Where in the ionosphere does auroral activity occur?

Auroral activity, commonly known as the Northern or Southern Lights, occurs primarily in the E-region of the ionosphere, which is located about 90 to 150 km above the Earth's surface. Charged particles from solar wind interact with gases at this specific altitude, ionizing them and causing them to emit light. Because this ionization happens in the E-region, radio signals that scatter off the auroral curtain are interacting with this specific atmospheric layer. Other layers, such as the D-region (which mainly absorbs signals) or the F-region (which facilitates higher-altitude HF propagation), do not host these auroral interactions.