Analysis of Chorus Wave Power on Burst‐Mode Timescales During the Van Allen Probes Era

Interactions between whistler‐mode chorus waves and electrons are a key driver of dynamics in Earth's radiation belts. These global dynamics are often described using Fokker‐Planck diffusion models.Whilst, in many cases, such models effectively describe the large scale changes within the region, they often rely upon spatially and temporally averaged representations of the wave properties. However, observations have shown that whistler‐mode chorus can display large sub‐second powers that challenge model assumptions and potentially give rise to non‐diffusive processes. Here, we investigate the power of whistler‐mode chorus on sub‐second timescales using the high‐resolution data capture mode on the Van Allen Probes' Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS). We show that peak chorus power on sub‐second timescales is regularly larger than the corresponding spacecraft “survey” power by over a factor of 100. The work also explores the magnetospheric conditions under which the largest sub‐second power variability of chorus waves is observed, and we find that trends vary across different chorus frequency bands. Notably, the largest powers are observed in the lower‐band frequency range during active conditions and between 21:00–12:00 MLT, where >46% of burst samples contain an instantaneous wave intensity that exceeds 2.25 × 104 pT2. Further, binning the lower‐band power by the ratio of plasma‐to‐gyrofrequency separates the waves into two distinct low and high variability populations. The results quantify sub‐second wave power variability that may influence energetic electron dynamics not currently captured in time‐averaged wave models.