The first sign of trouble was the jammed signals from Radio Free Europe into Russia. Next came a spectacular display of northern lights that were visible as far south as Florida and Cuba. Then satellites orbiting the Earth’s poles went on the fritz. Not long after, the massive solar storm began to pummel the Earth itself. In the early morning hours of 13 March 1989, the entire electrical grid in the Canadian province of Quebec collapsed, plunging six million people into a cold winter darkness that would last for nine hours and lead to hundreds of millions of dollars in damages and lost revenues.
That was two solar cycles ago. In early 2013, the Sun is expected to reach a peak in its activity once again. Since the 1989 incident, companies have strengthened their safeguards against solar storms taking out power grids. But since then we have also become more reliant on the very technologies that can be crippled by solar storms – a huge storm might affect radio communications and navigation signals from GPS satellites, as well as damage satellites and spacecraft in orbit around Earth. During a recent solar storm air traffic had to be re-routed away from polar regions to avoid losing communication. If there is a big one on its way, we need to know about it so that we can try to avert a major crisis.
Over the past few decades, scientists have stepped up their efforts to understand the Sun’s eruptions and the space weather created as a result. Detailed space weather forecasts that anticipate major solar storms would help companies and government departments that operate electrical grids, telecommunications satellites and radio stations.
But the accuracy of today’s forecasts is not high enough for operators to act upon them with confidence. Space weather forecasts are about as accurate now as terrestrial weather forecasts were two decades ago, says Daniel Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder and the chair of a 2008 US Space Studies Board report into space weather. There is plenty of room for improvement, “but we’re catching up rapidly,” he says.
The Sun goes through a cycle, in which the number of sunspots on its surface rises and falls over a period of roughly 11 years. These dark blotches on the solar surface are sites of intense magnetic activity. They emit explosions of energy called solar flares and balloon-shaped bursts of charged particles called coronal mass ejections that race through space at several million miles per hour. As the solar maximum approaches in 2013, so the number of sunspots, solar flares and coronal mass ejections will rise.
This solar cycle is relatively unusual, says Louise Harra, a solar physicist at Mullard Space Science Laboratory, at University College London. As well as the 11-year cycle there is also a much longer cycle that has produced 24 so-called “grand maxima” over the past 9,000 years – and the last grand maxima, which began in 1920, is reaching its end. The solar minimum in the current 11-year cycle lasted longer than expected and set a new record for low sunspot counts in 2008 and 2009, so scientists have predicted that the solar maximum will not be as impressive as earlier ones. “We are getting large events but we're not getting as many as we would have been in the previous cycle,” says Harra.
Not that this should make us complacent, says Mike Hapgood, head of the space environment group at RAL Space, in Didcot, UK. There is no evidence that these long-term trends affect the intensity of any individual burst of solar activity, he wrote in a commentary in the journal Nature. “We need to develop safeguards against the entire range of possible events that can be generated by [coronal mass ejections],” he said.
If Earth does find itself in the line of fire of any large event, we are reasonably well protected from solar flares. The Earth’s magnetic field and atmosphere shield us from much of the high-energy particles and radiation they produce. But X-rays blasted out in solar flares can penetrate deep into a part of the upper atmosphere called the ionosphere, which can disrupt radio waves, causing radio blackouts.
Coronal mass ejections pose a much greater problem. These charged plasma clouds move through space at speeds approaching 75,000 miles per minute (120,000km per min), continuously producing energetic particles as they go. The Sun emits one coronal mass ejection per week during a solar minimum, but as many as three per day during a solar maximum. They can damage or destroy satellites outside the protection of Earth’s magnetic field and force commercial airlines to re-route flights away from the polar regions. And it can happen very quickly, says Daniel Baker, “just a few hours after the disturbance on the Sun, or sometimes even less.”
When a coronal mass ejection collides with the Earth, it rattles the Earth’s magnetic field and can cause a geomagnetic storm. As the storm moves over long electrical transmission lines it produces current down the line, generating heat that can overload and blowout high-voltage transformers, and bring cities – or entire regions – to a standstill. Just like what happened in Quebec in 1989.
Today’s space-weather forecasters know whether a solar storm will hit the Earth about one or two days in advance. “That’s state of the art,” says Yihua Zheng, a chief forecaster at NASA’s Goddard Space Flight Center Space Weather Center in Greenbelt, Maryland. Zheng and other forecasters use data gathered by a trio of orbiting spacecraft to identify the presence, direction and speed of coronal mass ejections. “Slower [coronal mass ejections] can take between three and five days to reach the Earth, but we care more about the faster ones,” she says, because they tend to be more dangerous.
Zheng is part of a group developing a computer technique, known as ensemble forecasting, to improve NASA’s ability to predict the path and impact of severe solar storms. Ensemble forecasting is already used by meteorologists to track severe weather, like hurricanes, on Earth, but this is the first time is will be used to make sense of space weather.
The technique will allow Zheng and her colleagues to produce as many as 100 computerized forecasts by varying the speed, direction and other parameters of coronal mass ejections in their models, instead of being restricted to one set of solar-storm conditions, as they are now. It would decrease the margin of error, which currently stands at seven or eight hours, and lead to more reliable forecasts. Zheng expects the ensemble forecasting method will be up and running no later than the end of this year – just in time to catch the next solar maximum.
Still, forecasters would be at a major advantage if they could predict a coronal mass ejection in advance, rather than chasing it down after it had erupted. Stathis Ilonidis, a graduate student in physics at Stanford University in California, is tracking the sound waves that travel through the Sun’s interior to predict where a sunspot will appear one or two days in advance. And as coronal mass ejections often come from sunspots, this information could be of enormous help to space weather forecasters.
By some quirk that physicists do not yet entirely understand, sound waves travel faster through sunspots than through the rest of the sun’s interior. Ilonidis measures how long it takes a sound wave to travel from one point on the Sun’s surface to a depth of 37,000 miles and back up to another point. On average, it takes a sound wave an hour to bounce from one point to another 93,000 miles away, but a sound wave passing through a sunspot may shave 12 to 16 seconds off its time. By repeating the process with millions of pairs of points, Ilonidis can chart out a map that identifies regions where travel time is significantly shorter than expected – locations where sunspots are likely to appear. "This is the first time that we can actually detect sunspots inside the sun," says Ilonidis.
Ilonidis cannot run the technique in real time yet, mainly because he does not have access to computers powerful enough to run a live analysis, but he is hopeful that in the next couple of years it could be used to scan the whole surface of the Sun and predict the formation of new sunspots. Such an advanced warning system could buy us a few extra days notice of an impending solar storm.
Once a solar storm reaches Earth, forecasters need to know how it will react with the particles and magnetic field surrounding the planet. A trio of CubeSats, tiny satellites weighing around 3kg (6.6lb) and made with mostly off-the-shelf components, is about to join the larger missions already orbiting the Sun like Nasa’s Solar Terrestrial Relations Observatory (STEREO).
The miniature-satellite mission, called TRIO-CINEMA, is a collaboration between the University of California Berkeley, Kyung Hee University, South Korea, and Imperial College London. Each of the CubeSats will carry two instruments: MAGIC, which will measure variations in Earth's magnetic field, and STEIN, which will monitor fast moving particles.
MAGIC is around the size of a pound coin, making it smaller and less power-hungry than sensors that do the same job in larger satellites. "Mass, volume, and power are all very limited in these tiny spacecraft," says Robert Lin of UC Berkeley, who leads the mission. Though less sensitive, having sensors on a constellation of CubeSats will give scientists a global picture of what is happening in Earth's magnetic field, something not possible with a sensor on a single spacecraft. STEIN will monitor both charged and neutral particles as they interact with Earth's magnetic field and radiation belts, enabling scientists to create maps and movies charting the particles' behaviour.
The first CINEMA CubeSat will launch in summer 2012, with the other two later on in the year. To keep costs down the CubeSats will hitch a ride on other missions to reach their orbit 600km above Earth. Data from TRIO-CINEMA will help scientists understand the behaviour of the near Earth environment and feed into space weather forecasting models, says Lin.
At the moment, space weather alerts and reports are done on a piecemeal basis. The Goddard Space Flight Center forecasters provide space weather information to all Nasa robotic missions. A new European system called SPACECAST provides radiation forecasts to help satellite operators protect their equipment. And NOAA’s Space Weather Prediction Center provides alerts and forecasts to power grid operators, commercial airlines, radio operators and other companies who need them, as well as government agencies.
But the Space Weather Prediction Center relies on the strength of data available, and right now there are only a few dedicated operational space weather-monitoring systems around the world. Baker thinks the entire suite of monitoring and alert systems could be better integrated to provide a global effort to protect the Earth from space weather. “Let’s, as a nation, but also as a world, since space weather knows no boundaries or borders, really pool our resources, our assets and put together a much more dedicated, operational worldwide space weather system,” he says. A first step would be an international agreement to share all data, then agreements on observing responsibilities of each nation. “Every nation could do its share and everyone would benefit,” he says.
A global system could offer tailored forecasts and alerts, as not every industry or company has the same concerns about various types of space weather. For example, military systems are robust and can operate through almost every type of disturbance and would not benefit from a forecast, says Baker. But satellite operators and power companies could take some mitigating steps to reduce the likelihood that their spacecraft might fail or their grids might shut down. “They could be prepared to divert power from one sector to another. They could spin-up more back-up capabilities and really weather the storm, especially if they knew exactly where the most powerful electromagnetically induced currents were,” he says.
Since the 1989 storm that knocked out Quebec’s electrical grid, the Canadian energy company Hydro-Quebec has strengthened its transmission system to fend off a repeat event. It has increased trip levels across the grid to allow equipment to weather bigger disturbances without shutting down automatically, and put into action an alert system that enables real-time monitoring of the grid, among other things. Other power grid operators are looking for ways to brace themselves for a big solar storm too. The National Grid in the UK has plans that include preparing to bring all transformers into action to reduce the load on individual ones, and even making controlled power cuts to prevent damage to the grid.
But the world has also changed. Roughly two billion more people live on the planet today than in 1989. We are consuming more energy on a per capita basis today then we did then and our electrical grids are aging. “Compared to twenty years ago – two solar cycles ago – the power grid is probably operating much closer to the edge,” says Baker. “If we had a storm like that next week, I think it’s an open question as to how the world’s power system would respond.”
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