Monika C Korte, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Section 2.3 – Geomagnetism, Potsdam, Germany, Sanja Panovska, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany and Catherine Constable, UCSD, La Jolla, CA, United States