Sustaining the Quiet Photospheric Network: The Balance of Flux Emergence, Fragmentation, Merging, and Cancellation

Citations Over TimeTop 1% of 1997 papers

Abstract

The magnetic eld in the solar photosphere evolves as ux concentrations fragment in response to sheared ows, merge when they collide with others of equal polarity, or (partially) cancel against concentrations of opposite polarity. Newly emerging ux replaces the canceled ux. We present a quantitative statistical model that is consistent with the histogram of uxes contained in concentrations of magnetic ux in the quiet network for uxes exceeding B2 ] 1018 Mx, as well as with estimated collision frequencies and fragmentation rates. This model holds for any region with weak gradients in the magnetic ux density at scales of more than a few supergranules. We discuss the role of this dynamic ux balance (i) in the dispersal of ux in the photosphere, (ii) in sustaining the network-like pattern and mixedpolarity character of the network, (iii) in the formation of unipolar areas covering the polar caps, and (iv) on the potential formation of large numbers of very small concentrations by incomplete cancellation. Based on the model, we estimate that as much ux is cancelled as is present in quiet-network elements with uxes exceeding B2 ] 1018 Mx in 1.5 to 3 days, which is compatible with earlier observational estimates. This timescale is close to the timescale for ux replacement by emergence in ephemeral regions, so that this appears to be the most important source of ux for the quiet-Sun network ; based on the model, we cannot put signicant constraints on the amount of ux that is injected on scales that are substantially smaller than that of the ephemeral regions. We establish that ephemeral regions originate in the convection zone and are not merely the result of the reemergence of previously cancelled network ux. We also point out that the quiet, mixed-polarity network is generated locally and that only any relatively small polarity excess is the result of ux dispersal from active regions.

Related Papers

• → The fine structure of the quiet Sun(1985)59 cited
• → The Fine Structure of the Quiet Sun(1985)37 cited
• Mesostructure of the photosphere in quiet and active regions on the Sun.(1995)
• Time Variations of the Magnetic and Velocity Fields of the Quiet Photosphere(1974)
• The Size of Facular Points in the Quiet Photosphere(1981)