It's a normal evening in Thursday in September 1859, you're sitting in your living room and suddenly the sky outside lights up an eerie green. It's so bright the birds begin to chirp, thinking the sun has risen and the morning has come. You check your clock, s the sun is definitely not supposed to have risen yet. So what is happening? Is it the end of the world? Have aliens come to visit? Or are your eyes simply just deceiving you? In fact, none of those are true, what you can see outside your window is none other than the famed aurora borealis, or the northen lights. But in your southern English town you had never seen them before. So why now? What is going on? Well, you are experiencing an intense solar geomagnetic storm. In fact the most intense geomagnetic storm in history. A one in 100-year phenomenon known as the Carrington Event.
A solar flare, image taken from the NASA website.
The Carrington Event in 1859 was a remarkably intense solar storm that I first heard of when doing research as part of an internship looking at the effects of solar radiation on cabin crew. A further google search into the event told me about sparks showering from telegraph machines and setting things on fire, birds chirping at 3am thinking the day had started, compasses malfunctioning causing ships to get lost at sea, and the northern lights being seen as far South as Hawaii and the Caribbean. All this chaos caused by the magnetism of the sun. It seems like a crazy idea. I left it in the back of my mind however until I was cycling home in May after a late night in the Oxford library and saw for the northern lights for myself in the sky of Southern England. This was big in the news, the northern lights being visible all over Southern Britain. Once again I was left wondering, why have the lights come down this far South, what's that about?. The answer, another solar storm, no where near as big as 1859's Carrington Event but big enough to bring the Northern lights to Oxford, and big enough for me to do some more research as to why.
The sun has a magnetic field that is caused by positively and negatively charged ions moving around in it's plasma. You may have heard of a concept called the solar wind. As space is a vacuum this is not air being blown around like wind is here on Earth, but is a flow of the sun's charged particles being emitted away from the sun and out into space in something known as a solar flare. Back in 1859 it had just been discovered that the magnitude of solar activity, essentially how many solar flares were going on, varied in an 11-year cycle known as the sun spot cycle. The peak in solar activity coincides with when the north and south pole of the sun's magnetic field swaps place.
A photo of the Northern Lights in Oxford, taken by one of my friends.
On the night of the 1 September 1859 a British astronomer called Richard Carrington noticed a solar flare (being the first person to record observations of this alongside Richard Hodgson) and, after the events of the night and the next day, suspected a connection between the solar flare and the havoc being caused on Earth. For this reason, what we now know as a the Carrington event, is named after him. This solar flare Carrington noticed is what is known as a Coronal Mass Ejection (CME) and is routinely recorded by space craft and monitored by agencies such as America's NOAA and Europe's ESA. During the Carrington event, the CME ejected charged particles from the sun directly at the Earth. This is not always the case, and the particles can be ejected at any direction from the sun. When these particles reached the Earth they interacted with the Earth's own magnetosphere, causing it to distort. The high energy of these particles and the interaction with the Earth's magnetic field released an estimated 1035 electron volts of energy, which is about the same as 10 megaton nuclear bombs! This energy and disruption to the magnetic field caused the strong aurora as well as interference with compasses and telegraph lines. A similar thing happened back in May when a smaller solar flare sent charged particles towards the Earth, causing the aurora to be seen at lower latitudes, such as by myself in Oxford.
Back in 1859 the telegraph lines were effected, causing sparking and loss of communications. But we have developed a lot more technology since then with the potential to be affected by a solar storm. So what would happen if we were to experience an event the size of the Carrington event today? Well compared to the impacts back in 1859 it wold be quite frankly catastrophic. For starters, satellites would have their electronics fried, causing them to fail. The impacts on space based communications would be huge, navigation, weather monitoring and prediction, phone networks, even some of the internet would all go down. Flights would not be able to operate globally. Electricity would most likely go down around the world, and you can only begin to imagine the effects of a global power outage. Scientists would not even be able to monitor the event as our solar and geomagnetic monitoring systems are largely satellite based. All in all it would be a life altering event for people around the globe, and it would in no doubt take society a while to recover from. You can read more about what would happen if the Carrington event were to happen today in a Sky at Night Magazine article here.
Due to the potential grave impacts of a Carrington type event happening today, it is imperative that scientists keep a close monitoring eye on solar flare activity. Although we don't yet fully understand how to predict a CME, our understanding of the sun spot cycle has greatly increased since 1859 with agencies such as the US's NOAA having dedicated space weather prediction centres to monitor and record changes in sunspot size, number, and position to try and evaluate the likelihood of an Earth-bound solar flare. Sun scientists (known as heliophysicists) at NASA have been working on the DAGGER system which could theoretically give us 30 minutes of warning before a solar flare hits Earth, but more time than this would be needed to fully prepare for such an event.
According to what we know about the sun spot cycle, the next solar activity maximum is between 2024 and 2026, ie right now! This does not mean that we are going to experience another Carrington style event, but it does explain my Oxford viewing of the Northern lights. In the next few years scientists will continue to monitor the sun closely and hopefully learn even more about the CME events, their prediction, and their significance. If you want to learn more about the Carrington event there is more information on NOAA's website here.
Record's from the Greenwich observatory in London from the 1859 Carrington event can be viewed on the BGS website here. Defo worth a look if you are interested in knowing more about the geomagnetic observations.
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