In May 2024, farmers across many parts of the United States experienced sudden loss of GNSS positioning and high-accuracy correction services in the heart of one of their busiest seasons of the year — spring planting.
During the same timeframe, individuals across the same region were reporting Aurora Borealis sightings, commonly referred to as the “northern lights”. These encounters took social media by storm as they were quite unusual for the region. Aurora Borealis are most prevalent in higher latitudes and rarely make an appearance this far south.
Although this may seem like an odd coincidence, these events were both related to Solar Cycle 25, and similar occurrences can be expected to continue over 2025.
About Solar Cycle 25
Solar cycles follow a bell curve pattern in relation to solar activity with each cycle lasting roughly 11 years. At the beginning and end of the 11-year cycle, solar activity is at a low with the highest activity occurring in the middle of the 11-year period.
Solar Cycle 25 began in late 2019 and is anticipated to continue through 2030. Following the 11-year pattern, solar activity is expected to peak between 2024 and 2025.
The following graph from the Space Weather Prediction Center reflects the number of sunspots present over Solar Cycle 24 and Solar Cycle 25.
Photo Resource – May 2024 through August 2024 recorded more sunspots than the roughly 15 years prior. This timing correlates with the increased disruption farmers were experiencing in the field — a phenomenon called scintillation.
Sunspots, a form of solar activity, are temporary dark areas on the surface of the sun caused by intense magnetic activity. These areas eject particles which are then carried to the Earth via solar wind. As the particles reach Earth, they concentrate into a layer of the atmosphere called the Ionosphere.
The Ionosphere is made up of electrically charged atoms and molecules. When the level of atoms and molecules present increases, like during high solar activity periods where an increased number of sunspots are present, GNSS signals may not be able to pass through the Ionosphere. This phenomenon is known as scintillation.
Scintillation’s impact on GNSS signals can come in the form of signal degradation, fading or loss of signal lock for farmers utilizing high-accuracy correction services.
Focused Disruption in Equatorial Regions
Farmers in equatorial regions experience scintillation year-round as these regions experience a higher concentration of irregularities in the Ionosphere. The severity of scintillation is dependent on the current solar cycle. However, the most disruption is expected between September and March annually.
The following image from Trimble’s GNSS Planning tool showcases the varying levels of scintillation experienced across the South American region over a 24-hour time period on April 3, 2025.
Video Resource – Ionospheric scintillation occurs in pockets, impacting only a subset of satellites at a time. This explains why a loss of corrections is often temporary, sporadic, and unpredictable.
Identifying and Mitigating Scintillation-Related Downtime
Unfortunately, when downtime caused by scintillation occurs, there is no way for you to pinpoint ionospheric disturbances as the exact root cause which can be frustrating when searching for a solution. However, there are things you can look for that may indicate solar interference is occurring within your autosteer system.
The number of satellites the system is using may fluctuate or drop which may impact position accuracy.
Increased cross-track errors.
If accuracy is sufficiently degraded, the autosteer system may disengage.
Fieldwork is timely and losing an ideal window can be costly. So, what can you do to reduce downtime caused by scintillation?
If you can plan field work in advance, weather pending, Trimble's GNSS Planning Tool provides real-time information related to satellite health, as well as Total Electron Count (TEC) and scintillation maps.
Additionally, Trimble and PTx Trimble are pleased to introduce the availability of Trimble IonoGuard for the precision agriculture industry.
Trimble IonoGuard for Precision Agriculture
Trimble IonoGuard is a next-generation technology engineered to enhance RTK GNSS signal tracking and positioning performance during ionospheric disturbances, ensuring more reliable and accurate positioning while in the field. With IonoGuard enabled, users can expect improved GNSS positioning performance throughout periods of heavy scintillation.
Photo Resource –These images showcase horizontal position error in meters with IonoGuard enabled (red) versus IonoGuard disabled (blue). Horizontal position error is the level of inaccuracy when determining the horizontal coordinates of a position (latitude and longitude).
IonoGuard is available at no additional charge for NAV-900 and NAV-960 guidance controller users utilizing CenterPoint RTK or CenterPoint VRS correction services, as well as R750 and R780 base station users. The recommended hardware setup for optimal performance is a NAV-960 guidance controller and a Trimble ProPoint Base Station.
Interested in learning more about enabling IonoGuard on your device? Download the enablement instructions. If firmware requirements for enablement are not met on your device, contact your local PTx Trimble dealer to assist with the firmware upgrade process.
