India's first space-based solar observatory, Aditya-L1, has helped scientists uncover new details about how powerful solar eruptions expand through space, findings that could improve predictions of space weather events affecting satellites and communication systems on Earth.
The findings, announced by the Ministry of Science and Technology on November 3, 2026, focus on a coronal mass ejection observed on August 5, 2024, and challenge the long-held picture of such eruptions spreading outwards like a neat, symmetrical bubble.
The discovery was made using the Visible Emission Line Coronagraph, known as VELC, the primary payload aboard Aditya-L1. Researchers from the Indian Institute of Astrophysics combined VELC's observations with data from NASA's Solar Dynamics Observatory and three-dimensional computer modelling to reconstruct the eruption in full. What they found was that the eruption did not expand uniformly.
Instead, different parts of the expanding cloud of solar plasma moved at different rates, producing an asymmetric, uneven shape rather than a smooth sphere.
The research has been published in The Astrophysical Journal Letters. It was led by Indian Institute of Astrophysics doctoral student Saurabh Tripathi, with Dr Tanmoy Samanta as corresponding author and Jayant Joshi as co-author. Their work is significant because the shape of a coronal mass ejection matters enormously for what happens when it reaches Earth.
A coronal mass ejection, or CME, is a giant eruption of magnetised plasma, sometimes weighing billions of tonnes, hurled away from the Sun into interplanetary space. When a fast, Earth-directed CME strikes the magnetosphere, it can trigger geomagnetic storms that disrupt satellites, degrade GPS signals and high-frequency radio, increase drag on low-orbit spacecraft, and in extreme cases induce currents in power grids.
For years, the working assumption in much of space weather forecasting was that CMEs expand more or less evenly as they travel. The Aditya-L1 findings suggest a messier reality.
The researchers found that uneven lateral expansion and an inclined axis created distinct patterns in the eruption's movement, and that internal magnetic pressures and external drag forces from the surrounding solar wind warped the shape and speed of the plasma cloud as it hurtled through the inner heliosphere.
Because an asymmetric CME does not distribute its density and magnetic field strength evenly, the part of it that eventually hits Earth can be more concentrated, and therefore more intense, than a symmetrical model would predict.
This is where the practical value of the discovery lies. If forecasters can track how a CME is expanding unevenly from the moment it leaves the Sun, they can refine their estimates of when it will arrive at Earth, known as time-of-arrival predictions, and how hard it will hit. That extra warning time and accuracy matters to satellite operators, who may need to put spacecraft into safe modes, and to power grid managers, who may need to take precautionary measures.
The researchers are careful to note that the findings point towards more accurate forecasting techniques rather than proving that forecasting accuracy has already improved. The work is a step towards better prediction, not the finished product.
VELC itself is a remarkable instrument, and understanding it helps explain why this discovery was possible. A coronagraph blocks out the bright disc of the Sun so that the much fainter outer atmosphere, the corona, can be observed. VELC goes further than an ordinary coronagraph: it is also a spectrograph, meaning it can split coronal light into a spectrum and measure specific emission lines with great precision.
Its best-known channel watches the green emission line at 5303 angstroms, emitted by highly ionised iron in the million-degree corona. By tracking plasma at around 1.8 million kelvin through this green line, and combining that spectroscopic information with imagery from NASA's Solar Dynamics Observatory, the team could reconstruct the three-dimensional geometry of the eruption rather than settling for a flat picture.
That three-dimensional view is exactly what has been missing from much of CME observation. Traditional coronagraph images show a cloud of plasma spreading across the sky, but they struggle to show whether that cloud is moving towards Earth, away from it, or across the line of sight. For space weather forecasting, that is the most important question of all.
In related recent work, scientists at the Indian Institute of Astrophysics have used VELC data to produce Doppler velocity maps of the solar corona, which show whether plasma is moving towards or away from the observer.
In a paper on a CME observed on July 16, 2024, the team reported tracking the eruption's onset in the green line, measuring a Doppler redshift of about 10 kilometres per second, and spotting the event roughly an hour before it appeared in the field of view of the coronagraph aboard the SoHO spacecraft operated by the European Space Agency and NASA.
That early warning capability, combined with the new understanding of asymmetric expansion, gives forecasters two powerful new tools.
Aditya-L1 itself is a landmark mission for India. Launched on September 2, 2023, aboard PSLV-C57, it operates in a halo orbit around the Sun-Earth Lagrange point L1, about 1.5 million kilometres from Earth. From that vantage point, it can watch the Sun continuously without being blocked by eclipses, something no Earth-orbiting observatory can do.
VELC, the largest of its seven payloads, was designed and built by the Indian Institute of Astrophysics in collaboration with the Indian Space Research Organisation. It is the only operational instrument combining high-cadence coronagraphic imaging, spectroscopy and spectropolarimetry from the L1 vantage point, allowing it to capture the early acceleration of CMEs as close as 1.05 solar radii from the Sun's surface.
The timing of the findings adds to their importance. The Sun is near the maximum of its current activity cycle, Solar Cycle 25, a period when powerful eruptions are more frequent. As societies become ever more dependent on satellites for navigation, communication, weather forecasting and financial transactions, the stakes of space weather forecasting keep rising.
A single severe geomagnetic storm can disrupt services that millions of people rely on every day, and the economic costs can run into billions. Understanding that CMEs expand unevenly, and being able to track that unevenness from birth, could help risk models that currently may underestimate the localised intensity of solar storms.
The discovery also underlines the scientific return on India's investment in space science. Aditya-L1 was conceived as a mission to study the Sun, but its instruments are now producing results that feed directly into practical applications, from satellite protection to power grid resilience.
The collaboration with NASA data and the publication in a leading international journal also reflect how solar science has become a genuinely global effort, with observatories on different continents and in different orbits combining their views to build a complete picture of our star.
There is still much to learn. A single CME, however well studied, does not rewrite the whole of solar physics, and researchers will want to test whether asymmetric expansion is the rule rather than the exception across many eruptions. But the August 2024 event, captured in unprecedented detail by an Indian instrument watching from a million and a half kilometres away, has already changed how scientists think about these colossal explosions.
The Sun, it turns out, does not blow its bubbles evenly. Knowing that may one day be the difference between a storm that catches the world by surprise and one that is seen coming in time to prepare.
(Reporting based on News On AIR, The Hindu and The Astrophysical Journal Letters research reports.)