Summary of the year's work, to June 30, 1947, Department of Terrestrial Magnetism, Carnegie Institution of Washington

Abstract

This first year of post‐war operations marks a major change in the activities of the Department, with the completion of the observatory and field‐party work of the world magnetic survey.Much of our effort in the past has been concerned with obtaining and interpreting large numbers of observations on the magnetic and electric conditions of the Earth. During the first two decades after 1904 the Department was occupied with a world survey of the Earth's magnetic and electric fields, using the Galilee and the Carnegie to cruise all the oceanic areas, and organizing parties on land to occupy thousands of stations scattered over every continent and in the Arctic and Antarctic. At the end of World War I plans were inaugurated for establishing a number of observatories, to be located at the special sites needed to round out at least a rough approximation of a world coverage, in order to make systematic studies of the variations of the Earth's magnetic and electric fields and other related quantities, particularly in relation to solar effects and magnetic storms. Only two of the list of projected observing stations were established, one at Huancayo, Peru, and the other at Watheroo, Western Australia, but these were fortunately the most vital locations needed for a reasonable world picture. Largely by reason of the extensive and accurate observations made at these stations, comprehensive treatments of the daily, yearly, and sunspot‐cycle effects on the electrical currents in the upper atmosphere and in the Earth's crust have been made during the past 20 years, and many new facts brought out, especially in relation to magnetic storms and other aspects of solar activity. The addition of new analytical procedures based on the technique of observing echoes from radio‐pulse transmitters, first demonstrated by the Department's laboratory group in 1925, gave quantitative information of great significance, and this work was expanded into world‐wide activities of the Armed Services of many nations and all agencies concerned with radio communication. Numerous other cooperative activities, concerned with seismology, meteorology, cosmic and auroral rays, and other solar disturbances have fitted naturally into this program. The original planning for this observatory‐program contemplated the integration of our stations into the scientific life of their local areas, and the expected transfer of our activities to local sponsors at the end of 25 years.