  One of the unsolved questions in gamma-ray astronomy is whether the
extragalactic gamma-ray background is of the discrete-source origin. To respond
to this question, one first needs to reduce the data by differentiating charged
particles from gamma rays. This procedure is usually performed on the basis of
the detector responses. In this paper, we showed that the geomagnetic shielding
effect at GeV energies can, to some extent, be used for this purpose for
gamma-ray telescopes in a low Earth orbit. We illustrated this method by
applying it to the Fermi-LAT data. To partially decompose the charge-filtered
background, we examined the contribution from star-forming galaxies by implying
a radio/gamma connection in consideration of next generation radio surveys.
