Scientists have proved the existence of a magnetic effect that could explain why solar-like stars spin very slowly at the end of their lifetime.
Numerical Simulations show a strong disturbation of the magnetic fields inside a star for higher than critical magnetic field values
Credits:AIP
Researchers from the Leibniz-Institut für Astrophysik Potsdam (AIP) made simulations of the magnetic fields of stars and compared the results with measurements from a laboratory experiment done at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The aim and result of this experiment was to detect, for the first time, a magnetic instability that had been theoretically predicted but never directly observed in a star. This magnetic effect would enhance the viscosity of hot plasma inside a star, leading to a strong deceleration of its core.
“We have known for years that the Tayler instability is an effective mechanism to explain the deceleration of stars, but until now there was no proof of its existence,“ says Günther Rüdiger, the principal investigator at AIP. “This experiment confirms our numerical predictions very well!“ adds Marcus Gellert, who conducted computer simulations to prepare the experiment.
In order to correlate with the low rotation rates observed in white dwarfs, or neutron stars, which are stars at the end of their life cycle, the core rotation rate of a solar-like star would have to drop by ninety percent. A permanently active magnetic instability could decelerate the core of a star very effectively and would explain observations in a simple and elegant way. The extent to which these laboratory results can be transferred to a real star has to be shown via new simulations and comparisons with observations in the near future. The confirmation of the Tayler instability underlines the importance of magnetic fields in stars and could be an important step towards creating more consistent models of stellar evolution.
The GATE experiment is a successor to the award-winning “PROMISE“ experiment which, in 2010, proved the existence of so-called magnetorotational instability (MRI), demonstrating a second successful partnership between astronomers from AIP and scientists at HZDR in shedding more light on stars in the lab.
Magnetism is one of the four fundamental forces in nature. Magnetic fields of the order from 10-13 to 1011 Tesla have been measured by direct or indirect means, spanning a range of 24 orders of magnitude! Magnetic fields influence the structure of matter on all scales. They can accelerate electrons to nearly the speed of light, and they are the key to understanding solar and stellar activity. In order to realistically describe dynamic processes in the universe, we need a collective understanding of the interaction between magnetic fields and matter on all scales of density, time and length – from the early universe to our Sun as it is today.
Numerical Simulations show a strong disturbation of the magnetic fields inside a star for higher than critical magnetic field values
Researchers from the Leibniz-Institut für Astrophysik Potsdam (AIP) made simulations of the magnetic fields of stars and compared the results with measurements from a laboratory experiment done at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The aim and result of this experiment was to detect, for the first time, a magnetic instability that had been theoretically predicted but never directly observed in a star. This magnetic effect would enhance the viscosity of hot plasma inside a star, leading to a strong deceleration of its core.
“We have known for years that the Tayler instability is an effective mechanism to explain the deceleration of stars, but until now there was no proof of its existence,“ says Günther Rüdiger, the principal investigator at AIP. “This experiment confirms our numerical predictions very well!“ adds Marcus Gellert, who conducted computer simulations to prepare the experiment.
In order to correlate with the low rotation rates observed in white dwarfs, or neutron stars, which are stars at the end of their life cycle, the core rotation rate of a solar-like star would have to drop by ninety percent. A permanently active magnetic instability could decelerate the core of a star very effectively and would explain observations in a simple and elegant way. The extent to which these laboratory results can be transferred to a real star has to be shown via new simulations and comparisons with observations in the near future. The confirmation of the Tayler instability underlines the importance of magnetic fields in stars and could be an important step towards creating more consistent models of stellar evolution.
The GATE experiment is a successor to the award-winning “PROMISE“ experiment which, in 2010, proved the existence of so-called magnetorotational instability (MRI), demonstrating a second successful partnership between astronomers from AIP and scientists at HZDR in shedding more light on stars in the lab.
Stellar and planetary magnetic fields play a key role in the formation and evolution of life on planets, as magnetic fields are shields against high-energy cosmic rays. Their existence also ensures the further evolution and survival of civilizations like ours. The research area “Cosmic Magnetic Fields” is dedicated to the exploration of these fields and the underlying magnetohydrodynamic mechanisms, as well as to the study of particle acceleration processes.
Citations:
Rüdiger G., Gellert M., Schultz M., Strassmeier K.G., Stefani F., Gundrum Th., Seilmayer M., Gerbeth G.: Critical fields and growth rates of the Tayler instability as probed by a columnar gallium experiment (eingereicht bei ApJ, preprint http://arxiv.org/abs/1201.2318)
Martin Seilmayer, Frank Stefani u.a.: Evidence for transient Tayler instability in a liquid metal experiment, in: Physical Review Letters
More information
GATE: Experiment & Theory for probing the magnetic "Tayler Instability“
Contacts and sources:
Prof. Dr. G. Rüdiger
Prof. Dr. G. Rüdiger
Leibniz-Institut für Astrophysik Potsdam (AIP)
Citations:
Rüdiger G., Gellert M., Schultz M., Strassmeier K.G., Stefani F., Gundrum Th., Seilmayer M., Gerbeth G.: Critical fields and growth rates of the Tayler instability as probed by a columnar gallium experiment (eingereicht bei ApJ, preprint http://arxiv.org/abs/1201.2318)
Martin Seilmayer, Frank Stefani u.a.: Evidence for transient Tayler instability in a liquid metal experiment, in: Physical Review Letters
More information
GATE: Experiment & Theory for probing the magnetic "Tayler Instability“
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