Impact of High Intensity Long-Duration Continuous Auroral Electrojet Activity (HILDCAAs) on relativistic electrons of the radiation belt of Earth during Van Allen probe era

This study investigates the impact of High-intensity Long-Duration Continuous Auroral Electrojet Activity (HILDCAA) on the relativistic electrons in radiation belt of Earth. Utilizing data from Van Allen Probe mission of NASA, we conducted a comprehensive statistical analysis to understand the impact of HILDCAA events on the radiation belt fluxes. The super epoch analysis was carried out to determine the general response of L-shell, pitch angle, and energy-dependency of relativistic electrons to HILDCAAs. The analysis reveals a significant flux enhancement in the relativistic electron fluxes, predominantly occurring with a delay of 0 to 2 days following the onset of HILDCAA events. The general response indicates that the maximum energy of accelerated electrons reaches up to 6 MeV. Additionally, electrons with perpendicular pitch angles exhibit a significantly greater enhancement in flux and achieve higher maximum acceleration energies compared to those with parallel pitch angles. The observed time-delayed and pitch angle-dependent response related to the onset of HILDCAAs highlights the significant influence of wave-particle interactions, particularly in relation to ultra-low frequency (ULF) waves in this context. This is further supported by ground-based magnetometers and in-situ magnetic field observations from the RBSP probe, which demonstrated enhanced power of ULF waves during HILDCAA events. The study strengthens our current understanding of radiation belt particle acceleration processes and has potential implications for satellite operations and other space-based technologies, both on Earth and in the magnetospheres of other planets.