Northern Lights May Reach 8 US States Tonight as Alaska Faces Highest Odds

Q: Could a sudden shift in Earth's magnetic field turn tonight's faint aurora forecast into a spectacular, multi-colored light show?

No. A dramatic aurora upgrade tonight would not come from a sudden shift in Earth’s own magnetic field. It would come from space weather — especially stronger solar wind, additional coronal mass ejections, and a favorable southward orientation of the interplanetary magnetic field, known as Bz. Forecasters say Earth is being hit by a “convoy” of solar material, with at least one G1 minor geomagnetic storm already triggered and more impacts possible through Sept. 8–9. If later arrivals push conditions to G2, the aurora could brighten, expand farther south, and show more structure and color than the current faint forecast suggests. The key variable is not a rapid change in Earth’s field itself, but how the incoming solar magnetic field couples with Earth’s magnetosphere. When Bz turns strongly southward, it allows solar energy and particles to enter more efficiently, often intensifying auroras quickly. That can produce brief substorms and more vivid greens, reds, purples, and pinks. By contrast, shifts in Earth’s main magnetic field happen over years to thousands of years, not over a single evening. Even the long-term weakening of Earth’s field is not something that would suddenly transform tonight’s display. So the real wildcard is the sun. If incoming CMEs arrive at the right time and with favorable magnetic orientation, a low-end aurora forecast can still turn into a much brighter, more colorful show, especially in Alaska, Canada, and parts of the northern U.S.

3 articles · Updated · USA TODAY · Sep 8

NOAA said the aurora borealis could be visible Tuesday night in eight U.S. states, with northern Alaska carrying the strongest viewing chance.
Seven other states — Idaho, Minnesota, Montana, North Dakota, South Dakota, Washington and Wisconsin — have only a low chance, mostly near the U.S.-Canada border.
Solar flares and coronal mass ejections drive the display by sending charged particles toward Earth, where they collide with oxygen and nitrogen in the atmosphere.
Most of Canada is also expected to have a high likelihood of seeing the lights, which NASA describes as bright, moving ribbons of color across the sky.