There Are Tiny Bright Spots All Over The Sun, And We Can Finally Know Their Source

Sunspots aren’t the only spots decorating the dynamic face of our Sun. Solar physicists have closely studied tiny, fleeting patches of brightness that emerge and fade in less than a minute on average, in regions where loops of plasma rise from the solar surface.

They are called “sun points”. The analysis revealed that the short-lived phenomenon is likely the result of magnetic shenanigans – which wouldn’t be terribly surprising, given that magnetic field changes play a huge role in all sorts of wacky solar phenomena.

Nevertheless, the discovery suggests that the Sun is even more complex than we knew; analysis of these solar freckles could improve our understanding of the role of the magnetic field on solar dynamics, and of the magnetic field itself.

The fascinating spots were, ahem, spotted in images from the joint NASA-ESA Solar Orbiter, which was launched in 2020 as the Sun had just entered a new cycle and was becoming increasingly active.

On May 20, 2020, the spacecraft imaged some regions of magnetic flux, with magnetic loops emerging from the solar photosphere.

The solar magnetic field is a complicated beast. It is generated by a dynamo process inside the Sun – the movement of convective, conductive fluid that generates electric and magnetic fields. We don’t know exactly how it works, but the resulting magnetic field lines are numerous, dynamic and complex.

Sunspots, for example, are regions of particularly strong magnetic fields, and solar flares and coronal mass ejections are produced by magnetic field lines breaking and reconnecting.

The previously mentioned 11-year solar cycles are driven by the reversal of the magnetic field that takes place every 11 years, when the solar magnetic poles change places.

Led by astrophysicist Sanjiv Tiwari of Lockheed Martin’s Solar and Astrophysics Laboratory, a team of scientists took a closer look at one of these regions of magnetic flux, imaged in extreme ultraviolet wavelengths. They found tiny round dots of brightness almost hidden in the solar plasma.

Image processing highlighted the spots, allowing the team to study them in detail. In about an hour, they were able to observe and characterize about 170 points.

Overall, on average, the dots were about 675 kilometers (420 miles) in diameter (hey, that’s small for the Sun), were about 30% brighter than the surrounding plasma, and lasted on average only 50 seconds before to disappear again. About half of the dots remained isolated for the duration of their brief life, while the rest split into two, merged with other dots, or developed explosive loops or jets.

Comparison with data from NASA’s Solar Dynamics Observatory showing the Sun’s magnetic field revealed that the dots appeared throughout the field of view covered by Solar Orbiter, but were more densely clustered in more magnetically active regions, particularly the largest and brightest points.

The next step was to try to figure out what is causing the spots. This required the use of software simulating the magnetohydrodynamics of the solar atmosphere, Bifrost.

This simulation revealed that the points may be moments of magnetic reconnection between magnetic field lines emerging from the solar surface and magnetic field lines descending there.

Since magnetic reconnection in the solar atmosphere produces loops, this would explain why many points stretch into an extended loop as they evolve.

However, some of the dots did not appear in regions with entangled magnetic fields, suggesting that there could be multiple pathways for these mysterious features to form. One possible explanation, according to the team, is the propagation of magnetoacoustic waves in the solar plasma, which could produce shocks that result in dots.

But the mystery is far from solved. The dots imaged by Solar Orbiter aren’t the only dots seen on the Sun, and they’ve been observed in different wavelengths and different magnetic environments.

Future research, the team says, could help answer these open questions, bringing us closer to a true understanding of our fascinating star.

The research has been published in The Astrophysical Journal.

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