Electron flux measurements are an important diagnostic for interactions between ultralow-frequency (ULF) waves and relativistic (∼1 MeV) electrons. Since measurements are collected by particle detectors with finite energy channel width, they are affected by a phase mixing process that can obscure these interactions. We demonstrate that ultrahigh-resolution electron measurements from the Magnetic Electron Ion Spectrometer on the Van Allen Probes mission—obtained using a data product that improves the energy resolution by roughly an order of magnitude—are crucial for understanding ULF wave-particle interactions. In particular, the ultrahigh-resolution measurements reveal a range of complex dynamics that cannot be resolved by standard measurements. Furthermore, the standard measurements provide estimates for the ULF flux modulation amplitude, period, and phase that may not be representative of true flux modulations, potentially leading to ambiguous conclusions concerning electron dynamics.
Bibliographical noteFunding Information:
M. D. H. was supported by NASA NNX17AI53G and LANL-CSES. Work at The Aerospace Corporation was supported by RBSPECT funding provided by JHU/APL contract 967399 under NASA’s Prime contract NAS5-01072, and MagEIS processing and analysis was generally funded under NASA’s Prime contract NAS5-01072. The work by the EFW team was conducted under JHU/APL contract 922613 (RBSP-EFW). I. R. M. is supported by a Discovery Grant from Canadian NSERC. We acknowledge the NASA Van Allen Probes and Craig Kletzing for use of EMFISIS data. We acknowledge the NASA Space Science Data facility providing the solar wind, geomagnetic activity indices, and most RBSP satellite measurements used in this study. With the exception of ultrahigh-resolution electron fluxes, all data are publicly available using either the OMNIWeb interface (http:// omniweb.gsfc.nasa.gov for solar wind and geomagnetic activity indices) or CDAWeb interface (https:// cdaweb.sci.gsfc.nasa.gov/index. html/ for RBSP measurements). The ultrahigh-resolution electron fluxes are provided in the supporting information. SPEDAS software for plotting can be obtained from the THEMIS website (http://themis.ssl. berkeley.edu/index.shtml).
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- ULF wave
- drift resonance
- particle detector
- radiation belts
- wave-particle interaction