Red giants are swollen, aging stars. Deep inside, an ocean of plasma churns: heat forces its way from the core to the surface, generating waves like a mighty surf. The star's magnetic field acts like an invisible seabed – it steers these waves, changing their height and speed. Previously, astronomers could only account for a smooth, symmetrical 'seafloor,' but the real picture is much more tangled.
A new calculation method now lets us recreate waves in magnetic fields of any shape. It turns out a wave can change its nature on the fly: upon hitting a strong field, it doesn't disappear but morphs into a different type of wave. Where the field weakens, waves even leap over 'magnetic ridges,' preserving their energy.
These findings make spectral diagnostics of stars more accurate. After all, a similar fate awaits our own Sun: in billions of years, it will become a red giant with a restless magnetic heart.
Red giants are our Sun’s future. When the hydrogen in its core runs out, it will swell up, and its magnetic field may become as chaotic as those of the stars we’ve studied.