Speaker
Description
This study investigates chorus wave activity and relativistic electron dynamics in the radiation belts during the High-Speed Stream (HSS) event of July 7, 2016. Electron flux measurements from the REPT instrument and magnetic field data from EMFISIS aboard the Van Allen Probes were analyzed, along with solar wind and interplanetary magnetic field (IMF) parameters from the DSCOVR satellite. The interaction between fast and slow solar wind streams within the stream interaction region (SIR) led to a strong southward IMF Bz component, which favored intense chorus wave activity. High-amplitude chorus bursts were detected in both the lower (0.1–0.5 fce) and upper (0.5–0.9 fce) bands. Rising-tone elements and nonlinear wave signatures were observed, revealing coherent wave–particle interactions. Oblique and parallel chorus wave modes coexisted, suggesting a competition between acceleration and loss processes driving variability in the outer radiation belt relativistic electron flux. Local plasma conditions (ωpe/Ωce < 5) supported nonlinear wave growth. The observed pitch-angle scattering led to spatially localized enhancements and losses of relativistic electrons, particularly at L-shells greater than 5. Other wave modes—such as electromagnetic ion cyclotron (EMIC) and ultra-low frequency (ULF) waves—were also investigated. The results indicate that chorus waves likely played a significant role in the localized loss of relativistic electrons. However, the global flux depletion also involved contributions from EMIC and ULF wave activity as well as magnetopause shadowing, highlighting a combined loss process driven by the HSS-related solar wind structure. These findings reinforce the importance of identifying the dominant wave–particle interactions and external drivers responsible for radiation belt variability during high-speed stream events.
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