Extra exam question E3C05

WhyA southward orientation of Bz increases the likelihood that charged particles from the sun will cause disturbed geomagnetic conditions. When Bz points southward, opposite to Earth's own northward-pointing magnetic field at the point of contact, it lines up in a way that lets solar wind energy couple efficiently into Earth's magnetosphere, making disturbed geomagnetic conditions more likely, answer A. A northward Bz tends to shield against this coupling instead, and east-west orientation isn't the relevant axis for this particular effect.