The role of Trees of Fragmenting Granules (TFG) in the formation of the solar supergranulation: a comparison between the MHD simulation and three Hinode observations

We present an exceptional scientific dataset allowing to investigate the structure and evolution of the interior of the solar supergranulation cells. Trees of Fragmenting Granules (TFG) and associated horizontal flows were evidenced from a 27 H MHD numerical simulation and 3 sequences from Hinode (JAXA/NASA) observations, respectively of 48 H, 25 H and 24 H duration, at disk centre (in 2007, 2013 and 2014). The simulation and observations are in agreement and show that the TFG generate horizontal flows (less than 1 km/s) with lifetime of a few hours over a scale of 10 arcsec (the mesogranulation pattern). These flows act on the diffusion of the intra-network magnetic elements. We introduced corks in the flow and they migrate towards the cell boundaries. Hence, the TFG appear as one of the major agent involved in supergranular cell formation and evolution. Scientific data are available in FITS format for processing, and some MP4 movies illustrate what we did.

本研究提供一套高质量科学数据集，可用于探究太阳超米粒胞（solar supergranulation cells）胞内的结构与演化规律。本研究通过一项时长27小时的磁流体力学（Magnetohydrodynamics, MHD）数值模拟，以及3组由日出卫星（Hinode，JAXA/NASA）获取的观测序列——各序列时长分别为48小时、25小时与24小时，观测位置均为日面中心，观测时段分别为2007年、2013年与2014年——证实了碎裂米粒树（Trees of Fragmenting Granules, TFG）及其伴随的水平流场的存在。数值模拟与观测结果一致性良好，结果表明：TFG可产生时速低于1 km/s的水平流场，该流场的寿命为数小时，空间尺度约为10角秒，对应介米粒组织（mesogranulation pattern）。此类流场会对网络内磁元的扩散过程产生调控作用。我们在流场中植入示踪浮标，发现其会向超米粒胞的边界迁移。由此可见，TFG是参与超米粒胞形成与演化过程的核心作用机制之一。本数据集的科学数据以FITS格式提供，可用于后续数据处理，同时附带部分MP4格式视频以展示研究相关过程。