You may have noticed solar flares, sun spots and coronal mass ejections have been in the news this week, following a space weather event which led to aurora borealis sightings in some northern parts of the UK between the cloudy weather. While the event itself was moderate, it does showcase the move to a new solar cycle, as Met Office Space Weather Forecaster Krista Hammond explains in this blog.
The number of sunspots visible on the sun varies over a roughly 11-year period from one peak to the next, known as the solar cycle. The peak in sunspot frequency is referred to as solar maximum, whilst the period during which we see the fewest sunspots is known as solar minimum.
Sunspots are areas of intensely concentrated magnetic field on the sun’s surface. This causes them to be cooler than the surrounding area (the photosphere), and so they appear darker. Sunspots vary in magnetic complexity as well as size – the largest sunspot regions, often referred to as active regions, can be many times the size of the Earth.
Sunspots are important in space weather forecasting as they tend to be the origin of space weather phenomena that can have an impact at Earth, namely solar flares, solar radiation storms and coronal mass ejections (CMEs).
Solar flares are sudden releases of energy across the entire electromagnetic spectrum. They are hard to predict, and the energy can be detected in Earth’s atmosphere as soon as 8.5 minutes after the occurrence of a solar flare. In association with large flares, solar radiation storms may also occur. These consist of high energy charged particles, predominantly electrons and protons, and typically take between 10 minutes and several hours to arrive at Earth.
A CME, also often associated with a flare, is the ejection of material from the sun into interplanetary space. If the material is directed towards the Earth then the event may result in a disturbance to the Earth’s magnetic field and ionosphere. They can take days to reach Earth, carrying a local magnetic field from the Sun, and their arrival time is a key focus of space weather forecasting.
It follows then that since impactful space weather tends to originate from sunspots, the frequency of space weather events shows some correlation with the solar cycle. As we see an increase in the number of sunspots, we also expect to see an increase in space weather activity. The last solar minimum occurred in December 2019, with the next solar maximum expected around 2025. Over the coming years, as we continue towards solar maximum, we can expect to see an increase in the frequency of space weather events.
Space weather forecasting at the Met Office
The most recognisable and visible space weather effect is arguably the auroras (Northern and Southern Lights). The geomagnetic storm we have seen over the last few days that has been responsible for the aurora is nothing out of the ordinary, and aside from producing the northern lights will have very little impact on Earth. However, extreme space weather can have an impact upon our technology, national infrastructure, and communications systems. Luckily, these extreme events are very rare.
As we continue towards solar maximum, we can expect to see an increase in the number of space weather events of a similar magnitude to what we have seen this week. However, the most extreme events that can cause the largest impacts can take place at any point in the 11-year cycle. Therefore, space weather prediction is of crucial importance to many, including the government, satellite operators and the aviation industry, at any point in the solar cycle, day or night.
This is why the Met Office Space Weather Operations Centre provides 24/7 forecasts and warnings of space weather for Government and responder communities, critical national infrastructure providers and the public, to help them understand the risks and mitigate against the impacts.