In the early hours of the morning of 13 March, 1989, a powerful geomagnetic storm from the Sun hit the Earth, immediately inducing currents in long conductors on the Earth’s surface, such as power and railway lines. Most severely hit was the Hydro-Québec electricity transmission system that provides power to much of Canada and the north-eastern US.

The induced currents immediately began to destabilise the voltage on the grid. These grids have automatic circuit breakers that prevent electrical equipment from being damaged during periods of instability.

Within 90 seconds of the storm hitting, the circuit breakers began to trigger a wave of blackouts that spread across the entire grid. Minutes later, some 6 million people on the east coast of North America had lost power on one of the coldest nights of the year.

The blackout lasted in some places for days and the total cost to the power transmission company and the economy as a whole was measured in the tens of millions of dollars.

Thankfully, severe geomagnetic storms like this one are rare and many grids now have equipment that can prevent this kind of domino-style collapse. Nevertheless, Earth is continually bombarded by geomagnetic storms of varying intensity. So an interesting question is whether these lesser storms also cause damage and what kind.

Today we get an answer thanks to the work of Carolus Schrijver at the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, and a couple of pals who have taken an unusual approach to this question. These guys have performed a statistical analysis of insurance claims for damage to industrial electrical equipment to determine how these claims correlate with geomagnetic storms.

Their conclusions are surprising. They say that these kinds of claims are closely correlated with geomagnetic storms and therefore provide a fascinating insight into the previously unseen damage they cause.

Schrijver and co begin with over 11,000 insurance claims from between 2000 and 2010 for losses associated with damage to electrical equipment in North American businesses. This time covers the standard 11 year cycle associated with solar magnetic activity.

They started by removing all claims that were obviously not caused by geomagnetic storms, those which are related to water leaks, flooding, theft, intentional damage to equipment and so on. That left only claims associated with things like electrical surges, arcing, overheating and so on.

They then plotted the dates of these claims against the size of changes in the Earth’s geomagnetic field on a particular day. These changes are caused by the interaction between the Earth’s magnetic field and magnetic storms from the Sun. These are measured at two locations in the US at 30 minute intervals providing high-resolution data.

The results of the statistical analysis are persuasive. “We find that claims rates are elevated on days with elevated geomagnetic activity,” say Schrijver and co. And the claims increase by as much as 20 per cent on days that have highest geomagnetic activity.

What’s interesting about these claims is that they are not just related to the high-voltage networks associated with transmission grids. Instead, much of this equipment is connected to the low voltage power distribution network. “The claims statistics thus reveal that large-scale geomagnetic variability couples into the low-voltage power distribution network,” they say. That has never been revealed before.

All this has a significant commercial impact although exactly how much is hard to gauge. These claims come from an insurance company called Zurich NA which claims to have a market share of about 8 per cent in North America. That suggests that there must be some 12,800 claims of this kind every year in North America. Of these, Schrijver and co calculate that about 500 of these are directly attributable to geomagnetic storms.

Various economists have calculated that the annual loss due to power outages in the US could be as high as $188 billion per year. The amount associated with geomagnetic storms is only a fraction of this though. “The economic impact of power-quality variations related to elevated geomagnetic activity may be a few percent of the total impact, or several billion dollars annually,” say Schrijver and co.

Several billion dollars is not to be sniffed at. But these guys say that the numbers they have gathered lead to a very rough estimate and that more studies are needed to understand exactly what’s going on.

One interesting question is whether household insurance claims might reveal a similar effect on ordinary electrical equipment such as computers, iPads, smartphones and so on. Clearly, there is more to mined from this heap of data.

This is a fascinating insight into the impact of geomagnetic storms using a highly unusual lens to tease apart the details. Data mining at its most revealing best.

Ref: arxiv.org/abs/1406.7024 : Assessing The Impact Of Space Weather On The Electric Power Grid Based On Insurance Claims For Industrial Electrical Equipment