Aditya-L1's VELC coronagraph shows a solar eruption swelling unevenly, a clue for better space-weather forecasts

Solar eruptions are often drawn as neat, expanding bubbles. India's solar observatory suggests reality is messier. Scientists at the Indian Institute of Astrophysics (IIA), Bengaluru, using data from the Visible Emission Line Coronagraph (VELC) on board Aditya-L1, have found that a coronal mass ejection (CME) expanded unevenly in its early stages — a result ISRO highlighted in early November 2026 as revealing the "hidden third dimension" of a solar eruption.

The study

The work, published in The Astrophysical Journal Letters, is titled "Spectroscopic Signatures of Nonuniform Lateral Expansion of a Coronal Mass Ejection in the Low Corona with ADITYA-L1/VELC." Its authors are Saurabh Tripathi, Tanmoy Samanta and Jayant Joshi of IIA.

The team examined a CME observed on 5 August 2024. Rather than relying on images alone, they used VELC's spectroscopic capability, combining it with imagery from NASA's Solar Dynamics Observatory (SDO) and three-dimensional modelling.

What they found

When a CME erupts, the plasma moving towards and away from the observer shifts and broadens coronal emission lines. By analysing those spectral signatures, the researchers could test how the eruption was expanding — information that is largely invisible in two-dimensional images.

The key result: a model in which the CME expands symmetrically, like a uniform bubble, could not reproduce the observed spectra. A model with an inclined CME axis and asymmetric lateral expansion matched the observations far better. In other words, the eruption swelled more on one side than the other as it lifted off through the low corona.

ISRO and the authors note that further observations will show how reliably VELC can measure CME direction, expansion and speed on a routine basis.

Why this matters for space weather

CMEs are billion-tonne clouds of magnetised plasma. When one is aimed at Earth, it can trigger geomagnetic storms that disturb satellite operations, GPS and navigation signals, HF radio, power grids and astronaut safety. Forecasters try to predict when a CME will arrive and how strongly it will hit — and both depend on the eruption's direction, speed and how it expands.

ISRO notes that earlier CME observations and models often assumed a symmetric shape. If CMEs commonly expand unevenly from the start, arrival-time and impact estimates based on symmetric assumptions can be off. Spectroscopic measurements in the low corona — where VELC observes — offer a way to constrain those parameters early, potentially improving forecasts if the method proves reliable across more events.

For India, which now operates a large fleet of communication, navigation (NavIC) and Earth-observation satellites, better space-weather warnings have direct practical value.

About Aditya-L1 and VELC

Aditya-L1 is India's first dedicated solar mission. It was launched by ISRO on PSLV-C57 on 2 September 2023 and inserted into a halo orbit around the Sun–Earth Lagrange point L1, about 1.5 million km from Earth, in January 2024. From L1, it watches the Sun continuously without being blocked by Earth.

The spacecraft carries seven payloads. VELC, its largest instrument, was built by IIA. A coronagraph blocks the bright solar disc to reveal the faint corona, and VELC is designed to observe the corona close to the solar limb in both imaging and spectroscopic modes — the combination that made this study possible. VELC data have already been used in other recent work on CME onset and coronal emission-line broadening, and the new paper adds 3D expansion geometry to that growing body of results.

The broader significance

Aditya-L1's science output is a test of whether India can not only build sophisticated space observatories but also turn their data into internationally competitive research. Results such as this — combining Indian instrument data with global datasets and modelling — strengthen India's role in the international heliophysics community and its own space-weather preparedness as its orbital infrastructure grows.

Sources

• https://www.isro.gov.in/Aditya_L1_Reveals_the_Hidden_Third_Dimension_of_Solar_Eruption.html
• https://www.techexplorist.com/sun-hiding-third-dimension-aditya-l1-exposed/105951/
• https://currentaffairs.adda247.com/aditya-l1-reveals-asymmetric-expansion-of-solar-eruption-improving-understanding-of-coronal-mass-ejections/
• https://idrw.org/aditya-l1-velc-asymmetric-solar-eruption-space-weather/
• https://english.punjabkesari.com/business/aditya-l1-reveals-solar-eruptions-expand-asymmetrically-improves-space-weather-understanding
• https://en.wikipedia.org/wiki/Aditya-L1
• https://doi.org/10.3847/2041-8213/aea295