The interaction of a strong magnetic field with a cold plasma: The evolution of a magnetic bubble

An intense localized magnetic field is suddenly introduced into a stationar y, uniform, cold plasma and generates a region characterized by an intense field that excludes all particles ("magnetic bubble") enveloped by a spheri cal shell of very dense plasma ("snowplow"). Outside the shell, the field d isappears over a small distance scale and the plasma density tends to that of the undisturbed plasma. While a mathematically self-similar solution to the astrophysical problem associated with the early history of the magnetic bubble exists, the dynamical evolution maintains a subtle but significant difference from the self-similar solution. This MHD behavior can arise in t he evolution of young stellar objects, during the switch-on of an OB star, in the solar wind, and during the formation of a magnetized neutron star or "magnetar" immediately following a supernova explosion.