A research on the force-freeness of photosphere magnetic field

Abstract

In this paper, the statistical studies on the force-freeness of photosphere magnetic fields are given. The studies are based on the vector magnetic fields observed by Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) on board Hinode. Three parameters (Fx/Fp,Fy/Fp, and Fz/Fp) are introduced to investigate the force-freeness of active regions photosphere magnetic field. Various thresholds and reductions of original resolutions are selected to calculated parameters. As for the resolutions, the reductions of original resolution data by a factor of 2, 4 and 8 are applied. While for thresholds, they are calculated from individual active region with the average of 75/77/57 G for Bx/By/Bz for all original data. When the resolution are reduced by 2, 4 and 8, the corresponding averages are 72/75/55, 66/68/49 and 57/59/41 G for Bx/By/Bz, respectively. It is found that the forces indicated by Fx/Fp and Fy/Fp increase as thresholds/resolutions increase/decrease. While for Fz/Fp the trends become more complex. For low threshold, when the resolution decrease the trends of Fz/Fp are similar as those of Fx/Fp and Fy/Fp, while for high threshold the trends of Fz/Fp are different from those of Fx/Fp and Fy/Fp. For original resolution, the forces indicated by Fy/Fp increase as thresholds increase, while for others resolution they decrease as the thresholds increase contrarily.