A video recently released by the ESA’s Solar Orbiter and NASA’s Chandra X-ray Observatory showed a magnetic avalanche on the surface of the sun. A powerful solar storm of magnitude four, the strongest in the past 23 years, struck Earth on 18-19 January. The framework for the study, published recently in Astronomy & Astrophysics, was created in 2024; the Solar Orbiter recorded the video as it approached the Sun on 30 September of that year.
Why did such a severe solar storm happen?
Following an analysis of the recent footage, heliophysicists said that a magnetic avalanche triggers these solar flares. This process involves the violent snapping and reforming of twisted magnetic field lines. High-resolution images from the Solar Orbiter showed smaller reconnection events growing into a massive flare, producing fiery plasma blobs. Chandra’s X-ray observations substantiated the presence of high-energy emissions from accelerated particles as they entered the solar atmosphere.
Science behind magnetic avalanches
The Sun’s magnetic field is like a complex, tense web, similar to a tangle of rubber bands. Meanwhile, there is hot burning plasma inside the sun, which exerts pressure on the magnetic force lines. Because of this increasing pressure, the magnetic lines begin to stretch and eventually break. After being released, they are again connected to other lines immediately. This is known as magnetic reconnection. Due to this newly formed magnetic rearrangement, the Sun’s inner plasma is heated, and a plasma jet is released at high speed (about 1000 km/s).
The initial reconnection following the recent event, although short-lived, triggered a chain reaction. Each quick release of energy disrupted the surrounding areas, similar to a snowball gaining momentum. Superheated plasma, reaching millions of degrees, then collapsed, leaving behind visible ‘ribbons’ that traced the flare’s trajectory. This sequence of events demonstrates how flares can release energy comparable to billions of hydrogen bombs, all in just a few minutes. Unlike the consistent solar wind, these explosive outbursts lead to coronal mass ejections (CMEs)—massive, magnetised plasma clouds (consisting of electrons, protons, and some heavy nuclei) racing toward Earth at around 1,700 km/s.
The CMEs unleashed by the 18 January flare struck Earth’s magnetosphere on 19 January at precisely 2:38p.m. and saw the onset of a G4 geomagnetic storm, classified as severe and the second most intense on the scale. NOAA’s Space Weather Prediction Centre verified that the peaks persisted into the evening, and solar wind speeds exceeded 1,000 km/s.
At the same time, a severe S4 solar radiation storm pummeled satellites, the most powerful since the Halloween storms of 2003. High-energy protons surged through space, threatening blackouts for high-frequency radios, GPS malfunctions, and radiation surges for astronauts and flights over the poles. Auroras flared to life, visible as far south as France, Germany, and the U.S. Midwest. Charged particles, colliding with atmospheric gases, painted the sky with green and purple. This storm’s unusual strength is a product of Solar Cycle 25’s peak, a period when sunspots generate more intense flares.
Why do avalanches matter?
Magnetic avalanches connect solar physics with the realm of space weather. Solar flares and CMEs are not just spectacular; they have the potential to cause significant damage. They can knock out power grids through induced currents, interfere with satellites, and pose a threat to astronauts aboard the International Space Station. The 1989 blackout in Quebec and the Halloween storms of 2003 caused billions in damages, and those incidents triggered worldwide warnings.
It’s evident that reconnection speeds up particles: electrons spin in magnetic loops and send out X-rays, and ions erupt out in CMEs. Solar Orbiter’s close-up (within 0.3 AU) revealed structures as small as 250 km, showing fine features that Earth-orbiting telescopes can’t see. Chandra used X-rays to look into the hottest plasmas, which confirmed how intense the cascade was.
This January’s show highlights the Sun’s volatile nature. Although G4 storms are a regular occurrence, their conjunction with S4 radiation is rare, the last instance being in 2003. So far, no significant disruptions have been reported, but potential weaknesses remain. Satellite constellations, like those used by Starlink, are susceptible to atmospheric drag, and air travel is being adjusted. Researchers are now using avalanche models to improve predictions. Early warnings from the Solar Orbiter, positioned ahead of Earth, provide a crucial few hours of advance notice for grid operators. As Solar Cycle 25 approaches its conclusion in 2030, we can anticipate more of these displays, illustrating the importance of robust technology.