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.
Despite their beauty, geomagnetic storms can have detrimental effects on certain types of radio communications and power systems. On Land Mobile Radio (LMR) networks, however, they have only a minor impact.
Read along to discover why Tait radio networks are safe from geomagnetic storms, while other communications are not.
The 11-year cycle – How the fluidity of the Sun's surface creates geomagnetic storms
The Sun’s solar activity is cyclical, with peak activity (known as a solar maximum) occurring every 11 years.
Sunspot frequency increases leading up to the peak in activity of the Sun’s surface. 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 coronal mass ejections (CME) activity.
Solar flares and CMEs are two different types of solar activity
-
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 night-side magnetic field.
Solar activity from the Sun such as CMEs, solar flares and solar wind reaching the Earth's magnetosphere.
What systems do geomagnetic storms disrupt and how are they classified?
Both solar flares and CMEs can trigger auroral activity and disturbances in our atmosphere, impacting power systems, spacecraft operations, and high-frequency radio systems.
Geomagnetic storms are categorized on a scale from one to five with one being “minor” and five “extreme”. How severely each type of system is impacted depends on the category of the storm, but why is it only these systems that are disrupted?
The role of the ionosphere and how radio communications are disrupted by solar activity
One important function of the ionosphere (part of the magnetosphere; the second-most outer layer of Earth’s atmosphere) is that it reflects and modifies certain radio waves used for communication and navigation. Made up of charged particles, the density of the layers within the ionosphere changes according to the solar activity cycle.
When geomagnetic storms occur, they cause dramatic but temporary changes. 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 abnormal modification of the path of certain radio frequencies that pass through or "bounce-off" the ionosphere.
What types of radio communications are impacted by changes in the ionosphere?
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. Changes in the density of the ionosphere from geomagnetic storms can result in positioning errors in GPS locations.
The radio waves from HF communications (also often known as shortwave radio) 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 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 can become unreliable. HF radio waves may not propagate correctly during “severe” storms, meaning their dispersion becomes sporadic – resulting in disturbed communications.
Diagram outlining the radio communications affected by geomagnetic storms and the severity of impact.
The resiliency of LMR communications during 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 infrastructure for – don’t use the ionosphere for propagation. Hence, such storms will have minimal effect on these communications (as shown in the diagram above).
Radio waves in the VHF and UHF spectrum propagate along the line of sight, behaving similarly to light waves, and instead transmit through the troposphere (Earth’s lowest layer of atmosphere). Making these radio bands ideal for communication over a few kilometers.
The only way that LMR communication may be impacted is through a rise in noise floor, due the storm varying Earth’s magnetic field, which induces currents in the antenna (a conductor) of radios. This will slightly reduce the distance that is possible to communicate, more so with the VHF band.
Why do geomagnetic storms cause the greatest disruption to power systems?
Although the antennas on LMR devices may be slightly 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 power lines. The overheating of transformers and sudden collapses in power systems may result.
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 major disruption.
Notable geomagnetic storm events that made us monitor solar activity
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 in Canada and the United Kingdom!
The Carrington Event
The event was named after amateur sky watcher Richard Carrington, who was sketching sunspots in August 1859 and became momentarily blinded by a 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 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.
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 Quebec Blackout, AKA “The Day The Sun Brought Darkness”
Sunspot activity between 7 and 17 of March 1989.
Quebec is the 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-Quebec 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.
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.
Maintaining communications resilience – What if a geomagnetic storm hit today?
The media creates the greatest disturbance to radio communications nowadays. One example of such disruption is the 2024 “extreme” geomagnetic storm, the first of its severity to hit Earth in 20 years.
The storm consisted of five CMEs from the Sun colliding with Earth’s magnetic field, and as radiation from the storm peaked, the classification was moved from “severe” to “extreme”. News articles and social media speculation fostered public fear of complete disruption to modern energy and communication systems during the 2024 storm.
However, this narrative doesn't hold true for today or in future.
Today, power suppliers and radio spectrum providers can prepare for atmospheric disturbances as they are constantly monitored.
For LMR communications, Tait's terrestrial networks are resilient by design, meaning in the event of a geomagnetic storm your critical communications remain uninterrupted.
The impact solar activity has on satellite and high-frequency communications serves as a strong reminder of the reliability of LMR for critical communications for today and most importantly for the future.
This blog was written in collaboration with Tait Principal Design Engineer Ian Graham, who has over four decades of radio communications expertise, and specializes in radio frequency (RF) design.
Curious as to how Ian and the Tait team design resilient LMR networks?
Discover the ins and outs of RF design.
COMMENTS