  The behaviour of the magnetic field inside the superconducting quark matter
core of a neutron star is investigated in the framework of the Ginzburg-Landau
theory. We take into account the simultaneous coupling of the diquark
condensate field to the usual magnetic and to the gluomagnetic gauge fields. We
solve the problem for three different physical situations: a semi-infinite
region with a planar boundary, a spherical region, and a cylindrical region. We
show that Meissner currents near the quark core boundary effectively screen the
external static magnetic field.
