NASA/Solar Dynamics Observatory

In the fight to protect Earth from solar storms, the battle lines are drawn in space at a point 1.6 million kilometres away. There, a US National Oceanic and Atmospheric Administration (NOAA) satellite waits for electrons and protons to wash over it, a sign that the Sun has burped a flood of charged particles in our direction.

As early as the end of this month, NOAA should have a much better idea of just how dangerous those electromagnetic storms are. The agency will begin releasing forecasts that use a more sophisticated model to predict how incoming solar storms could fry electrical power grids. It will be the clearest guide yet as to which utility operators, in what parts of the world, need to worry.

“This is the first time we will get short-term forecasts of what the changes at the surface of the Earth will be,” says Bob Rutledge, lead forecaster at NOAA’s Space Weather Prediction Center in Boulder, Colorado. “We can tell a power-grid customer not only that it will be a bad day, but give them some heads-up on what exactly they will be facing.”

Powerful solar storms can knock out radio communications and satellite operations, but some of their most devastating effects are on electrical power grids. In 1989, a solar storm wiped out Canada’s entire Hydro-Québec grid for hours, leaving several million people in the dark. In 2003, storm-induced surges fried transformers in South Africa and overheated others at a nuclear power plant in Sweden. But if a power company knows that a solar storm is coming, officials can shunt power from threatened areas of the network to safer ones or take other precautions.

Until now, NOAA had warned of solar activity using the planetary K-index, a scale that ranks the current geomagnetic threat to the entire Earth. The new ‘geospace’ forecast, which draws on more than two decades of research, comes in the form of a map showing which areas are likely to be hit hardest (G. Tóth et al. J. Geophys. Res. Space Phys. 110, A12226; 2005).

Knowing that Canada, for instance, will be hit harder than northern Europe helps grid operators, says Tamas Gombosi, a space physicist at the University of Michigan in Ann Arbor who helped to develop the model. He compares it to having a hurricane forecast that says a storm will hit Florida, rather than just somewhere on the planet (see ‘Storms from the Sun’).

Source: NOAA

Magnetosphere model

Space-weather forecasting is as rudimentary as conventional weather forecasting was three or four decades ago, says Catherine Burnett, space-weather programme manager at the UK Met Office in Exeter. Researchers have developed different models to describe various portions of the Sun–Earth system, but linking them into a coherent framework has been difficult. The Michigan approach combines 15 models that collectively describe the solar atmosphere through interplanetary space and into Earth’s magnetic realm. The NOAA forecast incorporates three of those: one model describing Earth’s entire magneto­sphere, another focusing on the inner magneto­sphere and one for electrical activity in the upper atmosphere.

The inner magnetosphere chunk is crucial to the model’s overall success, says developer Gábor Tóth at the University of Michigan. It describes how energetic particles flow and interact as they approach Earth’s poles, and how the particles affect magnetism at the planet’s surface. Alerts can provide roughly 20 minutes to one hour of warning.

NOAA’s improved forecasts are part of a push by US agencies to implement a national space-weather strategy issued last year by the White House. Regulators will also soon require power-grid operators to produce hazard assessments that include the threat of solar storms. “Without those two pieces, we wouldn’t have remotely the interest we have now,” says Antti Pulkkinen, a space-weather researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It really has changed the game.”

NOAA plans to continue refining its forecasts as new research rolls in. The possible improvements include incorporating how the geology beneath power grids affects the intensity of a solar storm. Fluctuating magnetic fields can induce electrical currents to flow in the ground, which sets up further problems for transmission lines. “All of this is terrifically complicated,” says Jeffrey Love, a geomagnetics researcher at the US Geological Survey in Golden, Colorado.

In their latest paper, Love, Pulkkinen and their colleagues describe the most detailed map of these ‘geoelectric hazards’ across part of the United States (J. J. Love et al. Geophys. Res. Lett. http://doi.org/bqpm; 2016). Of the areas surveyed so far, those at the highest risk are the upper Midwestern states of Minnesota and Wisconsin, where complex geology induces strong electrical currents.

Adding in 3D models of these ground currents will improve the next generation of NOAA forecasts, Rutledge says. “This is by no means the end.”