In the marine atmosphere, small ions are produced mainly by cosmic radiation. The production rate q of small ion pairs at sea level is modulated in time by the 11-year sunspot cycle. Cosmic radiation is deflected in the magnetosphere by Lorentz forces and, consequently, q is also modulated with respect to geomagnetic latitude. Comparing empirical values of q, observed on different locations at different times, only makes sense when both the solar and the latitude modulations are accounted for. A review of the literature on cosmic radiation at sea level has resulted in a most probable parameterization of both of these modulations in the present study. ¿ American Geophysical Union 1994