WYOMING — Geomagnetic activity is expected to put on a light show in the sky on the night of Monday, Sept. 18, and the action might be visible as far south as Wyoming.
According to the National Weather Service’s office in Riverton, Wyoming, a coronal mass ejection was emitted by the sun on Saturday, Sept. 16, which will lead to its plasma interacting with upper levels of the earth’s atmosphere, generating the famous colors.
The Kp index is expected to reach level six between 3 and 6 a.m. in the early hours of Tuesday, Sept. 19, which would be the best time to catch the lights. Some activity might be detectable beginning as early as 9 p.m. tonight, when the Kp index is expected to hit level five.
Derived from the German “Planetarische Kennziffer,” or planetary index, the Kp scale runs from zero to nine.
As explained by Wyoming Stargazing, the Kp index “measures the disruption of the horizontal distribution of the geomagnetic activity…A value of zero means that even Fairbanks, Alaska would have difficulty in seeing the northern lights. One to three is most common, and that’s what is frequently seen in those northern latitudes of northern Canada and Alaska. A four would push them down into southern Canada, while a five, in the right conditions, might just barely be visible on the northern horizon here in Jackson Hole. To see them well, we typically need at least a six.”
A prediction by the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center forecasts the aurora’s “view line” as passing through the Cowboy State, bisecting it horizontally.
Jackson might be right on the cusp of visibility. Visitors to Yellowstone National Park and Grand Teton National Park could have a better vantage point.
The moon is waxing crescent, with illumination expected to be around 11% tonight, which could contribute to favorable visibility conditions.
Even if viewing conditions are perfect, though, it’s difficult to predict the aurora with much certainty.
“Space weather is very fickle,” National Weather Service Riverton meteorologist Chris Hattings says in the video above.