Figure 1
APS/Alan Stonebraker

Figure 1: The acceleration of relativistic electrons in the Earth’s radiation belts can be described as a two-step process: first, electrons are accelerated to about a hundred keV by the potential drop due to streams of double layers (here represented as a stairway). Once they have enough energy, they can interact resonantly with whistler waves and be quickly accelerated to MeV energies. In a sense, double-layer streams represent a stairway to whistlers.