The Auroras of May 11, 2024 − a historic event

On May 11, 2024, a historic event occurred: a powerful display of the polar Aurora. So powerful in fact, that it was seen with the naked eye at 20 degrees S of latitude, in Africa! The polar lights illuminated the night sky over Europe with their red colour for hours.

The source of this extremely rare aurora display was sunspot AR3446, a giant sunspot of Solar Cycle 25, which erupted sever times, with M and X-class flares hurling 5 CMEs towards our planet. The size of this sunspot could be compared to the one responsible for the Carrington Event back in 1859. The arrival of the May 2024 CMEs at Earth sparked the biggest geomagnetic storm in the last 20 years, a class G5 event (Kp index went high at 9 for several hours!).

A few images of the giant and complex sunspot group 3664 are shown below. The group was imaged on May 12, from the Solar Observatory at the Institute of Space Science.

The Aurora was observed by many in Europe and Romania, with a small team from the Institute of Space Science traveling East of Bucharest, near the town of Fundulea (Calarasi county), searching for a place with good visibility towards North and low light pollution. Arriving at the location at 23:15 Local Time, the Aurora was already easily visible with the naked eye, like a long red cloud stretching from North-West to North-East through North. The Aurora reached a height of 15 degrees for this first apparition. It lasted for a few minutes, and eventually faded from visibility with the naked eye.

However, a red glow was still detectable in photographs with long exposure time, for the rest of the night.

The second apparition occurred after midnight, starting at around 00:15 Local Time. This time the bright red glow started near the horizon and eventually reached the Zenith. The display became very complex and bright, with curtains (photographically they were purple) moving rapidly, and later on a Green hue near the horizon. This later hue was a sign of the intensity of this historic event. The show continued for quite some time and faded again from visibility after 02:30 Local Time, but was still detected photographically. 

Part of the team left the location, but while driving to Bucharest, the curtains of the Aurora were once again visible through the windows of the car, starting at 03:00 Local Time. The show continued towards Sunrise.

Such an historic event might not be occurring again anytime soon, but since the current solar maximum is only getting stronger, opportunities for Aurora sightings at our latitude might be more frequent in the following months.