Electron dropout echoes induced by interplanetary shock: Van Allen Probes observations

On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at approximate to 1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or dropout echoes, constitute a new phenomenon referred to as a drifting electron dropout with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from approximate to 1300 to 0100 LT. We conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. The dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.