Study on the Distribution and Source Mechanisms of Double‐Band Plasmatrough Exohiss

Abstract The plasmaspheric hiss and plasmatrough exohiss represent typical whistler‐mode waves found within the Earth's inner magnetosphere, playing a vital role in the dynamic alterations of the Van Allen radiation belts. Under specific conditions, plasmaspheric hiss waves can escape from the plasmapause and develop into exohiss waves. In this study, it was found that in some cases, exohiss exhibits an upper and lower band structure within the frequency range from 20 Hz to several kHz. Utilizing data collected by the Van Allen Probe A between 2012 and 2019, we successfully identified double‐band plasmaspheric hiss and double‐band plasmatrough exohiss. Based on these statistical results, we analyzed the amplitude (Bw) distribution of double‐band hiss and exohiss waves across various magnetic local times and L‐shells (L), as well as different magnetic latitudes. The results indicate that the amplitudes of both upper and lower bands of hiss waves are significantly stronger than those of upper and lower bands of exohiss waves. Further integration of the analysis of the Poynting vector and ray tracing simulation suggests that both upper and lower bands of exohiss waves may be derived from double‐band hiss waves inside the plasmapause. In addition, upper band seems to be damped more rapidly, which may experience severer Landau damping. Our findings about the source mechanisms of double‐band exohiss waves further improve our understanding of the distribution and formation of whistler waves in the magnetosphere.