Electrons gyrating along the lines of Earth's magnetic field make another orbit around Earth and strike the Van Allen Probe A AGAIN!
On March 17, 2016, Van Allen Probe A detected a pulse of high energy electrons in the radiation belts, generated by the impact of a recent coronal mass ejection striking Earth's magnetosphere. The gradient drift speed of the electron pulse was high enough, that it propagated completely around Earth and was detected by the spacecraft again as the pulse spread out in the radiation belt. Because the particles have a range of energies, the pulse spread out as it moved around Earth, generating a weaker signal the next time it hit the spacecraft.
Once the pulse of accelerated electrons are injected into the radiation belts, the magnetic gradient drift guides them around Earth where they serendipitiously strike the particle detectors of Van Allen Probe A.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0