The polarization of the SiO masers in Orion - Maser emission from a rotating, expanding disk?

A model is proposed to explain the total intensity and linear polarization profiles of the SiO masers located in the vicinity of IRc2 in Orion. The total intensity shows a double-peaked profile, and the polarization position angles rotate with velocity in a highly symmetric fashion in both components. The fractional polarization is constant across the line profiles and of the same magnitude in both components. It is shown that these characteristics can be the result of kinematic effects in a rotating and expanding disk of maser emission which contains a magnetic field that rotates in the direction with azimuth around the disk. Examples of simple field geometries with this property include radial or azimuthal fields, or a field which is parallel to the local velocity vector everywhere in the disk.