1024x768 Purple - Northern Lights Wallpaper | Nor...

: Sometimes, purple appears at extremely high altitudes (above 180 miles) when nitrogen ions are struck by sunlight near twilight, a phenomenon known as sunlit aurora . Cultural & Spiritual Meanings

: These colors form in the denser parts of the upper atmosphere, below 60 miles, where nitrogen is more abundant than oxygen. 1024x768 purple northern lights wallpaper | Nor...

: Unlike the common green aurora caused by oxygen, purple and blue hues are produced by ionized nitrogen . : Sometimes, purple appears at extremely high altitudes

Aurora colors: What causes them and why do they vary? - Space below 60 miles

: Because nitrogen is harder to "excite" than oxygen, purple lights generally only appear during strong geomagnetic storms when solar particles have enough energy to penetrate deeper into the atmosphere.