The Earth is under constant threat of attack. I know this because I am watching events unfold on screens in the darkened operations room of our first line of defence.
Staffed 24 hours a day, 365 days a year, the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center in Boulder, Colorado resembles the bridge of the Starship Enterprise. The walls are covered in TV screens, displaying live images of the Sun captured by telescopes and spacecraft. Two men sit at curved desks in front of me, each surrounded by a bank of computer monitors. Their faces are lit by the dancing reflections of our nearest star in a range of spectra, through blue to red and dazzling white. One of them is taking a particular interest in a dark patch on the left side of the Sun, displayed as a bleached-out image on one of his screens.
“All these images are daunting, a bit like the Louvre for space weather,” says my guide, space scientist Joe Kunches.
Space weather refers to everything the Sun throws at us – from the continuous stream of charged particles it constantly spews out, called the solar wind, to the belches of eruptions, ejections and flares. The Earth is protected from this onslaught, to a large extent, by its magnetic field, which generates a shield or bubble around the planet known as the magnetosphere.
But what forecasters at the centre are watching out for is a particularly violent solar event: for instance, a geomagnetic storm that could penetrate the Earth’s natural defences, causing surges in electricity grid and disrupting power supplies; a radiation storm that bombards orbiting astronauts with a lethal dose of high energy particles; or radio interference that renders aircraft communications or GPS useless.
This year is supposed to be the year of the solar maximum, the peak of the 11-year sunspot cycle. Yet this maximum has turned out to be a weak one so far, sunspot numbers and strong solar flares have been far below predicted values.
The solar max may have failed to live up to its violent billing up until now, but no-one here is complacent – hence the interest in the dark patch slowly evolving on the Sun, signifying a cluster of sunspots the size of our planet. “We want to understand where eruptions are most likely to occur,” says Kunches, “and in doing that, we look for strong magnetic fields and hotspots in the solar atmosphere.” By examining the conditions today, they can make decisions about the likelihood of an eruption. Then they need to decide whether that eruption is coming our way and, if it is, how strong it is going to be.
The centre issues daily advisory notices based on a five-point scale ranging from minor to extreme. This information is coordinated with other national space weather services and shared with governments. It is used by airlines, space agencies, satellite operators and power companies. Airlines flying over the poles for instance, where the magnetosphere is weaker, have specific thresholds for solar activity and may choose to alter flight paths to avoid exposing their passengers and crew to a dangerous dose of radiation. Satellite operators could decide to power-down their spacecraft to protect them. Electricity companies might prepare for overloads. Those solar events predicted as extreme will go as far as emergency planning agencies and even the White House.
So what’s the worst the Sun could throw at us? The event that goes down in the relatively brief history of space weather watching is a solar super storm of 1859. Now known as the Carrington Event after British astronomer Richard Carrington who first spotted it, this lit up the skies across the world with stunning aurorae. Electrical surges induced in the Earth’s magnetic field were reportedly sufficient to power the telegraph system without batteries. Some telegraph operators spoke of sparks flying from their equipment. It was all very dramatic but, other than some interference with Victorian communications, there were no long-term effects.