One-dimensional upward continuation of the ground magnetic field disturbance using spherical elementary current systems

Ionospheric equivalent currents are defined as spherical sheet currents, which reproduce the observed magnetic disturbances below the ionosphere. One way of determining these currents is to place several so called spherical elementary current systems (SECS) in the ionospheric height and to solve an inversion problem for the amplitudes of these systems. In previous studies this method has been applied to two-dimensional data sets, having both latitudinal and longitudinal spatial coverage (213 SECS method). In this paper a one-dimensional variant of this method (ID SECS) is developed. The ID SECS method can be used even in those situations where the data set is one dimensional, e.g. with one meridionally aligned magnetometer chain. The applicability of the ID SECS method is tested using both synthetic and real data. It is found that in real situations the errors in the ID SECS results are 5-10% in current density profiles and similar to5% in integrated currents, when compared to the results of the more accurate 2D SECS method.