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Influence of Loss Cone Widths on Electron Loss Timescales in Earth's Radiation Belts.

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Title: Influence of Loss Cone Widths on Electron Loss Timescales in Earth's Radiation Belts.
Authors: Hu, Jingle1 (AUTHOR), Xiang, Zheng1 (AUTHOR) xiangzheng@whu.edu.cn, Liu, Yangxizi2 (AUTHOR), Dong, Junhu1 (AUTHOR), Wang, Jianhang1 (AUTHOR), Guo, Haozhi1 (AUTHOR), Dai, Jiakun1 (AUTHOR), Ni, Binbin1 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Mar2026, Vol. 131 Issue 3, p1-12. 12p.
Subject Terms: *Geomagnetism, Radiation belts, Drift diffusion models, Charge carrier lifetime, Electron diffusion
Abstract: The electron lifetime is a critical parameter to describe the loss process of radiation belt electrons. The influence of pitch angle (PA) diffusion coefficients on electron lifetimes has been extensively studied, while the effect of loss cone width and the influence of different geomagnetic field models have received much less attention. To obtain a state‐of‐the‐art estimation of electron lifetimes, we investigated the impact of loss cone width on electron lifetimes using both the dipole and International Geomagnetic Reference Field (IGRF) models. We employ a drift‐diffusion model to simulate the temporal evolution of radiation belt energetic electron fluxes and then calculate the corresponding electron lifetimes. The results indicate that electron lifetimes decrease significantly with increasing loss cone width when assuming a flat distribution of PA diffusion coefficients. In contrast, a pronounced gap in diffusion coefficients significantly reduces the sensitivity of electron lifetimes to loss cone variations. Although the local loss cone values in the dipole and IGRF models have large differences, the corresponding lifetime differences remain minimal. We also compare the lifetime values calculated from simulation results with those derived from formulas. The lifetimes derived from the drift‐diffusion model agree well with those calculated from the precise formula of Lyons and Thorne (1972), https://doi.org/10.1029/ja077i019p03455, whereas the widely used approximate formula of Albert and Shprits (2009), https://doi.org/10.1016/j.jastp.2008.07.004 tends to produce higher values of electron lifetimes. These results unveil the influences of loss cone width on electron lifetimes and help to obtain reliable lifetime values. Key Points: Larger loss cone values lead to faster loss of energetic electrons under pitch angle (PA) diffusionDeep gaps in PA diffusion coefficients can mitigate the influences of loss cone widths on electron lifetimesThe differences in electron lifetimes between using International Geomagnetic Reference Field and dipole geomagnetic fields are slight [ABSTRACT FROM AUTHOR]
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Abstract:The electron lifetime is a critical parameter to describe the loss process of radiation belt electrons. The influence of pitch angle (PA) diffusion coefficients on electron lifetimes has been extensively studied, while the effect of loss cone width and the influence of different geomagnetic field models have received much less attention. To obtain a state‐of‐the‐art estimation of electron lifetimes, we investigated the impact of loss cone width on electron lifetimes using both the dipole and International Geomagnetic Reference Field (IGRF) models. We employ a drift‐diffusion model to simulate the temporal evolution of radiation belt energetic electron fluxes and then calculate the corresponding electron lifetimes. The results indicate that electron lifetimes decrease significantly with increasing loss cone width when assuming a flat distribution of PA diffusion coefficients. In contrast, a pronounced gap in diffusion coefficients significantly reduces the sensitivity of electron lifetimes to loss cone variations. Although the local loss cone values in the dipole and IGRF models have large differences, the corresponding lifetime differences remain minimal. We also compare the lifetime values calculated from simulation results with those derived from formulas. The lifetimes derived from the drift‐diffusion model agree well with those calculated from the precise formula of Lyons and Thorne (1972), https://doi.org/10.1029/ja077i019p03455, whereas the widely used approximate formula of Albert and Shprits (2009), https://doi.org/10.1016/j.jastp.2008.07.004 tends to produce higher values of electron lifetimes. These results unveil the influences of loss cone width on electron lifetimes and help to obtain reliable lifetime values. Key Points: Larger loss cone values lead to faster loss of energetic electrons under pitch angle (PA) diffusionDeep gaps in PA diffusion coefficients can mitigate the influences of loss cone widths on electron lifetimesThe differences in electron lifetimes between using International Geomagnetic Reference Field and dipole geomagnetic fields are slight [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2025JA034930