The Ly-α profile and the magnetic field

Magnetograms in grey, overlaid with Ly-α brightness contours (white) nicely outline the magnetic network. Pixels are sorted by the depth of the self-reversal of their profile and 25% of the extreme cases are shown in red and green.




















Obviously self-reversed profiles cluster in the cell interior and flat profiles in the network. This suggests a lower opacity above the magnetic network as compared to the low-lying loops in the cell interior. The deapest self-reversals (or highest opacities) were found in coronal hole spectra.