Motivated by recent observations that show increasing fractional linearpolarization with increasing wavelength in a small number of optically thin jetfeatures, i.e. "inverse depolarization", we present a physical model that canexplain this effect and may provide a new and complementary probe of the lowenergy particle population and possible helical magnetic fields inextragalactic radio jets. In our model, structural inhomogeneities in the jetmagnetic field create cancellation of polarization along the line of sight.Internal Faraday rotation, which increases like wavelength squared, acts toalign the polarization from the far and near sides of the jet, leading toincreased polarization at longer wavelengths. Structural inhomogeneities of theright type are naturally produced in helical magnetic fields and will alsoappear in randomly tangled magnetic fields. We explore both alternatives andfind that, for random fields, the length scale for tangling cannot be too smalla fraction of the jet diameter and still be consistent with the relatively highlevels of fractional polarization observed in these features. We also find thathelical magnetic fields naturally produce transverse structure for inversedepolarization which may be observable even in partially resolved jets.
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