OBSERVER: Understanding space weather events

OBSERVER: Understanding space weather events
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Our planet and the space environment surrounding the Earth are regularly affected by variations in solar activity. Though invisible to most of us, these fluctuations trigger space weather events, which can disrupt the operations of electronic  equipment and affect critical infrastructure we rely on every day, from communication and navigation to Earth Observation and even terrestrial power grids. The Space Weather Events service (SWE), part of the Space Situational Awareness (SSA) component of the EU Space Programme, is now being established to develop models, prediction capabilities, and early warning services which will help users anticipate, better prepare for, and mitigate adverse effects from space weather. In this Observer, we look at what space weather events are, why we need to better understand them, and how SWE will help support efforts to protect assets and people, both on Earth and in orbit. 

 

One of the many factors making the Earth liveable is the magnetic field that it generates, which protects our planet from high-energy cosmic rays arriving from beyond the Solar System, as well as from solar wind, the stream of charged particles constantly flowing from the Sun’s corona, or outer atmosphere. 

Apart from holding a compass in your hand, one of the only ways of visualising the presence of the Earth’s magnetic field is to witness an aurora, borealis or australis, in the night sky. Often called Northern or Southern Lights, depending on the hemisphere they occur in, these beautiful shimmering curtains of light appear when charged particles interact with the atmosphere, often during geomagnetic storms, which have their origins millions of kilometres away in the Sun. 

 

Types of space weather events

While most of us associate the Sun with bright or gloomy skies, there is another, mostly invisible kind of weather driven by solar activity: space weather. This umbrella term designates events reflecting changes in solar activity which influence both the Earth and the near-space environment around it. 

These fluctuations in solar activity manifest during the approximately 11-year solar cycle, during which the Sun’s magnetic poles reverse. At the peak of this cycle, solar activity intensifies, and the Sun produces different kinds of phenomena. The ones most closely associated with space weather are solar flares, coronal mass ejections (CMEs), and radiation storms.

Solar flares are colossal explosions which emit intense radiation across the electromagnetic spectrum. This radiation, travelling at the speed of light, can reach Earth in about eight minutes. Solar flares vary in intensity and are among the most energetic on the Sun’s surface; a single large flare can release energy equivalent to a billion hydrogen bombs. 

n image showing the Sun seemingly expelling matter at various places on the surface and on its periphery. On the right-hand side of the image, a small area of the Sun is enlarged as a close-up showing a patch of red colour adjacent to a smaller patch of blue.
A picture of a solar flare taken by Solar Orbiter and showing the different types of X-rays (in blue and red). Credit: ESA & NASA/Solar Orbiter/EUI & STIX Teams. 

 

Solar flares can be accompanied by another type of event: coronal mass ejections (CMEs), which are gigantic outbursts of solar plasma. In a single eruption, they can expel billions of tonnes of plasma beyond the sun’s outer envelope (the corona) into interplanetary space. Travelling at hundreds to thousands of kilometres per second, CMEs can reach the Earth in one to three days. When they interact with the Earth’s magnetic field, they can produce beautiful auroras at high latitudes, and in strong cases, trigger geomagnetic storms which disrupt satellites, power grids, and communications.

n illustration showing the Sun on the left and the Earth on the right. The Sun features an explosion, and a seemingly enormous arc of solar matter is expelled from the Sun’s surface towards space. Particles and solar wind are represented in orange, and reach the magnetic shield surrounding the Earth, represented by blue lines engulfing the planet in a protective layer that prevents harmful solar wind to damage it.
Illustration of a Coronal Mass Ejection expelling plasma into space, reaching the Earth and its magnetic field. Objects in the illustration are not to scale. Credit:SOHO/LASCO/EIT (ESA & NASA).

 

Radiation storms, also known as solar energetic particle (SEP) events, occur when particularly large solar flares or CMEs accelerate protons and heavier ions to near light speeds. These particles pose hazards to spacecraft and astronauts and can also affect high-altitude aviation.

 

How space weather impacts Earth

When space weather events are intense, their effects can be felt from satellites in orbit to the atmosphere and infrastructure on the ground.

Because solar flares release radiation across the electromagnetic spectrum, they can interfere with the ionosphere, disrupting radio communications within about eight minutes of an eruption. Weak flares may cause minor disturbances, but strong ones can lead to local or even global radio blackouts and trigger radiation storms in the upper atmosphere. Coronal mass ejections (CMEs) can drive geomagnetic storms which disrupt power distribution, as in 1989 when Quebec suffered a nine-hour blackout.

Beyond Earth’s atmosphere, high energy particles from large solar flares or CMEs pose further hazards, damaging spacecraft electronics, disrupting satellite navigation, and increasing radiation exposure for astronauts. In 2017, for example, astronauts aboard the International Space Station had to seek shelter to avoid exposure to radiation from a solar storm. Such high-energy particles can also impact electronic equipment and passengers in high-flying aircraft.

an illustration showing the earth at the bottom and the Sun at the top. The Earth is protected by a thin layer representing the magnetic shield. Space weather events are shown with the words “Cosmic rays”, “Solar energetic protons”, “Solar flare radiation”, “Coronal Masse Ejections”, “Single event upset” and “Energetic radiation belt particles”. Space weather effects are represented by the words “Astronaut radiation” near an astronaut. Close to a satellite, one can read “Solar cell degradation” and “Radiation damage”. Lines from the satellite point to a “Nagivation errors” for a car, a boat, and an aircraft. “Enhanced ionospheric currents and disturbances” affect the upper atmosphere. “Auroras and other atmospheric effects” can be read next to auroras. Next to an offshore drilling platform is written “Decreased directional drilling accuracy”. “Signal scintillation” and “Disturbed reception” point to a radar on the ground. Next to a radio tower, one can read “HF radio wave disturbance”. “Crew and passengers radiation” is written next to an aircraft. Next to high-voltage power grids, one can read “Geomagnetically induced currents in power systems”. “Induced geoelectric field and current” is written on the ground.
Space weather events affect multiple layers of the Earth’s environment, from the ionosphere and atmosphere to satellites in orbit and infrastructure on the ground. Credit: ESA/Science Office.

 

From risks to readiness

The Sun alternates between periods of low and high activity, affecting the frequency of solar storms, which gradually increase and decrease again over the course of an approximately 11-year cycle. However, knowing where the Sun stands in this cycle is not enough to prepare for the effects of space weather events. As modern societies increasingly rely on electronic- and satellite-based technologies for communication, transport, health, and many other aspects of daily life, the consequences of an extreme space weather event directed at Earth could be severe. 

Within the EU Space Programme, the Space Situational Awareness (SSA) component includes a dedicated subcomponent on Space Weather Events (SWE). The future SWE service is being established in response to the need for a deeper understanding of solar activity and its effects. The SWE service will develop models, prediction capabilities, and early warning systems to help anticipate the nature and timing of solar storms, as well as their potential impacts on Earth and in orbit.

The importance of forecasting becomes clear when looking at past solar storms. Sweden was struck by a strong solar storm in 2003, disrupting high-voltage power transmission systems and leaving 50,000 people without electricity for an hour. Even more strikingly, strong solar flares and CMEs struck Earth in September 1859, inducing auroras visible all the way to the equator and damaging telegraph wires. If similar storms were to occur today, they could disrupt power grids, satellite navigation, and communication services, potentially causing billions of euros in damage and putting lives at risk. The future SWE service will help reduce such risks by providing early warnings and forecasts, helping to protect critical infrastructure and the services on which society depends. 

 

Looking ahead

On 12 March 2025, the European Commission adopted an Implementing Decision which kicks off a process which will lead to selecting a service provider for a space weather service under the SWE subcomponent of the EU Space Programme. This marks the first of several milestones in establishing a service which will help keep assets in space and on Earth safe from adverse space weather events.

The Decision, based on Article 60 of the EU Space Regulation, was informed by an analysis of user needs, risk assessments, and technological maturity. It concluded that the space domain, covering spacecraft operations and space surveillance and tracking (SST) providers, was the most suitable to receive the SWE service. In practice, this means that future forecasts will be targeted first at operators in the space domain who are most directly exposed to the risks of space weather, such as radiation storms which can disable satellite electronics or geomagnetic storms which increase drag and complicate space traffic management.

The Implementing Decision has the backing of all 27 EU Member States, and upcoming milestones include a call for tender to procure the EU space weather service, the award of a contract to the selected provider(s), and the eventual kick-off of operational provision.

While the first users of SWE will be in the space domain, its impact will extend much further. By strengthening the resilience of satellites and space infrastructure, the service will help ensure that the essential applications societies and citizens depend on, from communications and navigation to Earth Observation, remain safe and reliable.

A photo showing night sky over a lake and snow-covered mountains. The sky is lit by bright, green light sheets curling above the landscape.