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Increasing number of amateurs to photograph auroras
When a solar storm becomes geoeffective, auroral phenomena can be visible even at lower latitudes. With advanced alarm systems in place, more and more people are ready to capture these stunning displays with their cameras.
Over the past two decades, camera technology has improved significantly, allowing an increasing number of amateurs to easily photograph auroras. Their contribution to auroral research has been critical the past 10 years.
Indeed, the increasing availability of images has led to the discovery of various types of auroras into polar regions, but also some new types of atmospheric emissions, such as STEVE (Strong Thermal Emission Velocity Enhancement) and SARs (Stable Auroral Red arcs) phenomena, which are part of a broader class of sub-auroral events.
Aurora observations at mid and low latitudes are rare, typically appearing as diffuse red illuminations of the sky above the Northern or Southern Hemispheres. This is because auroras usually occur at much higher latitudes, and their lower parts, including the green, purple, and blue emissions, fall below the horizon.
Exceptional auroral events
However, the May 10th event, often referred to as the Mother’s Day Storm, was an extraordinary exception.
It was one of the 10 most significant geomagnetic storms ever recorded, with the auroral oval extending as far south as the south of France. This rare event has been confirmed through numerous observations, ranging from all-sky cameras to images captured by astrophotographers, highlighting its uniqueness.
Another event, happening the night of September 24 to 25, 2023 was also rather exceptional: a single blue aurora was captured by an astrophotographer in France, leading to a scientific study trying to explain such phenomena. Reviewing different physical processes, only one remained plausible to explain the blue emission visible as such low latitudes.
The ionised N2+ from an auroral event is uplifted into the upper atmosphere, possibly up to 500 km, and will diffuse the sunlight, leading to a blue emission. This single event shows the possible synergy between amateurs and professional, helping in the understanding of auroral physics.
