Depolarization of VHF geostationary satellite signals near the equatorial anomaly crests

The nighttime polarization fluctuations of linearly polarized 136 MHz satellite signals received at Ascension Island, located near the southern crest of the equatorial anomaly, have been shown to be the manifestation of depolarization effect due to the diffractive scattering by small‐scale (<200 m) density irregularities with power law spectra. The theory can explain its coexistence with L band scintillation. The absence of this phenomenon at equatorial locations off the anomaly crests is attributed to two factors: (1) the ambient plasma densities are relatively low, and (2) the propagation angles of satellite signals are more nearly perpendicular to the geomagnetic field.