June 29, 2026 report
Solar storms leave their mark on cosmic rays that reach Earth
by Sam Jarman, Phys.org
edited by Gaby Clark, reviewed by Robert Egan
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A new study has revealed an unexpected link between solar storms and the flux of high-energy cosmic rays arriving at Earth. The findings, made using one of the world's largest cosmic ray detectors, could open up a new way to probe the magnetic structures inside solar storms—and potentially improve our ability to forecast their effects on Earth. The research has been published in Physical Review Letters.
Particle streams from space
Earth's magnetic field is constantly being bombarded by energetic charged particles, originating from two very different sources. While some of these particles are cosmic rays, which come toward Earth from all directions across the galaxy, the rest originate from solar storms: violent outbursts from the sun that hurl vast clouds of magnetized plasma into space.
So far, the effects of these two phenomena have often been treated as independent. Although scientists have long known that solar storms can reduce the number of lower-energy cosmic rays reaching Earth by trapping them in the storm's twisted magnetic fields, higher-energy cosmic rays were thought to be too energetic to be affected. At these energies, the particles were expected to punch straight through the magnetic structures without being deflected.
Detecting at higher energies
To test this assumption, a team led by David Ruffolo of Mahidol University in Thailand examined data from the Large High Altitude Air Shower Observatory (LHAASO): a giant detector array in China that measures the cascades of secondary particles produced when cosmic rays crash into the upper atmosphere.
LHAASO detects hundreds of millions of cosmic rays every hour at energies in the tera-electron-volt (TeV) range, roughly 10,000 times more energetic than those affected by solar storms in previous studies. However, detecting storm-related changes has so far proven difficult, since shifts in atmospheric conditions can mimic real variations in cosmic ray flux.
To sidestep this problem, the team focused not on the total number of cosmic rays arriving, but on whether they were arriving more from one direction than another: an imbalance that atmospheric effects are unlikely to produce.
When they analyzed data from a solar storm in November 2021, the team spotted exactly such an imbalance. For several hours, significantly fewer cosmic rays arrived from the northeast part of the sky compared with the rest.
To explain this result, they proposed that the outward-moving bubble of plasma associated with the storm contained magnetic turbulence at its leading edge. This plasma preferentially scattered cosmic rays traveling inward toward the sun, creating a detectable directional imbalance in the number of cosmic ray particles reaching Earth.
Preparing for solar storms
Based on this discovery, Ruffolo's team suggest that cosmic rays could serve as a new remote-sensing tool for mapping the magnetic structures inside solar storms. Whereas spacecraft can only sample the plasma environment at their precise location, cosmic rays trace out much larger regions of space.
With detector arrays like LHAASO operating around the globe, scientists may soon be able to build up a fuller picture of incoming solar storms—and buy more time to prepare for their impacts on satellites, power grids and communications systems.
Written for you by our author Sam Jarman, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
Publication details
Zhen Cao et al, Transient Large-Scale Anisotropy in TeV Cosmic Rays due to an Interplanetary Coronal Mass Ejection, Physical Review Letters (2026). DOI: 10.1103/mkk2-hbq5. On arXiv: DOI: 10.48550/arxiv.2601.02801
Journal information: Physical Review Letters, arXiv
Key concepts
coronal mass ejection Cosmic rays & astroparticles Space & astrophysical plasma Cosmic ray & astroparticle detectors Interplanetary magnetic fields Space weather Secondary cosmic raysWho's behind this story?
Sam Jarman
Science X contributing writer; covers astrophysics, novel materials, medical imaging, and bio-inspired tech. Full profile →
Gaby Clark
MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →
Robert Egan
Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →
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Citation: Solar storms leave their mark on cosmic rays that reach Earth (2026, June 29) retrieved 29 June 2026 from https://phys.org/news/2026-06-solar-storms-cosmic-rays-earth.htmlThis document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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