Scientists have measured the magnetic field of an eruption from the Sun's atmosphere, which offered a rare peek into the interior of the star, the Department of Science and Technology (DST) said on Thursday.
The study of the phenomenon happening in the Sun's atmosphere or the solar corona provides insights into its inner workings, it said.
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, the DST said in a statement.
Such eruptions are Coronal Mass Ejections (CMEs), which are the most powerful explosions happening in the solar system, it said. When a really strong CME blows past the Earth, it can damage electronics in satellites and disrupt radio communication networks on Earth. Hence, astronomers regularly study these events. This field of research helps to understand space weather, the DST said.
A team of scientists from the Indian Institute of Astrophysics (IIA), an autonomous institute of the DST, 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 detected on May 1, 2016, it said.
It was found with the help of radio telescopes of IIA in Gauribidanur, Karnataka, along with some space-based telescopes that observed the Sun in extreme ultraviolet and white light and were caught when the base of its activity was just behind the visible limb of the Sun, the statement said.
This allowed the researchers to detect a much weaker radio emission called thermal (or black body) 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, the statement said.
The results of the study by R Ramesh, A Kumari, C Kathiravan, D Ketaki, and TJ Wang have been published in the leading international journal Geophysical Research Letters.
"Though CMEs can occur anywhere on the Sun, it is primarily those which originate from regions near the center of the visible solar surface (called the photosphere) like the one we studied that are important for us, since they may propagate directly towards the Earth," Ramesh, professor at IIA, Bengaluru, and the lead author of the paper, said.
Kumari, a co-author, said these CMEs are usually studied in visible light, but because the disc of the Sun is so much brighter, they can be detected and followed only when they have traveled 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”, she added.
Knowing the source region of the CMEs, the associated magnetic field, and their kinematics in the region up to seven lakh kilometers either above the solar surface or off its limb are important to fully understand the characteristics of the CMEs in a holistic manner, said Kathiravan, another co-author of the study.