Multipoint Observations of Quasiperiodic Emission Intensification and Effects on Energetic Electron Precipitation

Abstract

The two Van Allen Probes simultaneously recorded a coherently modulated quasiperiodic (QP) emission that persisted for 3 h. The magnetic field pulsation at the locations of the two satellites showed a substantial difference, and their frequencies were close to but did not exactly match the repetition frequency of QP emissions for most of the time, suggesting that those coherent QP emissions probably originated from a common source, which then propagated over a broad area in the magnetosphere. The QP emissions were amplified by local anisotropic electron distributions, and their large‐scale amplitudes were modulated by the plasma density. A novel observation of this event is that chorus waves at frequencies above QP emissions exhibit a strong correlation with QP emissions. Those chorus waves intensified when the QP emissions reach their peak frequency. This indicates that embryonic QP emissions may be critical for its own intensification as well as chorus waves under certain circumstances. A Low‐Earth‐Orbit POES satellite observed enhanced energetic electron precipitation in conjunction with the Van Allen Probes, providing direct evidence that QP emissions precipitate energetic electrons into the atmosphere. This scenario is quantitatively confirmed by our quasilinear diffusion simulation results.

Quasiperiodic Emissions and Related Particle Precipitation Bursts Observed by the DEMETER Spacecraft

“…However, the results obtained indicate that mostly the particles with energies below about 250 keV are affected. This roughly corresponds to the upper energy in the simulation results (Li et al., 2021). Note that the lower part of the precipitating energetic electron spectrum is not measurable due to the experimental constraints, as the lowest energy channel of the DEMETER IDP instrument is as high as about 72.9 keV.…”

“…Titova et al (2015) used Van Allen Probes spacecraft measurements to identify energetic electron flux changes with periods corresponding to the QP modulation in the proximity of a tentative source region. Finally, Li et al (2021) used simultaneous measurements of QP emissions by the Van Allen Probes and energetic electron precipitation by the low-altitude POES satellite to demonstrate energetic electron precipitation in association with QP emissions.…”

“…Finally, Li et al. (2021) used simultaneous measurements of QP emissions by the Van Allen Probes and energetic electron precipitation by the low‐altitude POES satellite to demonstrate energetic electron precipitation in association with QP emissions.…”

Quasiperiodic ELF/VLF Emissions Associated With Corresponding Pulsations of the Geomagnetic Field

“…Recent survey by Li et al. (2021) based on Van Allen Probes wave measurements and the energetic electron data obtained by the Polar‐orbiting Operational Environmental Satellite present energetic electron precipitation simultaneously with QP emissions.…”

“…Titova et al (2015) studied Van Allen Probes spacecraft measurements and compare changes of the energetic electron flux with periods of the QP modulation. Recent survey by Li et al (2021) based on Van Allen Probes wave measurements and the energetic electron data obtained by the Polar-orbiting Operational Environmental Satellite present energetic electron precipitation simultaneously with QP emissions.…”