The poleward magnetic field streams on time-latitude diagram of the photospheric magnetic field of the Sun during 1975–2011 (Kitt Peak NSO, SOLIS NSO, SOHO MDI data) are modeled. We performed simulations in terms of probability density function and bipole orientation according to Joy's law and Hale's cycle. The difference between distributions of leading and trailing fluxes of bipolar sunspots defines the so-called surplus. Finally, magnetic field streams and polar field reversals are a result of meridional drift of a surplus to the poles.