On September 30, 2024, the Sun launched a powerful explosion, which caused the magnetic field lines to break and reconnect in a criss-cross pattern. The solar probe was there to watch it happen, gathering unprecedented data that helps scientists better understand the mechanism behind the sun’s burning.
Using the European Space Agency’s Solar Orbiter spacecraft, a team of scientists discovered that solar flares are caused by initially weak disturbances that grow violent, such as snow on snowy mountains. This process creates a cloud of plasma blobs that continue to rain down even after the solar flare subsides, according to new research published in Astronomy & Astrophysics.
A magnetic avalanche
Solar flares are large explosions from the Sun, throwing energy, light, and particles into the atmosphere. They occur when the energy stored in twisted magnetic lines is suddenly released. Powerful solar flares can disrupt technology on Earth, causing geomagnetic storms that can cause radio blackouts.
Scientists have observed solar flares for many years, but still do not have a detailed understanding of how this enormous amount of energy is released so quickly from the Sun. Using high-resolution data from the Solar Orbiter, scientists now have a better picture of the process that leads to violent explosions.
The Solar Orbiter approached the Sun’s surface through a dark arch-like ‘filament’ of twisted magnetic fields and plasma, linked by a cross-shaped structure of luminous magnetic field lines. Scientists directed the spacecraft’s Extreme Ultraviolet Imager (EUI) to the area about 40 minutes before the main eruption activity.
By zooming in, observations reveal new magnetic fields appearing in each frame of the image—the equivalent of every two seconds or less. Each wire was contained in a magnet and twisted like a rope. The region has gradually shrunk, like an iceberg.
The twisted magnetic lines began to break and reconnect, soon causing further instability in the region. As the wires broke, they began slowly energetic reconnection events and discharges, which appeared as increased brightness in the images.
Then, a sudden flash of light was followed by a black streak that cut off from one side, going out into space while violently unraveling at high speed. Scientists initially recorded a velocity of 155 miles per second (250 km/s), rising to 248 miles per second (400 km/s) at the termination point. Bright sparks of reconnection appeared throughout the filament in surprisingly high resolution as the flare exploded.
“We were very fortunate to see the events leading up to this big bang in great detail,” Pradeep Chitta, a researcher at the Max Planck Institute for Solar System Research in Göttingen, Germany, and lead author of the paper, said in a statement. “Such detailed views of flares are not always possible due to limited viewing windows and because data like this takes up a lot of memory space on the spacecraft’s on-board computer. We were in the right place at the right time to capture the fine details of this flare.”
The scientists conducting the study were surprised to learn that the large opening is driven by a series of small reconnection events that spread rapidly through space and time, creating a pattern of increasingly violent events.
Plasma rain
Even before the flare erupted, the Solar Orbiter revealed that the emission of gas from the Sun was gradually increasing when the spacecraft began observing the area. During the opening itself, the particles were accelerated to a speed of 40 to 50% the speed of light.
Detailed observations also revealed that energy is transferred from the magnetic field to the surrounding plasma during these reconnection events. “We saw ribbon-like features moving very quickly in the Sun’s atmosphere, even before a large flare,” said Chitta. “These streams of ‘raining plasma blobs’ are signatures of energy input, which become stronger as the flare progresses.”
Even after the fire subsided, the shower of plasma blobs continued for some time, Chitta added.
“Solar Orbiter’s observations reveal the central engine of the flare and emphasize the important role of the avalanche-like magnetic energy release mechanism at work,” Miho Janvier, ESA’s Solar Orbiter co-project scientist, said in a statement. “The exciting prospect is that this mechanism occurs in all flares, and in other burning stars.”
