Simulated prompt acceleration of multi-MeV electrons by the 7 September 2017 interplanetary shocks

Monday, 5 March 2018: 09:40
Longshot and Bogey (Hotel Quinta da Marinha)
Mary K Hudson1, Shrikanth G Kanekal2, Zhao Li3, Maulik Patel3 and John R Wygant4, (1)Dartmouth College, Physics and Astronomy Dept, Hanover, NH, United States, (2)Heliophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Dartmouth College, Hanover, NH, United States, (4)University of Minnesota, School of Physics and Astronomy, Minneapolis, MN, United States
PDF
Abstract:
Van Allen Probes measurements have provided unprecedented opportunity to examine prompt acceleration by CME shock compressions of the dayside magnetopause. The 8 October 2013 event was well documented with Van Allen Probes observations on the dayside1 and modeled with MHD-test particle simulations. A weaker event on 14 December 2015 benefited from simultaneous measurements by MMS and Van Allen Probes on the dayside2. The strongest storm of Solar Cycle 24 on 17 March 2015 produced clear evidence of shock compression and resulting drift echoes produced by the azimuthal electric field impulse propagating tailward, transporting electrons radially inward along the dusk flank. MHD-test particle simulations reproduced the pitch angle dispersion and drift echoes seen by Van Allen Probes A and B pre-midnight3. The most recent well-characterized event of this type occurred on 7 September 2017 when both Van Allen Probes spacecraft were on the dayside. Drift echoes as evidence for prompt acceleration were again detected by both Van Allen Probes spacecraft4. These have been modeled with MHD-test particle simulations, providing evidence for the importance of a steep radial gradient in producing the drift echoes. The overall effect of all of these events observed during the Van Allen Probes era is less critical to populating the outer zone and slot region than either the 24 March 1991 shock compression event observed by CRRES or the 2003 Halloween storm, both of which produced newly trapped populations in the usual slot region. The latter requires a much stronger Ephi ~ 100 mV/m on the dayside as inferred for the March 1991 event and modeled for the Halloween 2003 storm, vs. Ephi ~ 10 mV/m for Van Allen Probes era compression events. Nontheless, the radial transport and energization scales with Ephi and the mechanism is quantitatively verified for these recent injections. Thus it is possible to extrapolate to stronger events, where once injected into the slot region multi-MeV electrons persist for months to years.

1Foster, J. C., et al. (2015), J. Geophys. Res., 120, 1661–1674, doi: 10.1002/2014JA020642

2Cattell, C., et al. (2017), Geophys. Res. Lett., 44, 8712–8720, doi:10.1002/2017GL074895

3Hudson M.K., et al. (2017), J. Geophys. Res., 122, doi:10.1002/2017JA024445

4Kanekal, S., et al., Geophys. Res. Lett., submitted 2017.

<< Previous Abstract | Next Abstract