Residents of 17 states were able to catch a glimpse of the elusive aurora borealis, otherwise known as the Northern Lights, this Thursday. The predicted rainbow of colors illuminating the night sky as the solar wind hits the atmosphere is part of a solar cycle expected to peak in 2024 and will make the Northern Lights visible in points farther south.
[Related: We finally know what sparks the Northern Lights.]
The University of Alaska Geophysical Institute at Fairbanks has prediction auroral activity on July 12 and 13 sharing 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 of zero to nine — zero is not very active and nine is bright and active. Thursday’s storm has a forecast for Kp6, according to the Geophysical Institute.
The prediction predicts the storm will be highly visible Wednesday “low on the horizon from Seattle, Des Moines [Iowa]Chicago, Cleveland, Boston and Halifax [Nova Scotia].”
It will strengthen Thursday and can be seen overhead in cities such as Minneapolis, Milwaukee, Bay City, Michigan. The lights will be visible on the horizon in Salem, Boise, Cheyenne, Lincoln, Indianapolis and Annapolis.
The Northern Lights occur when the sun’s ongoing solar wind and solar storms, especially those so-called coronal mass ejections, interact with Earth’s magnetic field. The light show happens very often in northern areas such as Canada, Alaska and Scandinavia. Huge bursts of plasma are ejected via this wind, ejecting electrons into the magnetic field. These supercharged particles then combine with the field and blast into Earth’s atmosphere, following the path of the magnetic field to Earth’s poles. When these particles collide with molecules in the atmosphere, they produce the dazzling colored lights in our sky.
Robert McPherron, professor of space sciences at UCLA, told me PopSci in September 2022 that this process is similar to turning off old television sets. “When you turn them on, if you had good hearing, you would hear a very high-pitched whine indicating a very high frequency,” caused by a beam of electrons. And if you turned it off, you would see a spot in the middle of the screen.”
That glowing spot on the fluorescent screen is created when a beam of electrons hits it from the inside. “And that’s exactly what the aurora is,” McPherron said. “It’s electrons coming down 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 green, blue and red hues that result also come from the electrons. When they enter the Earth’s atmosphere, the electrons excite gases, specifically oxygen and nitrogen. Once the molecules in the oxygen and nitrogen are charged with this energy beyond their normal state, they emit photons when they return to their baseline levels. Oxygen emits green and red, while nitrogen glows blue.
In April, the Northern Lights were visible as far south as Arizona during a massive wave of solar activity. This next storm is the third severe geomagnetic storm since this current solar cycle started in 2019.
This is reported by the National Oceanic and Atmospheric Administration Space Weather Forecast Center, those wanting to catch a glimpse of the aurora should move away from city lights and that the best viewing times are between 10 p.m. and 2 a.m. local time.