A magnetic conjunction between Van Allen Probes spacecraft and the Balloon Array for Radiation-belt Relativistic Electron Losses (BARREL) reveals the simultaneous occurrence of broadband Alfvénic fluctuations and multi-timescale modulation of enhanced atmospheric X-ray bremsstrahlung emission. The properties of the Alfvénic fluctuations are used to build a model for pitch angle scattering in the outer radiation belt on electron gyro-radii scale field structures. It is shown that this scattering may lead to the transport of electrons into the loss cone over an energy range from hundreds of keV to multi-MeV on diffusive timescales on the order of hours. This process may account for modulation of atmospheric X-ray fluxes observed from balloons and constitute a significant loss process for the radiation belts.
Bibliographical noteFunding Information:
This research was supported by the NASA grants NNX15AF57G, NNX16AG69G, NNX17AD36G, and NNX17AI55G and Van Allen Probes (RBSP) funding provided under NASA prime contract NAS5-01072, including the EFW and EMFISIS investigations under JHU/APL contract 921647 and RBSP-ECT under JHU/APL contract 967399. Data generated from theoretical models are stored on Linux workstations at the Space Sciences Laboratory at UC Berkeley and can be accessed by contacting the first author. Van Allen Probes and BARREL measurements used in this study can be obtained from the following data repositories: EFW http://www.space. umn.edu/rbspefw-data/, EMFISIS http:// emfisis.physics.uiowa.edu/data/index, HOPE/MAGEIS/REPT https://www.rbsp- ect.lanl.gov/science/DataDirectories. php, BARREL http://www.dartmouth. edu/~barrel/data.html, and/or by directly contacting the first author.
- Alfven waves
- drift-bounce resonance
- energetic particles
- geomagnetic storms
- pitch angle scattering
- radiation belts