Journal Article

A Generation Mechanism of Banded Plasmaspheric Hiss

Wu, Zhiyong, Xiang, Zheng, Dong, Junhu, Ni, Binbin

2025

Overview

As a unique structure of plasmaspheric hiss emissions, banded hiss waves generally consist of an upper band above ∼200 Hz, a lower band below ∼100 Hz and a power gap in between. However, the generation mechanism of banded hiss remains unclear. Here we present a representative event of banded hiss co‐existing in both the plasmaspheric plume structure and the plasmasphere. The wave Poynting flux measurements and linear instability analysis suggest that banded hiss can be generated in the equatorial plume region. The ray tracing simulations further show that the plume structure enables banded hiss to propagate along the plasma density crest to higher latitudes, followed by the penetration into the plasmasphere. Our data analysis and modeling efforts provide a plausible mechanism for the generation of banded hiss, and also highlight the significant role of plume structure in the generation and propagation of magnetospheric whistler‐mode waves. Plain Language Summary Plasmaspheric hiss is a whistler‐mode emission usually observed within the plasmasphere and the plume structure, with frequency ranging from ∼20 to ∼2,000 Hz. Hiss can scatter energetic electrons from ∼10s keV to several MeV, which is known as the main mechanism of the formation of radiation belt slot region. Hiss can be excited from various source regions, which leads to differences of plasmaspheric hiss waves on frequency, morphology, and scattering effects. In this study, we use the wave and particle measurements from Van Allen Probes to investigate the generation mechanism of banded hiss, which usually shows an upper band above ∼200 Hz and a lower band below ∼100 Hz. Based on the analysis of banded hiss event and ray tracing method, the banded hiss is found to be generated in the equatorial plume region, propagate to higher latitudes along the plume structure, and eventually penetrate into the plasmasphere. The plume structure plays an important role in the generation and propagation of banded hiss, which can subsequently impact the wave‐particle interaction processes and their consequences in Earth's radiation belts. Key Points A physical mechanism is proposed to explain the generation of banded plasmaspheric hiss waves Wave growth rate calculations based on electron distributions suggest that banded hiss is likely generated in the equatorial plume region Ray tracing results indicate that the plume structure plays a crucial role in guiding the propagation of banded hiss into the plasmasphere

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Data analysis / Equatorial regions / Hiss / Latitude / Magnetospheres / Particle interactions / Plasma density / Plasmasphere / Plumes / Radiation / Radiation belts / Ray tracing / Whistlers