Title : STEVE Arc in Northern France
Copyright : Julien Looten (
https://linktr.ee/julienlootenphotographie)
Last night, during a large-scale geomagnetic storm, I captured a rather rare phenomenon: the STEVE arc. Have you ever heard of this phenomenon?
For millennia (and likely much longer), humanity has been fascinated by the sky, especially by polar auroras. But in recent years, a brand new type of aurora has been discovered by amateur scientists: the STEVE arc (Strong Thermal Emission Velocity Enhancement). It is a luminous phenomenon that appears as a shimmering plasma ribbon in shades of violet, blue to white, and is very fleeting. This aurora is sometimes accompanied by small, more unstable green shapes.
With the naked eye, along with my photographer friend Axel, who appears in the images, we were observing a SAR arc. It was this arc that changed appearance and took the form of a structure with well-defined, sharp contours. On it, very rapid light flashes appeared, and it was truly impressive... In fact, in the image, you can see Axel raising his arms and shouting when STEVE appeared: "What is happening?!" We were amazed.
Unlike traditional auroras, which are caused by solar particles colliding with Earth's atmosphere, the STEVE arc seems to result from a different interaction in the atmosphere. It is associated with fast-moving particle currents and very high temperatures in the magnetospheric zone, though scientists are still studying the exact mechanisms of its formation. Satellite data from the European Space Agency's (ESA) SWARM mission indicates that this phenomenon is caused by a ribbon of hot plasma, 3,000°C, 25 km wide, at an altitude of 450 km, flowing at a speed of 6 km/s.
In these three photos, taken one after the other (with a 1- or 2-second interval) and with 2.5-second exposures, you can see that in each image, the shape of STEVE is different, clearly showing the speed at which this phenomenon moves.
If any specialists have further insights into this arc, I'd love to hear them, as it's a subject I know little about. I am certainly eager for any additional information regarding the description of this phenomenon in my images.
Thanks in advance
exifs :
Camera: Sigma FP-L2 Astronomik
Lens: Sigma 14mm f1.8
Exposure Time: 2.5 seconds
ISO: 2000
Date and Time: 10/10/2024, 10:55 PM (French time)
Location: Northern France (Fort d’Ambleteuse)
Bridge to the Aurora by Andrea Girones, on Flickr
