Compared to the Sun, Earth’s magnetic field isn’t very complicated – it’s like that experiment we did as kids with a bar magnet, a piece of paper, and iron filings, but in 3D.
But because our Sun is basically one big, hot ball of plasma, and doesn’t all rotate at the same speed like Earth, its magnetic field gets very complicated. And these fluctuations are the main drivers for the incredible eruptions from its corona, the outermost part of the Sun’s atmosphere. These can be extreme bursts of radiation, called solar flares. Or they can be massive eruptions of its plasma, known as coronal mass ejections, or CMEs.
These are the two main events that cause impacts here on Earth and in near-Earth space. At the Australian Space Weather Forecasting Centre, we monitor the Sun all day, every day. We’re watching from satellites pointed towards it, and also from Earth-based optical and radio telescopes. If a solar flare occurs, it arrives here as a burst of radiation travelling at the speed of light. That means it has travelled 150 million kilometres in just eight minutes. A coronal mass ejection, on the other hand, is not quite as fast. They can take anywhere from 14 hours up to about three days to arrive.
When we see one of these events occur, we model it to try and understand which direction it’s travelling – whether it’s going to be shot out into space or whether it’s coming towards us. If it’s going to be coming towards Earth, we then want to know how long it will take to get here, and how big we expect the impact to be. We then issue warnings from those predictions.
These can be seen through our website, but we also have email alerts as well, or deliver warnings directly to our key customers.
Why does it matter if the Sun has an eruption when it’s so far away from us?
Most people know about auroras, which can be seen near the North Pole and South Pole. Very simply put, these are caused by charged particles from these solar weather events coming into contact with our atmosphere and magnetic field. The intensity of space weather activity can cause these to be visible further away from the Poles.
If any event came close in today’s power network, transformers could be damaged – worst case, transformers might be completely destroyed.
But aside from auroras, there are much more serious potential consequences of space weather. Coronal mass ejections (CMEs) can cause electric currents to flow through the Earth – and through power lines, so they can interrupt the power network. They can also impact satellites in space and high-frequency radio communications to name a few.
We work closely with the energy sector, with custom models that feed into their systems. If we’re expecting a space weather event, the energy sector operators will bring up a map in their control room that enables them to monitor any currents that we’re forecasting and take any mitigating actions.
Fortunately, these kinds of impacts are rare. The biggest example in history occurred in 1859 and is known as the Carrington Event, Earth’s most famous space weather storm. Vivid auroras lit up the sky all around the world for days, astounding everyone who saw them – even at the equator. Back then, telegraph systems were the most advanced communications technology that we relied on. The currents were so strong that telegraph operators were able to send messages through their systems without being connected to a power source. Operators were getting shocks through their equipment – telegraph poles caught on fire.
We haven’t seen any event directed toward Earth close to the magnitude of the Carrington Event since then. But if any event came close in today’s power network, transformers could be damaged – worst case, transformers might be completely destroyed. Satellites most certainly can be impacted if we had a storm of that size, resulting in interruptions to the global navigation system, plus all aspects of satellite communications.
It’s important to take action before a storm reaches Earth wherever possible. But it’s difficult for us to predict exactly when these CMEs are going to arrive.
There are lots of different space weather centres around the world, and we work closely with quite a few of them. One area in which we collaborate internationally is aviation. If a significant space weather storm is expected, it might affect pilot communication systems, in particular in polar regions. In these cases, airlines can deviate their flight paths away from those areas as a result of our alerts.
We have no way of predicting what the embedded magnetic field is going to be, and how it might change or fluctuate over time.
What’s the Next Big Thing? There are huge opportunities for advances, but space weather physics is a challenging and expansive field. We actually don’t have very many satellites pointed at the Sun that are used for space weather forecasting – about four that we are heavily reliant on. When a CME erupts from the Sun, it could go out in any direction. At the moment we’ve got one or at most two vantage points to monitor it. If we had more satellites for this purpose, we could triangulate the event, enabling us to better understand the CME’s direction and speed.
As I said, a CME can take around three days to arrive on Earth. But between the time it leaves the Sun and arrives on Earth, we only have one point where we can get any indication of the physical properties of the CME, and that’s when it’s about half an hour from Earth. When the CME arrives on Earth, it arrives with an embedded magnetic field. If that embedded magnetic field is northward, the impact won’t be very big. But if it’s southward, then it could be a huge impact. At the moment we have no way of predicting what the embedded magnetic field is going to be, and how it might change or fluctuate over time. It would be very helpful to be more accurate with this prediction.
We also don’t have the ability to predict when a solar flare will occur. We can predict the likelihood that the Sun will emit a solar flare, but not specify any point in time or how big it will be.
The Sun obeys an 11-year solar cycle, and we are approaching the solar maximum in the next year or two. It means we can expect more frequent and larger space weather events. It will certainly keep us busy at the Australian Space Weather Forecasting Centre at the Bureau of Meteorology.
As told to Graem Sims