IIA team makes key solar observation using radio telescope and Aditya-L1 satellite payload

Astronomers from the Indian Institute of Astrophysics (IIA) have made observations of shocks driven by coronal mass ejections (CMEs) from the Sun by using its Gauribidanur radio telescope and Visible Emission Line Coronagraph (VELC) payload onboard Aditya-L1 satellite.

Thunder-like noise

A sonic boom is a thunder-like noise that occurs when the speed of an aircraft traveling through the air faster than the speed of sound. Similarly, fast CMEs from the Sun drive shocks near the Earth leading to space weather disturbances.

“These shocks are primarily driven by the same set of CMEs, all the way from near the Sun through the interplanetary space. Shocks near the Sun are the birth stage of the shocks observed near Earth. The characteristic signatures of the shocks near the Sun are intense transient emission observed primarily with ground-based radio telescopes at low frequencies, typically <150 MHz,” the IIA team said.

The IIA operates a radio telescope in the above frequency range, at the Gauribidanur radio observatory, located about 100 km north of Bengaluru. It is presently the only low-frequency radio telescope for dedicated observations of the Sun.

The team said that with the launch of VELC, built by IIA, it has become possible to identify the CMEs that give rise to the shocks, particularly near the Sun and in the visible wavelength range. Combining data obtained with the Gauribidanur radio facility and VELC, the VELC team at IIA has precisely estimated the onset distance of the shock due to the CME that occurred on May 27, 2024. It is approximately 130,000 km from the Sun. The shock driven by the CME propagated at a speed of approximately 1,700 km per second near the Sun.

Prof. R. Ramesh, senior professor at IIA and principal investigator of the VELC project, said that this is the closest distance from the Sun at which a CME driven shock and the associated radio transient have been observed unambiguously as on date.

Unique capability

Prof. Ramesh, who is handling the operations in the Gauribidanur facility, added that the present result would not have been possible but for the unique low-frequency observing capability of the Gauribidanur radio telescope and the possibility to observe the near-Sun solar corona with the VELC. The results will appear soon in the Journal of Astrophysics and Astronomy, a leading international journal.

Dr. C. Kathiravan, lead author of the publication, said continuous and coordinated observations of the Sun with Gauribidanur facilities and VELC during the current maximum phase of the ongoing sunspot cycle 25, as well as beyond, are expected to identify CME driven shocks as close as thirty thousand kilometers from the Sun.

“Such a statistical data set would give significant insights into workings of the Sun and its connection to the disturbances in the near Earth space,” he said.