How to make a magnetosphere

On its journey from the Sun, the solar wind encounters bodies with various magnetic field strengths. The stronger planetary magnetic fields create a cavity or magnetosphere in the solar wind that greatly exceeds the scale lengths of the gyrating ions and exhibits self-similar behaviour. The weaker magnetic fields, associated with smaller bodies, create a spectrum of disturbances that differ from the planetary magnetospheres and in which ion scales are important. Global numerical simulations that resolve the ion motion enable us to examine the evolution of these disturbances from simple wakes to complex systems with features very similar to planetary magnetospheres. Examining this hierachy provides insight into the formation of planetary magnetospheres, including the origin of such features as the magnetotail, plasma sheet, magnetopause, magnetosheath, bow shock and trapped radiation belts.