The aurora borealis tend to be stronger around the equinox.
Reports are coming in of strong displays of aurora borealis—the Northern Lights—as a surprisingly strong geomagnetic storm strikes Earth’s magnetic field.
“Auroras spilled across the Canadian border into northern-tier US states during an unexpectedly-strong G2-class geomagnetic storm,” said Spaceweather.com, referring to displays late on Friday, March 19 and into Saturday, March 20, 2021.
A “G2-class geomagnetic storm” is a moderate solar storm that can bring hours of bright aurora. There could be even more displays coming this Saturday night and beyond.
In fact, according to SpaceWeather.com, the current heightened activity could mean our planet’s magnetosphere taking a hit for the next three days and nights. “The solar wind stream that sparked the outburst is still here,” said Spaceweather.com.
According to NOAA, periods of G1-class geomagnetic storming are likely on March 20 through March 22, 2021.
The National Oceanic and Atmospheric Administration (NOAA)’s Space Weather Prediction Center offers an aurora prediction service that’s worth keeping an eye on when it gets dark where you are.
“We’re having a couple of very interesting days at the moment with us occasionally reaching geomagnetic storm conditions,” said SpaceWeatherLive.com. “This morning we hit the minor G1 geomagnetic storm threshold.”
The displays of aurora are happening because Earth is right in the path of a high-speed solar wind stream coming from a “coronal hole” on the Sun spotted a few days ago:
On Friday night through Saturday morning bright displays of aurora were seen across Canada down to, and beyond, the Canada-US border, notably in Minnesota.
This heightened displays coincided with the spring or vernal equinox, which occurred at 09:37 Universal Time on Saturday, 20 March, 2021.
Bright displays of aurora around equinox are no coincidence.
The geometry of Earth at equinox means March is the most geomagnetically active month of the year, with geomagnetic disturbances twice as likely in spring (and also in fall) as in winter and summer.
Earth’s axis tilts by 23.5°, but as well as explaining the season also means that at equinox our planet is perpendicular—spinning side-on—to the Sun.
So during equinox our planet’s geometry is lined-up nicely for charged particles from the Sun to be accelerated down the field lines of the Earth’s magnetic field.
Aurora are a natural sky phenomenon seen near the Arctic Circle (aurora borealis or northern lights) and Antarctic Circle (aurora australis or southern lights). They’re caused by charged particles from the Sun being captured and accelerated by Earth’s magnetosphere to interact with atoms in the upper atmosphere.
Wishing you clear skies and wide eyes.
I’m an experienced science, technology and travel journalist and stargazer writing about exploring the night sky, solar and lunar eclipses, moon-gazing, astro-travel,