One solar eruption raced at 645 km/sec, another crawled at 145 km/sec: Bengaluru scientists uncover new clues about the Sun

One solar eruption travelled at 645 km per second, while another moved at just 145 km per second. The striking difference has offered scientists new insights into how powerful eruptions develop close to the Sun. Researchers at the Indian Institute of Astrophysics (IIA), Bengaluru, have analysed observations of the same two solar eruptions captured by India's Aditya-L1 mission and the European Space Agency's Proba-3. The events occurred on September 14 and 16, 2025.

The study examined coronal mass ejections (CMEs), massive bursts of magnetised plasma released by the Sun. By combining data from the two missions, scientists measured the eruptions' mass, density and energy, helping them understand how these events behave in the Sun's inner corona. According to the Indian Space Research Organisation (ISRO), the findings were published in the journal Astronomy & Astrophysics.

One solar eruption moved more than four times faster than the other

The two eruptions displayed markedly different speeds. The CME recorded on September 14 travelled at approximately 645 km per second. The eruption observed on September 16 moved at around 145 km per second. Scientists also found that the slower eruption's density declined more sharply as it moved farther from the Sun. This indicated stronger expansion during its early development.


The study examined how energy was distributed within the two eruptions. In the September 14 event, thermal energy accounted for about 1% of the total energy. In the September 16 eruption, thermal energy increased until it became comparable to kinetic energy, which is the energy associated with motion. The researchers also estimated that magnetic energy was comparable to or greater than kinetic energy.

These differences offer clues about the physical processes involved in solar eruptions. However, the observations do not establish a single reason why one CME travelled faster than the other.

Why scientists are studying solar eruptions close to the Sun

Coronal mass ejections occur when the Sun releases enormous quantities of plasma carrying magnetic fields into space. These eruptions can travel through the solar system and, when directed towards Earth, disturb its space environment. Their effects can include disruptions to satellites and other space-based systems. Understanding how CMEs develop in their earliest stages is therefore important for improving knowledge of space weather.

Observing these events close to the Sun has been challenging. Earlier space-based coronagraphs could not always capture the early development of faint eruptions in sufficient detail. Scientists consequently had limited information about how CMEs distribute energy among motion, heat and magnetic fields. The latest research brings together observations from two instruments designed to examine different aspects of the solar corona.

How Aditya-L1 and Proba-3 captured the same eruptions

Aditya-L1 carries the Visible Emission Line Coronagraph (VELC), an instrument that uses spectroscopy to study the Sun's corona. It helps scientists investigate properties such as the temperature and density of the gas surrounding the Sun. Proba-3 carries the ASPIICS coronagraph, which observes the corona using visible light and a green emission line.

The two instruments offer complementary views of solar activity. Combining their measurements allows researchers to compare estimates of the same eruption's physical properties using different observational methods. Although the instruments share a common field of view in the Sun's inner corona, simultaneous observations of the same CMEs were limited. Between July and December 2025, the two missions recorded just two eruptions together: those of September 14 and 16.

In both cases, Aditya-L1's VELC captured the eruption at an early stage, providing valuable information about its initial evolution. ISRO said the independently calculated estimates of mass and thermal energy from the two instruments showed good agreement. This consistency strengthened confidence in the measurements and highlighted the scientific value of combining data from different missions.

What are India's Aditya-L1 and Europe's Proba-3 missions?

Aditya-L1 is India's first dedicated solar mission. It was launched on September 2, 2023, and entered a halo orbit around the Sun-Earth L1 point on January 6, 2024. From this location, the spacecraft can observe the Sun and study its atmosphere and activity. Its instruments help scientists investigate solar phenomena that influence conditions in space.

Proba-3 is an European Space Agency mission launched on December 5, 2024, aboard India's PSLV-XL rocket. The mission uses two spacecraft flying approximately 150 metres apart to create an artificial solar eclipse. One spacecraft blocks the bright solar disc, allowing the other to observe the much fainter corona in greater detail.

This formation-flying technique helps scientists examine regions close to the Sun that are difficult to observe with conventional instruments. The joint analysis demonstrates how coordinated observations can improve scientists' understanding of solar eruptions. By studying their early development, researchers hope to build a clearer picture of the processes that shape these powerful events and influence the space environment around Earth.