The extraordinary auroras that turned skies over Poland pink, red and green in May 2024 were the visible result of something far more complicated happening between Earth and the Sun.
Scientists have now reconstructed how at least ten separate coronal mass ejections, or CMEs, interacted on their journey towards Earth before producing the strongest geomagnetic storm since 2003. Among the authors of the research is Stefaan Poedts, a physicist affiliated with Maria Curie-Skłodowska University (UMCS) in Lublin and KU Leuven in Belgium.
The international study, published in The Astrophysical Journal, used observations of the eruptions together with three-dimensional magnetohydrodynamic simulations to reconstruct one of the most significant space-weather events of recent decades.
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Its conclusion helps explain why the storm became so powerful: it was not simply one enormous eruption heading towards Earth.
It was a solar pile-up.
Ten eruptions, one extraordinary storm
Between 8 and 11 May 2024, a succession of CMEs — enormous clouds of magnetised plasma thrown out by the Sun — travelled into interplanetary space.
The faster clouds caught slower ones ahead of them. Some merged. Others compressed or accelerated earlier eruptions, while later CMEs travelled through regions already altered by those in front. By the time the disturbance reached Earth, instruments detected several complex magnetic structures rather than a neat sequence of ten independent events.
The researchers combined observations from the SOHO and STEREO-A spacecraft to estimate the shape, speed and trajectory of the eruptions from different viewing angles.
Those measurements were then fed into EUHFORIA, a model used to simulate the solar wind and the propagation of CMEs through the heliosphere. The published study says its best-performing simulation reproduced the storm’s arrival with a difference of about two hours and estimated its strength with roughly 70% accuracy.
That is impressive — but the remaining difference is part of the scientific story.
Small uncertainties in the initial direction, speed or internal structure of one CME can affect how it interacts with every cloud that follows. When ten eruptions are involved, those uncertainties accumulate.
The study therefore illustrates why extreme space weather can be substantially more difficult to forecast than simply observing one large solar eruption and estimating when it will arrive.
The night Poland looked north — and saw the aurora overhead
For people on the ground, the physics produced a much more memorable result.
On 10–11 May 2024, the geomagnetic disturbance reached G5 — the highest category on NOAA’s five-level storm scale. The US agency described it as the strongest geomagnetic storm since the Halloween storms of 2003.
Auroras consequently appeared much farther from the polar regions than usual.
In Poland, the phenomenon was spectacular enough to be visible high in the sky rather than only low above the northern horizon. Poland’s National Institute of Telecommunications later noted that the aurora could be observed near the zenith — an unusual occurrence at Polish latitudes.
Similar displays were recorded across large parts of the world.
NASA says the arriving CMEs effectively bunched together before reaching Earth, producing a long-lasting G5 storm and auroras across unusually low latitudes.
A Polish university connection to international space-weather research
The new paper was written by Shirsh Lata Soni, Anwesha Maharana, Sanchita Pal and Stefaan Poedts, bringing together researchers with affiliations in the United States, Belgium, India and Poland.
Poedts is a professor in UMCS’s Department of Theoretical Physics as well as being affiliated with KU Leuven. UMCS has previously highlighted his work on predicting extreme space weather and his involvement in developing modelling tools for solar storms. In February 2026, the university awarded him its 80th-anniversary medal for his contribution to the development of astrophysics in Lublin.
The May 2024 storm shows why that work matters.
Power grids, satellites, radio communications, navigation systems and other technologies can all be affected by strong geomagnetic disturbances. Forecasting when a storm will arrive — and how severe it will become — therefore has consequences far beyond predicting where the next spectacular aurora might appear.
The new reconstruction does not solve that forecasting problem. The authors explicitly identify continuing uncertainties and the need for better observations and faster, more accurate modelling.
But it does explain something that millions of people witnessed in May 2024.
The remarkable skies seen over Poland were not produced by one extraordinary blast from the Sun.
They were the final result of ten solar eruptions interacting across millions of kilometres of space before reaching Earth.
