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A group of solar physicists led by Laurent Gizon of the Max Planck Institute for Solar System (MPS) and Laurent Gizon of the University of Göttingen in Germany reported that the sun’s global oscillation period is very long, which can be compared with the 27-day solar cycle. Comparable. Rotation period. The oscillation appears as a rotating motion on the surface of the sun at a speed of approximately 5 kilometers per hour. These movements are measured by analyzing 10-year observations from NASA’s Solar Dynamics Observatory (SDO). Scientists have used computer models to show that the newly discovered oscillations are resonance modes, and their existence is attributed to the differential rotation of the sun. Oscillations will help establish new methods for detecting the interior of the sun and gain information about the internal structure and dynamics of our stars. The scientists described their findings in a letter published today in the journal Astronomy and Astrophysics.

In the 1960s, people discovered the high pitch of the sun: the sun rang like a bell. Millions of short-period (close to 5 minutes) acoustic oscillation modes are excited by convective turbulence near the sun's surface and are trapped inside the sun. Since the mid-1990s, ground-based telescopes and space observatories have been continuously observing these 5-minute oscillations, and they have been very successfully used by helioseismologists to understand the internal structure and dynamics of our stars—just like seismologists Understanding the interior of stars is the same. Come to the earth by studying earthquakes. One of the triumphs of helioseismology is to map the rotation of the sun as a function of depth and latitude (differential rotation of the sun).

In addition to the 5-minute oscillation, longer period oscillations were predicted in stars more than 40 years ago, but they have not been discovered on the Sun until now. "Long-period oscillations depend on the rotation of the sun; they are not acoustic in nature," said Laurent Gizon, lead author of the new study and director of MPS. "Detecting the long-period oscillations of the sun requires measuring the horizontal movement of the sun's surface over the years. Continuous observations from the on-board SDO and magnetic imager (HMI) are very suitable for this purpose."

The team observed dozens of oscillation modes, each with its own oscillation period and spatial dependence. Some oscillation modes have maximum velocities at the poles, some at mid-latitudes, and some near the equator. The fastest mode near the equator is the Rossby mode, which the team has already identified in 2018. How fast can a person walk," said Liang Zhichao of the Ministry of Public Security. Kiran Jain from NSO and B. Lekshmi and Bastian Proxauf from MPS confirmed this result with data from the Global Oscillation Network Group (GONG), the network It is composed of six solar observatories in the United States, Australia, India, Spain and Chile.

To determine the nature of these oscillations, the team compared the observed data with computer models. MPS graduate student Yuto Bekki explained: “These models allow us to see the inside of the sun and determine the complete three-dimensional structure of the oscillation.” In order to obtain the model oscillation, the team first inferred a model of the solar structure and rotation difference from helioseismology. In addition, the model also considers the strength of the upper convection drive and the amplitude of turbulent motion. The free oscillation of the model is found by considering the small amplitude disturbance to the solar model. The corresponding speed of the surface closely matched the observed oscillations and allowed the team to recognize patterns.

"All these new oscillations we observe on the sun are strongly influenced by the sun's differential rotation," said MPS scientist Damien Fournier. The correlation between the rotation of the sun and the latitude determines the position where the model has the largest amplitude. "Oscillations are also sensitive to the characteristics of the sun: especially the intensity of turbulent motion and the relative viscosity of the solar medium, as well as the intensity of convection drive," said Robert Cameron from MPS. This sensitivity is very strong at the bottom of the convective zone, about 200,000 kilometers from the sun's surface. “Just as we use sound wave oscillations to understand the speed of sound inside the sun through helioseismology, we can use long-period oscillations to understand turbulent processes,” he added.

"The discovery of a new type of solar oscillation is very exciting because it allows us to infer properties, such as the strength of the convective drive that ultimately controls the solar generator," said Laurent Gizon. The diagnostic potential of the long-term model will be fully realized in the next few years through the use of a new exascale computer model developed as part of the WHOLESUN project, which is supported by a collaborative grant from the European Research Council in 2018. Further exploration of distant stars are the roundest objects observed in nature. More information: Laurent Gizon et al. Solar Inertial Models: Observation, Recognition, and Diagnostic Commitment, Astronomy and Astrophysics (2021) DOI: 10.1051/0004-6361 /202141462 Journal Information: Astronomy Astrophysics

Citation provided by the Max Planck Association: Discovery of the long-term oscillation of the sun (2021, July 20), retrieved on December 14, 2021, from https://phys.org/news/2021-07-long- The period-oscillations-sun.html file is protected by copyright. Except for any fair transaction for private learning or research purposes, no part may be copied without written permission. The content is for reference only.

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