arXiv 1012.57062010-12-28astro-ph.SR

理解太阳黑子生长和衰变的新途径

A New Approach in Understanding Growth and Decay of the Sunspots

K. M. Hiremath, Lovely, M. R

备注：: Totally 32 pages that include 57 figures

摘要：

从既往研究（Hiremath，2009年b; Hiremath 2010），关于太阳周期和活动现象的成因，可以理解，太阳黑子是通过对流包络中强环向场结构的阿尔芬波扰动叠加在不同深度形成的，并且在达到临界强度后，由于浮力，沿具有正（0.7-0.935 $R_{\odot}$）和负（0.935-1.0 $R_{\odot}$）旋转梯度的旋转等值线朝表面升高。由于这两个旋转梯度的物理条件，从磁感应强度方程出发，分别求解了黑子面积增长和衰减问题。结果表明，黑子在不同深度演化过程中的面积增长率是环境介质洛伦兹力的定常和脉动部分、纬向流速度的脉动、自转梯度的径向变化和$cot(\vartheta)$（其中$\vartheta$为同纬度）的函数。而黑子演化过程中不同深度黑子面积的衰减速率主要取决于磁扩散率、自转梯度和$sin^{2}(\vartheta)$。研究的要点是黑子面积的增长和衰减主要取决于黑子起源于正或负旋转梯度区。对于不同纬度和寿命的太阳黑子在其演化历史的表面上，无论是解析推导出的理论面积增长和衰减曲线匹配合理以及与观测到的面积增长和衰减曲线。

英文摘要：

From the previous study (Hiremath 2009b; Hiremath 2010), on the genesis of solar cycle and activity phenomena, it is understood that sunspots are formed at different depths by superposition of Alfven wave perturbations of a strong toroidal field structure in the convective envelope and after attaining a critical strength, due to buoyancy, raise toward the surface along the rotational isocontours that have positive (0.7-0.935 $R_{\odot}$) and negative (0.935-1.0 $R_{\odot}$) rotational gradients. Owing to physical conditions in these two rotational gradients, from the equation of magnetic induction, sunspot's area growth and decay problem is solved separately. It is found that rate of growth of sunspot's area during its evolution at different depths is function of steady and fluctuating parts of Lorentzian force of the ambient medium, fluctuations in meridional flow velocity, radial variation of rotational gradient and $cot(\vartheta)$ (where $\vartheta$ is co-latitude). While rate of decay of sunspot's area at different depths during its evolution mainly depends upon magnetic diffusivity, rotational gradient and $sin^{2}(\vartheta)$. Gist of this study is that growth and decay of area of the sunspot mainly depends upon whether sunspot is originated in the region of either positive or negative rotational gradient. For different latitudes and life spans of the sunspots on the surface during their evolutionary history, both the analytically derived theoretical area growth and decay curves match reasonably well with the observed area growth and decay curves.

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