Astronomers do not know why the solar corona, the atmosphere of the Sun, is so much hotter than its “surface”, the photosphere. The photosphere is around 5,500 °C (9,940 °F) but the corona is about 1 million °C (1.8 million °F), almost 200 times hotter. A new study proposed a mechanism to heat it up with high-frequency magnetic waves.
The Sun is powered by nuclear fusion at its core. So there must be a mechanism to carry that energy from the interior of the Sun to the corona. Magnetism is seen as the key to delivering the heating, although the exact way this happens is not clear. Lately, evidence has suggested transverse oscillation to be key to that. The new work explains how.
The fastest oscillations are found in the smallest magnetic structures in the solar corona, observed in amazing detail by the Extreme Ultraviolet Imager (EUI) on board the European Space Agency’s Solar Orbiter.
“Over the past 80 years, astrophysicists have tried to solve this problem and now more and more evidence is emerging that the corona can be heated by magnetic waves,” co-author Professor Tom Van Doorsselaere at KU Leuven, said in a statement.
But the question the scientists had to ask was: do these high-frequencies contribute enough energy to the corona? Enough to explain the heating in the corona? Lead researcher Dr Daye Lim from the Royal Observatory of Belgium and KU Leuven ran a meta-analysis of everything that is known about the waves, both the low-frequency and the high-frequency ones. And the fast ones certainly can.
“Since her results indicated a key role for fast oscillations in coronal heating, we will devote much of our attention to the challenge of discovering higher-frequency magnetic waves with EUI,” Dr David Berghmans, the principal investigator of EUI from the Royal Observatory of Belgium, added.
We are living in a golden age of solar observations from Solar Orbiter to NASA’s Parker Solar Probe, adding to the already many eyes we had on the Sun from space. With the work done by the Big Bear Solar Observatory and now that the Daniel K Inouye Solar Telescope is finishing its commissioning phase, the hunt is on for a solution to this mystery.
The research is published in The Astrophysical Journal Letters.
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