Geomagnetic Storm Impacts: Radio Communications & Power Grids

For many people seeing an aurora in person is a bucket-list activity. Normally only seen in the far north and south, from time to time auroras can be spotted in regions much closer to the equator. These beautiful natural light shows are the visual product of geomagnetic storms hitting Earth’s atmosphere. And, despite their beauty, geomagnetic storms can have detrimental effects on radio communications and power systems. On Land Mobile Radio networks, however, they have only a minor impact. Read along to discover why our Tait systems are safe from geomagnetic storms, when other communications that use the ionosphere are not!

March 2024 Solar Storm

The first “extreme” geomagnetic storm in 20 years hit Earth’s magnetic field on the 14th of May… The cause? Five coronal mass ejections (CMEs) from the Sun colliding with Earth’s magnetic field – bursts of energy from spots on the sun’s scorching hot surface over an area 16 times wider than Earth. As radiation from the storm peaked, the classification was moved from “severe” to “extreme” by the National Oceanic and Atmospheric Administration (NOAA).¹

News articles and social media speculation caused some fear of a complete disruption to modern communication systems. Others were just fascinated by posts of the dramatic auroral show that extended far from the poles. The Aurora Australis (Southern Lights) was spotted as far north as Southern Queensland in Australia²; the Aurora Borealis (Northern Lights) were seen further south than predicted, all the way down to South Carolina.³ 

Image of the Southern Lights, in New Zealand photographed by Tait Communications staff member Elissa Mah, 11th of May 2024.

The Fluidity of The Sun’s Surface Across An 11-Year Cycle

Geomagnetic storms of this size are not a regular occurrence, the reason is that the Sun’s solar activity is cyclical, with a solar maximum occurring every 11 years. The Sun is approaching a solar maximum in 2025, so we may not see another light show like last month’s for another 11 years. Sunspot frequency increases leading up to these solar maximums. Sunspots are dark areas on the Sun where the magnetic field is more concentrated due to more magnetic flux pushing from the Sun’s interior, growing solar flare and CME activity.  

Solar flares and CMEs are different types of solar activity. Both can trigger auroral activity and communications disturbances in our atmosphere. Solar flares are sudden explosions of energy from the surface of the Sun in the form of a great flash of light and particles – it takes a solar flare less than 20 minutes to reach Earth. Although less powerful than solar flares, CMEs are a form of solar eruption that releases solar plasma and embedded magnetic fields into space. CMEs and solar flares look different under a telescope, with solar flares appearing as a flash of light and CMEs moving like large fans of gas flowing through space. Once these plasma clouds hit Earth’s atmosphere, the particles compress our Sun-facing (dayside) magnetic field and stretch out our nightside magnetic field.⁴

Solar activity from the sun such as CMEs, solar flares and solar wind reaching the earths magnetosphere.

The Role of the Ionosphere In Radio Communications and The Impact of Solar Activity

Only radio communications that pass through or use the ionosphere (part of the magnetosphere; the second-most outer layer of Earth’s atmosphere)  are affected by geomagnetic storms. Made up of charged particles, the ionosphere layers density changes according to the 11-year cycle of solar activity, with geomagnetic storms bringing about dramatic but temporary changes.⁵

One important function of the ionosphere is that it reflects and modifies radio waves used for communication and navigation. When geomagnetic storms occur they increase the density, and distribution of the density within the ionosphere by adding energy in the form of heat. These strong horizontal variations in the density result in the modification of the path of radio signals that go through or use the ionosphere.⁶

Radio Communications That Are Affected by Geomagnetic Changes In The Ionosphere

Luckily for Tait, Land Mobile Radio (LMR) communications don’t operate within radio bands that use the ionosphere, instead these communications are terrestrial. Examples of communications that use the ionosphere are satellite communications and High Frequency (HF) communications. Satellite communications, operating at frequencies of >1 GHz, such as GPS, pass through the ionosphere on the way to and from the satellite, where changes in the density of the ionosphere from geomagnetic storms can result in positioning errors in GPS locations.⁶ The radio waves from HF communications in the 2 to 30MHz band propagate by bouncing off the ionosphere; these waves are known as skywaves. They make communications possible across very large distances, beyond the horizon (see the diagram below).

HF frequencies (also often known as shortwave radio) are often used by the military and offshore workers to communicate across long distances, but in the case of geomagnetic storm activity this method of communication becomes unreliable.⁷ HF radio waves may not propagate correctly during “severe” storms, meaning their dispersion becomes sporadic – resulting in disturbed communications. In the instance of “extreme” storms HF radio propagation may be impossible in some areas for days at a time. For more info on the effects of geomagnetic storms on global communications systems and operations see the NOAA Space Scales here.   

Diagram outlining the radio communications affected by geomagnetic storms and the severity of impact.

Why Land Mobile Radio Communications Are Minimally Affected By Geomagnetic Storms

The LMR bands of VHF (Very High Frequency) operating from 136 to 225 MHz and UHF (Ultra High Frequency) operating from 330 to 530MHz –  that Tait provide radio equipment for – don’t use the ionosphere for propagation, hence such storms will have minimal effect on these communications (as shown on the diagram above). Radio waves in the VHF and UHF spectrums propagate along the line of sight, behaving similarly to light waves, and instead transmit through the troposphere (the earth’s lowest layer of atmosphere).⁸ Making these radio bands ideal for communications over a few kilometers. The only way that LMR communication may be impacted is through a rise in noise floor, due the storm varying the earth’s magnetic field, which induces currents in the antenna of radios (a conductor). This will slightly reduce the distance that is possible to communicate, more so with the VHF band.

Conductors, Geomagnetic Storms and Power Grids

Although LMR radio communications may be minorly impacted by a change in the magnetic field, other conductors such as power lines can be subject to a greater impact. So, how exactly are conductors affected by such geomagnetic disturbances? The answer is in a basic rule of physics: the rule states that when a magnetic field swings back and forth, electricity then flows through conductors in that area creating  a magnetic induction. Geomagnetically induced currents (GIC) are brought forth in the magnetosphere during geomagnetic storms, which then impacts the planet’s magnetic field and in turn induces currents in conductors such as powerlines. The overheating of transformers and sudden collapses in power systems may occur.⁹ 

However, most power companies today are prepared for these occurrences and take precautionary measures to prevent these outcomes from coming to fruition, learning from past events where citywide blackouts caused carnage. It’s not just areas close to the poles that may be affected, as auroral zones shift further towards the equator when solar activity increases. The New Zealand state-owned power transmissions company Transpower New Zealand switched off some electricity transmission circuits in both North and South islands during the May 2024 geomagnetic storm to prevent damage to equipment.¹⁰

Examples of Geomagnetic Storm Events

Now that we know our power professionals have not always been prepared for such phenomena… let’s explore two events where geomagnetic storms have shocked areas within Canada and the United Kingdom!

The Carrington Event

Image of Richard Carrington

Imaged sourced from

The event was named after amateur sky watcher Richard Carrington, who was sketching sunspots in August 1859 and became momentarily blinded by a magnificent white light that invaded his telescope lens, a flare that lasted 5 minutes. Richard, who saw this flash in a small town near London, reported what we now know as a CME to the Royal Astronomical society. The energy that wrapped the earth following this CME during September 1859, equated to that of a 10-megaton nuclear bomb, reaching the earth in less than 24 hours, with CMEs usually taking multiple days to reach earth.¹¹  

The damages that incurred were widespread, but the aurora was fantastic. Telegraph communications failed globally, with reports stating that there were sparks from telegraph machines, whilst papers caught alight from rogue sparks and telegraph wires became ablaze. Some telegraph operators received electric shocks, whilst other citizens claimed they experienced shocks from other metal objects such as doorknobs. The aurora was seen much further from than the poles during this event, extending as far north in the Southern Hemisphere as Chile, and southwards in Cuba and Hawaii in the Northern Hemisphere.¹² 

The Québec Blackout, AKA “The Day The Sun Brought Darkness”

Sunspot activity between 7 and 17 of March 1989.

Québec is an ideal target for GIC, as the city is located atop Precambrian era igneous rock – a layer of soil that is not ideal at conducting electricity. Just 90 seconds after a strong CME hit our planet on the 13th of March 1989, Quebec fell into complete darkness in the early hours of the morning, a blackout resulting from the Hydro-Québec power grid failing. The city’s transformers overheated and circuit breakers tripped. When this CME exploded on the 10th of March 1989 it almost immediately disrupted HF radio signals across the globe.⁹

The city of six million people were left without electricity for 9 hours, with many, including the electricity provider having no idea as to the cause of this event. The city’s residents arose to cold homes, and appliances refusing to operate when it came time to make breakfast. Schools and businesses were forced to close, the metro was shut down and the international airport ceased operations until the power grids were fixed. 

Some who saw the aurora from the event believed that they were witnessing a nuclear exchange, some speculated this may have been due to the space shuttle (STS-29) launch that occurred the same day. Onlookers spotted this aurora all the way down to Cuba and Florida.¹³

It was events such as the Québec Blackout that promoted the monitoring of solar activity and more comprehensive investigations into its effect on the earth’s communications and power systems. So, today power suppliers and radio spectrum providers make sound provisions for the increased solar activity that solar maximums send towards our planet’s atmosphere.

Do you want more detail about radio propagation basics? Take this radio academy course!

¹ “Why ‘Extreme’ Solar Storm Could Affect GPS, Communications Equipment,” Newshub, 2023, sec. World,

²  Tariq Malik and Daisy Dobrijevic, “Jaw-Dropping Northern Lights from Massive Solar Flares Amaze Skywatchers around the World. ‘We Have a Very Rare Event on Our Hands.’ (Photos),”, May 11, 2024,

³ “Aurora Australis and Borealis Put on Another Spectacular Show,” ABC News, May 12, 2024,

⁴ EarthSky, “Is a Solar Flare the Same Thing as a CME?,”, March 22, 2023,

⁵ “Ionosphere | NOAA / NWS Space Weather Prediction Center,”, n.d.,

⁶ “Geomagnetic Storms | NOAA / NWS Space Weather Prediction Center,”, n.d.,

⁷ Jackson Chen, “Everything You Want to Know about Shortwave Radio,” Radioddity, May 8, 2023,

⁸ “VHF/UHF Propagation – Radio Society of Great Britain – Main Site : Radio Society of Great Britain – Main Site,”, accessed May 31, 2024,

⁹ Dr Tony Phillips, “The Great Québec Blackout,”, March 12, 2021,

¹⁰ “Transpower Continues to Protect Power System as Solar Storm Upgraded to G5 | Transpower,”, May 11, 2024,

¹¹ Andrew May and Daisy Dobrijevic, “The Carrington Event: History’s Greatest Solar Storm,”, May 20, 2022,

¹² Andy Briggs, “What Was the Carrington Event, and Why Does It Matter?,”, October 22, 2023,

¹³ “Witness History, What the 1989 Solar Storm Did to Quebec,” BBC, n.d.,

Leave a Reply

Your email address will not be published. Required fields are marked *