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Researchers Get Distance of the Convective Overshooting Region in Low-mass Stars
Author: | Update time:2019-09-17           | Print | Close | Text Size: A A A

The convection occurs where the buoyancy is in the same direction as the velocity. This convection is turbulent in the stellar. Inside the stellar convection core, the turbulent can be treated with the local mixing-length theory model (classical convection model). Turbulent materials do not just stop at the boundary of convective core, and it will go beyond the boundary. This is convective overshooting.

The mixing of overshooting region is a problem that has not been solved. A k–ω model has been proposed to deal with the mixing in convective and overshooting regions based on fluid dynamics. This model is suitable to treat turbulent convection of the stars. It can describe not only the convection zone but also the convective overshoot zone.

Recently, GUO Fei and LI Yan from Stellar Astrophysics Group of Yunnan Observatories of the Chinese Academy of Sciences published their new results about convective overshooting in Low-mass Stars in The Astrophysical Journal. They found the distance of the overshooting region in Low-mass stars is about 0.072 pressure scale height(Hp).

By using the k–ω model in low-mass stars, they got the distance of the overshooting region. There are two parts in the overshooting region, one is the completely mixing region of about 0.027Hp, and the other is the partial mixing region of about 0.045Hp.

The mixing of semiconvection region is also uncertain. A semiconvective region develops naturally above the convective core computed with the classical model. However, it does not occurs computed with the k–ω model.

The researchers also calibrated the free parameter for the classical overshoot. Its value is determined usually by experience. By using the k–ω model, they found that a suitable value of the free parameter is about 0.008 for the low-mass stars.

Contact:

GUO Fei, Yunnan Observatories, CAS

guofei@ynao.ac.cn

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