Particle Acceleration in the Inner Magnetosphere

Particle acceleration is an important consequence of eruptive or catastrophic configuration changes in space plasmas. It is also a feature associated with more persistent structures, such as thin boundary layers, which exhibit strong gradients, instabilities, and turbulence. The most important acceleration regions in or near the magnetosphere are the bow shock, the magnetotail, the magnetopause, and the inner magnetosphere. The spatial and temporal properties of accelerated particles are the consequences of motion within the extant magnetic and electric fields. The characteristics of accelerated particles can provide insight into the underlying processes that shape the geomagnetic fields (for instance, magnetic reconnection). On the other hand, identifying the properties of the electric field combined with the magnetic field is a crucial complement to the study of the energetic particles themselves. The electric fields may be quasi-static, induced by magnetic field collapse, or the result of fluctuations related to plasma instabilities. The acceleration may produce suprathermal as well as very energetic particle populations. Highly energetic particles can be detrimental to satellite instrumentation and subsystems. The identification and modeling of acceleration mechanisms is therefore a crucial element in the prediction of energetic particle flux increases and the potential prevention of detrimental "space weather" effects. This review focuses on inner magnetospheric acceleration processes.