"This is the fourth in a series of data reports in support of the International Magnetospheric Study (IMS) and includes selected geomagnetic variation data for April 1976; the series began with UAG-60, which presented similar data for January 1976 (see Section I(5) below).. Included herein are analog records from eight auroral zone stations: preliminary AE indices based on these data; and various related tables, graphs, and statistics. It is expected that this series will continue on an increasingly timely schedule and with data from additional stations which may be processed in time for publication"--Introduction.

Technical Report

United States