Measurement of magnetic field offers rare peek into inner workings of the Sun

Vijay Mohan
Tribune News Service
Chandigarh, September 9

Indian scientists, along with international collaborators, have measured the magnetic field of an eruption from the Sun’s atmosphere offering a rare peek to the interior of the Sun. 

Observing the weak thermal radio emission associated with the erupted plasma for the first time, the study of the phenomenon happening in the Sun’s atmosphere or the solar corona provides insights into the inner workings of the Sun.

The Sun is an extremely active object, spewing out vast quantities of gas in many violent events and the corona is a region of very high temperatures, strong magnetic fields, and violent plasma eruptions.

A class of such eruptions are Coronal Mass Ejections (CMEs), which are the most powerful explosions happening in our solar system. When a really strong CME blows past the Earth, it can damage the electronics in our satellites and disrupt radio communication networks on Earth.

Hence, astronomers regularly study these events which also helps to understand space weather.

A team of scientists from the Indian Institute of Astrophysics (IIA), along with their collaborators, used data from their radio telescopes to measure the magnetic field and other physical conditions of the plasma in a CME.

The use of radio telescopes of IIA located in Karnataka along with some space-based telescopes allowed the researchers to detect a much weaker radio emission called thermal or blackbody radiation from the plume of gas that was ejected in the CME. 

They were also able to measure the polarisation of this emission, which is indicative of the direction in which the electric and magnetic components of the waves oscillate. Using this data, they then calculated the physical properties of the ejected plasma as well. 

“Though CMEs can occur anywhere on the Sun, it is primarily those which originate from regions near the centre of the visible solar surface, called the photosphere, that are important for us, since they may propagate directly towards the Earth,” R Ramesh, Professor at IIA, and the lead researcher of the study, said in a statement issued by the Ministry of Science and Technology today.

“These CMEs are usually studied in visible light, but because the disc of the Sun is so much brighter, we can detect and follow these CMEs only when they have travelled beyond the Sun’s surface. However, radio observations of the thermal emission, like in our study, lets us study the CMEs right from the surface itself,” added,” A. Kumari, a co-author.

“Knowing the source region of the CMEs, the associated magnetic field and their kinematics in the region up to seven lakh kilometre either above the solar surface or off its limb, is important to fully understand the characteristics of the CMEs in a holistic manner,” said C. Kathiravan, another co-author of the study.