Twenty years that astronomers wonder what really hides behind the dark structures that seem to fall towards the Sun during an eruption. The hypothesis of a consequence of the magnetic reconnection seemed attractive. But researchers are now offering a new explanation.
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[EN VIDÉO] Solar Flare, SDO A brilliant solar flare recorded in all wavelengths by the SDO satellite, November 29, 2020.
The solar flares classics come as streams emerging of our star. But in January 1999, astronomers observed strange movements within one of these eruptions. A downward flow. As if from matter was falling towards the Sun. Today, some researchers from Harvard-Smithsonian Center for Astrophysics (CfA, USA) offer an explanation for this phenomenon called supra-arch descending flow (SAD).
Since their discovery, astronomers have seen in these dark structures “resembling fingers”manifestations of magnetic reconnection. The equivalent in terms of magnetic fields of what happens when you pull a rubber band and cut it. “He goes back”remarks Kathy Reeves, astronomer, in a communicated. So these dark descending flows would correspond to magnetic fields broken “regaining” the Sun after an eruption.
According to researchers from Harvard-Smithsonian Center for Astrophysics (CfA, United States), the dark fingers that can be observed during solar flares are the result of the interaction of two fluids of different densities. © NASA SDO
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Nice theory! But that does not explain the speed “surprisingly slow” measured for these flows. So the researchers analyzed the downflow images captured by theAtmospheric Imaging Assembly (AIA) on board the probe SDO (Solar Dynamic Observatory) from NASA. Images taken every 12 seconds in seven wavelengths different.
By comparison with 3D simulations of solar flares, astronomers finally show that most SADs are not generated by a magnetic reconnection. But let them form themselves in the turbulent environment of thesolar atmosphere. As the result of the interaction of two fluids of different densities. So these “fingers” dark spots would mark a plasma deficit, a region in which the density appears much lower than that of the surrounding plasma.
By understanding the processes that drive solar flares, astronomers could ultimately help develop tools to predict the weather report space and anticipate its impacts.
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