If you see an M to X class flare, there will be about a 2 to 3 day lag before the geomagnetic storm particles impacts the earth's magnetosphere. If the flare tosses an earth directed coronal mass ejection, the prospects for a good aurora improve...along with a bad night to watch your DishNet or DirectTV movies. The impact of the particles is evidenced by a sharp shift in the GOES Hp trace. Protons tend to rise and the electron measurements become invalid owing to "poisoning" of the detectors by the masssive volumes of protons. The energetic mass strikes the magnetosphere and deforms it. Some of the particle mass just impacts the earth and stays. It is my theory that this energetic mass contributes to increased intensity in an ongoing weather system and increased volcanic/magma movement. Just theory, but fairly repeatable observations.