Is the solar convection zone in strict thermal wind balance?
Is the solar convection zone in strict thermal wind balance?
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DOI：
10.1051/0004-6361/200913166
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发表时间：
2010-02-01
影响因子：
6.5
通讯作者：
Chitre, S. M.
中科院分区：
文献类型：
--
作者：
Brun, A. S.;Antia, H. M.;Chitre, S. M.
上下文。太阳的旋转剖面是圆锥形的，而不是像经典旋转流体动力学（如泰勒-普劳德曼定理）所期望的那样是圆柱形的。热耦合与速斜、斜压效应和热的纬向输送被认为可以解释这种特殊的旋转状态。利用日震反演太阳对流区热风平衡的角速度、熵和温度波动的有效性。方法。本文将太阳对流区三维流体动力学数值模拟得到的熵和温度波动与日震反演得到的太阳剖面进行了比较。三维数值模拟得到的太阳对流区温度和熵的波动幅度比地震反演得到的要小。地震反演提供了从地表约1 K到对流区底部高达100 K的温度变化，而在三维模拟中，整个对流区温度变化为10 K数量级，最高可达0.96 r圆点。在三维模拟中，斜压效应被发现是重要的倾斜欧米茄等等高线远离圆柱轮廓在大多数对流区，帮助在某些位置的雷诺兹和粘性应力。相反，由日震学反演的斜压效应要比得到观测到的角速度剖面所需的斜压效应大得多。太阳对流似乎不处于严格的热风平衡状态，雷诺应力在赤道加速度和观测到的圆锥角速度剖面中都起着主导作用。
Context. The solar rotation profile is conical rather than cylindrical as it could be expected from classical rotating fluid dynamics (e.g. Taylor-Proudman theorem). Thermal coupling to the tachocline, baroclinic effects and latitudinal transport of heat have been suggested to explain this peculiar state of rotation.Aims. To test the validity of thermal wind balance in the solar convection zone using helioseismic inversions for both the angular velocity and fluctuations in entropy and temperature. Methods. Entropy and temperature fluctuations obtained from 3D hydrodynamical numerical simulations of the solar convection zone are compared with solar profiles obtained from helioseismic inversions.Results. The temperature and entropy fluctuations in 3D numerical simulations have smaller amplitude in the bulk of the solar convection zone than those derived from seismic inversions. Seismic inversion provides variations of temperature from about 1 K at the surface to up to 100 K at the base of the convection zone while in 3D simulations they are of an order of 10 K throughout the convection zone up to 0.96 R-circle dot. In 3D simulations, baroclinic effects are found to be important to tilt the isocontours of Omega away from a cylindrical profile in most of the convection zone, helped by Reynolds and viscous stresses at some locations. By contrast the baroclinic effect inverted by helioseismology is much larger than what is required to yield the observed angular velocity profile.Conclusions. The solar convection does not appear to be in strict thermal wind balance, Reynolds stresses must play a dominant role in setting not only the equatorial acceleration but also the observed conical angular velocity profile.