Using measurements from the Van Allen Probes, we show that field-aligned fluxes of electrons energized by dispersive Alfvén waves (DAWs) are prominent in the inner magnetosphere during active conditions. These electrons have preferentially field-aligned anisotropies from 1.2 to >2 at energies ranging from tens of electron volts to several kiloelectron volts (keV), with largest values being coincident with magnetic field dipolarizations. Comparisons reveal that DAW energy densities and Poynting fluxes are strongly correlated with precipitating electron energies and energy fluxes and also O+ ion outflow energies. These observations yield empirical inner magnetosphere relations between the DAW and electron inputs and the O+ ion outflow response, providing important constraints for models. They also suggest that DAWs play an important role in enhancing field-aligned electron input into the ionosphere that facilitates the outflow and subsequent energization of O+ ions in the wave fields into the inner magnetosphere.
Bibliographical noteFunding Information:
A.?J. Hull and/or C.?C. Chaston received support from Grants 80NSSC18K0835, NNX17AD36G, NNX17A155G, NNX16AG69G, NSF1602941, and 80NSSC19K0081 sub PO36751. P.?A. Damiano received support from Grants NSF1832207 and 80NSSC18K0835. Van Allen Probes funding is provided under NASA prime Contract NAS5-01072; including the EFW investigation, the EMFISIS investigation under JHU/APL Contract 921647, and RBSP-ECT JHU/APL under Contract 967399. We acknowledge use of the SPEDAS software to download and analyze data (Angelopoulos et al.,?2019).
- dispersive Alfvén waves
- field-aligned electrons
- geomagnetic storms
- inner magnetosphere
- oxygen ion outflow