Can the Heating of Sun's outer atmosphere mystery be solved with the 'Campfires' on the Sun?
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| Credit: ESA |
One of the biggest mysteries about our beloved star, the sun, well a mystery in solar physics as a whole not just limited to our Sun, is that what heats the solar corona, Sun's outer atmosphere. ESA's Solar Orbiter might be able to shine some light on that puzzle.
In this simulation, miniature solar flares nicknamed 'campfires' discovered by ESA's Solar Orbiter, may contribute to the hating of Sun's Corona.
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| Credits: ESA-S.poletti |
Well, the corona of the Sun is just an outer atmosphere that contains gases, which can have a temperature up to million degrees, whereas the surface of the sun is just 5500°C, which raises questions as to why is, and how? As if a body is very hot in the center, and as we further go out the temperature decreases, so it should be cooler the further we go away, but data shows that corona is way, way hotter than the surface of the Sun. We have had ideas that suggested it could be due to the Sun's magnetic field, but that does not answer how is the energy dissipated, or generated and transported.
Solar Orbiter's Extreme Ultraviolet Imager has revealed more than 1500 small, flickering brightenings nicknamed campfires, they are short-lived, only last for 10-200 seconds, and have a footprint between 400-4000 km. These were not observed before until the Solar Orbiter was launched last year and got first light images of the Sun.
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| Credit: Chen et al(2021) |
The above image shows the model of these 'campfires', made by Yajie Chen, a Ph.D. student from Peking University in china working with Professor Hardi Peter from Max Planck Institute for Solar System Research in Germany. Hardi explains that the model calculates the emission of energy from the sun, the generated brightenings like the campfires, and also traces the magnetic field lines, allowing us to see the changes of the magnetic field in and around the campfires over time. The process is called component reconnection. reconnection a phenomenon where the magnetic field lines of opposite direction break and then connect, releasing energy when they do so, but the field lines need to be pointing in opposite directions, but with component reconnections, the field lines are almost parallel, where the recognition only happens at very small angles. Furthermore, Yajie says, "Our model that the energy released from the brightenings through component reconnection could be enough to maintain the temperature of the solar corona predicted from the observations.", and also in one case study, they found the untwisting of a flux rope [helical (spiral) magnetic field lines winding around a common axis] initiating the heating instead, says Hardi.
The team says it's in the very early days, and they have used the model to look at seven of the brightest events generated in their simulation which likely correspond to the largest campfires observed by the EUI. For key advancing the study will need to be a joint observation between the EUI and the spacecraft's Polarimetric and Helioseismic Imager (PHI) and Spectral Imagin of the Coronal Enviourment (SPICE) spectrograph once Solar Orbiter's full science mission gets going in November. PHI will be used to reveal the magnetic field of the sun and how it changes on the surface and SPICE will measure the temperature and density of the Corona.
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| Credit: Solar Orbiter/EUI Team/ESA & NASA Berghmans et al (2021) and Chen et al (2021) |
TEAMWORK
ESA paired with NASA's Solar Dynamics Observatory, which is in orbit to triangulate the height of the campfires in the Solar atmosphere.
David Berghmans, principal investigator of EUI says that the campfires are just located a few thousand kilometers above the photosphere, solar surface, which is very low in the solar atmosphere.
Understanding the characteristics of the campfires and their place amongst other solar phenomenons will enable scientists to dive deeper into the solar corona heating problem. Solar orbiter is currently in the 'cruise phase', focused primarily on the instrument calibration, and will begin coordinated observations between its suite of ten remote sensings and in situ instruments from November this year.
Publications - DOI: 10.1051/0004-6361/202140638
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