Frolicking fire foxes light up the heavens!
Getty Images/Svenn-Inge Sellesbakk
Green, red and violet lights flicker across the sky – by turns fascinatingly beautiful, mysterious and even menacing. Throughout history, people have interpreted the Northern Lights in different ways: as heroic apparitions, the souls of the deceased or fire foxes racing through the sky, creating sparks as their tails brush over the mountaintops. Some even saw them as bad omens of events to come. Today, scientists understand the origins of the aurora – the visible effects on Earth of what we call space weather. And yet, there are still many open questions, which the DLR Institute of Solar-Terrestrial Physics in Neustrelitz is working to answer.
The sun at its peak
In recent months, auroras have been visible not only in the polar regions but also across parts of Germany, the UK, the Netherlands, Spain, the US and even Australia. The reason for this? The Sun has been particularly active of late. Observations of our star date back to antiquity, revealing dark spots on its bright surface. With the advent of the first telescopes, astronomers were able to count and document these sunspots, eventually discovering that their number rose and fell in an eleven-year cycle. Since 1755, astronomers have tracked these cycles, using sunspot numbers as an indicator of solar activity. According to this count, the Sun is currently in Solar Cycle 25, and reached its latest peak in October 2024.
ESA/NASA Solar Orbiter
Sunspots appear dark because they are cooler than the surrounding solar surface and emit less visible light. We now know they form where loops of magnetic field lines pierce the Sun’s surface. Periods with many sunspots are associated with heightened solar activity and an increased number of solar eruptions, such as coronal mass ejections which hurl vast quantities of charged particles – primarily electrons and protons – into space. When these particles encounter Earth's magnetic field, they are directed towards the magnetic poles, where the field is strongest. There, at altitudes of approximately 80 to 500 kilometres, they can penetrate the upper atmosphere and collide with oxygen and nitrogen molecules. These collisions excite the molecules, causing them to absorb energy. As the molecules return to their normal state, they release this energy in the form of light. This is what we see as the Northern – or Southern – Lights.
The colour of the aurora depends on which gas molecules are excited during the process and at what altitude: green auroras come from oxygen at approximately 100 kilometres; red from oxygen at over 200 kilometres; and blue or violet from nitrogen.
Solar events with consequences for Earth
In addition to creating this beautiful light show, solar activity can have serious consequences for life on Earth. While Earth's magnetic field protects us from the continuous stream of charged particles known as the solar wind, major events – known as solar storms – can overwhelm this shield and cause major disruptions to technological systems including satellites, navigation services like GPS, communications systems and power grids.
Data from millions of kilometres away
To make reliable predictions and prepare for extreme events, DLR researchers at the Institute of Solar-Terrestrial Physics in Neustrelitz study the influence of space weather on technical systems and services. They continuously monitor solar activity using satellites such as the Advanced Composition Explorer (ACE) and the Deep Space Climate Observatory (DSCOVR).
These satellites transmit data from a distance of 1.5 million kilometres, some of which is received directly at the German Remote Sensing Data Center in Neustrelitz. They are positioned at Lagrange point 1 (L1), one of several points in space where the gravitational pull of the Sun and Earth, combined with a satellite's centrifugal force, are in balance. This allows satellites positioned here to maintain a stable position relative to both celestial bodies. Researchers also use data from satellites that measure the solar wind – the constant stream of charged particles emitted by the Sun. These measurements are crucial for understanding how the solar wind affects Earth.
ESA
Space weather influences complex processes in the upper atmosphere, specifically the interconnected system of the ionosphere, thermosphere and magnetosphere. Researchers at the Neustrelitz institute, located in the northeastern German state of Mecklenburg-Western Pomerania, investigate the properties of these atmospheric regions and how they interact. By developing physics-based models, they can simulate the movement, distribution and impact of these solar particle streams, and ultimately forecast near-Earth space conditions and their potential effects on technical infrastructure.
Though the institute was only founded in May 2019, it already plays a leading role in Germany – for example, by hosting the National Space Weather Workshop, where experts meet regularly to exchange knowledge and provide information and advice to government bodies and businesses. Space weather researchers at Neustrelitz are also active on the international stage. Within the United Nations Committee on the Peaceful Uses of Outer Space, the institute coordinates Germany's participation in the International Initiative on Space Weather and provides data for global space weather forecasting.
The importance of accurate forecasts
A quick look at the possible impacts of solar storms shows just how crucial space weather science and reliable timely forecasts have become for our technology-dependent society. One example is the risk posed to communication systems that rely on radio signals – such as those used on aircraft, ships or in military operations. In extreme cases, disturbances can last for days, causing major problems. GPS signals, which are a type of radio wave, travel through the ionosphere – the ionised portion of the upper atmosphere. Changes in electron density can cause positioning systems to give inaccurate location data or even fail entirely.
Powerful solar storms can disrupt Earth's magnetic field and trigger geomagnetic storms. These can induce electric currents in power lines, damaging transformers and other parts of the power grid. In severe cases, this can lead to widespread power outages lasting for days or even weeks. One example is the Quebec blackout of 1989, when a solar storm knocked out the power grid in Canada and left millions without electricity.
NASA
Typically, scientists have about one day's warning before a solar storm reaches Earth – not much time for protective action. This makes early and accurate predictions all the more important, so that appropriate measures can be taken. For example, information about expected measurement inaccuracies can be passed on to the relevant companies and authorities. Switching off satellites can also be a protective measure.
Space weather forecasts
The Ionosphere Monitoring and Prediction Center (IMPC), developed and operated by DLR, provides near-real-time data and forecasts on the current state of the ionosphere, along with corresponding alerts. As the successor to the established Space Weather Application Center – Ionosphere (SWACI), the IMPC offers significantly improved ionospheric weather data and forecasts, while also complementing the SWACI long-term data archive.
Blind spots in space research
Although forecasting accuracy has improved in recent years thanks to better models and technology, the complexity of space weather still presents major challenges. In particular, many physical processes in Earth’s upper atmosphere are still not fully understood. One reason is the lack of data on the thermosphere – the layer of Earth's atmosphere that extends from approximately 90 to 500 kilometres in altitude, where auroras form and temperatures rise sharply due to the absorption of solar radiation. Most of the ionosphere lies within this region, and, between 100 and 300 kilometres in particular, the thermosphere remains insufficiently characterised due to limited measurements and the complexity of space weather interactions.
Forecasts could be further improved if researchers were able to determine the arrival time and intensity of solar activity at an earlier stage. For this, parameters such as speed, proton density and properties of the interplanetary magnetic field would need to be determined earlier, ideally already at L1. Additional observations from the Lagrange points L4 and L5 would also advance this research.
One ray of hope is the European Space Agency's Vigil mission – a space observatory that will monitor solar activity from Lagrange point 5, trailing Earth in its orbit. There, it will carry instruments from NASA, NOAA and others, to observe the 'side' of the Sun, detecting solar activity before it rotates into view from Earth – providing earlier warnings of potentially disruptive space weather. The launch of this first-ever mission to L5 is currently planned for 2031.
An article by Melanie-Konstanze Wiese from the DLRmagazine 177