  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 \log\tau_5 = -3 until
\log\tau_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 \tau_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.
