Courcy's Future Threats - May 2013

A topic to which we keep returning in Courcy’s Future Threats is the vulnerability of modern society to harmful natural phenomena. In the case of space weather, it is our susceptibility that is increasing. Every country in the world is becoming more and more reliant on electricity, and the US’ dependence on modern technology renders it particularly exposed.

Recent research suggests that a Carrington-level, extreme geomagnetic storm is almost inevitable in the future. While the probability of an extreme storm occurring is relatively low at any given time, one will occur eventually. Historical records, anecdotal descriptions and conclusions drawn from the analysis of ice cores suggest a return period of 50 years for Quebec-level storms and 150 years for very extreme storms, such as the Carrington Event.

Event terminology

Carrington Event

The Carrington Event was a solar storm that occurred in 1859. From 28 August – 2 September, numerous sunspots and solar flares were observed on the sun.

On 29 August aurora were observed as far North as Queensland, Australia. This first solar storm caused telegraph services to be disrupted.

At 11.18 EDT on 1 September the British astronomer Richard Carrington observed the largest flare, which caused a major coronal mass ejection (CME) to travel directly toward Earth, taking 17.6 hours. Such a journey normally takes three to four days. This second CME moved so quickly because the first one on 29 August had cleared the way of the ambient solar wind plasma.

On 1-2 September the largest recorded geomagnetic storm occurred. According to descriptions published in 2008 by Sten Odenwald and James Green, aurorae were seen around the world, even over the Caribbean; those over the Rocky Mountains were so bright that their glow awoke gold miners, who began preparing breakfast because they thought it was morning. And according to Richard Lovett, people who happened to be awake in the north-eastern US could read a newspaper by the aurora’s light. The aurora was visible from as far from the poles as Cuba and Hawaii.

Telegraph systems all over Europe and North America failed, in some cases shocking telegraph operators. Telegraph pylons and lines threw sparks, and fires started where the sparks ignited telegraph paper. Some telegraph systems continued to send and receive messages despite having been disconnected from their power supplies.

Solar storms of a similar magnitude, now referred to as Carrington-level events, are thought to occur approximately every 150 years. In 1859 the damage was minimal, but modern infrastructure comprises far more than a sparse network of telegraph cables.

Quebec event

On 13 March 1989 a powerful solar flare set off a major power blackout in Canada that left six million people without electricity for nine hours.

According to NASA, the flare disrupted electric power transmission from the Hydro Québec generating station and even melted some power transformers in New Jersey.

Although they are far less powerful than Carrington-level events, Quebec-level events are still able to do considerable damage, increasingly so as reliance on power-grids increases around the world. Quebec-level events are also much more frequent.

Cyclical risk

The threat from solar storms is not even. The sun goes through cycles, meaning there are peaks of activity, solar maxima, which correspond with periods of increased risk. The solar cycle is 11 years, and the current cycle is due to peak in 2015. Over the next two years it is possible we will see a growing number of solar flares, increasing in average intensity. It is not assured, of course, that we will see a large event in the current solar cycle. Even if Carrington- or Quebec-level storms do occur, they will not necessarily be directed at Earth. However, if we do pass the current peak without suffering damage from solar flares it does not mean the danger has passed. The sun’s cycle is only 11 years, and mitigation strategies for securing electricity grids will likely take longer than this to fully implement, even if companies and governments are fully committed to them.

Threat to the US

Recent analysis by Lloyd’s has produced some worrying conclusions that should be taken very seriously. As a highly technology-dependent society, the US is at particular risk. Within that, certain parts of the US are in greater danger than others.

Weighted by population, according to Lloyd’s, the highest risk of storm-induced power outages in the US is along the Atlantic corridor between Washington DC and New York City. This takes into account risk factors such as magnetic latitude, distance to the coast, ground conductivity and transmission grid properties. Other high-risk regions are the Midwest states, such as Michigan and Wisconsin, and regions along the Gulf Coast.

Lloyd’s believe the total US population at risk of extended power outage from a Carrington-level storm is between 20-40 million people, with durations of 16 days to 1-2 years. The duration of outages will depend largely on the availability of spare replacement transformers. If new transformers need to be ordered, the lead-time is likely to be a minimum of five months. Lloyd’s estimate the total economic cost for such a scenario is $0.6-2.6 trillion.

The authors of the Lloyd’s report believe that storms weaker than Carrington-level could result in a small number of damaged transformers (around 10-20), but the potential damage to densely populated regions along the Atlantic coast could be significant. The total number of damaged transformers is less relevant for prolonged power outage than their concentration. The failure of a small number of transformers serving a highly populated area is enough to create a prolonged period of outage.

Lloyd’s focus, of course, is providing analysis for insurance companies, and they predict that a severe space weather event that causes major disruption to the electricity network in the US could have major implications for the industry. If businesses, public services and households are without power for sustained periods of time, insurers may be exposed to business interruption and other claims, they say.

Early warning

A key element of risk mitigation strategies is early warning. If power companies know in advance that a serious solar storm is about to strike, they can shut down parts of the grid or reduce load to protect the network from the surge.

Some existing technologies can be used to provide this early warning, but continued viability is not assured, especially of space-based systems.

The two principal options for early warning are satellites that can detect an approaching storm, and terrestrial sensors that can detect the effects in the atmosphere from first wave of particles that arrive ahead of the main storm.

Currently, four space satellites (Solar and Heliospheric Observatory (SOHO), Advanced Composition Explorer (ACE), and Solar Terrestrial Relations Observatory (STEREO A & B) monitor the Sun. Situated between the Sun and Earth or along Earth’s orbit, these satellites can provide warnings of incoming CMEs on a timescale of a few days to hours. However, these satellites are all several years past their planned mission lives. SOHO was launched in 1995 and was originally intended to operate for just two years. ACE has enough fuel left to continue operating until 2024, but it was launched nearly 16 years ago in 1997, and its instruments are beginning to degrade.

The STEREO project (two satellites working together) are the youngest, having been launched in 2006. However, in 2015, coinciding with the solar maximum and thus the time when potentially we will have the greatest need for early warning, contact with the STEREO satellites will be lost for several months as the spacecraft pass behind the Sun.

Space-based sensors are still the favoured technology for early warning, and form the basis of NASA’s experimental Solar Shield early warning project. Nevertheless, there may be a better solution.

The other option, as we discussed last year in our July 2012 issue of Courcy’s Future Threats, is the use of neutron sensors based at the South Pole. Although these sensors have been in place for a long time, this technology is less developed than the satellites. However, there are advantages to using this technology in the quality and accuracy of the warnings it can provide. Sun-watching satellites can help monitor solar flares, but they cannot provide accurate estimates of when the radiation will arrive or how strong it will be. The neutron sensors can provide all of this information.

Neutron sensors

For decades, these sensors have been used to estimate the rate at which cosmic rays and other charged particles strike Earth’s atmosphere. The sensors actually detect the neutrons created in the upper atmosphere when high-speed particles slam into the nuclei of atoms of gases, knocking them apart and sending the neutrons towards the Earth. Some of those speeding particles are protons in solar flares.

Researchers analysed data gathered by the Antarctic neutron sensors during 12 particularly strong solar storms between 1989 and 2005, and then compared the readings with data gathered by radiation sensors on board an Earth-orbiting satellite. They found that protons with energies between 165 million and 500 million electron volts (corresponding to speeds of between 53% and 76% the speed of light) arrived at the sensors, on average, about 95 minutes after the flares’ first protons reached Earth. Slower-moving protons with energies between 40 million and 80 million electron volts (travelling from between about 29% and 39% the speed of light, respectively) arrived at Earth about 71 minutes later.

By comparing the numbers of neutrons detected by two different South Pole sensors, each tuned to detect neutrons of a different energy, the researchers found they could estimate how many protons of various energies were striking the upper atmosphere. That number, in turn, enabled them to estimate the maximum amount of radiation damage that might be expected from the flare. If the expected damage exceeds a certain level, for example, scientists could warn astronauts to take cover or suggest that engineers temporarily shut down satellites and terrestrial electricity grids.

Infrastructure hardening

Early warning is essential, but it is not the only mitigation strategy that must committed to. Shutting down parts f the grid and reducing the load help to protect networks, but even then some damage would be caused by a Carrington-level event.

Several steps can be taken to harden the electric grid against geo-magnetically induced currents (GIC): neutral-current-blocking capacitors can be installed to block GIC from flowing into at-risk transformers; series-line capacitors can be installed on autotransformers; improvements can be made to the tripping techniques to avoid false tripping from GIC harmonics; and the utilisation of GIC monitors at transformers will ensure that current levels remain stable.

Since the Quebec event Ottawa has invested $1.2 billion (about $34 per person) into protecting the Hydro-Quebec grid infrastructure, installing numerous blocking capacitors. While the capital outlay for these mitigation strategies can be high (estimated cost of $100k per blocking capacitor for a total of $100 million to protect the 1,000 most vulnerable transformers), the cost of prevention is potentially much smaller than the cost of the damage a single storm can do.