Figure 4

Figure 4. The X-ray observations and coincident observations of a nightside substorm can be explained by interaction of relativistic electrons with electromagnetic ion-cyclotron waves. The wave growth is driven by hot (~50 keV) protons drifting from the substorm injection into regions of high-density such as the plasmasphere or detached plasma regions. Calculations of wave growth and resonant electron energies show that this model provides a reasonable explanation for the observed energies, spectral characteristics and spatial localization of the event. This cartoon illustrates the main features of the model.