Summary of the year's work, Department of Terrestrial Magnetism, Carnegie Institution of Washington

Abstract

Effort has been chiefly concentrated during July 1, 1932, to June 30, 1933, as in the previous year, on the study of the extensive observational material in hand, particularly that obtained on the last cruise of the Carnegie and at the Department's two observatories, rather than to the amassing of new data. However, the Department has taken an active part in the inauguration and maintenance of the two American Polar Year stations at Point Barrow and College‐Fairbanks, Alaska, and has collected data for secular‐variation studies at a number of repeat‐stations in South America.General statistical methods for research on diurnal variations, together with schemes for numerical and graphical work suitable for handling the largest possible amount of material, have been developed in a series of papers. The procedure has been applied to magnetic diurnal‐variation at Watheroo and Huancayo observatories and has already yielded convincing results. Thus, the diurnal variation of declination at such an equatorial station as Huancayo is found to vary considerably even on very quiet days. At Watheroo, on quiet days in southern summer, the horizontal intensity has, on the average, a small diurnal variation, because Watheroo is situated in the transitional zone between the equatorial and the polar types of the variation ; individual days, however, exhibit either the equatorial or the polar type quite markedly, indicating that the focus of the diurnal atmospheric current‐system passes on some days several degrees of latitude south, on other days north, of Watheroo. Furthermore, the passage of the focus is retarded or accelerated on some days by a few hours, and the intensity of the current varies by a large fraction of its average value; these features are indicated in simultaneous changes of the diurnal variations of declination and of vertical intensity.