How do advances in coronal observation, such as Doppler velocity imaging, improve forecasts of Earth-directed coronal mass ejections?

Coronal mass ejections (CMEs) are huge clouds of hot plasma. They can travel in any direction and disrupt near-Earth space [1]. Scientists at the Indian Institute of Astrophysics (IIA) used data from Aditya-L1's VELC payload to make Doppler velocity images of the corona. These images add the part of a CME's motion along the Sun–Earth line, which was missing until now [1].

The forecasting gap

• Plane-of-sky limit: a coronagraph shows a CME only as it spreads sideways across the sky. A CME aimed at Earth looks like a "halo" around the Sun, so its speed towards us is hidden.
• Delayed warnings: after a halo CME, NOAA forecasters have had to wait for full analysis before saying when it would arrive and how strong it would be [2].

How Doppler imaging improves forecasts

• Line-of-sight velocity: the shift in the wavelength of coronal light shows whether material is moving towards or away from the observer, i.e., along the Sun–Earth line [1].
• Early identification: it can separate Earth-directed eruptions from those heading elsewhere as they erupt, which adds warning time [1].
• Uninterrupted vantage: the halo orbit around L1, about 1.5 million km from Earth, gives a view of the Sun free from eclipses. This suits continuous Doppler mapping [3][4].
• 3-D picture: VELC's line-of-sight speed can be combined with sideways views from operational coronagraphs such as NOAA's CCOR-2 on SWFO-L1 [5][6].
• Built-in check: Aditya-L1's 3 in-situ payloads at L1 can confirm whether a CME flagged as Earth-directed actually arrived [3].

Eruption → VELC Doppler (moving towards Earth?) + sideways coronagraph view → 3-D speed and direction → arrival model → alert → in-situ check at L1

Limits that remain

• Arrival time: CMEs speed up or slow down in the solar wind. Published forecasts still carry error windows several hours wide [7].
• Impact: in the May 2024 storm, several CMEs arrived in waves [8]. A "minor" storm in February 2022 still brought down 38 of 49 new Starlink satellites [9].
• Science, not service: VELC observing time is shared out through competitive AO cycles, not run as a 24×7 watch [10].

Doppler imaging measures the one direction that ordinary coronagraph images cannot show. This moves forecasting from simply detecting a CME to judging its direction early. The next steps are to test VELC's direction calls against in-situ data, submit Indian forecasts to NASA's CME Scoreboard, and build an operational warning pipeline for NavIC, satellite and power-grid operators. Together, these would turn a scientific milestone into self-reliant space-weather preparedness.