They travel at speeds of up to five kilometers per hour: researchers report massive spiral movements on the surface of the sun that can observe very long oscillations of the star. Using computer simulations, they were able to clarify that the newly discovered waveform is caused by what is called the differential rotation of the sun. Scientists say the findings could now be used for further research into the internal structure and dynamics of our parent star.
Streams of Seething Emperors: The surface and interior of the sun are constantly in motion. This dynamic characteristic causes vibrations: the sun has been known to produce “high sounds” since the 1960s. The plasma currents near the surface of the sun are called the patterns of millions of sound waves. The term mode describes the temporal properties of waves.
These rapid oscillations of the sun have been recorded by Earth-based telescopes and space laboratories since the mid-1990s because they can provide important information: they help make conclusions about the sun’s internal features – such as how seismologists study the interior of the earth in terms of the effects of earthquakes. Using what is called heliosysmology, researchers have already been able to document rotation with respect to depth and heliographic latitude: so the matter of the sun moves at different speeds at different latitudes – this is called different rotation.
In the path of long-term oscillations
Already 40 years ago, it was theoretically shown that stars must have vibrations with significantly longer intervals in addition to shorter ones. So far, however, these effects have been relatively elusive and have not been clearly demonstrated. As the international team led by Laurent Kison of the Max Planck Institute for Solar System Research (MPS) in Kottingen explains, it is necessary to observe the horizontal movements of the sun’s surface over many years to demonstrate long-term vibrations. Exactly such information is now available: Researchers have been able to evaluate data from NASA’s Solar Dynamics Observatory (STO) space probe, which includes observations of the Sun over a period of ten years.
Scientists have now been able to detect a few dozen vibrations similar to the predicted long-term versions. Some have their maximum velocity at the poles, others at mid-latitudes and some near the sun’s equator. “Long-term oscillations manifest themselves as very slow rotational movements at five kilometers per hour on the surface of the sun, which is as fast as a human being,” says Ji-Chao Liang, co-author of the MBS.
To more accurately classify the newly discovered vibrations, the scientists compared their observational data with the results of computer models on the dynamics of the sun. Simulations include data on the internal structure of the sun, the properties of convection currents in the upper layers, and different cycles derived from heliocytological research. “The models allowed us to look into the sun and reveal the full three-dimensional structure of vibrations,” says Yudo Becky, co-editor of MBS.
Possibility for solar research
It became clear that the surface velocities of the sample corresponded well with the observed vibrations. Simulations also showed that wave patterns extend from the surface of the sun to a depth of 200,000 kilometers. Above all, it became clear: “All these new oscillations that we observe in the sun are strongly affected by different rotations,” says Damien Bornier, co-author of MBS. The latitude determines where the speed of the relative patterns of rotation of the sun is greatest. “Vibrations also sense the properties of the sun’s interior. In particular, the strength of turbulent movements and the viscous and convective motion of solar media, ”says his colleague Robert Cameron from MBS.
This clarifies: Research on long-term vibrations may also provide new insights into the interior of the sun. “Long-term vibrations can be used to learn more about turbulent processes, just as sound vibrations can be used with heliosismology to learn more about processes within the sun,” says Cameron. First author Kison adds: “The discovery of a new type of solar oscillation is very exciting. This allows us to infer such properties as the strength of the convection drive controlling the solar dynamo. “
Source: Max Planck Society, NASA, Featured Article: Astronomy & Astronomy, Thoi: 10.1051 / 0004-6361 / 202141462