Singular variations in geomagnetic disturbance content at auroral latitudes

Abstract. The geomagnetic field consists of temporal variations induced primarily by the variations in the interplanetary magnetic field. This paper attempts to develop the latitude profile of fluctuations in the geomagnetic field for 34 observatories across the Earth during solar cycle 23 (1997–2008). It is noticed that the disturbance content is low for equatorial stations and high for auroral stations. We show that the latitude profile of disturbance exhibits `Knee’ behaviour, with the fluctuation content rising sharply beyond this critical latitude. The threshold latitude beyond which the stations are subject to high geomagnetic disturbance and hence become increasingly susceptible to associated geo-electric hazard is precisely determined near 52° latitude. The pattern of increasing geomagnetic fluctuations however ends around the auroral oval beyond where singular variations are observed.