Characterization of Magnetic Flux in the Quiet Sun

Abstract

Observations of the quiet Sun observed with the Advanced Stokes Polarimeter are used to explore the distribution of apparent flux density (Bapp) and size scales of internetwork regions. For a typical disk-center quiet-Sun observation with excellent seeing (at a quantifiable angular resolution of 1''), average |Bapp| of 18.6 and 10.7 Mx cm-2 are found for the entire quiet region map and the internetwork region (2 σ noise < |Bapp| < 40 Mx cm-2), respectively. The weak internetwork flux appears to consist of two components: the spatially concentrated "granular" internetwork fields and a more diffuse, weaker component that has a characteristic size scale of a few arcseconds. Most of the internetwork area is occupied by measurable fields: 69% of the area has apparent flux density greater than 4.5 Mx cm-2 (3 σ), or 84% with flux density greater than 3.0 Mx cm-2 (2 σ). If the results of Hanle depolarization measurements are accepted, the internetwork flux detected here must be close (within a factor of 2-3) to being spatially resolved and must be intrinsically weak (10-30 G). Examination of Stokes polarimetry in quiet regions away from disk center indicates that the central cores of network flux, as indicated by high-polarization signals, do not have a high degree of mixed polarity. In contrast, regions immediately surrounding the network elements have stronger linear polarization than would be expected from locally vertical fields, indicating a high degree of mixed polarity. This mixed polarity may be the result of the continual "sweeping" of mixed polarity internetwork flux toward the network boundaries. When a quiet region has a significant imbalance of flux of opposite polarities, the internetwork imbalance is of the same sign and typically that of the network. The smaller imbalance in the internetwork suggests that a local dynamo produces most of the internetwork flux.