A geomagnetic storm lit up parts of the US night sky during the first weekend of October. According to South Africa’s National Space Agency (Sansa), this storm originated from a solar flare that erupted from sunspot 3842 on October 3. Sansa reported that this was the strongest solar flare aimed at Earth recorded in the last seven years. The eruption caused temporary disruptions in high-frequency radio communications, leading to a radio blackout in parts of Africa for up to 20 minutes.
To understand geomagnetic storms, The Conversation Africa spoke with Amoré Nel from Sansa, who studies geomagnetics.
A geomagnetic storm is a disturbance in Earth’s magnetic field caused by solar activity. The Sun constantly undergoes nuclear fusion, producing vast amounts of energy. This energy is released in various forms, including light, radiation, and charged particles.
The Sun also emits a steady flow of charged particles known as the solar wind. Occasionally, it releases larger bursts of energy called coronal mass ejections, which send clouds of plasma hurtling through space. Nel likens this to the Sun “drinking a soda too fast and then burping,” with the burp being the cloud of plasma that travels through space. When these emissions collide with Earth’s magnetic field, they disrupt it, resulting in a geomagnetic storm.
Earth’s magnetic field acts like a protective shield, deflecting harmful solar radiation and charged particles from the Sun.
The solar flare from sunspot 3842 released both X-flares (radiation) and a coronal mass ejection. The X-flares reach Earth in minutes, which is what caused the communication disruptions on October 3. The coronal mass ejection, however, takes longer to arrive and reached Earth on the morning of October 8.
Geomagnetic storms are relatively common, with minor events occurring several times a year. The storm’s severity depends on the strength of the solar event that caused it. Larger storms are less frequent, happening every few years. These solar events are linked to the Sun’s 11-year solar cycle, which consists of periods of high and low activity. We are currently approaching the peak of Solar Cycle 25, expected in July 2025, which typically lasts two to three years.
While geomagnetic storms are not directly harmful to humans, they can pose risks to technology and infrastructure. One of the main dangers is to power grids. Strong storms can induce electric currents in power lines, which may overload transformers and cause blackouts, as seen in Quebec, Canada, in 1989.
Satellites in orbit are also at risk. A severe storm can damage onboard electronics, disrupt communication signals, and shorten the lifespan of satellites. In aviation, geomagnetic storms can interfere with radio communication and GPS signals crucial for navigation, particularly for flights near the poles, where storm effects are more pronounced. Astronauts and spacecraft can face additional radiation risks from these storms.
Despite the risks, geomagnetic storms have their upsides. They create beautiful auroras, or northern and southern lights, when charged particles from the Sun interact with Earth’s atmosphere near the poles, producing stunning light displays. Strong storms can even allow these auroras to be seen farther from the poles, as occurred in South Africa on May 11, 2024.
Studying geomagnetic storms provides valuable insights into space weather and helps scientists understand how solar activity impacts Earth. This research can improve predictions of future storms and protect vital technologies.
Geomagnetic storms are monitored using various instruments both on Earth and in space. On Earth, magnetometers measure changes in the magnetic field to track disturbances. Sansa has a network of Global Navigation Satellite System receivers and magnetometer stations across southern Africa, and they are establishing a new station in Ethiopia to enhance monitoring.
In space, satellites with sensors detect solar flares or coronal mass ejections before they reach Earth. This information feeds into prediction models used by space weather centers worldwide.
When a storm is detected, agencies like Sansa issue alerts and forecasts. These warnings enable industries like power grid operators, satellite companies, and aviation authorities to prepare for potential disruptions. For instance, power companies may shut down parts of the grid to prevent overloads, while satellite operators can switch their spacecraft to safer modes, and airlines can reroute flights.
While monitoring alone cannot prevent all damage from geomagnetic storms, it significantly reduces risks. Early warning systems help protect essential infrastructure and minimize the impact of these storms on everyday life.
