SOLAR SURFACE MAGNETO-CONVECTION AND DYNAMO ACTION
SOLAR SURFACE MAGNETO-CONVECTION AND DYNAMO ACTION
复制标题
太阳表面磁对流和发电机作用
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Å. Nordlund
中科院分区：
文献类型：
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作者：
R. Stein;Å. Nordlund
利用中尺度和近太阳表面颗粒尺度的磁对流模拟，研究了小尺度发电机活动和磁通管的出现和消失。对流运动在颗粒间通道中产生高度间歇性的磁场，这些磁场聚集在下面的中颗粒尺度单元的边界上。在观测这些磁场时，重要的是要注意到望远镜的点扩散函数和能见度显著降低了观测到的斯托克斯分布的幅度。由于强烈的层结，这些表层中的等离子体和场几乎没有再循环。相反，循环是通过与对流区的深层交换来进行的。等离子体和磁场从表面下降到对流区的底部，在那里它们再次上升到表面。由于深对流区的周转时间约为一个月，而且由于质量守恒，从对流区底部上升的等离子体只有一小部分到达地面，因此这种发电机的时间常数很长，几乎没有磁能存在于近地表。因此，作用于弱非相干场的发电机是全局的，而不是局部的表面发电机。
Magneto-convection simulations on meso-granule and granule scales near the solar surface are used to study small scale dynamo activity and the emergence and disappearance of magnetic flux tubes. Convective motions produce highly intermittent magnetic fields in the intergranular lanes which collect over the boundaries of the underlying meso-granular scale cells. When observing these magnetic fields, it is important to note that the telescope point spread function and seeing significantly reduce the amplitudes of the observed Stokes profiles. Because of the strong stratification, there is little recycling of plasma and field in these surface layers. Recycling instead occurs by exchange with the deep layers of the convection zone. Plasma and field from the surface descend to the bottom of the convection zone, where they rise again toward the surface. Because the turnover time in the deep convection zone is of order a month, and because only a tiny fraction of plasma rising up from the bottom of the convection zone reaches the surface due to mass conservation, the time constant for this dynamo is long and little of the magnetic energy resides in the near surface layers. Thus the dynamo acting on weak incoherent fields is global, rather than a local surface dynamo.