太阳轴对称流对超颗粒的平流作用
The Advection of Supergranules by the Sun's Axisymmetric Flows
摘要：
我们表明，超颗粒的运动是一致的模型，在该模型中，他们只是平流的轴对称流在太阳的表面剪切层。我们产生了一个10天的系列模拟多普勒图像在15分钟的节奏，再现SOHO/MDI多普勒数据中看到的大多数空间和时间特性。我们的模拟数据有一个细胞流的光谱，只有两个组成部分-一个颗粒组成部分，峰值在球形波数约4000和超颗粒组成部分，峰值在波数约110。我们包括这些细胞成分的平流的轴对称流-差分旋转和纬向流-其随纬度和深度（波数）的变化是一致的观测。我们通过引入随机变化的频谱分量的相位的速率，再现作为时间和纬度的函数的互相关的水平，模仿蜂窝图案的演变。我们的模拟数据不包括任何波状特征的超颗粒，但可以重现以前归因于波状行为的旋转特性。我们发现旋转速度出现比实际的旋转速度快，这归因于投影效果。我们发现，测得的纬向流准确地代表了实际流量和观测表明极流向$65\degr-70\degr$纬度与赤道反细胞在极地地区。
英文摘要：
We show that the motions of supergranules are consistent with a model in which they are simply advected by the axisymmetric flows in the Sun's surface shear layer. We produce a 10-day series of simulated Doppler images at a 15-minute cadence that reproduces most spatial and temporal characteristics seen in the SOHO/MDI Doppler data. Our simulated data have a spectrum of cellular flows with just two components -- a granule component that peaks at spherical wavenumbers of about 4000 and a supergranule component that peaks at wavenumbers of about 110. We include the advection of these cellular components by the axisymmetric flows -- differential rotation and meridional flow -- whose variations with latitude and depth (wavenumber) are consistent with observations. We mimic the evolution of the cellular pattern by introducing random variations to the phases of the spectral components at rates that reproduce the levels of cross-correlation as functions of time and latitude. Our simulated data do not include any wave-like characteristics for the supergranules yet can reproduce the rotation characteristics previously attributed to wave-like behavior. We find rotation rates which appear faster than the actual rotation rates and attribute this to the projection effects. We find that the measured meridional flow does accurately represent the actual flow and that the observations indicate poleward flow to $65\degr-70\degr$ latitude with equatorward counter cells in the polar regions.
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