Investigation of interaction between Pc 1 and 2 and Pc 5 micropulsations at the synchronous orbit during magnetic storms.

Coincident Pc 5 and Pc 1 and 2 micropulsations were observed at the synchronous equatorial satellite ATS 1 during the main phase of 11 geomagnetic storms that occurred in 1967. The Pc 1 and 2 oscillations were quasi sinusoidal, with periods of 5-20 sec and amplitudes of 1-2 gammas. Their average polarization was transverse to the ambient magnetic field. The oscillations were elliptical and rotation was to the left in relation to the main field. The observed characteristics suggest that the Pc 1 and 2 activity was due to ion cyclotron resonance of Alfven waves with energetic protons.