I will never figure out the aurora. Most of the time there’s a clear connection and forecast indicating that a flare or coronal hole on the sun will have a certain probability of zinging the Earth’s magnetic field. That might precipitate a display of the northern lights anywhere from the high Arctic to as far south as Arizona.
Like the weather forecast, sometimes space meteorologists get it wrong though not for lack of trying. Nature does not always follow expected pathways despite the best available data and computer modeling.
Last night northern lights were not in the forecast. The Kp index slumbered around 2 and space weather experts predicted quiet conditions. I even checked the POES satellite map to gauge the extent of the auroral oval and found it nestled far to the north above Hudson Bay. So why did the aurora make an appearance?
The northern sky up to about 20 degrees (two fists) glowed with colorless, amorphous light punctuated by occasional faint rays that rose like wisps of smoke from a smouldering campfire. This went on until at least 2 0′clock.
After scratching my head about the matter this morning, I decided to call Joe Kunches, a space scientist at NOAA’s Space Weather Prediction Center. He boiled it down to this: even though aurora wasn’t in the forecast, the constant wind of electrons and protons streaming off the sun (solar wind) “always causes some level of activity in Earth’ s polar atmosphere.”
Electrons in the wind excite the atoms of the upper atmosphere to give off characteristic auroral greens, reds and purples.
This permanent aurora is called the auroral oval; it normally resides in the high Arctic (and Antarctic) but expands further south over the U.S. during periods of enhanced solar activity.
Given dark skies and no moon, conditions were ideal to see even a minor aurora last night. Still, we both remained puzzled as to why the aurora was visible as far south as Duluth when magnetic indicators and satellite maps showed it residing far to the north in the oval.
“You shouldn’t have seen it,” Kunches joked. With that, we both had a good laugh.