Killer electrons are highly energetic electrons trapped in Earth’s outer radiation belt. As the name suggests, killer electrons are energetic enough to penetrate satellite shielding and the satellite can be damaged. How the energetic particles are accelerated in the Van Allen radiation belts is one of major problems in the space physics. Very Low Frequency (VLF) wave-particle interaction has been considered as one of primary electron acceleration mechanisms because electron cyclotron resonances can easily occur in the VLF frequency range. However, recently, by using four Cluster spacecraft observations, we have found that after interplanetary shocks impact on the Earth’s magnetosphere, the acceleration of the energetic electrons in the radiation belt started nearly immediately and lasted for a few hours. The time scale (a few days) for traditional acceleration mechanism of VLF wave-particle interaction to accelerate electrons to relativistic energies is too long to explain the observations. Interplanetary shocks interact with and the Earth’s magnetosphere manifests many fundamental important space physics phenomena including energetic particle acceleration.

The mechanism of fast acceleration of energetic electrons in the radiation belt response to interplanetary shock impact contains two contributing parts: (1) the initial adiabatic acceleration due to the strong shock-related magnetic field compression; and (2) then followed by the drift-resonant acceleration with poloidal ULF waves excited at different L-shells. The results reported in this talk cast new lights on understanding the acceleration of energetic particles in the Earth’s Van Allen radiation belt. The results of this study can be widely used in interplanetary shock interacting with other planets.