Magnetic storms, also known as solar or geomagnetic storms, are fascinating but complex phenomena that result from variations in solar activity. They occur when solar flares shoot charged particles towards the Earth at high speed. But how are they actually formed, and what impact do they have on our planet and our health?
Solar flares: the driving force behind magnetic storms
Magnetic storms originate within the Sun itself. When a solar flare occurs, it is generally accompanied by the ejection of a stream of plasma. This plasma, made up of ions and electrons, propagates through space in the form of what are known as coronal mass ejections (CMEs). These charged particles travel at high speed and can reach the Earth in a matter of hours or days, depending on their intensity.
On contact with our planet, these plasma flows penetrate the Earth's magnetic field, suddenly disrupting what is known as the magnetosphere. This disturbance generates rapid and intense fluctuations that influence not only the Earth's magnetic field, but also the various layers of the atmosphere, such as the ionosphere, which is itself made up of ions and electrons.
The impact of magnetic storms on our planet
The consequences of magnetic storms can vary according to their intensity, but certain effects are particularly noteworthy:
- 1. Aurora borealis: these magnificent veils of coloured light, visible in the skies over the polar regions, are one of the most spectacular effects of magnetic storms. They occur when charged particles interact with molecules in the Earth's atmosphere, releasing energy in the form of light.
- 2. Disruption to communications and GPS: solar storms can alter the operation of communications systems, particularly radios and telephones, by modifying the properties of the ionosphere. GPS satellite signals can also be deflected, making navigation more complex for both aircraft and ships.
- 3. Satellite malfunctions: charged particles can damage the electronic circuits of satellites in orbit, leading to service interruptions and even the loss of this expensive equipment.
- 4. Risks to power grids: the currents induced by these storms in power lines can cause power surges and, in extreme cases, massive blackouts, as has already happened in the past in regions such as Quebec in 1989.
- 5. Disruption to navigation: magnetic fluctuations can change the direction of the compass needle, making navigation more difficult for polar explorers and other users of conventional compasses.
The role of solar cycles
Solar flares do not occur randomly. Their frequency and intensity vary according to the Sun's activity cycle, which lasts around 11 years. During this cycle, solar activity increases progressively over the first six years before decreasing over the next five.
We are currently in a cycle that began in 2019 and is expected to peak around July 2025. During this period of high solar activity, flares are more frequent and more intense, increasing the risk of magnetic storms. Scientists keep a close eye on these cycles to anticipate their potential impact on the Earth.
What are the risks for humans?
While magnetic storms do not directly affect people on Earth, they can nevertheless pose risks for those at high altitudes. According to the French National Centre for Scientific Research (CNRS), ‘during a major eruption, aircraft crews and astronauts are exposed to high doses of radiation that can damage their health’.
Astronauts aboard the International Space Station (ISS) can take refuge in parts of the station that are better protected against radiation, but passengers and aircraft crews have no such protection. The risk is higher for long-haul flights, particularly those over the polar regions, where the Earth's magnetic field is weaker.
Predicting and preparing for magnetic storms
Scientists use various tools and satellites to monitor solar activity in real time and anticipate geomagnetic storms. Institutions such as NOAA (National Oceanic and Atmospheric Administration) issue warnings when major storms are forecast. For individuals, there are no specific measures to take, but those responsible for power grids, satellites and communications systems need to be vigilant and ready to react quickly to minimise the impact.
In summary, magnetic storms are impressive natural events that result from the interaction between solar activity and the Earth's magnetic field. Although they can have spectacular and sometimes dangerous effects, observing and studying them helps us to better understand our space environment and to anticipate their potential impact on our planet and its inhabitants.
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