Scientists Solve The Mystery Of STEVE, And Find It’s So Much More Than An Aurora

“Normally, aurorae are produced by the Sun’s charged particles striking the atoms in Earth’s upper atmosphere. The solar wind particles get bent by Earth’s magnetic field, exciting and ionizing oxygen, nitrogen, and hydrogen. When electrons recombine with ions, they cascade back down to lower energies, creating aurorae from their emission lines. STEVE is distinct from this for multiple reasons.”

It isn’t often that a naked-eye skywatcher gets a chance to observe an entirely new optical phenomenon that’s never been seen or recorded before. Yet earlier this century, that’s exactly what’s happened with a purple/green/mauve ribbon of light that sometimes appears in the sky. Known as STEVE, for strong thermal emission velocity enhancement, this ribbon includes colors never seen in an aurora, appears at lower latitudes than those where aurorae are typically found, and most importantly, isn’t created coincident with the precipitation of charged particles. In other words, it’s an entirely new phenomenon!