标题： 强分层对流中大规模发电机自发形成表面磁结构 显示英文标题

标题： Spontaneous Formation of Surface Magnetic Structure from Large-scale Dynamo in Strongly-stratified Convection

摘要： 我们报道了首次成功模拟从笛卡尔几何中的强分层热对流自发形成表面磁结构的大尺度发电机效应。在我们的强分层模型中观察到的大尺度发电机具有与早期弱分层对流发电机模拟相似的物理特性，表明该现象是由$\alpha^2$-型机制引起的。 除了大尺度发电机外，我们发现只有在强分层大气的情况下，垂直磁场的大尺度结构才会在对流区表面自发形成。 垂直磁场的组织过程在上部对流区于数十个对流翻转时间尺度内完成，并且在发电机饱和阶段反复出现带状双极结构。 我们检验了几种可能作为表面磁结构形成的起源的候选机制，然后建议存在一种尚未被发现的机制来实现大尺度磁场结构的自组织，这种机制应该存在于强分层的对流大气中。 显示英文摘要

摘要： We report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly-stratified thermal convection in Cartesian geometry. The large-scale dynamo observed in our strongly-stratified model has physical properties similar to those in earlier weakly-stratified convective dynamo simulations, indicating that the $\alpha^2$-type mechanism is responsible for it. Additionally to the large-scale dynamo, we find that large-scale structures of the vertical magnetic field are spontaneously formed in the convection zone surface only for the case of strongly-stratified atmosphere. The organization of the vertical magnetic field proceeds in the upper convection zone within tens of convective turn-over time and band-like bipolar structures are recurrently-appeared in the dynamo-saturated stage. We examine possibilities of several candidates as the origin of the surface magnetic structure formation, and then suggest the existence of an as-yet-unknown mechanism for the self-organization of the large-scale magnetic structure, which should be inherent in the strongly-stratified convective atmosphere.