ESA's Solar Orbiter has made new measurements that illustrate the chaotic origins of solar flares.

There is no big bang at the start of a solar flare. They begin modestly. In actuality, the early warning indicators were hardly noticeable to scientists until recently.

A big solar flare can develop from microscopic perturbations that quickly accumulate and spiral out of control, according to a new series of close-up studies of the Sun.

The delayed start was a sign of what was to come. Even after the major explosion was over, the Sun's atmosphere became a frenzied sight with incandescent blobs of plasma falling back toward the surface.

The entire incident appeared to be a chain reaction that fuelled itself rather than a single outburst.

The significance of solar flares on Earth

When tangled magnetic fields snap and reconnect, they release energy violently, causing solar flares. When they occur, the Sun can emit light, heat, and particles that move quickly in a matter of minutes.

The most powerful flares have the ability to interfere with satellites, disturb radio transmissions, and shock the Earth's magnetic field. For this reason, scientists closely monitor the onset and progression of these eruptions.

Researchers had known the fundamentals for years, but not the specifics. They knew that magnetic fields stored energy and later released it, but they couldn't explain how quickly or how much energy was released. The topic of what causes a flare to burst rather than fizzle out was still open.

An uncommon up-close look at the action

One of the most precise views of a huge solar flare ever recorded was taken by the Solar Orbiter spacecraft on September 30, 2024, during a near visit by the Sun.

Together, four instruments monitored the Sun's many layers, recording changes in certain areas every two seconds. According to the data, the flare gradually intensified over a period of almost forty minutes until peaking.

Pradeep Chitta, the study's principal author, is a specialist at the Max Planck Institute for Solar System Research (MPS).

"We were extremely fortunate to observe the prelude to this massive flare in such exquisite detail," Chitta added. “It is not always possible to make such detailed high-cadence observations of a flare.”

The short observational windows and the large memory usage of such data on the spacecraft's onboard computer are the causes of this. To capture the amazing details of this flare, the spacecraft had to be at the correct position at the right time.

The formation of a magnetic avalanche

As soon as the satellite started observing the area, there was already a black, arch-shaped filament of plasma and distorted magnetic fields. A cross-shaped pattern of magnetic lines gradually became brighter nearby.

New magnetic strands emerged every few seconds. Under pressure, each one remained contained and tightened like a rope. The system then tilted. The threads started to split and re-join. Failure followed failure. More and more energy was released as the reconnection occurrences swiftly expanded throughout the area. As the process accelerated, the photos displayed abrupt flashes that became brighter.

A solar flare unravels and rips loose.

At 11:29 p.m. Universal Time, one brightening stood out. Soon after this, the dark filament tore loose on one side, shot outward, and unraveled at high speed.

Its length was illuminated with bright sparks as the major flare burst at approximately 11:47 p.m.Solar Orbiter provided us with a look directly into the flare's foot, where this avalanche process started, and these minutes before the flare are crucial," Chitta added.

"The large flare is driven by a series of smaller reconnection events that spread rapidly in space and time, which surprised us."

A series of explosive incidents

It has long been hypothesised by scientists that solar flares could have an avalanche-like pattern, in which numerous little occurrences come together to form a major one.

That notion was primarily based on statistics from thousands of flares up until now. This observation demonstrates that it takes place within a single, intense flare.

The flare developed as a series of interacting reconnection events rather than a single clean eruption. The system was pushed toward a full-scale explosion by each one, which fuelled the others.

Extreme speeds and plasma rain

What happened to the energy after it was released was likewise disclosed by the same observations. Where rapid particles crashed into the Sun's atmosphere was monitored by instruments that measure X-rays and ultraviolet radiation. Bright streams raced downward as a result of these impacts, which heated the plasma.

Particles experienced an acceleration of 40–50 percent of the speed of light, or 431–540 million miles per hour, during the flare's peak.

Particles that escape the Sun can cause radiation hazards to satellites, humans, and equipment on Earth, therefore that kind of speed is important. "Even before the main episode of the flare, we saw ribbon-like features moving extremely quickly down through the Sun's atmosphere," Chitta said.

As the flare continued, these streams of "raining plasma blobs" grew more intense. The rain persists for a while after the flare has passed. Chitta clarified, "This is the first time we see this in the solar corona at this level of spatial and temporal detail."

Following the storm's passage

The scene calmed down when the primary portion of the flare was over. The cross-shaped, brilliant magnetic pattern loosened. The plasma cooled. Emissions of particles returned to their typical levels.

Observations of the Sun's visible surface revealed a distinct flare impression that connected activity from far below to far above.

The researchers were nonetheless taken aback by the amount of energy required. Chitta stated, "We were surprised that the avalanche process could produce particles with such high energy."

The overall image of stellar behaviour

The results extend beyond our Sun and even beyond a single outburst. They imply that flares on numerous stars may frequently exhibit avalanche-style energy release.

According to ESA project scientist Miho Janvier, "this is one of the most exciting results from Solar Orbiter so far."

Solar Orbiter's observations highlight the vital function of an avalanche-like magnetic energy release process at work and reveal the flare's fundamental engine. Whether this mechanism occurs in all flares and on other flaring stars is an intriguing question.

As of right now, the Sun has provided a unique and thorough instruction. Large space weather events might start out as minor, inconspicuous changes that swiftly grow into something much more significant.