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MODELING STATISTICAL PROPERTIES OF SOLAR ACTIVE REGIONS THROUGH DIRECT NUMERICAL SIMULATIONS OF 3D-MHD TURBULENCE

机译:通过3D-MHD湍流的直接数值模拟对太阳活动区域的统计特性进行建模

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Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents (ζ p ) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of the observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of ζ p against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase.
机译:已经使用太阳和日球天文台以及其他几种仪器拍摄的磁线图的视线数据研究了太阳光层湍流磁场的统计特性,特别是活动区域(ARs)的统计特性。这包括结构函数及其指数,平坦度曲线和相关函数。在这些工作中,使用非间歇K41模型对结构函数指数(ζp)与结构函数(p)的顺序的依赖性进行了建模。现在众所周知,AR是高度湍流的并且与强烈的间歇事件有关。在本文中,我们比较了Abramenko等人的一些观察结果。对数泊松模型用于对间歇性MHD湍流进行建模。接下来,我们分析在以下三种情况下从均质,不可压缩的3D-MHD湍流的直接数值模拟(DNS)获得的结构函数数据:三种情况:受力持续,自由衰减,以及最初被驱动并随后允许衰减的流动(情况3) 。各个DNS复制了在ζp对AR的p的图中看到的属性。我们还重现了AR平坦度和相关函数的间歇性中观察到的趋势和变化。从该分析表明,爆发开始阶段的AR可以以其最简单的形式被视为强迫3D-MHD湍流系统,并且爆发阶段代表衰减的3D-MHD湍流。还可以推断,从火炬的初始发作阶段到其最终的峰值发作阶段,间歇性的显着变化与系统到达初始发作阶段所花费的时间有关。

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