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The solar corona is the Sun's outer atmosphere, heated to millions of degrees. How it gets so hot is still unclear. One candidate is torsional waves: they twist magnetic field lines like a rubber band. Such waves were recently spotted with the new Daniel K. Inouye Solar Telescope.

But the telescope doesn't see the waves themselves; it sees light from iron ions that reaches us along the line of sight. Within that line, many different layers contribute, and their signals mix. Scientists simulated this on a computer: they took several magnetic tubes in the corona, launched waves along them, and calculated what light the telescope would see.

In quiet regions of the Sun, the torsional wave signal is visible but weaker than it actually is — due to line-of-sight mixing. In active regions, where the plasma is denser and more inhomogeneous, a similar signal appears even without torsional waves. It is created by strong eddies between the tubes, where the light is brightest.

So, in quiet regions torsional waves can be recognized, but in active regions it's easy to be misled. This matters for future observations: first you need to understand how inhomogeneous the medium is, and only then draw conclusions about waves.