Speaker
Description
First Name: Ajay kumar
Last Name: Yadav
Affiliation: Max Planck Institute for Solar System Research, Goettingen, Germany
All Authors: Ajay Kumar Yadav, Natalie Krivova, Theodosios Chatzistergos, Sami K. Solanki, Kinga Albert, Johann Hirzberger, Gherardo Valori, Daniele Calchetti, David Orozco Su´arez, Hanna Strecker, Artem Ulyanov, Julian Blanco Rodr´ıguez
Abstract: Brightness of the Sun in the Ca II K line is a good proxy of solar magnetic activity and can therefore be used to reconstruct past variations in solar magnetism and irradiance before magnetograms were available. To establish a quantitative relation between brightness and magnetic flux, the Ca II K brightness must be calibrated against the solar surface magnetic field on a pixel-by-pixel basis. Such calibrations have been successfully performed over most of the solar disc, but remain uncertain close to the solar limb due to the low signal-to-noise ratio and foreshortening. The unique vantage point of Solar Orbiter, particularly during its near- quadrature configuration with Earth, offers a solution. We combine observations of the Sun in the Ca II K line from the Kanzelhoehe Solar Observatory with near-simultaneous magnetograms from the Polarimetric and Helioseismic Imager (PHI) onboard Solar Orbiter. This configuration enables regions near the limb in Ca II K images to be observed close to the disc center by SO/PHI. This allows a significantly more reliable assessment of the magnetic field in the near-limb regions and thus a more accurate calibration of the Ca II K brightness to the magnetic field. We will present the resulting contrast – magnetic field relation for near-limb regions and compare it with previous studies.