Study Blames Millions of Sun Whirlpools for Its Superheated Corona

A new study argues that millions of small whirlpools of hot gas, churning across the Sun's surface, could supply the energy that keeps its outer atmosphere, the corona, far hotter than the surface below it. Universe Today reported on the paper by Katariina Nykyri of Embry-Riddle, published in The Astrophysical Journal Letters.

The idea is a proposed explanation, not a settled one. Universe Today notes that scientists still have to confirm that enough of this energy actually reaches the corona.

What the solar telescope saw

Earlier this year, the Daniel K. Inouye Solar Telescope, perched atop Haleakala on Maui, captured extremely sharp images of the Sun's surface. According to Universe Today, scientists could make out whirlpools of plasma for the first time, each a few dozen kilometers across and scattered over the surface. That work was published in August.

Nykyri had been studying Kelvin-Helmholtz waves, and a university press release described her reaction to the images as a eureka moment. On Earth, these waves show up in broken ocean swells and in clouds with a rippled pattern. They also drive gas patterns on Jupiter. On the Sun, they form when fast-moving plasma slides past slower, magnetized plasma, and the swirling structures they create are the same kind of vortices the telescope resolved.

How the whirlpools could heat the corona

Nykyri set out to calculate how much energy these vortices carry and whether it adds up to what the corona needs. After accounting for the velocity shear, the density difference and the vertical heights of the vortices, she estimated that each one holds around two septillion ergs, a unit of energy commonly used in solar physics. Across the Sun's 1.4-million-kilometer surface, millions of them spin up and fade every few minutes, according to Universe Today.

As the vortices churn, their motion energy is passed into the Sun's magnetic fields. Nearby field lines get squeezed together into ultra-thin current lines, ranging from a few centimeters to meters across. Pushed past a certain point, the lines snap and rearrange in a process called magnetic reconnection. That process turns stored magnetic energy into heat and fast plasma jets, which are basic ingredients of the corona. Solar physicists have long suspected that reconnection plays a key role in heating it.

Why the corona ends up hotter than the surface

The vortices also trigger reconnection at the surface itself, so the puzzle is why the corona is so much hotter. Universe Today explains the answer as particle density. When a magnetic line snaps at the surface, the released energy is shared among trillions of neutral atoms, and each one warms only slightly. In the corona, atoms are far less plentiful but the same amount of energy is released, so each atom heats up much more.

According to the paper, only five to eight percent of the mechanical energy stored in the vortices would need to travel upward to the corona to replace the heat it radiates away. Even in coronal holes, the darker regions of the corona, a maximum of 21% of the vortex energy would be enough to maintain its temperature.

Why it matters for understanding our star

The temperature gap between the Sun's surface and its corona is one of the best-known open questions in solar physics, and Universe Today says data from various missions keep feeding new research on it. This is the second article in a few weeks that the outlet has written on the topic. Nykyri's work offers a concrete energy budget: it suggests that a modest share of the energy in small surface vortices could be enough, rather than requiring some rare or exotic process.

The study does not change anything for daily life, but it shows how sharper images of the Sun are letting researchers test long-standing ideas against real structures instead of only models. If the theory holds, some of the extreme heat of our star would trace back to relatively small plasma tornadoes drifting across its surface.

What researchers still need to confirm

Universe Today describes the paper as a major step but not the final word. Scientists still need to track how waves are transmitted and polarized as they pass through the chromosphere, the layer between the surface and the corona. That work would show whether as much energy reaches the chromosphere as Nykyri says is necessary to sustain the corona's temperature. Until then, the whirlpool explanation remains a promising proposal rather than an established result.

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Around Prague, based on reporting by Universe Today