Coronal rain is the most dramatic display of cooling in the Sun’s corona. It corresponds to cool and dense clumps of plasma appearing over a timescale of minutes in the corona, that preferentially fall towards the solar surface along coronal loops. Now, solar astronomers using ESA’s Solar Orbiter have observed a never-before-seen ‘fireball’ phenomenon occurring within the coronal rain.
Coronal rain is a condensation process in which some of the Sun’s fiery material clumps together due to sudden, localised temperature drops.
The corona, which is the outermost part of the Sun’s atmosphere, is formed of gas at million-degree temperatures, and quick drops in temperature produce super-dense clumps of plasma that reach 250 km wide.
These fiery balls plummet back down towards the Sun as gravity pulls them in at over 100 km per second.
In spring 2022, ESA’s Solar Orbiter (SolO) cruised super close to the Sun at a distance of only 49 million km, allowing the best spatial resolution ever obtained of the solar corona.
Along with the first high-resolution images of the coronal rain clumps, SolO observed the heating and compression of gas immediately underneath them.
The resulting spike in intensity below the clumps indicates that the gas is heated up to a million degrees, which lasts for a few minutes as they fall.
On Earth, ‘shooting stars’ happen when meteoroids enter our atmosphere at high speeds and burn up.
But the Sun’s corona is thin and low in density and does not strip much material off the clumps, so scientists think most of the ‘shooting stars’ make it to the solar surface intact.
Their impacts have never been observed until now and SolO’s observations have revealed that this process can produce a brief, strong brightening with an upward surge of material and shock waves that reheat the gas above.
‘Shooting stars’ and meteors in Earth’s atmosphere are characterised by a trace behind the meteor’s path, formed when heated…
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