A test for the stationariness of the Sq current system

Abstract

We have shown here that a single chain of geomagnetic observatories, located at a fixed longitude, can provide the longitudinal gradients in the strength of the current system. The empirical model of Onwumechili [1967] for low latitude Sq currents, which is based on the diurnal variation of the horizontal component of the geomagnetic field, has been augmented to reproduce D variations that are consistent with the curl-free nature of the surface magnetic field variations. It is then possible to use variations in declination to obtain the longitudinal gradients in the strength of the current system using data from a single longitude zone. The model is applied to the data from the Indian zone. A clear linear relation between the longitudinal and temporal variations of the strength of the current system is brought out. The result appears to indicate that, at least locally, in the 75°E longitude sector, the current system is stationary and the time dependence can be used to replicate the longitudinal variations.