A new type of high-frequency acoustic wave propagating in the sun appears to be against expectations have discovered.
The waves appear on the Sun’s surface as patterns of swirling vortices moving against the Sun’s rotation. The worry is that these high-frequency retrograde vorticity waves appear to be moving three times faster than the theory predicted, and solar physicists are unable to find out why.
The discovery suggests that there is new solar physics to discover and also provides new insights into the Sun’s internal properties and activities.
Although we cannot really see inside the Sun, stars are outstanding in that their internal processes can frequently be inferred based on surface activity.
Acoustic waves in particular can tell us a lot. They’re generated near the surface and then partially or fully reflected inward, where they resonate and create acoustic oscillations. Solar scientists study these oscillations to learn more about the Sun’s interior.
A group of scientists led by solar physicist Chris Hanson of New York University, Abu Dhabi, studied & analyzed such data, using 24 years of observations from the ground-based Global Oscillation Network Group and 10 years of observations from the space-based Helio-seismic and Magnetic Imager.
In the data, researchers discover a very consistent signal that their analysis reveals as the presence of waves never seen before. These formed a vortices pattern on the sun’s surface with an anti-symmetry between the north and south poles moving against the solar rotation.
However, the fact that these waves are moving three times faster than expected poses a mystery. The team examined a number of possibilities for what was happening.
First, the Coriolis force, the way a spinning spherical object’s equator moves faster than its poles, excites vorticity waves that we know can occur here on Earth.
So, there are 3 mechanisms which could affect and modify the waves: magnetism, gravity or convection. However, none of them could explain the observation data.
“If high-frequency retrograde waves could be attributed to one of these three processes, then the finding would have answered some of the unanswered questions we still have about the Sun,” says Hanson.
“However, these new waves do not appear to be the result of these processes and this is exciting because it results to an entire new set of questions.
This suggests the researchers to say that our models of the Sun are missing or poorly constrained information that could solve the puzzle.
It is also relevant something closer to home. Scientists found high-frequency waves in the ocean, propagating up to 4 times greater than theory predicted, which have proven very hard to explain. Studying both phenomena together could help to resolve the mystery behind them.
“The very-existence of high-frequency retrograde modes and their origin is a real mystery and could allude to the exciting physics at play,” says physicist Shravan Hanasoge of New York University, Abu Dhabi.
“It has the potential to shed light on the otherwise unobservable interior of the Sun.
The research was published in Nature Astronomy.