标题： 太阳表层流的环图分析 显示英文标题

标题： Ring diagram analysis of near-surface flows in the Sun

摘要： 太阳振荡功率谱的环图分析通过对MDI数据获得的太阳外对流层中的速度场进行研究。三维功率谱被拟合到一个模型中，该模型在频率上具有Lorentzian轮廓，并包括波前被水平流动引起的波动，以获得作为水平波数和振荡模式径向顺序函数的次表面流的两个分量。 然后使用OLA和RLS方法对此信息进行反演，以推断水平流速随深度的变化。 通过这种方法获得的不同纬度的平均旋转速度与使用频率分裂数据进行的日震估计相当一致。 太阳表面下方的剪切层似乎由两部分组成，其中最外层达到约4 Mm的深度，在纬度不超过60度的情况下，速度梯度没有显示出任何反转。 在较深层部分，速度梯度在大约55度纬度附近显示出符号反转。 最外层得出的经向流速似乎与其他测量结果相似。 发现了一种从赤道向极地方向的经向流。 它在接近表面处的最大幅度约为30 m/s，且在外部剪切层中幅度几乎保持恒定。 显示英文摘要

摘要： Ring diagram analysis of solar oscillation power spectra obtained from MDI data is carried out to study the velocity fields in the outer part of the solar convection zone. The three dimensional power spectra are fitted to a model which has a Lorentzian profile in frequency and which includes the advection of the wave front by horizontal flows, to obtain the two components of the sub-surface flows as a function of the horizontal wave number and radial order of the oscillation modes. This information is then inverted using OLA and RLS methods to infer the variation in horizontal flow velocity with depth. The average rotation velocity at different latitudes obtained by this technique agrees reasonably with helioseismic estimates made using frequency splitting data. The shear layer just below the solar surface appears to consist of two parts with the outer part up to a depth of 4 Mm, where the velocity gradient does not show any reversal up to a latitude of 60 degrees. In the deeper part the velocity gradient shows reversal in sign around a latitude of 55 degrees. The zonal flow velocities inferred in the outermost layers appears to be similar to those obtained by other measurements. A meridional flow from equator polewards is found. It has a maximum amplitude of about 30 m/s near the surface and the amplitude is nearly constant in the outer shear layer.