Frequency‐Dependent Responses of Plasmaspheric Hiss to the Impact of an Interplanetary Shock

Plasmaspheric hiss waves are essential for the pitch‐angle scattering and precipitation of energetic electrons and interplanetary shocks may affect these waves. We present a case study on the responses of plasmaspheric hiss after an interplanetary shock arrival on September 7, 2017. Based on the observation by RBSP‐B, the plasmaspheric hiss in different frequency ranges shows three different responses simultaneously: hiss waves with frequency below 0.08fce are weakened, waves within 0.08–0.18fce are weakened in magnetic power and modulated by the ultra‐low frequency (ULF) waves in the electric power, while waves above 0.18fce are intensified in magnetic power and modulated by the ULF waves. Further analysis suggests that the hiss waves have different sources: low‐frequency (∼0.18fce) hiss waves are locally amplified. Our results provide a comprehensive view of the frequency‐dependent hiss wave behavior after the impact of interplanetary shocks. Plain Language Summary Plasmaspheric hiss waves are whistler‐mode emissions commonly observed in the plasmasphere. They can resonate with radiation belt electrons and significantly influence the radiation belt structure and change the space environment. After an interplanetary shock arrival, the power spectral densities of plasmaspheric hiss may increase or decrease. Our study presents a case of plasmaspheric hiss in response to an interplanetary shock in the inner magnetosphere at ∼23:00 UT on September 7, 2017. After the interplanetary shock arrival, plasmaspheric hiss in different frequency ranges shows various responses. We find that low‐frequency (∼0.08fce) hiss waves are modulated by the shock‐induced ultralow frequency (ULF) waves. The results suggest that the low‐frequency (∼0.18fce) hiss waves are locally generated as implied by previous studies. Our study contributes to revealing the mechanisms of the whistler‐mode wave generation and propagation as well as the modulation by ULF waves. Key Points Hiss waves show different responses in different frequency ranges simultaneously after an IP shock arrival on September 7, 2017 Hiss waves in the frequency range of 0.08–0.18fce originate from chorus outside the plasmasphere and modulated by the induced ULF waves