A team of radio astronomers and engineers from the Indian Institute of Astrophysics (IIA) have successfully demonstrated unambiguous measurements of magnetic fields in the Sun’s corona, located at a far away distance of 150 million kilometres.

The measurements were made using a unique and sensitive radio telescope system set-up at the IIA Gauribidanur observatory.

The radio telescope is fabricated inhouse in the Gauribidanur observatory, using raw materials available within the country.

The team captured the twist in the electromagnetic radio waves from the ‘undisturbed’ Sun, called polarisation, using their telescope.

What causes twist

The twist is caused by the magnetic field. The measured degree of polarisation is very small, approximately 0.01 to 0.02, and these are the very first reported direct measurements of this type.

According to Shaik Sayuf, PhD student at IIA, who observed and analysed the data, the associated magnetic field strengths are less than one thousandth of a Tesla, the fundamental measurement unit for strength of the magnetic field.

Mr. Sayuf’s PhD thesis supervisor in IIA, C. Kathiravan, said, “The estimated field strengths are similar to those created with the bar magnets in the school laboratory experiments. It is interesting that similar small field strengths in the Sun’s atmosphere can give rise to strong eruptions which create disturbances in the near-Earth environment and affect the functioning of the satellites.”

R. Ramesh, senior professor in IIA and in charge for the radio astronomy activities of IIA in the Gauribidanur observatory, said that presently, it is nearly impossible to carry out similar magnetic field measurements in the Sun’s corona with either ground-based or space-based telescopes that operate in other wavelength bands of the electromagnetic spectrum.

Training ground

Mr. Ramesh added that the results show how the Gauribidanur observatory is effectively used as a training ground to provide valuable hands-on experience to the students and testbed for developing new technologies in radio astronomy with minimal investment compared to major ground- and space-based observational facilities elsewhere.