A new space weather variation hazard index, developed by British Geological Survey researchers using data from the European Space Agency’s Swarm satellite constellation, provides a near-real time, global picture of geomagnetic variations to spot the local effects of space weather.

Space weather consists of fast-moving, charged material released from the Sun. This material, also known as solar wind, can cause auroras when it reaches Earth and interacts directly with Earth’s magnetic field.

A parameter called the Kp index tracks space weather activity and has acted as a guide to global geomagnetic disturbance since its introduction in 1939. Based on data from 13 ground stations worldwide, it provides an average measure of geomagnetic activity across the world on a scale of 0 to 9 every three hours, with 9 indicating the strongest geomagnetic conditions.

Kp has become a go-to guide for those chasing the aurora, particularly in recent years as the Sun reaches its period of solar maximum.

A variety of apps now ping many millions of worldwide users with red alerts, suggesting when might be a good time to seek clear, dark skies for a chance to spot the northern or southern lights. Many of these apps use real-time estimates of Kp.

Recent examples of widespread aurora include the nights of 10 May 2024 and 10 October 2024, when at latitudes as far south as Mexico the night sky was illuminated by a spectacular natural light show.

As beautiful as these spectacles are, however, space weather can pose significant hazards to satellites and Earth-based technologies. Infrastructure and technology, including global navigation satellite systems, telecommunications and power grids can be disrupted by strong geomagnetic activity.

Space weather indices are therefore useful not only for aurora-chasers, but by operators of vulnerable technologies.

When radio signals fade out over a certain region, or aviation telecommunications drop out, these indices can help to find out whether the cause was a technological defect, or potentially due to space weather interference.

Introducing a global index using Swarm data

Whilst the Kp index has proven a reliable tool, it has limitations. It represents a weighted average of global ground observatory coverage, and therefore localised space weather events might be missed, particularly over the remote oceans or polar regions.

It’s an issue that affects several other indices, including the HP30 and HP60 indices, which have a higher time resolution than Kp but are based on data from the same observatories. The distribution of ground stations is also uneven. There are many in Europe, for example, but fewer in the southern hemisphere or Pacific Ocean.

ESA’s three Swarm satellites, which measure changes in Earth’s magnetic field from space, can capture geomagnetic anomalies related to space weather all over the world. Whilst they do not offer the continuous time coverage at a single location that a ground station can offer, the trio’s global coverage provides our best-ever survey of Earth’s magnetic field.

Until recently, the data processing pipeline meant that Swarm data was only made available after four days, preventing its use in space weather hazard monitoring. That all changed in early 2024 with the introduction of a FAST data processing chain, which makes a lot of the mission’s data available in close to near-real time.

Swarm FAST data is now available as quickly as three hours after measurement, which is comparable to the Kp index in terms of time resolution.

“All space weather scientists want real time, global geomagnetic field data,” says Lauren Orr of the British Geological Survey, who used Swarm data to make a new space weather hazard index. “Swarm data isn’t quite real time yet, but it’s getting closer. We wanted to make sure the techniques were available to make use of the FAST data so that it would be available to space weather scientists in future.”

The new space weather hazard variation index developed by Lauren and colleagues at the British Geological Survey draws on over ten years of Swarm data. Using the mission’s long-term record of Earth’s geomagnetic field as a baseline, it is possible to spot sudden variations that depart strongly from the normal or expected level of variation.

“We took out the core field and other consistent magnetic sources, so that we isolate the space weather effects,” says Lauren. “We see how much the magnetic field changes every 20 seconds and compare it to a record of Swarm’s ten years of data, so you can immediately identify high levels of space weather activity.”

Whilst some storms, including the one of 10 May 2024, pose more obvious hazards attributable to space weather, the advantage of this tool is that you can spot anomalies that might otherwise have been missed.

“A big geomagnetic storm might be obvious,” says Lauren. “But if there was just a little blip over the Atlantic Ocean, and perhaps some aircraft were struggling to communicate, we could use this index to check if there was something more localised that could explain the comms dropping out.”

A space weather hazard index with potential

The space weather hazard variation index is currently a proof of principle, but it has great potential. The next step will be to turn it into an operational product that Swarm and space weather scientists can use.

“Space weather monitoring is precisely the sort of application we had in mind for Swarm FAST data, and it is wonderful to see it being used so effectively,” says Swarm Mission Manager, Anja Strømme. “It’s another great example of the applications and benefits the Earth Explorer satellites bring to Europe and the rest of the world.”

The index could also be applied to any geomagnetic satellite in orbit, offering tantalising opportunities for current and future satellites such as the Macau Science Satellite-1, which is working closely with ESA’s Swarm mission, and ESA’s future Scout mission NanoMagSat.

“There are other satellites you could do similar things with,” says Lauren. “You would have to recalibrate to see what their noise levels are, which might be higher than Swarm. But it would be great to make something that used lots of different satellites, so you’d have even better coverage.”

The study, “A regional space weather hazard variation index utilising Swarm FAST data”, was published in the Journal of Space Weather and Space Climate.