Update July 11, 2023, 5:22 p.m: An early forecast released by the University of Alaska Fairbanks Geophysical Institute initially indicated that given the right weather, the northern lights may be visible on Thursday July 13 in at least 17 states. The forecast was updated on Monday evening to show that aurora was unlikely to be seen in those initially forecasted regions, but may be visible in regions where they are more commonly seen, namely parts of Alaska and several Canadian provinces.
“The accuracy of the models to predict the auroral activity depend strongly on the accuracy and number of input measurements of the activity on the sun and the intervening space where the solar wind is flowing and evolving after it leaves the sun. There are only a few satellites and instruments dedicated to collecting these data, so the models typically have a wide range of predictions since the observations are relatively sparse. While large solar storms can be seen leaving the vicinity of the sun, and their direction and speed can be estimated, once they leave the local solar vicinity they cannot be tracked. During this time the solar storms can be slightly diverted or even reduced, and the final impact on Earth’s magnetic field may be different than predicted,” research associate professor Don Hampton, a space physicist at the University of Alaska Fairbanks Geophysical Institute, told PopSci in an email.
This prediction was made several days ahead of time and is based on models that are run by NOAA’s Space Weather Prediction Center. The Geophysical Institute doesn’t make long-term auroral predictions and this more short-term forecast is from the SWPC. (An article on EarthSky has contested the University of Alaska Fairbanks Geophysical Institute’s aurora forecast.)
Only a few satellites and instruments are dedicated to collecting this data, so models generally have a wide range of predictions due to more sparse observations. It’s possible large solar storms can be seen leaving the sun and their speed and direction can be estimated. However, once they leave the vicinity of the sun they can’t be tracked. During this time, solar storms can be slightly moved off course or even reduced which can change the final impact that the solar storm has on Earth’s magnetic field.
Additionally, Lieutenant Bryan R. Brasher from the SWPC said that this initial prediction for moderate geomagnetic storming on Thursday was influenced by the recurrence of a particular coronal hole in the sun. This spot caused higher geomagnetic activity.
“Some features –such as corona holes–can persist for many weeks and so a good starting point for predicting long range behavior is how these features affected the space environment the last time they faced Earth,” Brasher told PopSci in an email. “This was reflected in our weekly 27-day outlook product. As this particular coronal hole rotated back into view however–meaning we could see and analyze it–it was clear that it had diminished and we adjusted our forecast accordingly.”
Brasher added that while the immediate forecast doesn’t necessarily call for aurora activity this week, the Earth is approaching a solar maximum phase in the sun’s roughly 11 year cycle. This period is characterized by heightened solar activity, similar to the storms seen in March and April.
An earlier version of this story follows.
Residents of 17 states could catch a glimpse of the elusive aurora borealis, also known as the northern lights, this Thursday. The predicted rainbow of colors that light up the night sky when solar wind hits the atmosphere is part of a solar cycle that is expected to peak in 2024, and is making the northern lights visible in points further south.
[Related: We finally know what sparks the Northern Lights.]
The Geophysical Institute at the University of Alaska at Fairbanks has forecast auroral activity on July 12 and 13 parts of in Alaska, Oregon, Washington, Idaho, Montana, Wyoming, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, New York, New Hampshire, Vermont, Indiana, Maine, and Maryland.
The Kp index, or planetary index, ranks auroral activity on a scale from zero up to nine—zero being not very active and nine being bright and active. Thursday’s storm has a forecast for Kp6, according to the Geophysical Institute.
The forecast predicts that on Wednesday, the storm could be highly visible “low on the horizon from Seattle, Des Moines [Iowa], Chicago, Cleveland, Boston, and Halifax [Nova Scotia].”
On Thursday, it could get stronger and may be seen overhead in cities including Minneapolis, Milwaukee, Bay City, Michigan. The lights could be visible on the horizon in Salem, Boise, Cheyenne, Lincoln, Indianapolis, and Annapolis.
The northern lights occur when the sun’s continuous solar wind and solar storms, specifically those called coronal mass ejections, interact with Earth’s magnetic field. The light show happens very frequently in locales like northern parts of Canada, Alaska, and Scandinavia. Huge bursts of plasma are ejected via this wind, spraying electrons into the magnetic field. These super charged particles then combine with the field and shoot into Earth’s atmosphere, following the path of the magnetic field towards the Earth’s poles. When these particles collide with molecules in the atmosphere, they produce the dazzling colored lights in our sky.
UCLA space science professor Robert McPherron told PopSci in September 2022 that this process is similar to switching off old television sets. “When you turn them on, if you had good hearing, you’d hear a very high pitched whine indicative of a very high frequency” caused by a beam of electrons. And if you turned it off, you’d see a spot right in the center of the screen.”
That glowing spot on the fluorescent screen occurs when a beam of electrons hits it from the inside. “And that’s exactly what the aurora is,” McPherron said. “It is electrons coming down along a magnetic field line, and the screen is the atmosphere.”
[Related: Hold onto your satellites: The sun is about to get a lot stormier.]
The greens, blues, and reds that result come from the electrons as well. As they enter the Earth’s atmosphere, the electrons excite gasses, particularly oxygen and nitrogen. Once the molecules within the oxygen and nitrogen are charged with this energy beyond their normal state, they emit photons as they return back to their baseline levels. Oxygen emits greens and reds, while nitrogen glows blue.
In April, the northern lights were visible as far south as Arizona during a huge surge of solar activity. This next storm is the third severe geomagnetic storm since this current solar cycle began in 2019.
According to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center, those hoping to catch a glimpse of the aurora should head away from city lights and that the best viewing times are between 10 PM and 2 AM local time.
