Geomagnetic storm lights up the sky with the Northern Lights

SAN FRANCISCO -- While they were not visible in the San Francisco Bay Area skies Sunday night, you didn't have to drive too far to see a specular show from the Northern Lights.

A large-scale geomagnetic storm caused by disruptions in Earth's magnetic field was responsible for the heavenly show, but it came with a warning from the National Oceanic and Atmospheric Administration's Space Weather Prediction Center.

"Power grid fluctuations can occur," the center said. "High-latitude power systems may experience voltage alarms. Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible. high frequency radio propagation can fade at higher latitudes."

The center tracker uses the planetary k-index to quantify disturbances in the earth's magnetic field. The index runs from 1 being calm and 5 to 9 indicating a geomagnetic storm. 

The k-index value for much of Sunday afternoon and evening hovered between 7 and 8, indicating a storm big enough to push the Northern Lights into lower latitudes than they usually reach.   

Over the next few years, the Northern Lights might appear further south more regularly, said Robert Massey, executive director at the Royal Astronomical Society.

The sun goes through an 11-year solar cycle where the flare activity level fluctuates. Cycle 25, the latest one, began in December 2019 with a solar minimum — a period when the sun is still active, but it's quieter and has fewer sunspots.

We're now approaching a solar maximum, expected to occur in July 2025, which will be a time when there are a large number of sunspots and increased solar activity.

Massey said the solar events that cause auroras will become more common as we head toward the solar maximum.

This month's event is the third severe geomagnetic storm, following events in November 2021 and March 2023, since the new solar cycle began in 2019.

"This increased activity from the sun is consistent with the current state and timing of the solar cycle," said Rob Steenburgh, NOAA space scientist, in a statement. "Energetic events like solar flares and coronal mass ejections have become more frequent in the past year, and especially in the past month, and we expect activity to continue ramping up to the peak next year."

Fascination with the phenomena has filled up social media.