Lara S Wagner, Carnegie Institution for Science Washington, Department of Terrestrial Magnetism, Washington, DC, United States, Michael J Walter, Carnegie Institution for Science, Geophysical Laboratory, Washington, DC, United States, Yanhao Lin, Carnegie Institution for Science Washington, Geophysical Laboratory, Washington, DC, United States and Dionysis I Foustoukos, Geophysical Laboratory, Washington Dc, DC, United States