Giant pulsations recorded at Sodankylä during 1914–1938

Giant pulsations (GP) are a special kind of regular oscillations which at times appear in magnetic and earth‐current records 1 . They are registered as very characteristic and easily recognized series of sinusoidal waves; specimens of such registrations are reproduced in Figures 1, 2 and 3 2 . The period of these oscillations remains constant in general throughout individual registrations and the amplitude shows generally a certain regularity also—either it develops continually to a maximum, decreasing thereafter (this may happen repeatedly), or the amplitude remains on the whole constant during a considerable part of the time of the pulsations. During the 25 years from 1914 to 1938 there were recorded 150 pulsations of this kind at Sodankyla or in other words, on the average, six pulsations every year.