“MAGNETIC STORMS and substorms affect the electromagnetic field configuration in the inner magnetosphere over time scales of minutes to hours and days. During substorms, the intense current sheet can stretch the quasi-dipolar field lines at geostationary orbit to highly taillike ones, which together with the enhancing electric field causes significant changes in particle drift paths and allows for penetration of the plasma sheet plasma deep inside the inner magnetosphere.”
https://link.springer.com/article/10.12942/lrsp-2007-1