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All eyes on the sun

This year marks the 100th anniversary of solar energy. In 1921, three waves of a major geomagnetic event wreaked havoc in various parts of the world. Have advances in science meant that lessons can be learned to avoid catastrophes as history repeats itself?

Over three days in May 1921, a series of coronal mass ejections (CMEs) struck the Earth as three major geomagnetic storms. During a geomagnetic storm, Earth’s magnetic field fluctuates wildly over the course of a few minutes or hours.

These fluctuations are greater closer to the Earth’s poles, but during very large storms, the magnetic field variation is large and extends farther. In May 1921, towns and cities around the world reported strange events.

There were dazzling displays at dusk of aurora borealis (created by electrically charged particles from the sun), but at much lower latitudes than usual. Intense aurora sightings have been reported in England and France, and as far south as San Antonio, Texas, and the island of Tongatabu in the South Pacific.

One morning, observers in Europe and North America reported at least five high-intensity peaks in a five-hour period. Power surges also damaged transatlantic cables, interrupting shipping signals along the west coast of North America and the Philippines.

There was interference in telegraph traffic in Europe and North America and in telephone exchanges. Sparks at a power plant caused a fire in Karlstad, Sweden, and long-distance telephone lines at a power plant in New Brunswick, Canada, were burned out.

Conversely, there were reports of improved long-range radio signals over the Atlantic and Pacific, as improved ionization resulted in stronger signals.

New York stations received stronger signals from Berlin and Bordeaux, while connections between stations in Samoa and Awanui, north of New Zealand, were recorded as “unusually good”.

The first CME on May 13 at around 1 PM GMT was followed in the evening by a second, smaller CME (around 7:30 PM). In quiet periods, the magnetic field at the Earth’s surface is between 10 and 50 nT.

An article by Mike Hapgood of the Rutherford Appleton Laboratory notes that the first CME pair, peaking at about 100 nT, would have cleared up the density in the region between the sun and Earth, allowing the second and third CMEs to move faster. to travel.

The moderate magnetic activity may have preconditioned Earth’s magnetosphere so that it reacted strongly to subsequent CMEs over the next few days. A second CME on May 14 caused a sharp increase in intensity to +230 nT over India and then waves of depression over Hawaii for two hours, with lows of -150 nT.

In Europe, the opposite happened, with a field of waves reaching +350 nT at their peak. The periods of magnetic waves were followed by seven hours of magnetic field activity so intense that it could not be measured by contemporary instruments.

The intensity can only be estimated on the basis of the effects. A geoelectric field capable of melting fuses in copper wires and causing fires (as happened in the Swedish telephone exchange) should have been 10V/km, resulting in line voltages of 1,000V over a typical line length of 100-200km.

On May 16, a third CME occurred, causing intense activity, similar to the first event on May 13. One phenomenon that was particularly noticeable in 1921 was the effect of geomagnetically induced currents (GICs) on radio waves.

The energy added to the ionosphere by the CME changes the way radio waves propagate; for example, high frequency (HF) radio is lost because it uses the ionosphere to bounce the radio waves.

In 1921 this meant an interruption of information transfer, communication and radio broadcasting. Today, CMEs can affect aircraft in the polar regions, which use HF radio for their communications systems.

There may also be some risk of increased radiation doses to airline passengers and crew members on long-haul flights, which take flight paths at high altitudes. The charged particles can also cause the autopilot to disengage every few minutes.

CMEs can also affect satellites in orbit. When electrically charged particles enter the satellite’s computer systems, they can cause ‘single event disturbances’ that disrupt its operation.

Satellites are also used for Global Positioning Systems (GPS). The GPS signal normally travels from a satellite directly to Earth, but if the ionosphere has regions of different densities, the radio waves are diverted or slowed down.

GPS relies on accurate timing to determine a position in a navigation system, for example. Today, airplanes and ships, as well as smartphones and car navigation systems, use GPS, which relies on the timing of received signals for location and positioning.

On some public transport systems, GPS will let the train know if it is in the station and allow the doors to be opened. An incorrectly timed GPS signal can mean the train won’t recognize where it is and the doors will remain locked.

Retail payment systems and ATMs also rely on a GPS signal to operate, so a GIC can temporarily affect shoppers. Financial trading, especially high-frequency trading, uses GPS to timestamp transactions, confirming the price.

Any disruption or outage could lead to the suspension of financial trading around the world. In the event of a major CME, emergency services may need to rely on backup radio systems such as VLF (very low frequency) or standard radio broadcasts with radio transmitters.

Local radio communications are unlikely to be affected, but navigation systems that rely on satellite signals will. This can delay the response to emergencies, but can also hinder road systems that rely on satellite signals for traffic control, such as traffic lights or highway systems.

One of the main effects of a power surge is the overload of the power grid, causing power loss.

In 1989, a large solar magnetic impulse caused a voltage surge, disabling the security system at the Hydro-Quebec power station, causing a power outage that lasted nine hours.

“What happens is that Earth’s magnetic field changes very quickly, and that magnetic field variation penetrates into the Earth’s subsurface, which is somewhat conductive,” explains Ciaran Beggan, senior geophysicist at British Geological Survey, out.

A changing magnetic field in a conductive material generates an electric field, like a generator with a rotating magnet in a coil that generates electricity. The rapid changes over a large area can produce an electric field of up to a few volts per km.

The field is harmless to humans, but in a high-voltage network, the high-voltage lines have a very low resistance, so they can transfer energy. Transformers in the power grid increase or decrease voltages and neutralize the extra electric field created by the magnetic storm.

They balance the current load in the power lines, but extra current from the ground, due to GICs, causes energy to leak from the transformer.

This heats refrigerant oil in the transformer and when it reaches a critical temperature, the transformer shuts down automatically to protect itself.

According to Andrew Richards, modeling manager at National Grid ESO in the UK, the Armageddon scenario people are imagining is unfounded. He believes the effects of a CME will be localized and “similar to what we would see in a terrestrial storm, which can knock out power lines and leave small areas without power.

” The structure of the electricity grid in the UK makes it resilient. Due to the size of the island, it does not have very long power cables and redundancy is built into the network.

This is not the case in North America, where there is less redundancy and long power lines along coastal areas. In the eastern half of the US, the electrical grid is highly interconnected; outages at some point can cause a knock-on effect, potentially resulting in power outages for days.

The UK grid has backup transformers, but if too many transformers are lost in one location, homes and businesses supplied by that power station could lose power.

This is still an unlikely scenario, says Richards. What’s more likely is that there will be a surge in voltage causing the lights to dim. Many associations, agencies and government departments work together to identify possible CME.

There can be very little warning of impact, perhaps 30 minutes from when the CME’s magnetic field position can be determined, to predict whether it will cause an impact.

The focus of the research is to identify the formation of space weather systems that can predict when solar flares are likely to occur.

The Automated Solar Activity Prediction (ASAP) system, developed by Rami Qahwajii, professor of visual computing in the Faculty of Engineering and Computer Science at the University of Bradford, detects, records and predicts sunspot activity.

It uses image processing and artificial intelligence to compare sunspot images from NASA’s Solar Dynamic Observatory (SDO) with historical patterns to predict whether a sunspot is becoming more complex, likely to produce more flares, or if there is no cause for concern.

The ASAP system is integrated into NASA’s Community Coordinated Modeling Center portals, which shares data with all space weather observers around the world.

Predicting the timing and intensity of an event is a growing technology as scientists learn from the sun’s current activity and use historical data to try to gain as much knowledge as possible about the magnitude of an event.

Solar flares happen all the time, but only a few become significant CMEs that damage the Earth.

Our reliance on electricity and satellite signals will make a major geomagnetic event more disruptive than in the past, but parallel technological advances have also implemented security measures in infrastructure, while interagency collaboration ensures that advances in early warning systems are shared worldwide.


TIMELINE

Lessons from history

1859: The Carrington Event – named after British astronomer Richard Carrington, who made the first observation of a solar flare (also seen independently by Richard Hodgson) and linked the increased activity to the massive geomagnetic storm of September 1859 – the largest ever registered.

This storm is estimated to range in strength from -800 to -1,750 nT. It toppled telegraph systems in Europe and North America and allowed northern and southern auroras to be seen in the mid-latitudes. May 1921: A series of coronal mass ejections struck, reaching 350 nT at the peak of geomagnetic activity. March 1989:

The Canadian province of Quebec was plunged into a blackout for nine hours when the electrical grid shut itself down within 90 seconds of being hit by a major solar storm and geomagnetic currents. January 1994:

The Anik-E satellites are believed to have been hit by a solar storm that damaged the circuitry, causing them to lose ground lock and spin. The backup systems were not activated in time due to the loss of data and the Canadian TV broadcast for several hours.

Satellite systems and communications were disrupted and aircraft changed flight paths to avoid high altitudes over the polar regions. Auroras were visible over the Mediterranean, Florida and Texas. February 2011:

The Valentine’s Day eruption was the largest solar flare in four years, sparking fears of increased activity as the sun entered its maximum solar phase. January 2012: NASA’s Solar Dynamics Observatory observed a solar flare measuring the intensity of M8.7. The spacecraft recorded its speed at more than 2,000 km/s.

The storm hit Earth, but the magnetic activity wasn’t strong enough to set off anything more than stunning auroras at high latitudes. July 2012: A solar storm similar in magnitude to the one in 1859 crossed Earth’s orbit but failed to catch on.


PHYSICS

What makes a solar flare produce a geomagnetic storm on Earth?

Earth’s magnetic field reverses once or twice every million years, but the sun’s reverses every 11 years as part of its solar cycle. As the cycle develops, the ball of gas that makes up the sun rotates faster than its poles, and the magnetic field beneath the surface can pierce through it.

“Sunspots and the magnetic field start to revolve around each other and when the magnetic field spins in a loop, kind of like an elastic band, it stores energy. And when it ‘pings’, it releases an enormous amount of energy in a very short time,” says geophysicist Ciaran Beggan.

Energy can be released in a fraction of a second or in minutes, creating a very bright white spot of light or solar flare. This solar flare is an enormous amount of electromagnetic energy, light or gamma rays, that travels to Earth in just eight minutes.

When it hits the dayside of the Earth, it ionizes the atmosphere and changes the way radio waves propagate to the ionosphere. The release of energy pushes ionized gas away from the sun in a coronal mass ejection (CME).

The gas, or plasma, has the magnetic field it created embedded in it. “You can think of it as a cloud of rolling gas moving toward Earth with the built-in magnetic field constantly spinning,” Beggan says.

This takes between 16 and 30 hours to reach Earth, traveling at a speed of between 1,000 and 2,000 km per second. If the magnetic field in the CME is negative (downwards) and the Earth’s magnetic field is positive, the CME injects energy into the Earth’s magnetic field, creating a magnetic storm.

“The energy from the CME now connects directly to the Earth’s magnetic field, creating a charge of current systems in space that flow around the Earth. It also peels the Earth’s magnetic field off and around the back, where it reappears.

connects and then pushes more energy into the atmosphere,” Beggan continues. This creates electric currents, or aurora borealis electrojets, which generate a secondary magnetic field.