Liviu Constantinescu and Andrei Soare
Abstract
Employing the records of sixteen European geomagnetic observatories (Table
1) the paper considers eleven geomagnetic bays characterized by maximum deviations
as compared with the quiet variation in D (Table 2), in H (Table 3) and in
Z (Table 4). Maps point out either the geographic distribution of perturbations
by means of the 
Z
and D
isanomalic lines (Fig. 1–8) or their evolution
in time, by means of the moments of apparition of the maxima H
at the different observatories (Fig. 9–11).
General features of the phenomenon are noticed, mainly in the distribution
of the horizontal component values of the disturbance field, showing the prevalence
of external causes represented by ionospheric currents. On the contrary, the
distribution of the vertical component values shows the intervention of internal
causes represented by telluric currents, influenced by the electric conductibility
of the deep underground. These two kinds of informations allow to obtain an
image both of the geographic distribution and the propagation of geomagnetic
bays and to point out some elements of their physical substratum.