Stereoscopic disambiguation of vector magnetograms: first applications to SO/PHI-HRT data

TL;DR

This paper demonstrates the first application of the Stereoscopic Disambiguation Method (SDM) to real solar data, successfully resolving the 180-degree ambiguity in vector magnetograms using only observations from two vantage points.

Contribution

The study applies the SDM to actual HRT data from Solar Orbiter, showing it can disambiguate vector magnetograms without model assumptions, unlike previous methods.

Findings

Successfully disambiguated vector magnetograms from Solar Orbiter and HMI data.

Produced spatially homogeneous and consistent magnetic field maps.

Identified sources of error and strategies for future improvements.

Abstract

Spectropolarimetric reconstructions of the photospheric vector magnetic field are intrinsically limited by the 180$^\circ$-ambiguity in the orientation of the transverse component. So far, the removal of such an ambiguity has required assumptions about the properties of the photospheric field, which makes disambiguation methods model-dependent. The basic idea is that the unambiguous line-of-sight component of the field measured from one vantage point will generally have a non-zero projection on the ambiguous transverse component measured by the second telescope, thereby determining the ``true'' orientation of the transverse field. Such an idea was developed and implemented in the Stereoscopic Disambiguation Method (SDM), which was recently tested using numerical simulations. In this work we present a first application of the SDM to data obtained by the High Resolution Telescope (HRT) onboard Solar Orbiter during the March 2022 campaign, when the angle with Earth was 27 degrees. The method is successfully applied to remove the ambiguity in the transverse component of the vector magnetogram solely using observations (from HRT and from the Helioseismic and Magnetic Imager), for the first time. The SDM is proven to provide observation-only disambiguated vector magnetograms that are spatially homogeneous and consistent. A discussion about the sources of error that may limit the accuracy of the method, and of the strategies to remove them in future applications, is also presented.