  We analyze the micromagnetics of short longitudinal modulations of a
high-magnetization material in cylindrical nanowires made of a soft-magnetic
material of lower magnetization such as permalloy, combining magnetic
microscopy, analytical modeling, and micromagnetic simulations. The mismatch of
magnetization induces curling of magnetization around the axis in the
modulations, in an attempt to screen the interfacial magnetic charges. The
curling angle increases with modulation length, until a plateau is reached with
nearly full charge screening for a specific length scale~$\Delta_\mathrm{mod}$,
larger than the dipolar exchange length of any of the two materials. The
curling circulation can be switched by the Oersted field arising from a charge
current with typical magnitude $10^{12} A/m^{2}$ for a diameter of $\sim$100
nm, and reaching a maximum for $\Delta_\mathrm{mod}$.
