About the world-wide magnetic-background noise in the millihertz frequency range J. Marfaing, J.-J Bois, R. Blancon, E. Pozzo di Borgo, G. Waysand, S. Gaffet, M. Yedlin, P. Barroy, M. Auguste, D. Boyer and A. Cavaillou EPL, 88 1 (2009) 19002 Published online: 26 October 2009 DOI: 10.1209/0295-5075/88/19002