Variation of sunspot numbers, R (black shaded area), and modeled near-Earth IMF, B _m (blue line). Even- and odd-numbered solar cycles are shaded white and gray and the Maunder minimum (MM) is in cyan. R is the international sunspot number extended back to before the MM using a linear regression of the group sunspot number ( R/30 is shown to allow use of a common vertical scale). B _m is derived from the OSF modeled from R using the continuity equation (Owens & Lockwood 2012), which is subsequently converted into near-Earth IMF using an empirical relationship (Lockwood et al. 2009; Lockwood 2013). The mauve point and error bar is the estimate of IMF for the end of the MM from cosmogenic isotopes (Steinhilber et al. 2010).