Main Entry: mag·ne·to·sphere

Pronunciation: \mag-ˈnē-tə-ˌsfir, -ˈne-\

Function: noun

Date: 1959

: a region of space surrounding a celestial object (as a planet or star) that is dominated by the object's magnetic field so that charged particles are trapped in it

— mag·ne·to·spher·ic \-ˌnē-tə-ˈsfir-ik, -ˈsfer-\ adjective