The quiet daily variation in the total magnetic field: Global curves

Abstract

Most magnetic mapping exercises involve measuring the amplitude, or total-field component, of Earth's magnetic field. Removing the time-varying part of the field is a task of data reduction, and the most common time variation is the quiet daily variation, Sq . It is thus valuable to have for reference type curves of the quiet daily variation in the total field. To meet this need, global data obtained during the 1965 International Year of the Quiet Sun have been used to derive type curves describing the Sq variation of the total magnetic field, in addition to the traditional field components. As for the traditional components, the total-field curves show significant seasonal and latitudinal variability in amplitude and phase. The effect of the equatorial electrojet is clearly evident. In both hemispheres of the globe there are bands of reduced amplitude in total-field signal between the equator and the path of the Sq focus. These bands, here termed the total-field "doldrums", persist throughout the year.