  A new model has been proposed for magnetic field determination at different
distances from the Sun during different solar cycle phases. The model depends
on the observed large-scale non-polar photospheric magnetic fields and that
measured at polar regions from 55N to 90N and from 55S to 90S,which are the
visible manifestations of cyclic changes in the toroidal and poloidal
components of the global magnetic field of the Sun. The modeled magnetic field
is determined as the superposition of the non-polar and the polar photospheric
magnetic field cycle variations. The agreement between the model predictions
and magnetic fields derived from direct, in-situ, measurements at different
distances from the Sun, obtained by different methods, and at different solar
activity phases is quite satisfactory. From a comparison of the magnetic fields
as observed and as calculated from the model at 1 AU, it should be concluded
that the model magnetic-field variations adequately explains the major features
of the IMF Bx component cycle evolution at the Earth's orbit. The model
CR-averaged magnetic fields correlate with CR-averaged IMF Bx component at the
Earth's orbit with a coefficient of 0.688, and for seven CR-averaged data the
correlation reaches 0.808. The model magnetic-field radial profiles were
compared with that of the already existing models. In addition, the decrease in
the non-polar and polar photospheric magnetic fields has been revealed. Both
magnetic fields during solar cycle maxima and that during minima phases
decreased from Cycle 21 to Cycle 24. It means that both the toroidal and
poloidal components and therefore, the solar global magnetic field decreased
from Cycle 21 to Cycle 24.
