Classical helioseismology, which relies on acoustic waves, has been successfully applied to image the Sun’s interior rotation and structure. However, acoustic waves are insensitive to parameters such as magnetic fields, turbulent viscosity, and entropy gradients in the deep convection zone. Hence, scientists need to rely on interpreting the surface signatures of various waves to image the interiors.
By using helioseismic and correlation-tracking analyses of ground- and space-based observations, scientists from NYU Abu Dhabi’s (NYUAD) Center for Space Science have discovered a new set of waves in the Sun. These waves are high-frequency retrograde (HFR) waves that travel much faster than predicted by theory.
Scientists analyzed 25 years of space and ground-based data to detect these waves for this discovery. The high-frequency retrograde (HFR) waves – which move in the opposite direction of the Sun’s rotation – appear as a pattern of vortices (swirling motions) on the surface of the Sun and move at three times the speed established by current theory.
According to scientists, complex interactions between other well-known waves and magnetism, gravity, or convection could drive the HFR waves at this speed.
Research Associate Chris S. Hanson said, “If the HFR waves could be attributed to any of these three processes, the finding would have answered some open questions about the Sun. However, these new waves don’t appear to result from these processes, which is exciting because it leads to a whole new set of questions.”
Shravan Hanasoge, a co-author of the paper, said, “The very existence of HFR modes and their origin is a true mystery and may allude to exciting physics at play. It has the potential to shed insight on the otherwise unobservable interior of the Sun.”
- Hanson, C.S., Hanasoge, S. & Sreenivasan, K.R. Discovery of high-frequency retrograde vorticity waves in the Sun. Nat Astron (2022). DOI: 10.1038/s41550-022-01632-z