How Solar Flares Affect GPS and Communications

Solar flares can disrupt GPS and radio communications, especially when their radiation affects the upper layers of the atmosphere.

Changes in the ionosphere can make radio signals travel differently than a receiver expects, affecting positioning accuracy and the reliability of communications. A solar flare does not mean GPS will necessarily stop working, but reception conditions may worsen.

Exactly how solar flares affect GPS and communications depends on the strength of the disturbance and the type of signal. Let’s look at which systems are vulnerable and what users may notice.

• 0,5–4,0 angstroms (0,05–0,4 nm) One range used for X-ray observations of solar flares
• 1–8 angstroms (0,1–0,8 nm) Another range used for X-ray observations of solar flares

How does a flare cause interference on Earth?

A solar flare degrades GPS and high-frequency radio communications when it changes the state of the ionosphere—the region of the upper atmosphere through which radio signals travel.

A flare is a sudden increase in the Sun’s radiation. During one, plasma heats up to tens of millions of kelvins, and particles accelerate to nearly the speed of light.

A coronal mass ejection is a different, though related, phenomenon: it carries plasma and a magnetic-field structure into space. Radiation and ejected plasma affect Earth in different ways and do not arrive by the same route. A flare and an ejection should therefore not be treated as a single effect.

Why signals are affected

Radiation from a flare can alter the ionosphere, and a disturbed ionosphere can disrupt the passage of radio signals. For GPS, this means poorer reception and navigation conditions; for high-frequency radio communications, it means interference with signal transmission.

A coronal mass ejection acts differently: its plasma and magnetic field can interact with the near-Earth environment. This distinction between the rapid effects of radiation and the later arrival of ejected material is key to understanding why the resulting interference varies.

What do X-ray bands measure when observing flares?

X-ray observations

X-ray bands show how the radiation from a solar flare changes. It is observed in the 0,5–4,0 angstroms (0,05–0,4 nm) and 1–8 angstroms (0,1–0,8 nm) bands.

• 0,5–4 angstroms: In GOES 15 observation plots, this band is shown in blue.
• 1–8 angstroms: In GOES 15 plots, measurements in this band are shown in red.

Comparing the two curves helps track a flare’s development through changes in X-ray emission. This observation describes the Sun’s radiation, not the trajectory of a coronal mass ejection or its interaction with Earth’s magnetic field.

So an X-ray plot alone cannot tell you whether a coronal mass ejection will reach Earth. Forecasting space weather also relies on observations of solar activity and the properties of the solar wind: these help assess possible effects on Earth’s environment.

Which systems are vulnerable to space weather?

Satellite navigation and communications, high-frequency radio communications, aviation systems, and power lines are vulnerable to space weather. The effects depend on how the ionosphere and near-Earth space change.

• GPS navigation. Ionospheric disturbances change the medium through which satellite signals travel and can reduce positioning accuracy. The effects depend not only on the satellite system but also on the conditions in the signal’s path.
• High-frequency radio communications. Ionospheric disturbances can disrupt the propagation of radio waves. This matters for aviation when routes and operational systems depend on the high-frequency band: both communications and navigation may be affected.
• Satellites and communications systems. Their operation depends on conditions in near-Earth space. Space weather can therefore affect signal transmission, although the specific effect depends on changes in the medium through which the signals travel.
• Power grids. Strong geomagnetic disturbances can induce currents in wires and disrupt power lines. This is not a satellite-signal failure, but an effect on wired infrastructure.

For GPS and radio communications, the key question is how the disturbance changes signal propagation; for power grids, it is what currents are induced in the wires.

When can a space weather forecast help inform a decision?

A space weather forecast helps inform a decision when the expected effects give operators time to check vulnerable systems and prepare for possible deteriorating conditions.

Monitoring solar activity and the solar wind is useful for more than observation alone: it helps assess in advance the possible effects on Earth’s electromagnetic environment, satellite systems, and power grids. Forecasts also matter for aviation when they point to conditions that could affect navigation or radio communications.

What to watch for

The fact that a solar flare has occurred does not, by itself, determine what measures are needed. The expected effects are what matter:

• Radiation effects: Possible effects of solar particles on satellites and aviation.
• Ionospheric conditions: Changes that could disrupt the propagation of GPS and high-frequency radio signals.
• Interaction between a coronal mass ejection and the magnetosphere: Possible effects on the electromagnetic environment and power grids.

A satellite operator can check vulnerable systems, an airline can assess current communications and navigation advisories, and a power company can prepare for possible effects on the grid.

Specific measures depend on the system and the advisory. There is no universal response to every flare: an emission plot alone is not enough to determine the consequences for a particular network.

When does a solar flare not mean GPS failure or a power outage?

A solar flare by itself does not mean GPS will fail or the power will go out: increased radiation and a plasma ejection are different phenomena, even though they may occur as part of the same solar activity.

What you cannot conclude from a single signal

The occurrence of a flare does not prove that a particular satellite, navigation receiver, or power line will fail. To assess the risk, it is important to know exactly what happened on the Sun and how the event affects the near-Earth environment.

• For satellites and communications: The nature of the solar event and the state of the magnetosphere, which shields Earth from some solar effects, are important.
• For GPS: The effects depend on the state of the ionosphere—the atmospheric region through which navigation signals travel—as well as the receiver’s location and the system being used.
• For the power grid: The consequences depend on whether induced currents arise in power lines and on the vulnerability of the specific infrastructure.

A brief loss of GPS accuracy is not the same as navigation failing everywhere. Reception may worsen in one place while the system continues to work in another; the outcome depends on signal-propagation conditions and the specific equipment.

When assessing the situation, check not only reports of a flare but also space weather advisories relevant to your region and the communications or navigation system you use.

Frequently asked questions

Key takeaways

• A flare and a coronal mass ejection are different phenomena.
• Ionospheric disturbances can interfere with GPS and high-frequency radio communications.
• GOES 15 shows the 0,5–4 and 1–8 angstrom X-ray bands in different colors.
• The risk to satellites, aviation, and power grids depends on the event and the vulnerability of each system.