What particles from the Sun chiefly cause Earth's auroras when they interact with the atmosphere?

Charged particles from the Sun chiefly cause Earth's auroras when they interact with the atmosphere.

The solar wind carries electrons and ions outward from the Sun. Earth's magnetosphere guides many of these particles toward polar regions, where collisions with oxygen and nitrogen atoms and molecules excite atmospheric gases. When those gases return to lower-energy states, they emit colored light.

Auroras are therefore electrical and magnetic phenomena as well as atmospheric displays. Oxygen commonly contributes green and red emissions, while nitrogen can contribute blue and purplish colors. Strong solar storms can expand auroral activity toward lower latitudes, but the lights are not caused simply by sunlight reflecting from clouds.