Scattering effect of very low frequency transmitter signals on energetic electrons in Earth’s inner belt and slot region

Abstract

Whistler mode very low frequency (VLF) waves from man-made ground-based transmitters in a frequency range of 10–30 kHz are mainly used for submarine communication, and they propagate primarily in the Earth-lower ionosphere waveguide and part of their energy can leak into the inner magnetosphere, leading the energetic electrons in inner radiation belt and slot region to precipitate into atmosphere and then affect the energetic electron dynamics in the near-Earth space. The scattering effects of artificial VLF signals from NWC, NAA and DHO38 transmitters on energetic electrons in Earth’s inner belt and slot region are investigated in detail in this work. Based on the quasi-linear theory and the Full Diffusion Code, we calculate the bounce-average pitch angle diffusion coefficients induced by NWC, NAA and DHO38 VLF transmitter signals, for which the resonance harmonics |<i>N</i>| ≤ 10 are considered, respectively. We further implement the one-dimensional Fokker-Planck diffusion simulations by using the available pitch angle diffusion rates to model the dynamic evolutions of energetic electrons caused by the scattering of the VLF transmitter signals in the inner belt and slot region in 200 d. The simulation results indicate that the NWC VLF transmitter signals are dominant in scattering ~100 keV electrons with pitch angles less than 60° at <i>L</i> ≤ 1.8, and the mainly scattered electron energy values increase with <i>L</i>-shell decreasing , from <i>L</i> = 1.8 to <i>L </i>= 1.5, the mainly scattered electron energy increases from 90–120 keV to 550–650 keV. The NAA and DHO38 VLF transmitter signals are important in scattering < 20 keV electrons with pitch angles less than 70° at higher <i>L</i>-shells (2.2 ≤ <i>L</i> ≤ 2.7), from <i>L</i> = 2.2 to <i>L</i> = 2.7, the mainly scattered electron energy decreases from 10–20 keV to several keV. The VLF transmitter signals are found to have a slight influence on the loss of energetic electrons with pitch angles larger than 80°.

Long‐Term Variations of Energetic Electrons Scattered by Signals From the North West Cape Transmitter

“…The flux levels of nightside quasi‐trapped electrons (blue) in Figure 5 can be 2 orders of magnitude higher than dayside quasi‐trapped electrons (yellow) while the largest difference between yellow and blue curves in Figure 4 is around 1 order of magnitude. The phenomenon is attributed to the fact that PA diffusion coefficients induced by NWC transmitter signals at L = 1.8 are higher than those at L = 1.6 (e.g., Liu et al., 2021; Ma et al., 2017). Thus, the enhancement of quasi‐trapped electrons induced by NWC transmitter signals is much more significant at L = 1.8.…”

“…10.1029/2023SW003827 coefficients induced by NWC transmitter signals at L = 1.8 are higher than those at L = 1.6 (e.g., Liu et al, 2021;Ma et al, 2017). Thus, the enhancement of quasi-trapped electrons induced by NWC transmitter signals is much more significant at L = 1.8.…”

“…To quantitively evaluate scattering effects of VLF transmitter signals, some studies have been performed to calculate the corresponding PA diffusion coefficients using the quasi‐linear diffusion theory and statistical models of VLF transmitter signals (Abel & Thorne, 1998; Liu et al., 2021; Ma et al., 2017; Meredith et al., 2019; Xiang et al., 2021). Those results showed that the lifetime of electrons with 100's keV can decrease by 1–2 orders of magnitude under the influence of VLF transmitter signals in the inner belt, suggesting that VLF transmitter signals are an important loss mechanism for energetic electrons in the inner belt and slot regions (e.g., Albert et al., 2020; Claudepierre et al., 2020; Ma et al., 2017; Ross et al., 2019).…”

Influences of Solar Wind Parameters on Energetic Electron Fluxes at Geosynchronous Orbit Revealed by the Deep SHAP Method

“…The energetic electron fluxes can vary over several orders within a short period during geomagnetic activity times Guo et al, 2021Guo et al, , 2023Shin et al, 2016;Thorne, 2010;Wang et al, 2023;Xiang et al, 2021). Energetic electrons can cause irreversible damage on satellites including deep medium charging and single event upset (Liu et al, 2021;Novikov et al, 2008;Pilipenko et al, 2006;Y. Zhao et al, 2022).…”

“…The energetic electron fluxes can vary over several orders within a short period during geomagnetic activity times (Baker et al., 1997; Guo et al., 2021, 2023; Shin et al., 2016; Thorne, 2010; Wang et al., 2023; Xiang et al., 2021). Energetic electrons can cause irreversible damage on satellites including deep medium charging and single event upset (Liu et al., 2021; Novikov et al., 2008; Pilipenko et al., 2006; Y. Zhao et al., 2022). Consequently, understanding underlying physical mechanisms and predicting the variations of energetic electron fluxes at GEO are critical for the safety of spacecrafts.…”