Speaker
Description
First Name: Jonas
Last Name: Sinjan
Affiliation: Max Planck Institute for Solar System Research
All Authors: Jonas Sinjan, Johann Hirzberger, Daniele Calchetti, Gherardo Valori, Xiaohong Li, Sami K. Solanki and the PHI team
Abstract: Active regions are the source region for the most energetic phenomena on the Sun. Maps of active regions’ photospheric magnetic fields, and derived quantities such as magnetic free energy and current density are often used as the primary inputs in flare forecasting models. One limitation of these magnetic field maps, and hence the derived quantities, is that they have always originated from observatories with the same singular view point: that from Earth. It is well known that the inference of the photospheric magnetic fields suffers off disc centre (heliocentric angles > 45-60 degrees), thus further restricting the time of reliable data for building forecasting models. With the Solar Orbiter mission, and the PHI instrument on board, during favourable orbital configurations, we can augment existing Earth-based observations and provide a longer coverage of reliable observations of an active region. Concurrently we can use these periods to investigate the true systematics of near limb observations now that a different vantage point is available. From 12 - 17th October 2023 Solar Orbiter observed an active region (NOAA 13465), initially separated from Earth by an angle of 80 degrees decreasing to 54 degrees. NOAA 13465 was just visible inside the East limb as seen by Earth at the start of the campaign. In this work we compare high resolution SO/PHI observations with the SHARP (Space Weather HMI Active Region Patches) maps from SDO/HMI. These observations provide a broad range of different viewing angles (μ=cos(θ)) between SO/PHI and SDO/HMI where one instrument can probe the impact of the viewing direction on the magnetic field inference.