Are there field-free gaps near tau=1 in sunspot penumbrae?
arXiv:0806.4454 · doi:10.1086/591220
Abstract
The vertical stratification of the magnetic field strength in sunspot penumbrae is investigated by means of spectropolarimetric observations at high spatial resolution from the Hinode spacecraft. Assuming that the magnetic field changes linearly with optical depth we find that, in those regions where the magnetic field is more inclined and the Evershed flow is strongest (penumbral intraspines), the magnetic field can either increase or decrease with depth. Allowing more degrees of freedom to the magnetic field stratification reveals that the magnetic field initially decreases from \logτ_5 = -3 until \logτ_5 \simeq -1.0, but increases again below that. The presence of strong magnetic fields near the continuum is at odds with the existence of regions void of magnetic fields at, or right below, the τ_5=1 level in the penumbra. However, they are compatible with the presence of a horizontal flux-tube-like field embedded in a magnetic atmosphere.
arXiv comment10 pages, 11 figures (3 color figures, f2,f3,f5,f10,f11 low resolution). Accepted for publication in ApJ. To appear in issue 1, vol 686, October 2008
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