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The emergence of active regions (ARs) closely relates to the solar dynamo andthe dynamical atmospheric phenomena.With high-resolution and long-lastingobservations from the New Vacuum Solar Telescope, we report a new dynamicactivity phenomenon named "fan-shaped activity (FSA)" in the emerging phase ofNOAA AR 12700. The FSAs are clearly observed at Ha wavelength and are closelyrelated to the dynamics of the adjacent arch filament system (AFS), includingthreads deformation and materials downward motions. On 2018 February 26, thetwo most representative FSAs appeared around 05:21 UT and 06:03 UT,respectively, and they firstly ascended and then decayed in around 10 minutes.At the ascending phase, accompanied by the uplifting of an adjacent AFS, eachFSA launches up at one end of the AFS and extends for up to 11 Mm. At thedecaying phase, the FSA gradually vanishes, and materials downflows towards theother end of the AFS are detected. After checking the evolution of the magneticfields of AR 12700, we find that each FSA is located between the end of an AFSand an adjacent magnetic patch with the same polarity and launches at the onsetof the collision and compression between these two magnetic patches. We proposethat the collision lifts up the AFS, and then the initially compact AFSlaterally expands, resulting in the formation of FSA. A cartoon model isproposed to depict the activities.

The dynamics of AR 12700 in its early emerging phase II: fan-shaped activities relevant to arch filament systems