Are the sun’s magnetic arcs an optical illusion

(ORDO NEWS) — In extreme ultraviolet light, the Sun resembles a crumpled ball of yarn. Its surface is covered in abundance in giant radiant arcs, known as coronal loops, that float in the sun’s corona, or outer atmosphere.

Coronal loops are considered fundamental to the operation of the Sun. Understanding how they form, change and move is one of the key goals for understanding our nearest star.

At least that’s what researchers thought for a long time. Solar physicist Anna Malanushenko and her colleagues argue that some coronal loops may not be what they seem. It is possible that they are optical illusions created by folds or wrinkles in the much larger “sheets” of solar material that scientists call coronal veils.

Ever since the first images of coronal loops were taken in the late 1960s, scientists have been hypothesizing what their three-dimensional structure might be. The traditional model viewed them as magnetic “tubes” formed by the lines of the Sun’s magnetic field.

The tubes themselves are invisible; we catch the bright solar material that flows over them like water through a garden hose.

This “garden hose” model of coronal loops is in good agreement with known physics, and there was no reason to doubt it, at least at first. But over time, observations began to accumulate that did not fit into this model.

Something did not add up, and Malanushenko began to doubt the observations themselves. After all, the Sun’s corona is “optically thin,” or translucent, like fog or smoke. She wanted to understand what kind of optical tricks could take place in such an environment.

Malanushenko decided to simulate the process of observing coronal loops using a computer. She used a 3D simulation of the Sun, which was originally used to study flares, and then wrote a program to “observe”.

She ran a simulation, and her program took 2D “pictures” of the Sun, much like telescopes give us real 2D pictures of the Sun. Of course, bright arcs were visible on the frames – artificial coronal loops on the simulated Sun.

But unlike the real Sun, Malanushenko could pause the simulation of the Sun and look at the three-dimensional structures behind them.

“I have no words, this formation looks like clouds of smoke, or maybe a veil, or crumpled curtains,” says the physicist.

She created a simple model to illustrate how a veil can create the illusion of coronal loops. The shadow created on the wall is a two-dimensional image that we see with solar telescopes. The folds and wrinkles of the veil create a pattern of darker and lighter threads, somewhat similar to the image created by real tubular threads.

“But many of the threads that you can see are just a projection effect. They are not real,” says Anna Malanushenko.

Scientists were quick to clarify that not all coronal loops are visual illusions. There have been many cases where structures that look like garden hoses actually formed, even in the simulation that Malanushenko was studying.

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