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The Earth's magnetic field influences electromagnetic waves passing through the ionosphere. Dipole fields emitted from satellites above equatorial regions generate ground signals of different strength, depending on whether the waves propagate in east-west or west-east direction. This effect is investigated analytically within a plane three-layer model consisting of the near-Earth space, a homogeneous ionosphere, and the atmosphere. The obtained quotient of the “east-west” and “west-east” ground field strengths increases with increasing electron density of the ionosphere and decreases with increasing collision frequency of the electrons. Beyond that, this quotient shows an interesting frequency dependence caused by the anisotropy and the waveguide effect of the ionosphere. It could be proved that the gained results are also valid for short-term fluctuations of the ionosphere.