A massive geomagnetic storm hit the Northern Hemisphere on Sunday night, but most Californians’ hopes of seeing the colorful waves of light known as the aurora borealis, or northern lights, were dashed by overcast conditions on the West Coast that obscured the rare sightings.
While powerful geomagnetic storms create beautiful auroras due to disturbances in Earth’s magnetic field, they can disrupt navigation systems and satellites and create damaging currents in power grids and pipelines, according to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center.
The agency predicted Sunday that the lights could be visible overnight in northern California, but later revised its forecast several times to say it would only reach as far south as Oregon or Washington. NOAA maps show that people in Oregon and Washington had a 20% to 50% chance of seeing the aurora under clear weather conditions.
Some observers held out hope, but the coast’s famously overcast skies did not cooperate.
A layer of fog settled over the Bay Area on Sunday evening and clouds shrouded much of the West Coast, meaning most hopes of seeing any celestial event were out of luck, meteorologists said. The approach of summer – with its longer daylight hours – didn’t help either.
“By the time it’s dark enough to see any aurora on the West Coast, the aurora will have moved to higher latitudes,” said University of Southern California physics and astronomy professor Vah Peromian.
Meteorologists with the National Weather Service in Riverton, Wyo. — a city on roughly the same latitude as Eugene, Ore. – Captured a stunning aurora with light waves in streaks of green, pink and purple against the night sky.
While the chance of seeing the aurora in California was slim, Parromian said it’s still worth keeping an eye out until 11 p.m., or until the storm reaches its peak.
Geomagnetic storms occur when energy from the Sun’s outer atmosphere disrupts Earth’s magnetic field, causing bands of green and red to glow in the night sky. Natural electrical phenomena are especially visible near the North Pole, but sometimes extend down into Canada and the northern United States, where they are often captured by wildfire cameras.
The aurora borealis brightens the northern horizon over Wolf Lake in Cloquet State Forest in Minnesota in 2019.
Alex Korman/Getty Images 2019NOAA trackers indicated that the disruption in Earth’s magnetic field had more than doubled by Sunday evening. That flow of energy had the potential to increase power grid fluctuations and drag on low-orbiting satellites. But NOAA scientists predicted that people living above 50 degrees latitude in northern Canada would feel the worst overnight.
“The Sun releases massive amounts of energy from its core in explosive displays we call solar flares,” said Chronicle meteorologist Gary Diaz, who added that flareups propel charged particles toward Earth that are deflected by the planet’s magnetic field.
As the particles slam into Earth’s atmosphere, they produce flashes of colorful light. When large numbers of particles hit the atmosphere, they can appear to move or “dance” across the night sky.
NOAA’s Space Weather Prediction Center tracker uses a scale called the Planetary K-Index to quantify the disturbance in Earth’s magnetic field, with 1 being calm and 5 to 9 indicating a geomagnetic storm. Most of Sunday afternoon and evening k-index values ranged between 7 and 8, indicating a storm large enough to push the aurora to much lower latitudes than it normally reaches.
Reach Nora Mishanec: nora.mishanec@sfchronicle.com
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