Abstract

The relationship in the variations of geomagnetic horizontal component (H) and vertical component (Z) in Boulder station (40.1°N, 254.8°) has been investigated. In the analysis, series of significant changes in amplitude and period are observed in H as well as in Z during the day-time. The changes in H and Z for the average yearly diurnal variations and for the monthly variations do not exhibit consistent similar pattern for the years under study. The variations in H component of the field exhibit no significant peak around noon as should have been expected. The H component peak is observed to be positive throughout the period of study. The Z component variation was nearly mostly negative for all the years. Cause of these variations is expected to have arisen largely from different sources, either external or internal. It therefore seems that variations in H and Z component fields in mid-latitude as compared to those in equatorial electrojet regions are in contrast. The reason is attributed to the fact that cause of variation in equatorial electrojet (EEJ) regions emanate from the same source, while that in the mid-latitude emanate from different source.

Key words: Geomagnetic components, mid-latitude, disturbance field, variations, electrojet.