Pc 1–2 magnetic pulsation spectra and heavy ion effects at synchronous orbit: ATS 6 results

Two types of Pc 1–2 wave events have been identified in ATS 6 flux gate magnetometer data recorded approximately 12° off the geomagnetic equator. Left‐hand polarized waves observed in the afternoon are typical of IPDP ground events. Highly elliptical and linearly polarized waves occur around local noon. Spectra often show slots near the equatorial helium and oxygen cyclotron frequencies. The linear polarization may be interpreted in terms of propagation at a large wave normal angle or a crossover frequency that is a consequence of propagation in a multicomponent plasma. The spectral slots may be associated with either heavy ion cyclotron resonance pr propagation effects.