This spring’s space storm painted the midnight sky with mesmerizing light and brought GPS-reliant farm machines to a rumbling halt. Farmers have since made up ground. But while the aurora borealis might be out of sight for the time being, the possibility of another space storm shouldn’t be out of mind.

“The sun seems to alternate between periods of high activity and low activity,” says Bryan Basher, project manager of the Space Weather Prediction Center at the National Oceanographic and Atmospheric Administration. “There’s about 11 years that separates peak to peak, trough to trough. Right now, we’re approaching solar maximum — peak solar activity.”

Given the season, the possibility of another extreme solar storm capable of disrupting precision guidance over the next year is at an all-time high. Whether or not that event impacts farm equipment depends on when and where it takes place.

Solar storms, categorized by NOAA from G1 to G5, are marked by bright solar flares and coronal mass ejections. The former are flashes of light. The latter describes when “plasma from the corona is thrown out into space,” Basher says. The most recent storm was a G5. These phenomena can happen dozens of times per day.

Earth is only impacted when its orbit brings it into the firing line. That’s when “a billion tons of plasma traveling at a million miles per hour impacts our magnetic field,” Basher says. The supercharged collision roils the planet’s magnetic field, disrupting communications and skewing satellite signals. Massive storms can even cause terrestrial electrical currents to surge.

Distorted signals from space

“When you’re out there in the field with your GPS signal, you’re receiving a signal from at least four GPS satellites. Those signals have to go through this now disturbed ionosphere,” Basher explains. “The signal is distorted. Not only is it distorted, it’s getting bent. The path that it takes to get to you might not be a straight line. That additional distance means time.”

INNACURATE GPS: Disturbances in the Earth’s magnetic field can impact the accuracy of precision guidance systems, which are relied on by most modern agricultural machines.

Precision farm machines triangulate centimeter-level location data by tracking the time it takes for guidance signals to arrive from orbiting satellites and terrestrial base stations. If it’s longer than expected, machines misinterpret calculations. Maximilian Hiltmair, who leads correction services for Trimble, says satellite companies are constantly making corrections to adjust for these time discrepancies. Even so, they can only do so much.

The Earth’s ionosphere “usually has an even distribution and a certain density. But in a solar storm, an explosion from the sun charges the layer so it’s like the ocean,” Hiltmair says. “It makes it impossible at certain times to do any positioning. In such a storm, [guidance] will never survive completely.”

During those extreme solar events, Hiltmair says guidance systems that rely on data from multiple base stations and can receive signals from multiple satellite constellations typically fare better. Four major global navigation satellite systems orbit the Earth:

Trimble, which guides vehicles in many different sectors, has a dense network of hundreds of base stations positioned around the globe. The base stations feed data into processing centers, which analyze the data and broadcast corrections through geostationary satellites in space to vehicles on the ground.

Prepare for space weather

Farmers can build resilience against future outages by making sure they invest in the right technology.

“GPS receivers can be single or dual frequency,” Basher says. “The bending of that signal through the atmosphere is a function of the frequency of the signal. GPS satellites transmit on [two frequencies], L1 and L2. If you have a dual-frequency receiver, it can compare the two and then calibrate.”

Farmers can also prepare for solar storms by tracking them via NOAA’s Space Weather Prediction Center at spaceweather.gov. Basher says forecasters can predict impending storms between one and three days in advance. Farmers can sign up for notifications when NOAA issues an extreme space weather watch from categories G3 to G5, which are the most likely to impact precision guidance equipment.

Before the most recent storm, “the last time we had a G5 storm was in 2003,” Basher says. “There’s nothing to say we can’t have another G5 storm next week. Historically, it doesn’t happen often. The next storm might not be as widespread. It might not be as long in duration. But it might happen.”

Reporting a disruption

Was your precision planter affected by the recent geomagnetic solar storm? If so, the Federal Communications Commission  would like to hear about your experience.

According to the FCC notice, the agency requests the following feedback by June 24: