Why Geomagnetic storms funnel charged particles into the polar ionosphere, creating auroral curtains of dense, highly ionized gas. That ionization can scatter or reflect VHF signals, especially 6 meters and 2 meters, letting stations at northern latitudes work auroral contacts that are impossible under quiet conditions. The signals have a characteristic buzzy, distorted sound, so CW and narrow modes work best.
Watch out The HF choices have it backwards: high geomagnetic activity absorbs and disrupts HF paths, particularly those crossing the polar regions, so polar HF signals get weaker, not stronger.
Storms hurt HF but help VHF: high A and K indices mean aurora, so look up to 6 and 2 meters.