Aurora - the sound of the polar lights (Instrumental)

The Sky Over Germany

On the night of January 19th to 20th, something happened that has filled people with awe for millennia: The sky over Germany glowed with the colors of the aurora borealis. From Schleswig-Holstein down to the Alps, green, pink, and reddish veils danced across the firmament. The German Weather Service reported sightings from all federal states; even images from the Alpine foothills and Austria came in. It was as if someone had lifted a cosmic curtain, behind which usually only Scandinavians and Icelanders are allowed to peer. Meteorologist Markus Bayer explained laconically what had happened: A powerful solar flare had reached us.

The cause was a G4 geomagnetic storm, the second-highest category on the five-level scale of the American weather service NOAA. The plasma cloud of a coronal mass ejection had traveled the 150 million kilometers between the sun and Earth in just 25 hours, an extraordinary speed that normally takes three to four days. The Kp index, the three-hour measure of geomagnetic activity introduced by Julius Bartels in 1949, reached values ​​of 8 to 9 on a scale ending at 9. It was the most powerful solar storm in over twenty years, an event that astonished even seasoned astronomers.

The Physics of Light

But what exactly did people see in the sky up there? The physics behind it is both prosaic and poetic: High-energy particles from the solar wind, mainly protons and electrons, collide with Earth's atmosphere. Our planet's magnetic field guides them toward the poles, where they collide with oxygen and nitrogen molecules at an altitude of about 100 kilometers. These molecules are excited and emit light as they return to their ground state. Oxygen glows green at lower altitudes, red in the thinner air above 200 kilometers. In mid-latitudes like Germany, we usually see the reddish glow because the particles only reach the upper layers of the atmosphere here. The human eye is not sensitive enough to these faint lights, which is why long exposure cameras often see more than we do.

The Language of Diagrams

Today, anyone wanting to hunt for the Northern Lights no longer needs shamans, but rather a smartphone app. The diagrams show the crucial values: The Kp index measures geomagnetic activity, with a value of at least 6 required for northern Germany and 7 to 8 for southern Germany. The hemispheric force in gigawatts shows the energy flowing into the atmosphere. The solar wind speed should be above 600 kilometers per second; at 700 km/s, it becomes spectacular. The density of the solar wind, measured in particles per cubic centimeter, should be above 8. Crucially, however, the Bz value, the z-component of the interplanetary magnetic field, is decisive: If it becomes negative, ideally below minus 10 nanotesla, the Earth's magnetic field opens like a gateway to the solar wind. The Bt value shows the overall strength of the interplanetary magnetic field. The more negative the Bz and the higher the Bt, the better the chances of sighting the aurora borealis, even in the south.

The more negative the Bz and the higher the Bt, the better the chances of seeing the aurora borealis, even in the south. The good news for all aurora hunters: We are currently in the high plateau of the 25th solar cycle. The sun goes through an activity cycle roughly every eleven years, moving from a minimum to a maximum and back again, and it is currently particularly active. Strong solar storms are not unique occurrences during this phase, but rather expected events. NASA scientists confirm that the activity is likely to remain high for some time. Anyone looking north under clear skies in the coming months has a good chance of witnessing the spectacle again. However, prediction remains difficult, as the crucial moments are often brief and rarely come with much warning.

The Carrington Event

But with the beautiful comes the ominous. On September 1, 1859, the British astronomer Richard Carrington looked through his telescope at the sun and saw something that dazzled him: a tremendous flash of light above a group of sunspots, a so-called megaflare. Less than twenty hours later, the most powerful geomagnetic storm ever scientifically documented broke over the Earth. Auroras shone as far away as Rome, Havana, and Hawaii. In Europe and North America, sparks flew from telegraph lines, and paper strips in receivers caught fire. Telegraph operators received electric shocks, and compass needles whirled wildly. The fledgling global communications network, the internet of its time, collapsed under the cosmic load.

But something else strange, almost uncanny, happened: Even after the operators disconnected their equipment from the power grid, they could continue communicating. The induced currents of the solar storm were so powerful that they powered the telegraphs—free energy from space, a detail that still fascinates today. Ice core analyses show that an event of this magnitude occurs on average every 500 years on Earth. The plasma cloud at that time traveled at a speed of over 2,000 kilometers per second, twice as fast as the one that illuminated Germany this week.

The Vulnerable Civilization

What would a Carrington Event mean today? The answer is sobering, not to say frightening. Our interconnected civilization is more vulnerable than the telegraph society of 1859. The main problem lies with the high-voltage transformers, those massive installations that distribute electricity across continents. Geomagnetically induced currents would flow through the extensive transmission lines, causing these installations to overheat and burn out. Studies for the US paint a grim picture: Approximately 300 transformers could be destroyed, leaving 130 million people suddenly without power. And here lies the real problem: These transformers are not built in advance. Their manufacture takes months, sometimes years. And without electricity, there is no production; without production, there is no replacement. A self-reinforcing cascade.

The Guardians at the Lagrange Point

Fortunately, NASA, NOAA, and ESA have developed a sophisticated monitoring system. The Deep Space Climate Observatory (DSCOVR) satellite orbits the L1 Lagrange point, about 1.5 million kilometers from Earth, halfway to the Sun. From there, it detects coronal mass ejections before they reach us. The warning time is 15 to 60 minutes, sometimes several hours. This is enough time to put sensitive satellites into a safe mode and to preemptively disconnect transformers from the grid. A power outage would then occur, but it would be short and controlled. A planned outage is preferable to months of chaos. The European Space Agency (ESA) is also planning the Vigil mission, a new satellite designed to predict space weather even more precisely.

How likely is such an extreme event? Scientists disagree. Some studies suggest once every 100 to 200 years, others once every 2,000 years. In July 2012, a solar storm of comparable intensity narrowly missed Earth; the plasma cloud crossed our orbit at a point where we had been just a week earlier. The research satellite STEREO-A was hit and delivered valuable data: had it reached Earth, the consequences would have been devastating. We were simply lucky. But statistically speaking, another Carrington event is long overdue. The question is not if, but when.

Before anyone starts stockpiling canned goods and building Faraday cages in their basements, let it be said: humanity has existed for hundreds of thousands of years under the same capricious sun. We have survived all previous eruptions, including those that occurred before the invention of writing and of which we know nothing. Energy companies are investing in more resilient grids, warning systems are becoming more precise, and international cooperation in the field of space weather is better than ever. The solar storm of May 2024, the strongest in two decades, caused no significant damage, only a few inaccuracies in GPS tracking and spectacular auroras as far away as the Mediterranean. The chances are good that we will be spared.

The Poetry of the Sky

And it is this beauty that remains, that touches us, that humbles us. Anyone who has ever stood beneath a dancing aurora borealis never forgets it. The colors seem alive, the veils billow like silk in the wind, sometimes slow and majestic, sometimes wild and flickering, as if a cosmic conductor had raised his baton. It is a natural spectacle that seems to border on the supernatural, a window to the cosmos, as the aurora researcher Harald Falck-Ytter called it, one of those phenomena that allows humankind on Earth to experience a connection to the universe.

Literature has repeatedly embraced this fascination. In 1910, the expressionist poet Theodor Däubler wrote his powerful verse epic, *The Northern Lights*, a work of monumental proportions comprising over 30,000 verses, which was enthusiastically received in the then-emerging Expressionist movement. The aurora became a metaphor for the sublime, for those moments when nature confronts humankind with its insignificance while simultaneously bestowing upon it a sense of cosmic connection. Aristotle, too, contemplated the phenomenon, calling the bizarre shapes in the sky leaping goats. In ancient China, astronomers attempted to predict floods, droughts, or famines from the colors of the aurora borealis.

The Myths of the Peoples

The peoples of the North have always known all this, in their own way. For the Inuit of Alaska, the Northern Lights were the spirits of the animals they hunted: seals, salmon, deer, and beluga whales. In western Alaska, the dancing lights were believed to be the spirits of boys playing ball with walrus skulls, the aim being to throw them so that the tusks remained stuck in the ground. The Greenland Inuit saw the lights as the souls of stillborn children playing in the sky—a bittersweet belief. The Cree Indians were convinced of the cycle of life and believed that the lights were a way to communicate with their ancestors. When dogs barked at the appearance of the aurora, they recognized their lost companions.

Some tribes believed that the lights could be summoned by soft whistling, and messages could be sent to them for the deceased. The Algonquin people said that the creator, Nanabozho, had retreated to the far north and occasionally ignited powerful flames to show humanity that he had not forgotten them. Finnish legend tells of the fire fox Revontulet, whose bushy tail strikes sparks as he sweeps across the snow-covered mountains, which is why the Northern Lights still bear this name in Finnish. In Iceland, one was forbidden to wave, sing, or whistle when the lights appeared, lest the spirits come to claim one. The Canadian Eskimos believed the lights were created by spirits enveloped in mystical light, who began to dance and frolic because of the lack of sun.

Between Awe and Fear

Perhaps the deepest truth about the Aurora Borealis lies in this ambivalence between awe and fear. It is both: beauty and danger, gift and warning, a dance of spirits and the eruption of a fusion reactor. It reminds us that we live on a small blue planet orbiting a massive sun whose whims we cannot control. And it reminds us that this universe, despite our indifference to our worries, is sometimes breathtakingly beautiful.

For those who want to go aurora hunting themselves in the coming weeks, here's a tip: Find a location far from urban light pollution, with an unobstructed view to the north. Install one of the many space weather apps that will alert you to rising Kp values ​​and negative Bz. Bring a camera with a tripod, because it sees more than the naked eye. And be patient. The peak moments are often brief, sometimes only minutes, before the activity fades away. Those who are prepared win. Anyone who expects nature to follow their schedule will be disappointed.

During these January days, when the sun is particularly active and the solar cycle is at its peak, it's worth looking north on a clear night. Perhaps you'll see only the familiar stars, cool and distant. Or perhaps a reddish shimmer on the horizon, slowly building, gaining color, beginning to dance. Then you'll know: The sun has something to say again. And for a moment, you're part of a cosmic conversation older than humanity itself. The Inuit would say: Whistle softly. Perhaps your ancestors are listening.

Sapere aude!

S.

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