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Description
The photosphere-corona system is governed by magnetohydrodynamic (MHD) processes spanning multiple scales. Photospheric plasma turbulent convection continuously reconfigures magnetic field topology, while coronal plasma dynamics respond to the underlying magnetic boundary conditions. This plasma-magnetic coupling produces coronal holes (CHs)—regions where coronal plasma flows freely along open magnetic field lines, forming high-speed solar wind streams that drive geomagnetic activity.
Coronal holes (CHs), the sources of high-speed solar wind, are characterized by photospheric magnetic flux imbalance, yet the spatial organization scale of this imbalance remains unclear. We combine statistical analysis of 60 CHs observed by SDO/HMI with numerical simulations to identify where magnetic imbalance emerges.
Applying sign-singularity analysis to line-of-sight magnetograms, we find CH regions exhibit lower cancellation exponents than quiet Sun regions, indicating reduced magnetic field oscillations. Significantly, 83% of CHs show cancellation function plateaus at 36 ± 12 Mm—the supergranular scale—indicating the field becomes magnetically smooth (non-oscillating) beyond this scale.
We validated these results through 1000 simulations using Voronoi tessellation to model supergranular networks with controlled magnetic imbalance. Synthetic magnetograms with unipolar magnetic elements along supergranular boundaries successfully reproduce observed CH cancellation functions, with plateaus at 27 ± 2 Mm matching the simulated supergranular network spacing.
Our results demonstrate that CHs form through magnetic field organization at supergranular scales, with unipolar elements concentrated along supergranular cell boundaries. This confirms that coronal funnel footpoints originate from the supergranular magnetic network, providing crucial insight into fast solar wind generation and space weather dynamics.
