PLASMAS AND FIELDS. “While the magnetospheric field in general excludes the solar wind plasma from the magnetosphere, at times the solar wind can gain entry into the magnetosphere through the magnetopause. This occurs when the IMF and the magnetospheric fields are antiparallel and magnetic reconnection creates an “open magnetosphere” configuration with a field component normal to the boundary.” (IMF= interplanetary magnetic field).
https://link.springer.com/article/10.12942/lrsp-2007-1