Alpenglow is the reddish light you can sometimes see on the tops of mountains, especially snow-covered mountains, just before the sun rises or right after it sets.
Alpenglow is a phenomenon that's unique to the mountains. When the sun is below the visible horizon, tall mountains can still catch the sun's rays. Just before sunrise and after sunset, longer-wavelength red and orange sunlight reflects down onto the mountain peaks from particles high up in the atmosphere, creating a warm glow. The word alpenglow comes from the German Alpenglühen, which literally means "Alps-glow." The Alps are an often snow-capped mountain range in central Europe; the highly reflective snow intensifies the alpenglow.