India’s Aditya-L1 solar mission has provided scientists with new clues that could help explain one of the biggest mysteries surrounding the Sun: why its outer atmosphere, or corona, is dramatically hotter than the surface below it.

The findings, led by Indian solar astrophysicists, have been published in the Astrophysical Journal Letters and could improve scientists’ understanding of how the Sun’s corona maintains its extreme temperatures.

Why Is the Sun’s Corona So Hot?

The Sun has a temperature of around 15 million degrees Celsius at its core. However, its visible surface, known as the photosphere, is much cooler at approximately 5,500C.

What puzzles scientists is that the temperature rises again dramatically farther from the surface.

The corona can reach around 2 million degrees Celsius, and during particularly energetic events its temperature can rise as high as 40 million degrees.

According to Prof R Ramesh of the Indian Institute of Astrophysics, who led the study, these temperature variations challenge conventional expectations from physics.

Aditya-L1 Provides Important Observations

Aditya-L1 is India’s first dedicated space-based mission to study the Sun.

The spacecraft observes the Sun from a special location called the Lagrange point 1 (L1), allowing it to continuously monitor solar activity without Earth blocking its view.

Scientists have been using its observations to study the behaviour of the solar atmosphere and the mechanisms responsible for heating the corona.

The latest findings could help researchers understand how energy is transferred through the Sun’s atmosphere.

Solar Eruptions Release Huge Amounts of Energy

The corona is also the source of some of the Sun’s most powerful eruptions, including solar flares and coronal mass ejections (CMEs).

During a CME, enormous quantities of solar material and energy are released into space.

These events can produce spectacular auroras when they interact with Earth’s magnetic field. However, powerful solar storms can also cause problems for modern technology.

Geomagnetic storms can interfere with satellites and communications systems and, in extreme cases, affect electrical power grids.

The Sun’s Energy Puzzle

During relatively quiet periods, the Sun can produce around two to three CMEs a day. During the peak of its approximately 11-year solar activity cycle, that number can rise to 10 or more per day.

This creates an important scientific question.

If the corona continually loses enormous amounts of energy through these eruptions, scientists need to understand how that energy is replenished.

Prof Ramesh argues that the continued high temperature of the corona indicates that an underlying mechanism must be supplying or redistributing energy.

Without such a mechanism, the Sun would gradually lose its available energy, fundamentally changing conditions throughout the solar system.

Why Understanding the Corona Matters

Studying the Sun’s corona is not only about solving a long-standing scientific mystery.

Solar activity directly affects the space environment around Earth. Powerful eruptions can disrupt satellites, navigation systems, radio communications and electrical infrastructure.

A better understanding of how the corona is heated and how solar eruptions are produced could therefore help scientists improve predictions of space weather.

India’s Growing Role in Solar Science

The latest research highlights the scientific value of India’s Aditya-L1 mission and the country’s growing contribution to solar physics.

As scientists continue analysing data from the spacecraft, its observations could help answer fundamental questions about how the Sun’s atmosphere works and why its outer layers behave so differently from its surface.

The mystery of the Sun’s superheated corona is not completely solved, but Aditya-L1 is providing researchers with valuable new evidence that could bring them closer to an explanation.