Aditya-L1 Study Reveals Sun’s Magnetic Fields Heat Corona

Core News & Key Facts

A team of researchers from the Indian Institute of Astrophysics (IIA), Bengaluru, has found new observational evidence that the Sun’s changing magnetic fields may account for most of the energy responsible for heating its extremely hot outer atmosphere, known as the corona.

The study examined signatures of a coronal mass ejection (CME), a powerful event in which large quantities of hot plasma are expelled from the Sun. The observations were obtained by Aditya-L1, India’s dedicated space-based solar observatory, which was launched in 2023 and is positioned about 1.5 million km from Earth.

The Sun’s visible surface has a temperature of about 6,000 degrees, while its corona is typically around a million degrees and can become tens of millions of degrees hot during major eruptions. Explaining this apparent temperature difference has remained a major puzzle in solar physics.

Context & Official Statements

Scientists have proposed two broad mechanisms for coronal heating. One involves waves travelling through the Sun’s magnetic environment and transferring energy into the corona. The other involves the explosive release and redistribution of energy when magnetic fields snap, reconnect and rearrange themselves.

The IIA team, led by R. Ramesh, found that waves accounted for only about 7% of the energy in the region associated with the eruption. The results, published in The Astrophysical Journal, indicate that changing magnetic fields could be responsible for the bulk of the energy transfer.

“What was missing was direct observational evidence of how the energy is actually transferred during such eruptions,” Ramesh said, according to the source material.

The researchers used Aditya-L1 observations to examine changes in plasma motion and physical conditions during the CME. Solar physicist Dibyendu Nandi of the Raman Research Institute described the work as demonstrating the unique capability of continuous Aditya-L1 observations, while noting that the result currently comes from a single CME observed in August 2024.

Impact & What to Expect Next

The findings add observational support to the idea that magnetic-field activity plays a dominant role in maintaining the Sun’s extraordinarily hot corona. They may also help scientists understand how energy lost during solar eruptions is rapidly replenished.

However, the researchers and outside experts caution that more observations are needed. Nandi said establishing whether the result holds across a statistically significant number of events would be an important next step.

The IIA team plans to analyse additional CMEs using similar methods. Such studies could strengthen understanding of solar eruptions and the processes that transfer energy through the Sun’s atmosphere.

The mystery itself dates back to observations made during a total solar eclipse in 1869, when astronomers detected a mysterious green spectral line. Decades later, scientists determined that it came from highly ionised iron, revealing that the corona reaches temperatures far above the Sun’s visible surface.