Northern Lights on May 10, 2024 were seen throughout the Iberian Peninsula

A night for history

Two weeks ago in Spain, something as rare as the historic floods in the Basque Country in 1983 occurred. In that year, torrential rains caused rivers such as the Nervión and Cadagua to overflow, submerging cities and towns under water. According to records, nothing like this had ever been seen in the region before.

People in the Basque Country did not know what to do. The water swept away cars, houses and businesses, leaving thousands homeless. The current tore down bridges and destroyed essential infrastructure. No one was prepared for something like this. Older locals talked about other floods, but none compared to what they were experiencing. People pulled together, trying to salvage what they could. They worked day and night, building makeshift dikes and helping to evacuate those affected. Finally, after days of rain, the skies cleared. The region was devastated, but the community pulled through. This story is still told today, remembering that year when nature surprised them all.

Two weeks ago, Spain experienced another unusual event: a geomagnetic storm that caused an aurora borealis visible in a large part of the country. I do not want to compare the damage of one and the other, since this geomagnetic storm did not cause visible damage. But this phenomenon left everyone in awe, reminding us how unpredictable nature can be.

May 10, 2024 will be remembered as a historic date for Spain. That night, the northern lights, a phenomenon normally reserved for arctic regions, illuminated our skies. From Catalonia to Andalusia, passing through Madrid, Segovia and Mallorca, the sky was tinged with shades of pink and purple. For many, it was a dream come true.

It was only known a few hours before

It all started when NOAA, the U.S. National Oceanic and Atmospheric Administration, raised the solar storm warning to its highest category, G5. One of the biggest solar storms in decades, comparable only to historic events like Halloween in 2003, was about to happen.

To understand the magnitude of this phenomenon, we must go back in time. The Carrington Event of 1859, named after British astronomer Richard Carrington, was the strongest geomagnetic storm on record. Carrington observed a bright solar flare and connected this event with the geomagnetic storm that followed. The auroras were visible even at latitudes as low as the Caribbean and caused failures in the telegraph systems of the time.

Another notable event was the Geomagnetic Storm of March 1989, which collapsed the Quebec power grid in Canada. During that storm, northern lights were seen as far south as Texas in the United States. Communication systems and satellites also suffered major disruptions.

And then we have the Halloween Storm of 2003, which took place October 29-31. Northern lights were visible in such unexpected places as Texas and Florida. This storm also caused problems with satellites and communication systems.

The night of May 10, 2024 now joins these historic events. During this night, the geomagnetic storm, originated by a sunspot 15 times larger than the Earth, launched solar particles that interacted with our magnetic field, creating the northern lights visible throughout Spain.

Why were they pink?

In Madrid, the skies were filled with a pinkish glow, visible even with the city's light pollution. Residents captured the phenomenon with their cell phones. In the outskirts and in the mountains, where the light from the city did not interfere, the auroras were even more impressive. The skies of Segovia and Salamanca were also illuminated, offering a spectacle that many will not forget.

Further north, in Aragon and Catalonia, and in the Balearic Islands, the aurora borealis showed their splendor in reddish tones. But it was in Andalusia that the phenomenon became truly unusual. From Almeria to Cadiz, the skies were filled with colors normally reserved for places near the Arctic Circle.

Why were the auroras pink this time? Normally, northern lights appear at altitudes between 100 and 300 kilometers above the Earth's surface. At that altitude, oxygen particles interact with solar wind particles, emitting a green light. But during this solar storm, the solar particles managed to penetrate lower, down to 100 kilometers, where nitrogen predominates. The nitrogen, when excited, glows with a pinkish hue.

This event reminded us that northern lights are not common in our latitudes. They are usually restricted to higher latitudes, but the arrival of this powerful geomagnetic storm, linked to very high solar activity, allowed us to see them in Spain.

May 10, 2024 will be remembered as the night when the Spanish sky was illuminated by the northern lights. An event that reminded us of the power and beauty of nature, and our small position in the vast universe.