Protecting the grid from weather geomagnetic storms

“One of the problems we need to solve is predicting the direction of the magnetic field embedded in a CME,” said Pulkkinen. “They only generate major storms within the magnetosphere if they’re pointed opposite Earth’s magnetic field when they hit — otherwise, it may give an initial punch and then just kind of fizzle.”

If the storm is particularly strong, however, our power grids may need some protection. The quick-changing magnetic fields in the magnetosphere can create electric currents at Earth’s surface, called geomagnetically induced currents, or GICs. Because much of our planet is criss-crossed with long metal structures – from oil pipelines beneath the surface to power lines yards above our heads – these electric currents have perfect, wire-like pathways that allow them to flow across long distances. For example, a powerful geomagnetic storm in 1859, known as the Carrington Event, caused GICs so strong that telegraph wires were unable to handle the huge amount of electricity, interrupting communications.

NASA notes that the consequences of GICs in modern power lines are more direct. In order to transmit power effectively, there must be the right combination of voltage and current in power lines. The extra current of GICs can disrupt this balance, possibly resulting in stressed transformers or voltage collapse. The GICs brought on by the March 1989 geomagnetic storm introduced so much extra current to the Quebec power grid that protective relays were tripped and the voltage collapsed.

To better understand what space weather situations cause the most intense GICs, scientists working on Solar Shield use CME measurements, solar wind observations, and other physical parameters to model the timing, location, and strength of the GICs. Using pictures of CMEs from a special type of instrument called a coronagraph – which blocks out the overwhelmingly bright disk of the sun, allowing us to see the comparatively faint atmosphere, known as the corona – they estimate the size, speed and direction of these CMEs, one of the driving forces behind geomagnetic storms. Measurements of fast solar wind streams currently come from NASA’s Advanced Composition Explorer, or ACE, which resides between us and the sun at a distance of about a million miles from Earth. Solar wind data from NOAA’s Deep Space Climate Observatory, launched in 2015, will replace ACE data later this year.

Scientists input their estimates of the characteristics of these solar events into computer models, which simulate when, where, and at what speed the solar material will strike Earth, as well as the location and strength of the resulting induced currents. The models that Solar Shield scientists use are tested and validated at the Community Coordinated Modeling Center, or CCMC, at Goddard. Once they have GIC simulations from the model, scientists compare them to measurements taken at six power substations around the U.S. By comparing the predicted characteristics with the actual characteristics of the GICs, scientists can improve the Solar Shield simulations.

With accurate advance warning, power engineers have quite a few options to protect the grid. With a day or two of notice, power grid companies can alter maintenance schedules to make sure that as many critical lines are up and running as possible. Even with just 20 minutes of lead time – which is how long it could take for a CME to travel from our advanced warning satellite to Earth, a distance of nearly a million miles – grid operators can take steps to prevent blackouts and damage. One such step is injecting reserve power into the system, helping to stabilize the system voltage.

As projects like Solar Shield help improve our space weather models, the hope is that forecasting will improve just as terrestrial weather forecasts have improved, and – like meteorologists who fine tune their warnings of hurricanes as the storm waxes and wanes – space weather prediction can provide highly accurate details on the force of any incoming solar storm