On the origin of reverse polarity patches found by Hinode in sunspot penumbrae

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain e-mail: jos@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
³ Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan e-mail: ichimoto@kwasan.kyoto-u.ac.jp

Received: 19 May 2009
Accepted: 17 September 2009

Abstract

Context. The topology of penumbral magnetic fields is poorly known. The satellite Hinode has recently revealed penumbral structures of a magnetic polarity that is opposite to the main sunspot polarity. They may be direct confirmation that magnetic field lines and mass flows return to the solar interior throughout the penumbra, a configuration previously inferred from interpretation of observed Stokes profile asymmetries.

Aims. We try to point out the relationship between the reverse polarity features found by Hinode, and the model Micro-Structured Magnetic Atmospheres (MISMAs) proposed for sunspots.

Methods. The work is based on synthesis and inversion of sunspot Stokes profiles.

Results. Existing model MISMAs produce strongly redshifted reverse polarity structures as found by Hinode. Ad hoc model MISMAs also explain the asymmetric Stokes profiles observed by Hinode. The same modeling may be consistent with magnetograms of dark cored penumbral filaments if the dark cores are associated with the reverse polarity. This hypothetical relationship can only be identified in the far red wings of the spectral lines.

Conclusions. The reverse polarity patches may result from aligned magnetic field lines and mass flows that bend over and return to the solar interior throughout the penumbra.