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Astron. Astrophys. 335, 341-350 (1998)

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The motion patterns of intranetwork magnetic elements

Jun Zhang 1, Jingxiu Wang 1, Haimin Wang 2 and Harold Zirin 3

1 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, P.R. China (zhj@sun10.bao.ac.cn)
2 Big Bear Solar Observatory, New Jersey Institute of Technology, USA
3 Solar Astronomy, 264-33 Caltech, Pasadena, CA 91125, USA

Received 29 December 1997 / Accepted 27 March 1998

Abstract

By tracing individual elements, we have measured horizontal velocity and studied motion patterns of Intranetwork (IN) magnetic elements for the first time. The magnetograms obtained at Big Bear Solar Observatory span an interval of 10-hour and cover an area of 310[FORMULA] arc sec2. In general, IN elements move radially and isotropically outwards from emergence centers to boundaries of supergranule cells at first. However, when they reach halfway between cell centers and boundaries, the motion of IN elements is non-isotropic, there are prior directions. Most of IN elements move towards the edges of network elements. There are two components of the velocity fields: radial velocity and circular velocity. From the centers to the boundaries of supergranule cells, the magnitude of the radial velocity decreases gradually; but that of the circular velocity increases obviously, at halfway between cell center and boundary, the circular acceleration reachs the maximum, about 10-1 m s-2. The mean circular velocity near the boundary is about 0.4 km s-1. The horizontal speeds deduced by tracing 768 intranetwork elements range from 0.05 km s-1 to 0.8 km s-1 with a peak distribution at 0.4 km s-1. Both within the supergranule cells and on the boundaries, there are convergence centers, but divergence centers always exist within supergranule cells.

Key words: Sun: granulation – Sun: magnetic fields – Sun: photosphere

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© European Southern Observatory (ESO) 1998

Online publication: June 12, 1998

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