Differential rotation of the Sun and magnetic diffusivity after the Maunder minimum as well as numerical models of the solar dynamo

太阳黑子是太阳活动的关键指标，因为我们有大约400年的信息。太阳黑子的位置直到1874年才被利用。在17世纪蒙德极小期，观测到的黑子很少，为了填补1874年开始的观测与蒙德极小期的零散观测之间的空白，我们计划对1749-1796年的约1000次观测进行精确分析。将确定18世纪太阳的微分旋转和当时的磁扩散率，并进行活动经度的搜索。将研究南北不对称和南北半球周期的一致性。这些太阳图像将提供给虚拟太阳天文台。这项工作将包括发电机过程的理论建模，该过程可能导致观察到的行为，基于测量的微分旋转和蒙德极小值后不久的扩散率。我们特别要解决的问题是，螺旋通量必须允许发电机增长足够快，并达到足够高的饱和振幅。虽然这些研究大多是在笛卡尔盒子中进行的，但我们计划在球壳中进行模拟，基于驱动的螺旋湍流和更现实的对流。

Sunspots are the key indicator for solar activity, since we have information about them for about 400 years. The positions of sunspots have been utilized only since 1874. During the Maunder minimum period in the 17th century, very few spots were observed, in order to fill the gap between the measurements starting in 1874 and the scattered observations known from the Maunder minimum, we plan the precise analysis of about 1000 observations made by in 1749-1796. The differential rotation of the Sun in the 18th century as well as the magnetic diffusivity at that time will be determined, and a search for active longitudes will be performed. North-south asymmetries and the coherence of the cycle in the northern and southern hemispheres will be studied. The solar images will be made accessible to the Virtual Solar Observatory.The work will include theoretical modelling of dynamo processes that can lead to the observed behaviour, based on the measured differential rotation and diffusivity shortly after the Maunder minimum. We are particularly addressing the issues of helicity fluxes necessary to allow for dynamos growing fast enough and to high enough saturation amplitudes. While most of these studies were performed in Cartesian boxes, we plan to run simulations in spherical shells, based on both driven helical turbulence and more realistic convection.