| Summary: | UAG R-220; Scientific Report. Edited by V. P. Hessler, Geophysical Institute, University of Alaska and V. A. Troitskai͡a, USSR Academy of Sciences. Type Pc 1 micropulsation activity at high latitudes by R. R. Heacock, Geophysical Institute, University of Alaska; Matti Kivinen, Geophysical Division, Finnish Meteorological Institute, Helsinki; Main regularities of micropulsations at the geomagnetic poles by V. A. Troitskai͡a and O. V. Bolshakova, Institute of the Physics of the Earth, USSR Academy of Sciences, Moscow; V. P. Hessler, Geophysical Institute, University of Alaska; Micropulsations associated with polar magnetic substorms, by V.P. Hessler and R. R. Heacock, Geophysical Institute, University of Alaska; Jens Olesen, Ionosphere Laboratory of Danish Meteorological Institute, Technical University, Lyngby; Christian Sucksdorff, Geophysical Division, Finnish Meteorological Institute, Helsinki; Jorma Kangas, Physics Department, University of Oulu, Finland. Type Pc 1 micropulsation activity at high latitudes: Statistical analyses were made on structured Pc 1 micropulsation data recorded at College (Alaska), Thule (Greenland), and Sodankyla and Nurmijarvi (Finland) from November 1967 through January 1970. Hourly occurrences of Pc 1 were scaled for mid-frequencies, amplitudes, and “sameness” of event as seen at two or more sites. The data give evidence for the existence of a global effect in Pc 1 activity. The effect is thought to be related to drifting trapped solar wind protons, i.e. to some form of proton ring current. The existence of a midday maximum in Pc 1 production at source latitudes is verified. The Pc 1 diurnal variations observed at other latitudes, including Thule (89°), are mainly shaped by characteristics of propagation in the ionosphere horizontal duct. An event occurring on 23 Feb 1967 propagated from the vicinity of Finland, completely over the polar cap, to Alaska, at a time when the disturbance level over the polar cap was minimal. The evidence suggests that E-region electrojets and other ...
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