Contribution to the Solar Mean Magnetic Field from Different Solar Regions

摘要: Seven-year-long seeing-free observations of solar magnetic fields with the Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO) were used to study sources mean field, SMMF, defined as net line-of-sight flux divided over disk area. To evaluate contribution different regions we separated all pixels each SDO/HMI magnetogram into three subsets: weak ( $B^{\mathrm{W}}$ ), intermediate $B^{\mathrm{I}}$ strong $B^{\mathrm{S}}$ ) fields. The component represents areas densities below chosen threshold; is mainly represented by network fields, remains decayed active (ARs), ephemeral regions. consists elements in ARs. derive a subset total linear regression coefficients between corresponding SMMF calculated. We found that i) when threshold level 30 Mx cm−2 applied, components together contribute from 65% 95% while fraction occupied area varies range 2 – 6% area; ii) as magnitude lowered 6 Mx cm−2, $B^{\mathrm{I}}+B^{\mathrm{S}}$ grows 98%, reaches value about 40% disk. In summary, regardless level, only small part contributes SMMF. This means photospheric structure an intermittent inherently porous medium, resembling percolation cluster. These findings suggest long-standing concept continuous vast unipolar surface are source may need be reconsidered.