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Journalism of Courage
Even though the Sun is the primary source of energy for most lifeforms on the planet, there is a lot that we do not know about it. For example, we are not quite sure why its corona, in the outer atmosphere, is hotter than its surface.
But now, the European Space Agency’s (ESA) Solar Orbiter may have taken a step towards solving that eighty-year-old mystery.
Just a few months after its nominal mission, on March 3, 2022, the Solar Orbiter’s Extreme Ultraviolet Imager (EUI) captured data that showed for the first time a magnetic phenomenon called reconnection happening on tiny scales, according to ESA.
During that time, the orbiter was about halfway between our planet and the Sun. Due to this, it was possible to coordinate observations with NASA’s Solar Dynamics Observatory and the Interface Region Imaging Spectrograph (IRIS) missions. Astronomers combined data from these three missions for their analysis.
Magnetic reconnection happens when a magnetic field transforms into a more stable configuration. It is an important energy release mechanism in a state of matter called plasma and it is believed that this magnetic reconnection is also behind large-scale solar eruptions. Being a direct cause for space weather, it is also a prime candidate to explain the heating of the Sun’s outer atmosphere
Since the 1940s, it has been known that the Sun’s corona, or its outer atmosphere, is much hotter than its surface. The surface of the sun is about 5,500 degrees Celsius while the gases in the corona measure about 2 million degrees Celsius. But it has so far proven hard to explain why that is the case. But magnetic reconnection could be one potential explanation.
For a long time, magnetic reconnection was observed during large-scale explosive phenomena, But astronomers now have ultra-high-resolution observations of persistent small scale reconnection in the corona. Of course, the word small-scale here is relative as this phenomena measure 390 kilometres across on the Sun.
These observations turned out to be long-lived and “gentle” sequences of magnetic reconnection, contrasted with the sudden explosive release of energy that the phenomena is usually associated with.
These new observations suggest that there could be even smaller and harder-to-observe instances of magnetic reconnection on the Sun, and this could perhaps explain how the Sun is injecting so much heat into its outer atmosphere.
