James Judd, of Havelock North, asks :-

How and why does space weather affect the power grids, satellites, and electronic equipment?

Craig Rodger, a physicist at the University of Otago, responded.

Space Weather is a generic term for how the changing space environment impacts our technological systems, and most commonly how processes which start on the Sun drive activity in and around the Earth which can pose a hazard to such systems. In that sense this is a complex question, as it lumps a lot of specifics together.

Its probably better to give a specific example around the space weather hazard to power grids. Sometimes explosions on the Sun can produce a massive cloud of matter which is thrown out into space, called a Coronal Mass Ejection (CME). The CME is a magnetised plasma, and might be directed at the Earth. If the CME strikes the Earth's magnetic field it will distort the magnetic field, triggering what is termed a magnetic storm. Faraday's law tells us that changing magnetic fields induce currents in conductors. In this case we are specifically thinking about Geomagnetically Induced Currents (GIC) induced in the conductors on the surface of the Earth which make up the electrical transmission network. Transformers in the electrical network are generally designed to operate with zero to low levels of DC current passing through the transformer core - GIC can cause the transformer to saturate, causing local heating and possible damage to the transformer.

It has been estimated that the GIC produced during an extreme geomagnetic storm, occurring roughly once every 100-200 years, would destroy more than 10% of the transformers that are the backbone of the U.S. electric grid, causing widespread blackouts and in excess of $2 trillion of damage and lost productivity.

We are currently working with more than 14 years of Transpower measurements to better understand the effect of geomagnetic storms and GICs on the New Zealand electrical network.