SOLARNET Conference: The Many Scales of the Magnetic Sun

For a long time, the study of the evolution of active regions in the solar photosphere has been limited by the transit time of the active regions over the solar disk as seen from Earth. Since its launch in February 2020, ESA/NASA's Solar Orbiter spacecraft provides us, from time to time, with the possibility to see the solar far side. The Polarimetric and Helioseismic Imager (SO/PHI), one of its ten instruments, delivers data of the solar photosphere in intensity and vector magnetic field. In February 2021, during Solar Orbiter’s first superior conjunction, the full disk telescope of SO/PHI acquired the first polarimetric data of the photospheric solar far side. We combine this data with data from the Helioseismic and Magnetic Imager (HMI) flying on board NASA’s Solar Dynamic Observatory. This enables an almost 360º view of the Sun and allows, for the first time, the tracking of active regions over a full solar rotation almost without interruption, from the near-Earth side to the far side. We study the evolution of four active regions in intensity and LOS magnetograms while they rotate from the near-Earth side, seen by HMI, to the solar far side, into the field-of-view (FOV) seen by SO/PHI. Three of the active regions decay on the solar far side and do not show any signal in intensity when reaching the FOV of SO/PHI. One active region crosses the disk as seen from Earth while appearing to decay. However, new flux emerges on the solar far side leading to the development of pores and a small sunspot before the region reaches the limb as seen in SO/PHI and reappears on the near-Earth side. We will present the longest almost uninterrupted study of the evolution of the magnetic field of active regions, achieved so far. This demonstrates the uniqueness of combining Solar Orbiter and near-Earth side observations to continuously study the evolution of active regions from their emergence to their decay.