Micropulsations in the electric field near the plasmapause, observed by Isee 1 (paper 80A0033)

Based on 1 year of data from the double‐probe electric field instrument on Isee 1, a survey of occurrence of micropulsations near and inside the plasmapause has been made. The observed pulsations are classified as Pc 3 and Pi 2. In addition one single event of Pc 1 is observed. Pc 3 events are common during the local day, with a maximum percentage of occurrence as high as 72 in the morning hours. They occur on all frequencies in the Pc 3 band, but the most dominant frequencies are 30–50 mHz (20–33‐s period), and the amplitudes range from 0.1 to 4–5 mV/m peak to peak. The strongest Pc 3 events are nearly linearly polarized. Based on the azimuth angle of the polarization, the orientation is usually either radial from the earth or east‐west. The direction of rotation for the electric field vector is most often left‐handed in the morning sector and right‐handed in the afternoon sector. The Pi 2 events are concentrated on the local nightside. The amplitude for these pulsations is typically of the order of 2 mV/m peak to peak but can range as high as 20 mV/m peak to peak. These pulsation events are usually composed of several frequency components, with the dominant frequency most often in the band 10–16 mHz (62–100‐s period).