Electron-Driven Magnetic Dip Embedded Within the Proton-Driven Magnetic Dip and the Related Echoes of Butterfly Distribution of Relativistic Electrons

In this study, a magnetic dip event in which a small-scale magnetic dip is embedded within a large-scale magnetic dip is analyzed based on the observations of the Van Allen Probes. The small-scale dip is contributed by a sharp electron injection at the energy range of 1 to 10 keV, but the large-scale dip is contributed by a smooth proton injection at the energy range higher than 10 keV. The formation of dip caused by the suprathermal electrons is supported by the self-consistent magnetic model. Moreover, the echoes of butterfly distributions of relativistic electrons at the energy range of 0.5 to 3.4 MeV is observed. The time separations of the neighboring butterfly distributions are comparable to the drift periods of the electrons at the different energies. We suggest that the potential nonadiabatic processes in response to the magnetic dips possibly account for the butterfly distribution echoes.