“Campfires”, or mini solar flares that occur on the surface of the Sun, are helping shed light on a mysterious solar heating phenomenon that has baffled experts for decades.
New data from the European Space Agency’s (ESA) Solar Orbiter suggests these campfires are driven by a process that may also contribute to heating of the Sun’s outer atmosphere, or corona.
The Sun’s corona is much hotter, around 300 times, than the layers below – a strange feature that has puzzled scientists and is thought to be one of the biggest mysteries in solar physics.
Solar flares are brief eruptions of high-energy radiation from the Sun’s surface, which can cause radio and magnetic disturbances on the Earth. Experts have previously wondered whether these eruptions are linked to the mysterious solar corona heating phenomenon.
In June 2020, the ESA released the closest images ever taken of the Sun which, for the first time, showed campfires dotted across its surface.
These images were captured by Solar Orbiter, a probe designed and built in the UK, when it came within 76 million kilometres (47 million miles) of the Sun’s surface. They revealed around 1,500 small, flickering brightenings that last for between 10 and 200 seconds and span between 400km and 4,000km.
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The latest findings are based on computer simulations conducted by an international team of researchers collaborating with the ESA.
“Our model calculates the emission, or energy, from the Sun as you would expect a real instrument to measure,” said Professor Hardi Peter, from the Max Planck Institute for Solar System Research in Germany. “The model generated brightenings just like the campfires.”
The simulations also revealed a process known as component reconnection around the campfires, where magnetic field lines of opposite direction break and then reconnect, releasing energy when they do so.
“Our model shows that the energy released from the brightenings through component reconnection could be enough to maintain the temperature of the solar corona predicted from observations,” said Yajie Chen, a PhD student from Peking University in China.
However, the researchers caution that their work is still in its early stages and requires further observations to confirm their findings.
“We’re looking forward to see what further insights our models bring to help us improve our theories on the processes behind the heating,” Peter said.
Aside from helping unlock the mysteries of coronal heating, the Solar Orbiter will also help scientists piece together the Sun’s atmospheric layers and analyse the solar wind, the stream of highly energetic particles emitted by the star.
Understanding more about solar activity could also help scientists make predictions on space weather events, which can damage satellites in orbit and disrupt the infrastructure on Earth that mobile phones, transport, GPS signals and the electricity networks rely on.
The spacecraft, which was constructed by Airbus in Stevenage, has been designed to withstand the scorching heat from the Sun that will hit one side, while maintaining freezing temperatures on the other side of the spacecraft as the orbit keeps it in shadow.
The Solar Orbiter is currently in “cruise phase” as it calibrates all its scientific instruments and will begin co-ordinated observations from November this year.