Vector magnetic fields of Solar Granulation

Observations of quiet Sun from the Solar Optical Telescope/SpectroPolarimeter (SOT/SP) aboard the Hinode spacecraft would reveal the magnetic characters of the solar photosphere. By making use of the deep mode observations of three quiet regions, we have statistically studied the vector magnetic fields of solar granulation. More than 2000 normal granules are manually selected to form a sample. It is recognized that some granules are even darker than the mean photosphere in intensity, and there is a linear correlation between intensity and Doppler velocity in granules. The distributions of longitudinal and transverse apparent magnetic flux densities, Doppler velocity and continuum intensity of granules are obtained, and their unsigned magnetic flux measured. Two approaches are carried out in this study. First we obtained the magnetic properties of granulation by averaging the measurements for all the sampling granules. Secondly, we reconstructed an average granular cell based on a sub-sample, and obtained the detailed distribution of apparent magnetic flux density within the model granular cell. All the results have been compared with that of inter-granular lanes and a few typical abnormal granules. Our statistic analysis reveals the following results: (1) The unsigned magnetic flux of individual granule spans the range from 1.1× 10 Mx to 3.3× 10 Mx with a peak distribution at 1.6×10 Mx; (2) The unsigned longitudinal apparent flux density of granules ranges from almost zero to 212 Mx cm with a mean longitudinal apparent flux density of 12 Mx cm, while the transverse apparent flux density of granules ranges from 4 to 218 Mx cm with a mean transverse apparent flux density of 79 Mx cm. The longitudinal and transverse apparent magnetic flux densities of granules are positively correlated, and the longitudinal apparent flux density of granules is weaker than the corresponding transverse apparent flux density; (3) The magnetic inclination of granules with respect to the surface that’s perpendicular to the line-of-sight falls in the range of 4.8 to 76.7 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; E-mail: [email protected], [email protected], [email protected]