Journey · from the Sun to power grids
Key points
A solar eruption is a sudden release of magnetic energy in the Sun’s atmosphere. Its radiation reaches Earth in about 8 minutes. It can also expel a cloud of magnetised plasma, a coronal mass ejection. This reaches Earth in one to three days and can trigger a geomagnetic storm, exposing satellites and power grids.
Follow one eruption, from its source on the Sun to its effects on satellites and power grids. Scroll to move along the chain.
Illustrative visualisation.
01 · The source
Above an active region, a twisted magnetic structure, the flux rope, rises and then erupts. The coronal mass ejection (CME) carries magnetised plasma into interplanetary space.
This is where SKEION’s physics focuses: the magnetic configuration before the eruption, the subject of research published on the cover of Nature in 2014 and 2018.
02 · The transit
A CME typically reaches Earth in one to three days, the fastest in under 18 hours. A shock runs ahead of it and compresses the solar wind.
Here: a front at 1,000 km/s; the shock reaches Earth in about 38 hours, the ejecta front about 4 hours later.
03 · The shield
When the shock arrives, the magnetosphere is compressed on the dayside: here the magnetopause moves from 11 to about 6 Earth radii, inside the geostationary orbit (6.6).
Then comes the ejecta. Its magnetic field, pointing south (negative Bz), largely determines the intensity of the storm. That orientation is tied to the flux rope’s configuration at its source, where SKEION’s physics focuses.
04 · Satellites
A geostationary satellite near local noon finds itself outside the shield, in the shocked solar wind. The auroral oval spreads towards lower latitudes.
Status: Vision Sector alerts, delivered by API.
05 · Power grids
Under the auroral oval, the electrojet surges within minutes. It induces an electric field in the ground and currents in long high-voltage lines (geomagnetically induced currents). These currents can saturate transformers: on 13 March 1989, the Québec grid collapsed in 92 seconds.
According to NOAA, about 91% of the estimated economic benefits of its Space Weather Next observation programme (United States, 2025–2050) relate to power grids.
06 · The complete chain
Our ambition: to cover this whole chain, from the Sun’s magnetic configuration to the impact on satellites and power grids, through propagation in space. We are building it, starting from the physics of the source.
We are looking for pilot partners, first in the satellite and energy sectors. In a pilot project, we explore with you how our solutions can meet your specific needs and solve your problems. From your case, we adapt and improve them so they fit the way your teams work.
In detail
Above an active region, a twisted magnetic structure rises and then erupts. The Sun’s magnetic field can twist into a magnetic flux rope: a bundle of twisted field lines. The magnetic arches that lie over it hold it down: its “cage”. Energy builds up in it over days. When the balance breaks, the rope rises faster and faster and releases that energy within minutes to hours. If the rope breaks through its cage, it carries away a cloud of magnetised plasma, a coronal mass ejection (CME); otherwise, the eruption stays confined. This configuration before the eruption is the subject of Tahar Amari’s work published on the cover of Nature in 2014 and 2018.
A CME typically reaches Earth in one to three days, the fastest in under 18 hours. It leaves the Sun at speeds from about 250 to nearly 3,000 km/s. A fast CME drives a shock wave ahead of it, which compresses the solar wind. Behind the shock comes the sheath, a dense and turbulent plasma, then the magnetic cloud itself. What matters on arrival is the direction of its magnetic field. When it points south, opposite to Earth’s field, the solar wind can transfer its energy into the magnetosphere. Not every CME is aimed at Earth: only those heading towards it, or grazing it, will count.
When the shock arrives, Earth’s magnetic shield is compressed on the dayside. The magnetosphere, the region ruled by Earth’s magnetic field, normally holds the solar wind back at about 11 Earth radii on the dayside. When the shock and then the dense sheath arrive, the pressure of the solar wind rises about twentyfold. In the example shown, the magnetosphere’s boundary, the magnetopause, moves in from 11 to about 6 Earth radii. It passes inside the geostationary orbit (6.6 Earth radii from Earth’s centre, or 35,786 km in altitude). This is the sudden commencement of the geomagnetic storm.
A geostationary satellite near local noon finds itself outside the shield. It then sits in the magnetosheath, the shocked solar wind plasma between the magnetopause and the bow shock. Within hours, the geomagnetic storm sets in: the auroral oval spreads towards lower latitudes, and the upper atmosphere heats up and slows down satellites in low orbit. In February 2022, a minor storm (Kp 5) raised drag enough to cost 38 of 49 newly launched Starlink satellites.
The satellites use case · The EU Space Act and natural hazards
On the ground, the storm drives currents into long power lines. Under the auroral oval, strong electric currents flow at about 110 km in altitude: the auroral electrojet. When it intensifies within minutes, the magnetic field changes at the ground and induces an electric field in the subsoil. That field is all the stronger where the rock is resistive, as in the Canadian Shield. In long high-voltage lines, this field drives quasi-direct currents, geomagnetically induced currents (GIC). They enter transformers through their grounded neutral and can saturate them. On 13 March 1989, the Hydro-Québec grid collapsed in 92 seconds, leaving Québec without power for nine hours.
Our ambition is to cover this whole chain, from the Sun’s magnetic configuration to the impact on satellites and power grids. Each link depends on the one before, from an active region to the current in a transformer. SKEION starts from the source. MeshMHD, the magnetohydrodynamic model of the Sun developed at CPHT (CNRS / École polytechnique) under the direction of Tahar Amari, reconstructs in 3D the magnetic structures behind eruptions. We are building the chain step by step: first the physics of the source, then propagation in space, up to the impact on infrastructure.
Questions
It is a sudden release of magnetic energy above an active region of the Sun, lasting from minutes to hours. Its X-ray flash, the flare, is classed A, B, C, M or X, each class ten times stronger than the one before. This radiation reaches Earth in about 8 minutes and can disrupt high-frequency (HF) radio links on the dayside. An eruption can also expel a coronal mass ejection, or stay confined at the Sun.
They are three stages of one chain. A solar eruption happens at the Sun: a release of energy, seen as a burst of radiation. A coronal mass ejection is the cloud of plasma and magnetic field that the eruption can expel into space. A geomagnetic storm is the disturbance of Earth’s magnetic field. It happens when that cloud, or a fast solar wind stream, reaches Earth with a southward magnetic field. NOAA rates it from G1 to G5. “Solar storm” is the everyday term for the whole sequence.
Three timings coexist. The eruption’s radiation arrives in about 8 minutes, at the speed of light. The fastest energetic particles follow within tens of minutes. A coronal mass ejection typically takes one to three days. The fastest arrive in 15 to 18 hours, and the record, in August 1972, is 14.6 hours. The shock ahead of it is detected at the L1 point, 1.5 million km from Earth. It arrives 15 to 60 minutes later.
In low orbit, the storm heats the upper atmosphere, which raises drag and pulls satellites down. In February 2022, 38 of 49 newly launched Starlink satellites were lost. In geostationary orbit, a satellite can end up outside the magnetosphere, and energetic particles disturb electronics. Satellite positioning (GNSS) and high-frequency (HF) radio links can degrade. On the ground, geomagnetically induced currents can saturate, or even damage, transformers: in March 1989, Québec was without power for nine hours.
In part. Space weather centres such as NOAA’s publish daily flare probabilities based on observations of active regions. Once a CME has left the Sun, they publish an estimate of its arrival time. On that arrival time, the mean absolute error of published estimates is about 13 hours (Riley et al., 2018). The hardest part is knowing, before onset, whether an active region will erupt. It is just as hard to know whether the eruption will eject matter or stay confined. Our vision, Early Alert: to warn you before the eruption. We want to spot when the magnetic structure of a region of the Sun becomes unstable, then refine the alert hour by hour. It would state its uncertainty and be more precise in time and place, starting from the physics of the source.
From the magnetic field. Motions at the solar surface twist and shear the field lines that emerge in active regions. The energy builds up in a twisted magnetic flux rope, held down by the arches above it, its “cage”. In 2014, Tahar Amari and his colleagues reconstructed the flux rope behind a major eruption (class X3.4, December 2006). They started from observations taken in the four previous days. In 2018, they showed that the outcome depends on the balance between rope and cage. On 24 October 2014, a class X3.1 eruption stayed confined because the rope lacked the energy to break through its cage. With a weaker cage, a major coronal mass ejection would have left the Sun.
Glossary
Sources
