  We present a model to explain the decrease in the amplitude of the pulse
profile with increasing energy observed in Geminga's soft X-ray surface thermal
emission. We assume the presence of plates surrounded by a surface with very
distinct physical properties: these two regions emit spectra of very distinct
shapes which present a crossover, the warm plates emitting a softer spectrum
than the colder surrounding surface. The strongly pulsed emission from the
plates dominates at low energy while the surroundings emission dominates at
high energy, producing naturally a strong decrease in the pulsed fraction. In
our illustrative example the plates are assumed to be magnetized while the rest
of the surface is field free.
  This plate structure may be seen as a schematic representation of a
continuous but very nonuniform distribution of the surface magnetic field or as
a quasi realistic structure induced by past tectonic activity on Geminga.
