Spatial and temporal distributions of transient horizontal magnetic fields with deep exposure

Abstract

We obtained a long exposure vector magnetogram of the quiet Sun photosphere at the disk center with wide FOV of $51"\times 82"$. The observation was performed at Fe I 525.0 nm with the shutter-less mode of the Narrow Band Filter Imager of the Solar Optical Telescope (SOT) on board Hinode satellite. We summed the linear polarization ($LP$) maps taken with time cadence of 60 seconds for 2 hours to obtain a map with as long an exposure as possible. The polarization sensitivity would be more than 4.6 (21.2 in exposure time) times the standard observation with the SOT spectro-polarimeter. The $LP$ map shows a cellular structure with a typical scale of $5"-10"$. We find that the enhanced $LP$ signals essentially consist of the isolated sporadic transient horizontal magnetic fields (THMFs) with life time of 1-10 min, and are not contributed by long-duration weak horizontal magnetic fields. The cellular structure coincides in position with the negative divergence of the horizontal flow field, i.e., mesogranular boundaries with downflows. Azimuth distribution appears to be random for the scale size of the mesogranules. Some pixels have two separate appearances of THMFs, and the measured time intervals are consistent with the random appearance. THMFs tend to appear at the mesogranular boundaries, but appear randomly in time. We discuss the origin of THMFs based on these observations.

17 pages, 2 figures, published in The Astrophysical Journal Letters

References in corpus (9)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• A Substantial Amount of Hidden Magnetic Energy in the Quiet Sun
• Magnetic Landscape of Sun's Polar Region
• Emergence of Small-Scale Magnetic Loops in the Quiet Sun Internetwork
• Quiet Sun internetwork magnetic fields from the inversion of Hinode measurements
• Emergence of small-scale magnetic loops through the quiet solar atmosphere
• Transient horizontal magnetic fields in solar plage regions
• Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun
• DOT tomography of the solar atmosphere. IV. Magnetic patches in internetwork areas

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