Last night I got a couple of texts that the northern lights were out. By the time I got to the beach here in northern lower Michigan, they had died back to a soft arc on the horizon. Up on the Keweenaw however, they were pretty spectacular!
In addition to being spectacular, Eric’s photos introduced me to a new northern lights term, the mysterious proton arc or proton aurora. which NASA’s Astronomy Picture of the Day explains in this link filled post (picture is below):
What are auroras made out of? Triggered by solar activity, normal auroras are caused by collisions between fast-moving electrons and the oxygen and nitrogen in Earth’s upper atmosphere. The electrons come from the magnetosphere, the region of space controlled by Earth’s magnetic field. As the excited oxygen and nitrogen molecules return to their low energy state, they emit light, seen as the auroral glow.
Sometimes, however, auroras can be caused by collisions with heavier protons, causing a more energetic display with strong ultraviolet emission. In addition, protons can temporarily capture an electron and emit light for themselves. Such a proton aurora is seen above, recorded by the IMAGE satellite. A special feature is the bright spot near picture center, embedded in a ring of auroral emission around the north magnetic pole of planet Earth.
Most solar wind protons never reach the Earth to cause auroras because they are completely deflected away at a great distance by the Earth’s magnetic field. The bright spot in the auroral ring indicates a particularly deep crack in the Earth’s magnetic field where protons were able to flow along a temporarily connected region between the Sun and the Earth, relatively undeflected, until they impacted the Earth’s ionosphere.
Read on for lots more. The good news? It looks like the wide coronal hole that was responsible for last night’s aurora will continue to kick out the celestial jams for a couple of days, meaning this weekend offers a great chance to see the northern lights in Michigan!
Much more about the northern lights / aurora borealis on Michigan in Pictures!
Photo courtesy NASA: