Aditya-L1's Coronagraph Yields Doppler Velocity Maps of the Sun's Corona, Showing Which Way Solar Plasma Moves
Indian Institute of Astrophysics scientists have used Aditya-L1's VELC coronagraph to produce Doppler velocity images of the solar corona, showing whether plasma is moving towards or away from Earth, a capability that could sharpen warnings of Earth-directed solar storms.
Coronagraphs have a basic limitation. They show the Sun's outer atmosphere, the corona, as a flat picture on the sky. When a coronal mass ejection (CME) erupts, a coronagraph shows a cloud of plasma spreading out. It cannot easily 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.
Scientists at the Indian Institute of Astrophysics (IIA) in Bengaluru say India's solar observatory Aditya-L1 is helping answer it. According to reports published around 20–21 October 2026, the IIA team has used data from the spacecraft's Visible Emission Line Coronagraph (VELC) to produce Doppler velocity images of the solar corona, which map whether coronal plasma is moving towards or away from the observer.
How Doppler imaging works
The method relies on the Doppler effect, the same physics that changes the pitch of a passing siren. Light from gas moving towards the observer shifts slightly towards shorter (bluer) wavelengths, and light from gas moving away shifts towards longer (redder) wavelengths.
VELC is more than a camera. It is a coronagraph with spectrographs, which means it can split coronal light into a spectrum and measure specific emission lines very precisely. Its best-known channel watches the 5303 Å "green line", emitted by highly ionised iron in the million-degree corona. VELC records the full profile of that line at many points across the corona. By measuring how far the line's peak moves from its rest wavelength at each point, scientists can turn those measurements into a map of line-of-sight velocity.
Reports credit the processing and software work to a team that includes V. Muthupriyal of IIA, and say the method has been published in the Astrophysical Journal after peer review.
Building on earlier VELC results
The new maps follow several years of steady calibration and science work by the VELC team:
- In a paper on a CME observed on 16 July 2024, the team reported tracking the eruption's onset in the 5303 Å line. They measured a Doppler redshift of about 10 km/s and saw the event roughly an hour before it appeared in the field of view of the SoHO/LASCO-C2 coronagraph run by ESA and NASA.
- Later preprints analysed VELC "sit-and-stare" observations of limb CMEs and calibrated the instrument's green-line measurements.
Moving from velocity measurements along a slit to two-dimensional velocity images is what makes the new result significant.
Why it matters for space weather
CMEs are the main drivers of severe geomagnetic storms. When a fast, Earth-directed CME hits the magnetosphere, it can disrupt satellites, degrade GPS and HF radio, increase drag on low-orbit spacecraft, and in extreme cases induce currents in power grids. India now operates a large and growing fleet of satellites, including NavIC navigation, communications and Earth-observation spacecraft, so early warning has real economic value.
Velocity information tells forecasters which way the plasma is heading. That can help separate Earth-directed eruptions from harmless ones earlier and with more confidence than images alone.
The mission behind it
Aditya-L1 was launched on 2 September 2023 aboard PSLV-C57 and operates in a halo orbit around the Sun–Earth Lagrange point L1, about 1.5 million km from Earth. From there it can watch the Sun continuously without eclipses. VELC, the largest of its seven payloads, was designed and built by IIA. The new Doppler maps are an example of a home-built instrument producing scientific capabilities that ISRO and IIA can share with the global solar-physics and space-weather community.
Sources
- NewsBytes: https://www.newsbytesapp.com/news/science/aditya-l1-captures-doppler-velocity-images-of-the-suns-corona/tldr
- Indian Defence News: https://www.indiandefensenews.in/2026/10/aditya-l1-generates-first-ever-doppler.html
- Insights IAS: https://www.insightsonindia.com/2026/10/21/the-aditya-l1-mission/
- C4S Courses (Daily Current Affairs, 20–21 October 2026): https://c4scourses.in/current-affairs/daily-current-affairs-dca-2021-october-2026
- arXiv, VELC CME onset paper: https://arxiv.org/pdf/2411.09408
- arXiv, VELC CME line-broadening preprint: https://arxiv.org/pdf/2607.04087
- ISRO, Aditya-L1 CME observations: https://www.isro.gov.in/Aditya_L1_Observations_Coronal_Mass_Ejection.html
- Wikipedia, Aditya-L1: https://en.wikipedia.org/wiki/Aditya-L1