Near Instantaneous Energization of Electrons to Ultra-relativistic Energies in the Earth's Radiation Belts during the Strong Shock event of 17 March 2015

During the latter part of March 2015, the Earth’s magnetosphere was impacted by a strong interplanetary shock. The resulting geomagnetic storm was the strongest one seen in the past decade. Instruments onboard Van Allen Probes observed near instantaneous energization of electrons to ultra-relativistic energies. Furthermore, these electrons were seen deep within the magnetosphere at L~3.3 injected as a result of the shock impact. We present electron measurements from the Relativistic Electron-Proton Telescope (REPT) and the Magnetic Electron Ion Spectrometer (MagEIS) onboard the twin Van Allen Probes mission. These high-energy electron observations are complemented by the electric and magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument. In-situ measurements from the WIND and Themis fully characterize the interplanetary shock properties.