Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations

Abstract

Abstract. This research focuses on the inversion of geomagnetic variation field measurement to obtain source currents in the ionosphere. During a geomagnetic disturbance, the ionospheric currents create magnetic field variations that induce geoelectric fields, which drive geomagnetically induced currents (GIC) in power systems. These GIC may disturb the operation of power systems and cause damage to grounded power transformers. The geoelectric fields at any location of interest can be determined from the source currents in the ionosphere through a solution of the forward problem. Line currents running east-west along given surface position are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground having the magnetic north and down components, and the electric east component. Ionospheric currents are modelled by inverting Fourier integrals (over the wavenumber) of elementary geomagnetic fields using the LevenbergMarquardt technique. The output parameters of the inversion model are the current strength, height and surface position of the ionospheric current system. A ground conductivity structure with five layers from Quebec, Canada, based on the Layered-Earth model is used to obtain the complex skin depth at a given angular frequency. This paper presents preliminary and inversion results based on these structures and simulated geomagnetic fields. The results show some interesting features in the frequency domain. Model parameters obtained through inversion are within 2 % of simulated values. This technique has applications for modelling the currents of electrojets at the equator and auroral regions, as well as currents in the magnetosphere.

Estimating ionospheric currents by inversion from ground-based geomagnetic data and calculating geoelectric fields for studies of geomagnetically induced currents

“…However, we keep a general model formulation so that we may easily accommodate the nonlinear parameters of the current system in the future. In this way, we remain consistent with De Villiers and Cilliers (2014). The objective function is a sum-of-squares of residuals that contain Eq.…”

“…The motivation for using the field inversion method to compute ionospheric line currents (De Villiers and Cilliers 2014) lies in using the interaction of solar effects outside of the Earth's magnetosphere, such as the solar wind, with the geomagnetic field. The line current strength can be used as an intermediary parameter for modelling techniques that determine the geomagnetic field at selected locations from the solar wind parameters.…”

“…In this paper, we used the same inversion method as in De Villiers and Cilliers (2014) that used simulated data at a single frequency to test the inversion. But there are alterations to that inversion method: the distance parameters (height and latitude) is fixed and taken out of the inversion, while the current is now complex-valued.…”

“…The main purpose is to show that the inversion method, successfully used for artificial single frequency data by De Villiers and Cilliers (2014), also works for measured geomagnetic data. In this paper, the inversion method (Eq.…”

The Applicability of Governance Method for DC Bias Due to Different Causes

“…On the one hand, the solar storm will induce the geoelectric field in the Earth [1,2],which would drive the GIC in the power system as the voltage source. GIC [3] .The GIC is able to cause the transformer DC bias and damage to the transformer body [4], relay action failure, and even fatal accidents grid blackout of [5,6]; On the other hand, with the construction of the HVDC, the DC grounding will cause a potential gradient exists surrounding the earth, the transformer neutral point of different ground potential difference exists, this potential difference is formed by the land, transmission lines, grounding transformer circuit driving DC current is generated, causing the transformer DC bias [7,8], causing the transformer vibration, noise, harmonics and reactive power losses increase [9], raised to the power system and other stable and safe range of issues, especially the modern compared to conventional power system, it has a distance power transmission, substation long distance, high-voltage and large-scale, in the role of geomagnetic storms and HVDC same level, the greater will be the ground potential difference between the grounding transformer neutral point, flowing through the transformer neutral point of the DC current increases, the DC bias caused by the more severe [10].…”