Coronal magnetometry through the Hanle effect in the He I 1083 line

The magnetic field vector of the solar corona is not regularly and comprehensively measured, because of the complexity and degeneracy inherently present in the types of observations currently available. To address some of the current limitations of coronal polarimetry, we present computations that demonstrate the possibility of magnetometry using the unsaturated Hanle effect of the He I 1083 nm line. The main purpose of this investigation is to show how the geometric properties of the linear polarization of this line can be used to routinely diagnose the orientation of the field in erupting prominences, thus providing an important constraint on the Bz determination at 1 AU. In particular, observations from the Sun-Earth Lagrange points are found to provide excellent locations for the deployment of synoptic instruments aiming at the estimation of the magnetic field of Earth-directed Coronal Mass Ejections, achievable with a small (∼5 cm) space-borne coronagraph. We also present results from the  HAO eclipse expedition for the April 8 2024 total solar eclipse that point against the notion of coronal ``diffuse’’ coronal He I 1083 signals in favor of local (Earth) origin of those signals.