Physical causes and consequences of the solar magnetic activity cycle

太阳磁场是定义太阳活动的所有物理现象的能源和动力驱动力。反过来，太阳磁场的时空演变又由流体磁发电机过程提供动力，利用其在太阳内部的导电流体流动中的能量，主要是湍流对流和差异旋转。这种流-场相互作用是一个基本的非线性过程，对于太阳内部条件，磁流体动力学(MHD)近似很好地描述了这一过程。一个非常突出的演化时间尺度是所谓的11年太阳磁活动周期，与全球太阳磁场的规则极性反转有关。这一周期调节了所有地球效应太阳喷发现象的频率，以及影响地球上层大气和地球空间环境的辐射和颗粒变异性。因此，了解和预测太阳磁活动周期是空间气象研究的基石，也是研究在更长时间尺度上展开的现象(称为空间气候)的基石。在过去的15年里，我的研究小组在国际舞台上稳固地定位自己，主要是通过制作第一个全球(3D)MHD模拟太阳对流产生规则的类似太阳的磁周期，最近通过成功地将这些模拟扩展到太阳类型恒星的观测恒星周期。另一个重要的最新突破是发展了一个混合发电机模式，它能够自洽地详细研究不断演变的表面磁性对磁周期后续演变的影响，这是将太阳数据同化成基于发电机的周期预测模拟的基本过程。*拟议研究的主要目的是加深我们对太阳(和恒星)磁活动周期(S)的物理理解，主要是通过全球磁流体模拟，但也通过几何和动态简化的模型，允许非常长的时间积分。研究目标包括：(1)了解决定磁周周期和幅度的物理机制；(2)了解磁周的变异性，包括强烈抑制活动的时期，例如17世纪的蒙德极小期；(3)通过将数据同化为发电机模式，改进太阳周期预报计划；(4)通过将数据同化为耀斑能量释放的雪崩模式，改进太阳耀斑预报计划。

The solar magnetic field is the energy source and dynamical driver of all physical phenomena collectively defining solar activity. The spatiotemporal evolution of the solar magnetic field, in turn, is powered by a hydromagnetic dynamo process, tapping its energy in the flow of electrically conducting fluid within the solar interior, chiefly turbulent convection and differential rotation. This flow-field interaction is a fundamentally nonlinear process, which for solar interior conditions is well-described by the magnetohydrodynamical (MHD) approximation. A very prominent evolutionary timescale is he so-called eleven year solar magnetic activity cycle, associated with the regular polarity reversals of the global solar magnetic field. This cycle modulates the frequency of all geoeffective solar eruptive phenomena, as well as radiative and particulate variability influencing the Earth's upper atmosphere and geospatial environment. Accordingly, understanding and predicting the solar magnetic activity cycle is a cornerstone of space weather research, as well as investigations of phenomena unfolding on much longer timescales (known as space climate).******Over the past 15 years my research group has solidly positioned itself on the international scene, primarily through the production of the first global (3D) MHD simulations of solar convection generating regular solar-like magnetic cycles, and more recently via the successfull extensions of these simulations to observed stellar cycles in solar-type stars. Another important and recent breakthrough is the development of a hybrid dynamo model allowing to investigate self-consistently in detail the impact of evolving surface magnetism on the subsequent evolution of the magnetic cycle, an essential process towards solar data assimilation into dynamo-based cycle prediction simulations.******The proposed research aims primarily at furthering our physical understanding of the solar (and stellar) magnetic activity cycle(s), primarily through global MHD simulations, but also via geometrically and dynamically simplified models allowing very long temporal integrations. Research objectives include: (1) understanding the physical mechanisms setting the magnetic cycle's period and amplitude; (2) understanding the origin of the cycle's variability, including epochs of strongly suppressed activity, such as the seventeenth century Maunder Minimum; (3) improving solar cycle forecasting schemes by data assimilation into dynamo models; (4) improving solar flare forecasting schemes by data assimilation into avalanche models for flare energy release.