What orientation of Bz (B sub z) increases the likelihood that charged particles from the Sun will cause disturbed conditions?

Explication

The Earth's field points northward at the front of the magnetosphere, so an interplanetary field pointing southward is antiparallel to it and reconnects readily, opening a route for solar wind energy and charged particles to enter and disturb conditions. A northward Bz is parallel to the Earth's field and largely shields the magnetosphere instead.