Cape Town:
A geomagnetic storm illuminated the night sky in parts of the US during the first weekend of October. The National Space Agency of South Africa (Sansa) told reporters that the storm came from a solar flare “that erupted from sunspot 3842 on October 3.” It said this was the strongest Earth-bound solar flare Sansa has recorded in the past seven years and that the eruption briefly affected high-frequency radio communications, “resulting in a total radio blackout in the African region that lasted up to 20 minutes.” .
What is a geomagnetic storm? The conversation Africa asked Sansa’s Amoré Nel, who conducts research into geomagnetismto explain.
What is a geomagnetic storm and how often do they occur?
A geomagnetic storm is a disturbance of the Earth’s magnetic field caused by solar activity. There is a reaction called nuclear fusion this happens all the time deep in the core of the sun. This produces enormous amounts of energy. Some of the energy is released as light (sunlight), some as radiation (solar flares) and some as charged particles.
The sun also continuously emits a stream of charged particles known as the solar wind. Occasionally the sun releases larger bursts of energy, called coronal mass ejections. It sends clouds of these charged particles, or plasma, through space. I like to explain it to children this way: the sun sometimes drinks a soft drink too quickly and then burps. This “burp” is the plasma cloud that then travels through space. These emissions do not always affect us. But when they do, they collide with Earth’s magnetic field, disrupting it and leading to a geomagnetic storm.
Earth’s magnetic field is an invisible force that surrounds our planet and acts like a giant magnet with a north and south pole. It helps protect us from harmful solar radiation by deflecting charged particles from the sun.
The solar flare of 3842 emitted both X-flares (radiation) and a coronal mass ejection. X-flares are radiation; they travel at almost the speed of light and reach Earth within minutes. That’s what caused the brief communications outage Sansa mentioned on October 3rd. But it will take much longer for the coronal mass ejection to reach us. We had already predicted this last weekend, but in reality it only reached us on the morning of October 8.
Geomagnetic storms are quite common. Smaller cases occur several times a year. The severity of a storm depends on how strong the solar event was that caused it. Larger, more intense storms are less common, but can occur every few years. Solar events are closely linked to the sun’s 11-year solar cycle, which has periods of high and low activity. During the peak of the cycle, called solar maximum, more sunspots and solar flares occur, increasing the chance solar storms.
We are now heading towards the top of Solar cycle 25that will be in July 2025. Solar maxima typically last between two and three years.
Are these storms dangerous? What damage can they cause?
Geomagnetic storms are generally not directly harmful to humans, but can pose risks to modern technology and infrastructure. One of the most notable dangers concerns electricity networks. Strong storms can cause electrical currents in power lines, potentially overloading transformers and causing power outages. as happened in Québec, Canada, in 1989.
Satellites in space are also vulnerable. A strong storm can damage onboard electronics, disrupt communications signals and shorten the lifespan of the satellites themselves.
In aviation, geomagnetic storms can disrupt radio communications and GPS signals, which are essential for aircraft navigation. This is especially important for flights passing close to the polar regions, where the effects of geomagnetic storms are more pronounced. Astronauts and spacecraft are also at risk; the extra radiation can be dangerous to equipment and human health.
Are there any advantages to this phenomenon?
Auroras are a visually stunning aspect of geomagnetic storms. These colorful phenomena in the night sky occur when charged particles from the Sun become trapped in Earth’s magnetic field lines and flow toward the poles. Here they interact with the Earth’s atmosphere, releasing energy that produces shimmering lights.
Auroras can be seen at both the north and south poles, aptly called the northern and southern lights. If storms are large enough, it is possible to see them in areas much further away from the poles. This happened in South Africa on May 11, 2024.
Studying geomagnetic storms provides valuable insights into space weather. By understanding how the sun’s activity affects Earth, scientists can better predict future storms and work to protect the technologies we rely on. The study of geomagnetic storms also contributes to our understanding of the Sun and space in general.
Can monitoring the storms limit the risks?
Geomagnetic storms are monitored using various instruments on Earth and in space. On Earth, magnetometers measure changes in the magnetic field, allowing scientists to monitor disturbances as they occur. For this reason, Sansa has a dense network of Global Navigation Satellite System receivers in Africa, as well as magnetometer stations in various parts of southern Africa. The agency is also currently setting up a magnetometer station in Ethiopia. This will improve our ability to monitor geomagnetic storms.
In space, satellites equipped with sensors monitor the sun’s activity and detect solar flares or coronal mass ejections before they reach Earth. This data is used in forecasting models used in space weather centers around the world.
Once a storm is detected, agencies like Sansa issue warnings and forecasts. These warnings help industries such as power grid operators, satellite companies and aviation authorities prepare for a storm.
For example, energy companies can temporarily shut down or reconfigure parts of the electricity grid to prevent overload during a storm. Satellite operators can put their spacecraft into safer operating modes, such as turning off electronic components, and airlines can divert flights away from high-risk areas.
Monitoring alone cannot prevent all damage caused by geomagnetic storms. But it can greatly reduce the risks. Early warning systems help us protect critical infrastructure and minimize the impact of these storms on our daily lives.
(Author: Amore Elsje NelApplied geomagnetic researcher, South African National Space Agency)
(Disclosure Statement: Amoré Elsje Nel works for the South African National Space Agency. She receives a Thuthuka Grant (TTK210406592410) from the National Research Foundation)
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