Early Weather Prediction
Weather is a topic that humans have been fascinated by for centuries and, dating back to the earliest civilisations ’till the present day, we have been trying to predict it. In the beginning, using the appearance of clouds or observing recurring astronomical events, humans were able to better predict seasonal changes and weather patterns. This was, of course, motivated by reasons of practicality such as agriculture or knowing when the best conditions to travel were, but additionally it stemmed from the innate human desire to develop a better understanding of the world around us.
Weather prediction has come a long way from it’s primordial beginning, and with the exponential growth of technological capabilities in the past century we are now able to model conditions in the Earth’s atmosphere with unprecedented precision. However, until the late 1800’s, we had been blissfully unaware that weather is not confined solely to our planet, but also exists in space.
Weather in Space
Weather, in this context, refers to the changing conditions in the Solar System and can affect not only our planet, but other solar system planets too. But what is the source of this weather in space? The answer is the biggest object in our solar system, the Sun. Our humble, middle-aged star is the reason we are here at all in the first place and has been our reliable source of energy for the past 4.6 billion years.
However, the Sun is not as stable or dependable as we perceive it to be. The Sun is in fact a very dynamic object, made up of extremely high temperature gases (also known as plasma). Just like the Earth, the Sun also generates its own magnetic field, albeit on a much larger scale than our planet. This combination of strong magnetic fields, and the fact that the Sun is not a solid body, leads to the build up of energy and, consequently, energy release. This energy release is what is known as a solar flare, simply put it is an explosion in the atmosphere of the Sun that produces extremely high-energy radiation and spits out particles that can travel at near-light speeds into the surrounding interplanetary space.
The Sun: Friend or Foe?
Sounds dangerous, right? Well yes, if you were an astronaut floating around in space, beyond the protection of the Earth, you would find yourself in a very undesirable position if a solar flare were to happen at the same time. For us here on Earth, the story is a bit different when it comes to being hit with the by-products of a solar flare. As I said earlier, our planet Earth produces its very own magnetic field, similar to that of a bar magnet. For those who chose to study science at secondary school, I’m sure you may recall the lead shavings and magnet experiment. Well, that’s pretty much what our magnetic field looks like, and luckily for us it acts as a protective shield against the high-energy particles that come hurtling our way on a regular basis from the Sun. One of the most well-known phenomena caused by the Sun is actually the Aurora Borealis, i.e., the northern lights (or southern lights depending on the hemisphere of the world you live).
This phenomenon has been happening for millennia, yet until recent centuries we didn’t really understand why. What we know now is that the aurorae are caused by high-energy particles from the Sun colliding with our magnetic field, spiralling along the field lines and making contact with our atmosphere at both the north and south magnetic poles. While the aurorae are actually a favourable effect of space weather, as they are astonishingly beautiful to watch and photograph, there are unfortunately some negative effects too. These effects here on Earth range from satellite damage (GPS in particular), to radio communication blackout, to the more extreme case of electrical grid failure. Other effects are illustrated in the image below:
My PhD – Space Weather Forecasting
So, how do we predict when there is an event on the Sun that could have negative impacts here on Earth? Science, of course! In particular, in the area of Solar Physics there has been increasing focus on understanding the physical processes that lead to space weather phenomena and trying to find the best methods to predict when something such as a solar flare might occur.
It is well known that one should not directly view the Sun with the naked eye, therefore traditionally the image of the Sun was projected onto pieces of paper. Using this method, one of the first features observed on the Sun were large, dark spots that are now known as sunspots. These fascinated astronomers for quite some time and there is an extensive record of sunspots kept since the early 1800’s. These sunspots were initially traced by hand, on a daily basis, until photographic plates were invented and this practice became redundant. After many decades of recording these spots there appeared to be a pattern emerging, corresponding to a roughly 11-year cycle, where the number of spots would increase to a maximum and gradually decrease again. It was shown that this 11-year cycle was correlated with the level of solar activity, in other words the number of solar flares and how much energy they release can also be seen to follow this pattern.
Leading on from this, it is clear that there exists a relationship between sunspots and solar flares, so logically they are the place to start when trying to forecast. My PhD project focuses on sunspots and how they evolve to produce flares. For a long time, sunspots have been classified according to their appearance. One of the most famous classification schemes was developed by Patrick McIntosh and has been used widely by the community to group sunspots by their size, symmetry and compactness (how closely packed are the spots) . Generally, the biggest, baddest and ugliest groups of sunspots produce the most energetic, and potentially hazardous, flares. Our most recent work has been studying data from past solar cycles (1988-2010) and looking at how the evolution of these sunspot groups relates to the flares they produce . I found that those that increase in size produce more flares than those that decrease in size. This has been something that has been postulated before in the past, and additionally it helps to answer an open question in the community as to whether sunspots produce more flares when they increase in size (grow) or when they decrease in size (decay). Using these results, I am now implementing a new way to predict the likelihood of a sunspot group to produce flares and additionally the magnitude of those flares.
Space weather is a topic that is now, more than ever, of great importance to our technology-dependent society. That is not to say that there will definitely be any catastrophic event in the near-future, but it is certainly a potential hazard that needs to be addressed on a global scale. In recent years there has been some significant investment in space weather prediction, with countries such as the UK and the U.S. both establishing dedicated space weather forecasting services. Here in Ireland, our research group at Trinity College has been working on improving the understanding of and prediction of space weather for the past ten years. I hope, in the near future, space weather forecasting will reach the same level of importance as the daily weather forecast, but for now – watch this space.
- McIntosh, Patrick S (1990), ‘The Classification of Sunspots’, Solar Physics, p.251-267.
- McCloskey, Aoife (2016), ‘Flaring Rates and the Evolution of Sunspot Group McIntosh Classifications’, Solar Physics, p.1711-1738.