The small bright campfires also appear in the simulated solar atmosphere. 'Quite purposefully, we took the perspective of EUI to relate our calculations to the actual measured data,' says first author Yajie Chen, a researcher at Peking University and MPS. In their computer model, the group simulated the interplay of hot plasma and magnetic fields in the region between the solar surface up to the corona, and then calculated how their artificially created solar atmosphere would appear in measurements from EUI. 'To evaluate what role the campfires really play, we first need to understand what physical processes are responsible for them,' says MPS scientist Hardi Peter, one of the authors of a second study, also forthcoming in the journal Astronomy & Astrophysics. 'It could be that their influence on coronal heating has been underestimated so far,' she adds. 'As we see now, the smallest, previously undetected flares occur much more frequently than the larger ones,' explains EUI team member Regina Aznar Cuadrado of MPS. Various wave phenomena, spicules, magnetic processes, and radiation bursts are just some of the suspects. It is still unclear which processes supply the necessary energy and convert it into heat. There, the temperature rises steeply: from a few thousand degrees to more than a million. The region between the lower and upper solar atmospheres has long fascinated solar physicists. To do so, the EUI team took into account less highly resolved images from NASA's Solar Dynamics Observatory (SDO) probe, which were taken at the same time and show the campfires from a second perspective.Ĭomparison of a computer-simulated solar campfire (left) and the associated, local magnetic fields and field lines (right). In addition, for some of the campfires the researchers were able to calculate the altitude in which they occur: in the lower solar corona, about 1000 to 5000 kilometers above the Sun’s visible surface. 'They reach temperatures of more than one million degrees many have an elongated, curved shape,' describes MPS scientist Luca Teriaca of the EUI team. According to the study, the campfires last no more than a few minutes.

The corresponding study will be published in the journal Astronomy & Astrophysics. The team, led by David Berghmans of the Royal Observatory of Belgium, has now studied the properties of 1500 such campfires, thus offering the most comprehensive characterization of the phenomenon to date. EUI scientists have come to refer to the bright areas as 'campfires'. 'The smallest ones we now see for the first time”, he adds. 'We are already familiar with larger flares of this type from the measurement data of other space probes,' says MPS scientist Udo Schühle, EUI Co-Principal Investigator. In the images, they appear as tiny, bright spots. After all, the 50 images taken by EUI about halfway between Earth and the Sun show the Sun's hot outer atmosphere, known as the corona, in almost unprecedented detail.ĮUI sees areas between 4 kilometers in size that emit extremely short-waved ultraviolet light of high intensity for a short time. However, even the data obtained during the instrument's technical commissioning last year were eagerly awaited. Regular scientific measurements are not scheduled until the end of this year, when the spacecraft will have reached its targeted, highly elliptical orbit around the Sun. Strictly speaking, Solar Orbiter’s instrument EUI is not even in service yet. © Sun image: Solar Orbiter/EUI Team/ESA & NASA Data: Berghmans et al (2021) and Chen et al (2021)

Sun corona solar flares