SPATIAL VARIATIONS IN GEOMAGNETIC MICROPULSATIONS

Abstract

Micropulsation fields measured simultaneously at pairs of stations are compared in order to describe their recognizable geographical extent and the perturbations due to local terrain. Some characteristics of coastal and inland sites are shown. The micropulsation field gradients were too small to be measured over a homogeneous earth but were clearly evident near the seacoast. Estimates are made of the extent of the anomaly at the seacoast, and of the fraction of the signal accounted for by geology of the site. Separations between sites range from 1 km up to 1750 km. The distribution of the micropulsation amplitude in different directions and its dependence on period are shown for each site. Its correlation with Kp is also shown.The data refer only to regular micropulsations of period from about 500 seconds down to 2 seconds, observed simultaneously at pairs of stations situated in mid-latitudes.