Investigating the Drivers of Geomagnetically Induced Currents

The Earth's magnetic field sits within the changeable, dynamic environment of the solar wind. The interaction of the two regimes drives rapid reconfigurations of the Earth's field, which induce currents to flow in conductors on the ground. These Geomagnetically Induced Currents (GICs) can be 10s to 100s of Amps, and can cause transformer heating and higher harmonics in power grids, degradation to metal pipelines, and signalling malfunctions on railway systems. The Lloyd's of London 2013 Space Weather report concluded that a once-in-a-Century event 'would cause major disruption to transport, food supplies, emergency and hospital services amongst other things...The absence of such fundamental services could lead to major and widespread social unrest, riots and theft with ramifications for the insurance industry and society in general'. The cost of such an event to the UK has been estimated at £0.9-15.9 billion, and while such huge events are rare, smaller, damaging, events are routinely observed.

The key to predicting the location and magnitude of GICs is understanding the chain of causality from the Sun to the Earth's surface, and having instrumentation in key locations to make the measurements required for forecasting. Typical solar wind structures that drive powerful GICs have been identified, and can provide some early warning of extreme dynamics in the Earth's system. The other end of the chain, inducing currents in conductors on the ground due to a variable magnetic field, may be addressed through the application of Faraday's Law, given the conductivity of the local regolith, and the conductivity, length and orientation of the conductor. Typically, this research is funded by individual nations focussing on operational risk to their own critical infrastructure, and therefore the global picture is less well understood. The missing link required for accurate GIC forecasting is the physics of the central part of the chain: understanding how the highly dynamic ionospheric current systems generate the geomagnetic disturbances that drive GICs measured in infrastructure, thus enabling the coupling of existing solar wind/magnetosphere models with ground-based conductivity maps.

We will use data from ground-based magnetometers (>200 stations) spread across every continent, to determine the location, timing and intensity of all geomagnetic disturbances over an eight-year period (2010-2017). These signatures will be related to their ionospheric drivers using a constellation of 66 satellites in low-Earth orbit which provide continual 2-minute snapshots of the magnetic energy stored in the system during this time period, and accurately characterise the location, direction and magnitude of the ionospheric current systems. The novelty of this approach is combining these two data sets for the first time to allow a global, statistical analysis over an entire solar maximum period.

We will largely focus on high latitude regions (including northern Europe, Canada and the northern United States) where the most intense GICs are observed. Our work is relevant to space weather service providers (such as the UK Met Office), the energy and rail industries, and governments who monitor risk to critical infrastructure, as well as for future infrastructure planning. We will also study equatorial and mid-latitude disturbances, as these have the potential to disrupt infrastructure supporting major population centres, and the combination of equatorial and higher-latitude events could be highly damaging to infrastructure on a continental scale (such as in South America). This work will be a pathfinder for the feasibility of nowcasting, and perhaps even forecasting, of GICs, using acombination of existing satellite networks and solar wind monitors.