On Monday night, the Aurora Borealis, also know as the Northern Lights, made a rare appearance in the lower latitudes of the US. These geomagnetic storms are normally limited to the polar regions, where the earth’s magnetic field is strongest.
An aurora is an optical phenomenon that is the result of charged solar particles becoming trapped in the Earth’s magnetic field. These particles ionize or excite the gases that make up our atmosphere. As these gases return to their ground state, they emit light energy that we see as neon-like colors dancing in the sky. The different colors can depend on the amount of energy absorbed, but in general, oxygen tends to produce a green light and nitrogen gives off a red glow.
Auroras at the poles are connected to the solar wind, a continuous flow of charged particles outward from the sun. Monday’s unusual display, however, was caused by an intense storm on the surface of the sun and coronal mass ejection. This tremendous eruption of solar wind temporarily allowed the auroral zone in our atmosphere to expand southward.
Auroral activity tends to be strongest around the seasonal equinoxes. In the southern hemisphere, auroras are called Southern Lights or Aurora Australis.
Northern Lights
Photo credit: dakotalapse.com