Solar Magnetic Flux as a Function of Disk Position over the Solar Cycle

A novel analysis of a SOHO/MDI full-disk magnetogram time series from March 1996 to November 2004 is presented. Each of the 26,052 magnetograms in the series are segmented into sectors of constant μ = cos θ, each sector having a width of Δμ = 0.05. Within each sector, a histogram of signed magnetic flux density, corrected for the line-of-sight angle θ, is compiled. For each magnetogram we thus obtain a distribution of signed magnetic flux density as a function of μ. Summing the signed flux in each μ bin gives the total signed flux as a function of μ. Plotting these totals for each μ-sector as a function of time over the course of Solar Cycle 22 reveals that cycle minimum and maximum are differentiated only by the magnitude of the flux distributions. In other words, in contrast to analogous plots of flux versus heliocentric latitude, there is no discernible pattern, or "Butterfly Diagram", of flux seen on the solar disk from Earth. The finding is relevant to investigations of total solar irradiance (TSI) since it is known that the primary cause of the ~ 0.1% TSI variation over the solar cycle is the distribution of non-sunspot magnetic flux at smaller μ-values (so-called "faculae").