A moderate geomagnetic storm is predicted to engulf Earth’s atmosphere tonight, with the northern lights likely to become visible further south than usual. According to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center (SWPC), the aurora may reach as low as New York, and it’s all thanks to a wave of “dark plasma” that was hurled out by the Sun over the weekend.
As with the many other geomagnetic storms we’ve experienced in the last few months, the upcoming spectacle owes its existence to a coronal mass ejection (CME). Enormous plumes of solar plasma and magnetic field, CMEs erupt from active areas on the Sun’s surface, such as sunspots.
Earlier this year, a particularly gnarly sunspot triggered Earth’s largest geomagnetic storms in over 20 years, although this week’s CME differs slightly in that it originates from a type of structure known as a magnetic filament. These are long waves of relatively dense, cool gas that are suspended above the Sun’s surface by magnetic fields and appear dark in relation to the much hotter solar disk.
When the magnetic forces supporting a filament become destabilized, the whole structure can collapse, triggering CMEs or solar flares as they release huge amounts of energy. According to the SWPC, a filament eruption on September 8 resulted in a CME that is due to reach Earth around midday (UTC) today (September 10).
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September 8’s CME.
Credit: Solar and Heliospheric Observatory
As the charged particles within this plume of dark plasma collide with our magnetosphere, they are likely to spark a G2 geomagnetic storm. While this is not as strong as the G5 storm that lit up the skies across North America and Europe in May, it’ll still be worth casting an eye skywards tonight if you happen to live in the northern half of the US.
“The aurora may become visible over some northern and upper Midwest states from New York to Idaho,” explains the SWPC in its latest update. “Any geomagnetic storming effects that linger into 11 Sep (UTC) will likely taper off into minor storming levels,” it adds.
And with the solar maximum drawing ever closer, more geomagnetic storms are extremely likely in the near future, which means there could be plenty of upcoming opportunities to catch a glimpse of the aurora in locations that wouldn’t usually get the chance to see it.
