that the magnetosonic waves excited by the ring distribution protons can form a rising‐tone structure with frequency of the structure ranging from about0.5Ω_lhto nearlyΩ_lh, whereΩ_lhis the lower hybrid frequency. It is further demonstrated that the rising frequency of magnetosonic waves can be accounted for by the scattering of ring distribution protons. Moreover, the rising‐tone timescale obtained by PIC simulation is compared with the satellite observation. Our findings provide some new insights to understand the nonlinear evolution of plasma waves in the Earth's magnetosphere. 

Abstract Radiation belt electrons can be accelerated and scattered by magnetosonic waves in the Earth's magnetosphere, and the scattering rate of electrons is sensitive to the wave normal angle. However, observationally it is difficult to identify the wave normal angle within a few degrees. In this study, using 2‐D particle‐in‐cell (PIC) simulations, we investigate the wave normal angle distribution of magnetosonic waves excited by ring distribution protons. Both the linear theory and simulations have shown that the wave normal angles are distributed over a narrow range (82°–89°) with a major peak at about 85° during the linear growth stage when the proton ring velocity is close to the Alfven speed. In addition, 2‐D PIC simulations further demonstrated that the waves tend to have larger wave normal angles (84°–89°) during the saturation stage since the waves with smaller wave normal angles are dissipated faster. It is also found that wave normal angles decrease with the increase of wave frequency. With the increase of the ring velocity of the proton ring distribution, the perpendicular wavenumber of excited magnetosonic waves decreases, which leads to the decrease of the wave normal angle. The simulation results provide a valuable insight to understand the property of magnetosonic waves, and the findings are useful for the global simulations of radiation belt dynamics. 

Abstract In this study, we use the observations of electromagnetic waves by Detection of Electromagnetic Emissions Transmitted from Earthquake Regions satellite to investigate propagation characteristics of low‐altitude ionospheric hiss. In an event study, intense hiss wave power is concentrated over a narrow frequency band with a central frequency that decreases as latitude decreases, which coincides to the variation of local proton cyclotron frequencyf_CH. The wave propagates obliquely to the background magnetic field and equatorward from high latitude region. We use about ∼6 years of observations to statistically study the dependence of ionospheric hiss wave power on location, local time, geomagnetic activity, and season. The results demonstrate that the ionospheric hiss power is stronger on the dayside than nightside, under higher geomagnetic activity conditions, in local summer than local winter. The wave power is confined near the region where the localf_CHis equal to the wave frequency. A ray tracing simulation is performed to account for the dependence of wave power on frequency and latitude.