Scientists have generated Doppler velocity images of activities taking place in the solar corona using data obtained with the Visible Emission Line Coronagraph (VELC) payload onboard India’s maiden solar mission, Aditya-L1.

The Aditya-L1 satellite generates Doppler velocity images of the solar corona, and these images are expected to provide information on the propagation of coronal mass ejections (CMEs) along the Sun-Earth direction, which has been unavailable to date.

Scientists at the Indian Institute of Astrophysics (IIA), who generated the Doppler velocity images, said it is well known that solar activity leads to the ejection of hot plasma.

They said that the massive and energetic plasma cloud ejected during powerful eruptions like the CMEs can travel either in the direction of the Earth or in any other direction from the Sun.

Scientists said that because CMEs can disrupt near-Earth space, it is important to infer their direction of propagation from the Sun as they erupt.

“Universally, it is taught in high schools that the Doppler effect in sound helps to understand whether a train is approaching the railway station platform or moving away from it. A person standing on the platform would hear a steady increase in the pitch of the sound waves due to the train’s whistle or horn when the train is coming into the station. The pitch would steadily decrease when the train is moving away from the station,” scientists said.

Using a similar Doppler effect concept in light waves, they have now generated Doppler velocity images.

“The positive and negative Doppler velocities indicate solar plasma moving away from and towards the direction of the observer, respectively,” they said.

The detailed software for processing the VELC data is developed by Dr V. Muthupriyal, Senior Project Scientist with the VELC payload operations team in IIA, and her team. The technical details related to the data processing have been published recently in the Astrophysical Journal after international peer review.

According to Prof.R.Ramesh, Senior Professor in IIA and Principal Investigator, VELC project, the Doppler velocity images of the solar corona are unique.

He said that only VELC has the capability to generate such images at present due to its one-of-a-kind spectroscopic observing capability in the visible wavelength range from the Lagrangian L1 position in the Sun-Earth system.

He added that the related processed images will be disseminated to the scientific community, in addition to the data which is already there in the public domain.