The first out-of-ecliptic observations of the polar magnetic field of the Sun

TL;DR

This paper reports the first direct remote-sensing measurements of the Sun's polar magnetic fields from out-of-ecliptic vantage points using Solar Orbiter, revealing new insights into polar magnetic flux distribution.

Contribution

It presents the first measurements of solar polar magnetic fields from out-of-ecliptic observations, demonstrating the capability of Solar Orbiter's instruments for high-latitude solar magnetic studies.

Findings

Different latitudinal flux distributions for north and south poles.

Observed flux dependence on viewing angle.

First high-resolution measurements of polar magnetic fields from outside the ecliptic.

Abstract

Direct remote-sensing observations of the solar poles have been hindered by the restricted view obtained from the ecliptic plane. For the first time ever, Solar Orbiter with its remote-sensing instruments observed the poles of the Sun from out of the ecliptic in the Spring of 2025. Here we report the first measurements of the magnetic field of the solar poles taken when Solar Orbiter was at heliographic latitudes ranging between 14.9$^\circ$ and 16.7$^\circ$. The data-sets were collected by the High Resolution Telescope of the Polarimetric and Helioseismic Imager (SO/PHI-HRT) on board Solar Orbiter. Two sets of observations, approximately one month apart, for the south and north pole are considered in this work. The magnetic flux and flux density measured during these campaigns are reported as a function of the heliographic latitude observed by SO/PHI-HRT. The net fluxes show a different latitudinal distribution for the two polar caps. We also discuss the observed dependence of the measured fluxes on the viewing angle. These first results highlight the importance of high-resolution direct measurements of the polar field, paving the way to the high-latitude observations planned for SO/PHI-HRT in the coming years.