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arXiv 0807.1625astro-ph
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宁静太阳中的磁场分布:一个简化的模式方法

Magnetic field distribution in the quiet Sun: a simplified model approach

F. Berrilli, D. Del Moro, B. Viticchie

摘要:

我们模拟的动力学和安静的太阳磁性元素的演变产生的概率密度函数的磁场强度与这些元素。磁场的动态模拟通过一个数值模型,其中磁性元素被动驱动的平流场呈现时空相关性,模仿的粒化和mesogranulation尺度上观察到的太阳表面。由于在磁性元件会聚的地方发生的放大过程,场强度可以增加。从一个类似三角洲的概率密度函数为中心的B=30 G,我们得到的磁场强度高达2 kG(绝对值)。为了导出磁性元件的统计特性,执行若干模拟运行。该模型能够产生kG的磁场在一个时间间隔的顺序的造粒时间尺度。在静止区,合成太阳的平均无符号通量密度和平均磁能密度分别达到100 G和350 G。推导出的磁场强度的概率密度函数从B=30 G到B=100 G迅速减小,并在B=2 kG时出现次极大值。从这个结果可以得出,磁场>700 G主导无符号通量密度和磁能密度,尽管场强的概率密度函数在B=30 G时呈现最大值。

英文摘要:

We simulate the dynamics and the evolution of quiet Sun magnetic elements to produce a probability density function of the field strengths associated with such elements. The dynamics of the magnetic field are simulated through a numerical model in which magnetic elements are passively driven by an advection field presenting spatio-temporal correlations which mimicks the granulation and the mesogranulation scales observed on the solar surface. The field strength can increase due to an amplification process which takes place where the magnetic elements converge. Starting from a delta-like probability density function centered on B=30 G, we obtain magnetic field strengths up to 2 kG (in absolute value). To derive the statistical properties of the magnetic elements several simulation runs are performed. The model is able to produce kG magnetic fields in a time interval of the order of the granulation time scale. The mean unsigned flux density and the mean magnetic energy density of the synthetic quiet Sun reach respectively 100 G and 350 G in the stationary regime. The derived probability density function of the magnetic field strength decreases rapidly from B=30 G to B=100 G and presents a secondary maximum for B=2 kG. From this result it follows that magnetic fields >700 G dominate the unsigned flux density and magnetic energy density although the probability density function of the field strength presents a maximum for B=30 G.

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