Using the VELC payload onboard India’s first dedicated space based solar mission, Aditya-L1, scientists at the Indian Institute of Astrophysics (IIA) along with NASA have collaborated to estimate the crucial parameters of a coronal mass ejection (CME), very close to its lift-off from the Sun. Scientists associated with the project said that these are the very first spectroscopic observations of a CME in the visible wavelength range. They said that the unique spectroscopic observations with the VELC has let them study the CMEs very close to the Sun’s visible surface itself, for the first time.

“In addition, it provides a sustained view of the Sun for 24 hours everyday because of being at the Sun-Earth Lagrangian L1 location where the Sun never sets,” they said. Taking advantage of these, Dr.

V. Muthupriyal (VELC Project Scientist) and her colleagues in the VELC payload operations centre at the IIA estimated the electron density, energy, mass, temperature and speed of a CME very close to the Sun. Senior Professor at IIA and principal investigator of the VELC project, Prof.

R. Ramesh, told The Hindu that the observations are by far the closest to the Sun where spectroscopic observations of a CME in the visible wavelength range have been obtained with a space coronagraph.

His team calculated that there are about 370 million electrons per cubic centimetre in the CME observed with the VELC. The corresponding number for the non-CME corona near the Sun is much lesser, in the range 10 – 100 million electrons per cubic centimetre.

“The CME energy in the present case is approximately 9. 4 * 1021 Joules.

For example, the yield of the atomic bombs (nicknamed “Little Boy” and “Fat Man”) used on Hiroshima and Nagasaki are about 6. 3 * 1013 Joules, and 8. 8 * 1013 Joules, respectively.

The mass in the CME is nearly 270 million tons. For comparison, the mass of the iceberg that sank the Titanic is estimated to be 1. 5 million tons.

The initial speed of the CME is 264 km/sec. The CME temperature is 1.

8 million degrees on the Kelvin scale,” Prof. Ramesh said.

He also added that though there are observations of CMEs at comparatively larger distances from the Sun, with instruments other than the VELC, an understanding of the parameters of a CME in relation to how much is lost from the Sun during a CME per se is crucial, and the unique near-Sun spectroscopic observations with the VELC is precisely providing us the necessary data. Prof. Ramesh added that with the Sun nearing the maximum activity phase of th ecurrent sunspot cycle 25 and with the VELC now stabilized in its operations, more massive and energetic eruptions from the Sun are expected to be observed with the VELC in the coming months.