By Angus Dalton
The sun has reached the crux of its 11-year energy cycle, heralding a chaotic period of powerful solar storms and flares that could knock out satellites, inflict blackouts and disrupt global communication, NASA has announced.
“Roughly every 11 years, at the height of the solar cycle, the sun’s magnetic pole flips … and the sun transitions from being rather sluggish to being really active and stormy,” astronomer Kelly Korreck from NASA’s heliophysics division told a press briefing.
A NASA image capturing the strongest solar flare of this solar cycle on October 3.Credit: NASA/SDO
“We anticipate additional solar and geomagnetic storms leading to opportunities to spot the aurora over the next several months, as well as potential technology impacts.”
The so-called “solar maximum” phase of the current cycle, Solar Cycle 25, will last a year or two before activity begins to wane.
In May, the most powerful solar storm in two decades struck Earth and conjured some of the strongest auroras in 500 years. Earlier this month, another geomagnetic blast unleashed lashes of purple aurora australis across the sky as far north as Queensland.
“The bigger the storm, the more visible the aurora,” said Bill Murtagh from NOAA’s Space Weather Prediction Centre. “But we can’t be hoping for these big displays because with them comes the threat to our critical infrastructure.
“We always have to be careful with what we wish for.”
A $2.6 trillion risk
In 1972, about 25 sea mines off the coast of Vietnam blew up, baffling the US military. Later inquiry suggested the magnetically triggered mines had been detonated by a lash of solar energy.
During the so-called “Halloween solar storms” of 2003, geomagnetic blasts disrupted half of all Earth’s satellites and destroyed a US satellite worth $640 million. Crew on the International Space Station had to take cover from the increased radiation.
The most powerful flare measured with modern methods was in 2003, during a solar maximum. It overloaded the sensors as it was measured as X28 but was later estimated to have reached X45.Credit: SOHO/EIT (ESA & NASA)
Airlines spent up to $100,000 a flight rerouting commercial planes to avoid spikes of radiation at Earth’s poles. (There’s more cosmic radiation at the poles due to the shape of the Earth’s protective magnetic field – the same reason auroras are usually seen in high latitudes.)
But the largest solar storm on record was the Carrington Event in 1859, when auroras lit up the tropics and telegraph machines reportedly caught fire. The strongest solar flares are dubbed category “X” with a number to denote extra strength – a flare associated with the Carrington Event was rated X45.
Only one other recorded flare in modern times matched that level, in 2003. The flare overloaded NASA monitoring equipment but, thankfully, missed Earth.
Some solar eruptions create bursts of solar energetic particles. The high-energy solar radiation can impact humans and sensitive electronics aboard satellites, as shown in this conceptual animation.Credit: NASA’s Conceptual Image Lab/Krystofer Kim
A storm of Carrington Event magnitude today could inflict devastating blackouts and up to $US2.6 trillion ($3.9 trillion) in economic costs just in America, according to a report by insurance company Lloyd’s and Atmospheric and Environmental Research Inc.
We’ve made ourselves more vulnerable to a Carrington Event-level storm, says solar physicist Dr Hannah Schunker from the University of Newcastle.
“We are much more reliant now on space-based technology like GPS. If those satellites fall out of orbit, or if they are irreparably damaged, this can affect banking, location services, transport … it could be a serious issue,” Schunker said.
What does a solar flare sound like?
Scientists track the solar cycle by observing the number of sunspots – planet-sized patches of magnetic flux – that blossom on the star’s surface.
These sunspots spew solar flares and blasts of plasma called coronal mass ejections. There are one or two sunspots during the solar cycle’s weakest point and more than a hundred during its maximum.
Visible light images from NASA’s Solar Dynamics Observatory highlight the appearance of the Sun at solar minimum (left, Dec. 2019) versus approaching solar maximum (right, August 2024).Credit: NASA
Solar flares are flashes of X-ray and ultraviolet light that can cause radio blackouts. (In 2018, a radio operator was monitoring hurricane weather in Mississippi when a solar flare knocked out his signal – it sounded like sizzling bacon.)
Coronal mass ejections, on the other hand, are eruptions of the sun’s plasma. They appear as twisting “flux ropes” lashing out from the sun.
With the right trajectory, ejections can slam into Earth between 15 and 18 hours later, unleashing a geomagnetic storm. At solar minimum, there’s about one ejection a week. During solar maximum, there are two or three a day.
Solar material erupts from sunspots, which increase in number during the solar maximum period.Credit: NASA/SDO
The storms can temporarily weaken Earth’s magnetic field, allowing more solar radiation to enter Earth’s atmosphere and potentially reach astronauts and plane passengers. The ejections can accelerate particles to almost the speed of light, pelting satellites and damaging their circuitry.
Magnetic fluctuations could also induce unwanted electric currents on power grids, overloading systems and causing blackouts, said RMIT Associate Professor Brett Carter.
Energy companies and satellite operators normally get a few days’ warning to prepare for coronal mass ejections. “But the problem is their magnitude isn’t known until it gets here,” Carter said.
Schunker is working to understand how sunspots arise, aiming to improve our geomagnetic storm forecasting time from a few days to a week.
“If we can understand the physics of how sunspots form, the signatures before they occur, we better predict space weather,” she said.
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