Using Observations of Solar Vector Magnetic Field from Dual View Points to Remove the 180^∘ Ambiguity

Abstract

With Solar Orbiter (SO) being put into successful operational observation, solar magnetic observation has entered the era of remote sensing from dual view points. In this paper, we carried out a simulation of correcting the 180^∘ ambiguity of transverse magnetic field with magnetograms from dual view points using an analytical formula as well as the observations made by the Helioseismic and Magnetic Imager (HMI). Magnetograms of a small mature sunspot at different times were used to simulate magnetograms from dual view points. We find that in order to correct the 180^∘ ambiguity of the vector magnetograms, it is sufficient to have a line-of-sight magnetogram from another view point to help to judge the direction of the transverse magnetic field. For the measuring accuracy of HMI, we estimate that a ∼ 30^∘ angle formed from two observational points is the smallest angle to correct the 180^∘ ambiguity around the place with the magnetic field strength of < 50 Gs. Correction for weaker magnetic fields surely needs larger separation angles, but considering projection effect, we propose that separation angles of ∼ 30^∘ are the optimal angles for future space missions with the scientific aim of correcting the 180^∘ ambiguity of vector magnetograms.