Astronomers at the Indian Institute of Astrophysics (IIA) have made observations of shocks caused by coronal mass ejections (CMEs) from the Sun using their Gauribidanur radio telescope and the Visible Emission Lines Coronagraph (VELC) payload aboard the Aditya-L1 satellite.
A noise like thunder
A sonic boom is a thunder-like sound that occurs when the speed of an aircraft flying through the air is greater than the speed of sound. Similarly, fast CMEs from the Sun drive near-Earth shocks leading to space weather disturbances.
“These shocks are primarily driven by the same set of CMEs, all the way from near the Sun through interplanetary space. Near-Solar shocks are the birth stage of shocks observed near Earth. Characteristic features of near-Solar shocks are intense transient emissions 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 currently the only low-frequency radio telescope for specialized observations of the Sun.
The team said that with the launch of VELC, built by the IIA, it was possible to identify CMEs that cause shocks, especially near the Sun and in the visible wavelength range. By combining data obtained from the Gauribidanur radio facility and VELC, the VELC team at IIA accurately estimated the distance to the start of the shock caused by the CME, which occurred on May 27, 2024. It is approximately 130,000 km from the Sun. The CME-driven shock propagated near the Sun at approximately 1,700 km per second.
Prof. R. Ramesh, a senior professor at the IIA and principal investigator of the VELC project, said this is the closest distance from the Sun at which a CME-driven shock and associated radio transition have been unambiguously observed to date.
A unique ability
Prof. Ramesh, who manages operations at the Gauribidanur facility, added that the current result would not have been possible without the Gauribidanur radio telescope’s unique low-frequency observation capabilities and the ability to observe the solar corona near the Sun with VELC. The results will soon appear in the Journal of Astrophysics and Astronomy, a leading international journal.
Dr. C. Kathiravan, lead author of the publication, said that continuous and coordinated observations of the Sun by the Gauribidanur and VELC facilities during and after the current maximum phase of the ongoing sunspot cycle 25 are expected to identify CME-driven shocks up to thirty thousand kilometers from the Sun.
“Such a set of statistical data would provide significant insight into the workings of the Sun and its connection to near-Earth space perturbations,” he said.
Published – 26 Feb 2026 21:52 IST
