Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun*
Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan e-mail: email@example.com
Accepted: 25 October 2008
Aims. The properties of transient horizontal magnetic fields (THMFs) in both plage and quiet Sun regions are obtained and compared.
Methods. Spectro-polarimetric observations with the Solar Optical Telescope (SOT) on the Hinode satellite were carried out with a cadence of about 30 s for both plage and quiet regions located near the disk center. We selected THMFs that have net linear polarization (LP) higher than 0.22%, and an area larger than or equal to 3 pixels, and compared their occurrence rates and distribution of magnetic field azimuth. We obtained probability density functions (PDFs) of magnetic field strength and inclination for both regions.
Results. The occurrence rate in the plage region is the same as for the quiet Sun. The vertical magnetic flux in the plage region is ~8 times more than in the quiet Sun. There is essentially no preferred orientation for the THMFs in either region; however, THMFs in the plage region with higher LP have a preferred direction consistent with that of the plage-region's large-scale vertical field pattern. PDFs show that there is no difference in the distribution of field strength of horizontal fields between the quiet Sun and the plage regions when we avoid the persistent vertical flux concentrations for the plage region.
Conclusions. The similarity between the PDFs and the occurrence rates in plage and quiet regions suggests that a local dynamo process due to the granular motion may generate THMFs all over the Sun. The preferred orientation for higher LP in the plage indicates that the THMFs may be somewhat influenced by the larger-scale magnetic field pattern of the plage.
Key words: Sun: photosphere / Sun: magnetic fields / Sun: faculae, plages
© ESO, 2009