The biggest solar flare since 2017 is a burst of trouble
On Friday morning NZ time, a massive X-class solar flare – the strongest kind – launched off the Sun. It was the most intense of the Sun’s current 11-year cycle, and the most powerful observed since September 10, 2017.
Solar flares are intense bursts of radiation originating from sunspots. X-class flares are the most intense, followed by M-, C-, B- and A-class flares. Yesterday, the Sun unleashed an M-class flare on the heels of Friday’s massive eruption.
After Friday’s flare, high-energy particles bombarded Earth just eight minutes later, having surfed through space at the speed of light.
They triggered a shortwave radio blackout over Central and South America, which the United States National Oceanic and Atmospheric Administration (NOAA) described as an “amazing event” and “likely one of the largest solar radio events ever recorded”. A number of US National Weather Service aviation centres reported interference and degraded signal quality.
Now attention turns to how magnetism and solar material from the flare’s associated “coronal mass ejection”, or CME, could affect Earth.
The slower-moving matter takes a couple of days to reach Earth. Once it arrives, however, it is known for causing geomagnetic storming, pulsing through the planet’s magnetic field as it’s transformed into visible light – the aurora, or northern and southern lights.
Predicting aurora is difficult. There are only two main ways to directly observe a possible coronal mass ejection before its arrival.
Immediately after one happens, we see it from the Solar and Heliospheric Observatory satellite that peers at the Sun’s corona, or atmosphere. Scientists need to wait about two days until the CME arrives at the Deep Space Climate Observatory (DSCOVR) satellite, about 1.6 million km from Earth. That gives barely an hour’s warning before a CME actually hits.
This is like a tsunami happening on the far side of an ocean. You know that it’s happened, but don't know if it’s actually aiming towards you until a long time later. By then, it’s a bit late to prepare.
In this case, we know that a CME was
launched into space by the flare. We’re in that weird time frame before DSCOVR can provide us with last-second confirmation.
At this point, it’s likely that the shoulder of the CME will at least sideswipe Earth, potentially causing geomagnetic storming. That expectation is based on modelling, which shows the “shockwave” propagating through space.
NOAA’s Space Weather Prediction Centre is forecasting geomagnetic storming intermittently during the next three days.
The original solar flare’s intensity is impressive. There are an average of 100 to 150 X-class flares per 11-year solar cycle. We’re approaching the peak of the solar cycle, which should come some time in 2024.
The solar cycle results from opposing bands of magnetism, which stretch across the Sun in horizontal belts. They begin near the poles and slowly migrate towards the Sun’s equator.
The bands of magnetism interfere, creating sunspots, or bruiselike discolourations that crackle with chaotic magnetic energy. The closer the bands get, the more interference, and the more sunspots.
Solar flares and coronal mass ejections originate from sunspots. The more sunspots, the better the chance of flares and CMEs. That’s why solar activity is expected to continue to increase through the solar cycle’s peak. Skywatchers should remain alert – the odds of seeing aurora will be greatest in the months ahead.