Small Scale Magnetic Flux Emergence Observed with Hinode/Solar Optical Telescope

TL;DR

This study observed small-scale magnetic flux emergence in a sunspot moat region using Hinode/SOT, revealing detailed dynamics and properties of emerging flux tubes with high-resolution imaging.

Contribution

First detailed observational analysis of small-scale magnetic flux emergence in a sunspot moat region with Hinode/SOT, including flux tube expansion and footpoint separation.

Findings

Footpoints separate at 4.2 km/s initially, slowing to 1 km/s.

Dark lanes and filaments appear almost simultaneously within 2 minutes.

Flux tube expands laterally at 3.8 km/s.

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 in the wavelengths of Fe 6302 angstrom, G-band and Ca II H. In Stokes I images of Fe 6302 angstrom, emerging magnetic flux were recognized as dark lanes. In G-band, they showed their shapes almost the same as in Stokes I images. These magnetic flux appeared as dark filaments in Ca II H images. Stokes V images of Fe 6302 angstrom showed pairs of opposite polarities at footpoints of each filament. These magnetic concentrations are identified to correspond to bright points in G-band/Ca II H images. From the analysis of time-sliced diagrams, we derived following properties of emerging flux, which are consistent with the previous works. (1) Two footpoints separate each other at a speed of 4.2 km/s during the initial phase of evolution and decreases to about 1 km/s in 10 minutes later. (2) Ca II H filaments appear almost simultaneously with the formation of dark lanes in Stokes I in the observational cadence of 2 minutes. (3) The lifetime of the dark lanes in Stokes I and G-band is 8 minutes, while that of Ca filament is 12 minutes. An interesting phenomena was observed that an emerging flux tube expands laterally in the photosphere with a speed of 3.8 km/s. Discussion on the horizontal expansion of flux tube will be given with refernce to previous simulation studies.