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.