Polar Facular Observations by the Zurich Observatory: A Window to the Evolution of the Polar Fields during the Weakest Cycles of the Last 200 Years

The solar polar magnetic fields are believed to be a surface manifestation of the large-scale field that acts as the seed for each solar cycle. Because of this, they have received a lot of recent attention as the best proxy for solar cycle prediction.Polar magnetic fields have been measured systematically since the 1970s and polar facular counts (which are directly correlated with polar field strength) have been used to infer the evolution of the polar fields going back to 1906. However, this period does not cover the solar minima of cycle 12 and 13 which preceded the weakest cycles of the last 200 years. These cycles are of great interest due to their similarity with solar cycle 24, which was preceded by the deepest minimum observed so far during the space age.Here we present the results of a project to count polar faculae using recently digitized and released observations taken by the Zurich Observatory (1887 to 1937). These observations have the potential of extending our proxy for the polar fields further back into this period of great interest and help us test the validity of our understanding.