Journal article
Analysis of Chorus Wave Power on Burst‐Mode Timescales During the Van Allen Probes Era
Journal of geophysical research : Space physics (2013 - Present), Vol.131(5), e2026JA035082
05/2026
DOI: 10.1029/2026JA035082
Abstract
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 . 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. Whistler‐mode chorus is an electromagnetic emission excited in Earth's magnetosphere that can interact with electrons in the outer radiation belt. Through such interactions, electrons can be accelerated, or scattered into the atmosphere. Over long timescales, the resulting global changes in the electron population are typically modeled as a diffusive process. The wave power spectrum is a key input to these models. However, spacecraft measurements show that chorus wave power can be intense and highly variable on short timescales. These features may not be captured in traditional wave statistics due to a variety of spatial and temporal averaging. Such intense and rapidly varying waves may also violate assumptions required for the diffusive framework, and can instead result in interactions with distinct particle responses. Using high‐resolution spacecraft data, we show that maximum chorus wave powers on short timescales can be orders of magnitude larger than those inferred from averaged spacecraft surveys. Under certain magnetospheric conditions, we also identify a population of waves for which up to half may violate assumptions in current radiation belt modeling. Our study motivates further work to investigate how the short‐timescale variability of chorus wave power could affect modeling of wave‐particle interactions. Sub‐second chorus wave power in different frequency bands are investigated using the EMFISIS burst‐ and survey‐mode data Lower‐band power was largest during active times (AE > 300 nT) whilst power variability peaked at low (<5) across all activities Large ratios of maximum burst‐to‐survey power were observed in lower‐band at low (<5), and upper‐band over all conditions
Details
- Title: Subtitle
- Analysis of Chorus Wave Power on Burst‐Mode Timescales During the Van Allen Probes Era
- Creators
- R. Black - British Antarctic SurveyO. Allanson - University of ExeterN. P. Meredith - British Antarctic SurveyA. Hillier - University of ExeterD. P. Hartley - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research : Space physics (2013 - Present), Vol.131(5), e2026JA035082
- DOI
- 10.1029/2026JA035082
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Publisher
- Wiley
- Grant note
- Science and Technology Facilities Council: ST/R000891/1, ST/V000659/1, ST/Y00230X/1 National Aeronautics and Space Administration: 80NSSC20K1324, 80NSSC21K0519 Natural Environment Research Council: NE/S007504/1, NE/V013963/2, NE/V00249X/1, NE/X000389/1, NE/R016038/1 National Science Foundation: 2350235
The authors acknowledge the Van Allen Probes project team for EMFISIS data at https://emfisis.physics.uiowa.edu/data/index, and the Omniweb project team for the provision of AE index data at https://omniweb.gsfc.nasa.gov/. RB would like to acknowledge support from the University of Exeter, the British Antarctic Survey and the United Kingdom Research and Innovation (UKRI) Natural Environment Research Council (NERC) GW4+ DTP2 NE/S007504/1 studentship project 2697077. OA would like to acknowledge support from the University of Birmingham, and also from the UKRI NERC Independent Research Fellowship NE/V013963/1 and NE/V013963/2. NM would like to acknowledge funding from the NERC Grants NE/V00249X/1 (Sat-Risk), NE/X000389/1 and NE/R016038/1. DPH acknowledges support from the National Aeronautics and Space Administration under Grants 80NSSC20K1324 and 80NSSC21K0519, in addition to support from the National Science Foundation Geospace Environment Modeling program under Grant 2350235. AH would like to acknowledge support from STFC Research Grants ST/R000891/1, ST/V000659/1 and No. ST/Y00230X/1. This research was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project 'Beyond Diffusion: Advancing Earth's Radiation Belt Models with Nonlinear Dynamics' (ISSI Team project # $\#$25-640). For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.
- Language
- English
- Date published
- 05/2026
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9985164716602771
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