Aditya-L1's VELC Spectroscopy Shows Solar Eruptions Expand Asymmetrically in Three Dimensions

Key facts

• ISRO reported on 3 November 2026 that scientists at the Indian Institute of Astrophysics (IIA), Bengaluru, used Aditya-L1 to study how a solar eruption expands near the Sun; the study was published in The Astrophysical Journal Letters.
• The study combined spectroscopic observations from Aditya-L1's Visible Emission Line Coronagraph (VELC) with images from NASA's Solar Dynamics Observatory (SDO) and three-dimensional modelling of a coronal mass ejection (CME) observed on 5 August 2024.
• The analysis found the CME did not expand like a simple symmetric bubble but underwent non-uniform expansion and developed an asymmetric shape; a symmetrically expanding model could not reproduce the observed spectra, while asymmetric lateral expansion with a tilt matched VELC observations well.
• VELC measured line-of-sight plasma velocities of up to 218 km/s, a projected radial speed of 1,135 km/s and a plane-of-sky lateral speed of 692 km/s for the August 2024 eruption.
• VELC's Doppler spectroscopy of the Fe XIV 5303 Å green coronal line revealed two distinct blue- and red-shifted emission branches, showing plasma in the CME bubble moving both towards and away from the observer — line-of-sight motion that imaging-only coronagraphs cannot directly measure.
• Differences in CME expansion can affect its speed and trajectory towards Earth, making arrival-time prediction and space-weather impact assessment more challenging; CME shape may also influence the drag it experiences from the solar wind.
• The study demonstrates that VELC can constrain the three-dimensional geometry of an eruption from a single vantage point by combining Doppler spectroscopy with imaging observations, which is especially valuable in the low corona where CMEs evolve most rapidly.
• VELC, developed by IIA Bengaluru with substantial support from ISRO, observes the inner corona from roughly 1.05 to 3 solar radii, a region important for tracking CME initiation and early acceleration; Aditya-L1 operates in a halo orbit around the Sun–Earth L1 region.