BOULDER, Colo. — According to the Space Weather Prediction Center (SWPC) in Boulder, a solar flare detected on the sun Thursday was the strongest flare since the beginning of this solar cycle in 2020. It unleashed a fast-moving storm of X-ray energy that hit the Earth about 8 minutes after the eruption.
It’s the type of energy that can disrupt certain types of radio communications.
“Nothing related to the cellular network problems going on the other day," said Shawn Dahl, a space weather forecaster at SWPC. "I think we made that quite clear that was not associated with any of the flare activity.”
He said it’s unusual for a solar flare to release energy waves in the frequencies that operate cell phones, although he said it can happen occasionally. But when those frequencies do get disrupted, the impact is only for a few minutes.
He said Thursday’s flare may have briefly impacted ham radios and some transoceanic airplane communications, especially over the Pacific because it was closer to the middle of the daylight hours there when the flare occurred.
Aurora Borealis
The powerful solar flare will also not bring an aurora to Colorado or any notable aurora to anywhere on Earth.
Dahl says it’s a different type of eruption called a Coronal Mass Ejection or CME that brings the geomagnetic energy that causes the Northern Lights.
A CME often accompanies a strong solar flare but not this time.
“That’s not unusual with solar flares but with flares of this intensity it was a little strange," he said. "But these were also very impulsive meaning very quick flares. They only lasted some minutes.”
He said there were a total of three strong solar flares in less than two days from the same sunspot region on the sun, and there was no CME with any of those flares.
The area where this flare happened on the sun was also not facing directly towards the Earth. So, if there was a CME with that strong flare, it may have still not been strong enough to cause an aurora to stretch down to Colorado, but it likely would have had some impact closer to the North Pole.
“That location certainly could have impacted Earth," said Dahl. "It wouldn't have been maybe a direct hit, but it could have been what we call a glancing blow meaning a partial hit here at Earth.”
SWPC forecasts and warns for three different kinds of solar energy storms, solar flares, radiation storms, and geomagnetic storms. They all tend to originate in sections of disturbed magnetism on the sun, areas known as sunspots.
Solar Flares
A solar flare is a release of energy from the sun which happens when the magnetic field lines in a sunspot get stressed from mixed up magnetic polarities. Solar flares release a variety of energy in different wavelengths, but scientists focus on the X-ray emissions to measure the flare's intensity.
"The big flare on Thursday reached over 100 times the background flux of the sun at the time of solar maximum," said Dahl. "If the sun was in solar minimum, that flare would have been anywhere from 1,000 to 10,000 times the flux of the sun."
X-rays travel at the speed of light so it only takes about 8 minutes for the energy to reach the Earth. That gives SWPC very little time to issue a warning to those on Earth who need notification but their forecast leading up to Thursday's flare called for a high probability of a strong solar flare occurring from the active sunspot region that it originated from.
He said SWPC has an intensity scale for solar flares based on the physical solar flux measurement of the x-rays. It's sometimes known as the Radio Blackout scale. R1 being a minor solar flare, while R5 is extreme.
The strong flare that happened on Thursday had a solar flux measurement of X6.3 which made it an R3 or Strong flare on the scale. He said all three solar flares this week were rated R3. Those are the three strongest solar flares of solar cycle 25, the current cycle.
There is an average of 174 solar flares rated R3 in each roughly 11-year solar cycle, so they are fairly common. There's an average of eight R4 solar flares per cycle and R5's are extremely rare. There has not been an R4 in the current solar cycle, nor was there one in the previous cycle (Solar cycle 24). Solar cycle 23 had three R4 flares in its more than 12-year cycle.
The last R5 solar flare to impact the Earth happened on Aug. 16, 1989. Its solar flux measurement was X20.
Coronal Mass Ejections
A coronal mass ejection (CME) is another type of magnetic field ejection from the sun, but it's accompanied by plasma from the Sun's corona. It is common for a CME to occur at about the same time as a solar flare, but as we saw on Thursday, a CME doesn't always follow a flare.
A CME travels much slower than the energy from a solar flare. Dahl said fasted they usually reach Earth is about 18 hours, although scientists believe that it could even be as little as 15 hours.
But he said normally they take 2-4 days to reach Earth which gives them ample time to issue watches and warnings.
When the plasma from a CME reaches the Earth's magnetic field there is an electrical interaction which is known as a geomagnetic storm. It manifests visually as the aurora borealis or northern lights. It can cause malfunctions or even damage to power systems, spacecraft operations and communication systems.
Geomagnetic storms are also measured and rated on an intensity scale. G1 being minor while a G5 is extreme. There have been several G4 storms in the current solar cycle including most recently in March and April of 2023.
The last G5 storm to hit Earth happened in October of 2003.
Solar Radiation Storms
Solar radiation storms occur when large quantities of charged particles, protons and electrons, are accelerated by processes at or near the Sun. They are also commonly tied to solar flare events and can cause CMEs.
The Earth's atmosphere and ozone layer provide substantial protection from radiation storms but great risk to space and satellite operations including human astronauts.
They are also tracked on an intensity scale from S1 - S5. The scale is based on measurements of energetic protons taken by the GOES satellite in geosynchronous orbit.
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