Small-Scale Magnetic-Flux Emergence Observed with Hinode Solar Optical Telescope
Matsumoto, Takuma; Shibata, Kazunari; Tsuneta, Saku; Shimizu, Toshifumi; Ichimoto, Kiyoshi; Katsukawa, Yukio; Nagata, Shin'ichi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Lites, Bruce; Kitai, Reizaburo; Ueno, Satoru; Otsuji, Kenichi; Nakamura, Tahei; Watanabe, Hiroko; Title Alan M.
Japan, United States
Abstract
We observed small-scale magnetic-flux emergence in a sunspot moat region by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We analyzed filtergram images observed at wavelengths of Fe 6302Å, G band, and CaII H. In Stokes I images of Fe 6302Å, emerging magnetic flux was recognized as dark lanes. In the G band, they showed to be their shapes almost the same as in Stokes I images. These magnetic fluxes appeared as dark filaments in CaII H images. Stokes V images of Fe 6302Å showed pairs of opposite polarities at footpoints of each filament. These magnetic concentrations were identified to correspond to bright points in G band/CaII H images. From an analysis of time-sliced diagrams, we derived the following properties of emerging flux, which are consistent with those of previous studies: (1) Two footpoints separate each other at a speed of 4.2kms-1 during the initial phase of evolution, and decrease to about 1kms-1 10minutes later. (2) CaII H filaments appear almost simultaneously with the formation of dark lanes in Stokes I in an observational cadence of 2minutes. (3) The lifetime of the dark lanes in the Stokes I and G band is 8minutes, while that of Ca filament is 12minutes. An interesting phenomena was observed, that an emerging flux tube expanded laterally in the photosphere with a speed of 3.8kms-1. A discussion on the horizontal expansion of the flux tube is given with refernce to previous simulation studies.