Geomagnetic storms: Auroras and the power grid

When powerful solar storms unleashed by the sun reach Earth, they emit colorful light shows known as auroras. Commonly seen in the night skies of the polar regions where they’re referred to as the northern or southern lights, these solar storms can pose a risk to power grids. 

How solar storms affect the power grid

The sun is constantly releasing particles, sometimes emitting large flares and even larger solar storms. Think of a solar storm like a cannon shooting massive amounts of accelerating energy into space. When this energy reaches Earth, it disrupts our planet's magnetic field and creates electrical currents that form a geomagnetic storm. We can’t feel these electrical currents, but if the resulting storm is large enough, the currents can affect power lines and equipment in the following ways:

  • Overwhelming transformers: Transformers change the voltage of the electricity traveling on power lines. The geomagnetic currents from solar storms can alter the power balance within transformers, causing malfunctions or overheating. 
  • Confusing electric safety systems: Power stations have safety systems called protective relays that shut off power if they detect something is wrong. The geomagnetic currents from solar storms can trick these systems into sensing there's a problem.
  • Strange voltages on power lines: Because the supply of electricity traveling on power lines must equal the demand for power, any extra energy from a geomagnetic storm can negatively impact that delicate balance, potentially causing blackouts.

What do power companies do to prevent impacts? 

While we can't control space weather, we can prepare for it. Scientists and engineers work together to protect our power grid and keep the lights on for everyone.

BPA works to protect the Northwest power grid from geomagnetic storms a few ways:

  • BPA measures the geomagnetic currents impacting our grid and rebalances the grid based on the new values. The public can view these measurements across BPA’s system in 5-minute intervals for the previous four days. 
  • BPA builds better modern transformers that can handle the extra energy.
  • BPA works with science partners at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center to help validate their forecast models for better prediction tools.  
 

What causes auroras?

Sometimes solar storms are so strong that they tug on the Earth's magnetic field as they pass. When the Earth’s magnetic field snaps back – like a stretched rubber band recoiling – it creates powerful waves.

As electrons in Earth’s upper atmosphere hitch a ride on these fast-moving waves, they release the lights we know as auroras. This is the result of the electrons colliding with oxygen and nitrogen molecules.

Because the Earth’s magnetic field is weakest at the northern and southern poles, solar storms pass most easily through the atmosphere at these higher latitudes.

Fun Fact

The color of an aurora depends on which type of particle is hit. Red and green colors result from oxygen collisions, while blue comes from nitrogen. 

Historical impacts to the grid from geomagnetic storms

The most notorious example of a space weather impact to the power grid occurred in March 1989, when a severe geomagnetic storm knocked out the power grid for nine hours in Quebec, Canada, leaving millions without electricity. The same storm damaged transformers as far south as New Jersey and nearly caused a cascade of failures across the United States.

For more information

NOAA’s Space Weather Prediction Center is the premiere space weather forecast entity, globally recognized for its expertise. It produces an Electric Power Community Dashboard with helpful tools that predict the severity, impact, timing and location of space weather impacts.