Journal Article

Quantifying Spatial and Temporal Extents of Plasmaspheric Hiss Through Modeling of POES/MetOp Electron Observations

Tu, Weichao, Selesnick, Richard, Li, Zhi‐Gu, Ma, Qianli, Blum, Lauren

2025

Overview

We present a novel method to quantify the event‐specific spatial evolution of plasmaspheric hiss wave power using a Drift‐Diffusion model. Constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data, the model simulates low‐altitude electron distributions, accounting for azimuthal drift, pitch‐angle diffusion, and atmospheric backscatter. Applying to an event on 15 October 2016, the model quantifies the spatial evolution of hiss waves at L = 3.9, which contributes to the steady decay of electron flux observed by Van Allen Probes (VAPs). The model reproduces local‐time dependent features and shows excellent agreement with hiss wave power observed by VAPs. The model shows increased wave power and spatial spread following increased activities in the AL‐index, consistent with previous statistical results. The model also suggests the presence of “low”‐frequency hiss, which was undetected by VAPs, likely masked by instrument noise. This is the first time low‐altitude measurements are used to quantify event‐specific wave distributions which include both diffusion and drift effects. Plain Language Summary We present a novel method to estimate the location and strength of plasmaspheric hiss waves in the Earth's magnetosphere during specific events. These waves play a critical role in shaping the dynamics of Earth's radiation belts by scattering energetic electrons into the atmosphere. However, directly measuring these waves everywhere in the magnetosphere is unfeasible given the inherent limited coverage of satellites. Our approach uses a Drift‐Diffusion model, a physics‐based simulation on how electrons behave in the presence of these waves, and through iteratively best‐fitting model to observations from Polar Operational Environmental Satellites/Meteorological Operational Satellites, we can quantify the free parameters in the model, such as wave power and its location. The model shows remarkable agreement with hiss wave observations from Van Allen Probes (VAPs) during an event on 15 October 2016. It also shows how the waves intensify and spread following increases in AL‐index activity, consistent with past statistical studies. The model also suggests the presence of “low”‐frequency hiss waves, though they were not detected by VAPs, likely due to instrument noise. This method provides a powerful tool to study wave activity in areas where direct measurements are unavailable. Key Points A novel method using a Drift‐Diffusion model constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data estimates the event‐specific spatial evolution of wave power The model reveals increase in hiss wave power and spatial spread during high AL activity, consistent with previous statistical results The model suggests the presence of low‐frequency hiss waves during the event, though they were not observed by Van Allen Probes

• Publisher: John Wiley & Sons, Inc
• Subject: Altitude / Backscatter / Diffusion / Drift / Electron flux / electron precipitation / Evolution / Hiss / hiss wave distribution / infer wave power / plasmaspheric hiss / POES satellites / proxy wave model / Satellites / Statistical models / Time dependence / Time measurement / Wave power / wave spatial evolution