Imaging the AURORA

The altitude, latitude and intensity of a sightings are all of interest

The aurora is a popular photographic target. Its ephemeral light, combined with the sense of awe you can’t help feeling when you’re standing beneath a display, creates a combination that is hard to resist. Science can be done with regular cameras as long as each image carries with it at least the date, time and location information.

On average, auroral activity tends to occur in a ring around each magnetic pole, which is known as an auroral oval. The closest the northern hemisphere’s auroral oval comes to the UK is above northern Norway and Iceland.

In times of weak activity the oval may shrink back towards the magnetic pole, while in periods of enhanced activity it can expand in size, becoming visible across the whole of the UK. The probability of seeing the aurora increases as you get closer to the oval, so in the UK this means that the north has a greater chance than the south.

With any auroral sightings, the extent, structure and how visible they are at various latitudes are of particular scientific interest, and records of displays that happen away from the regular oval viewing locations are very valuable. You can estimate the altitude of aurora features in your photographs by capturing a reference star in the image.

Recordings of the phenomenon known as ‘STEVE’ (Sudden Thermal Emissions Velocity Enhancement) are currently of particular interest. STEVE is a recently recognised feature that was thought to be associated with some auroral displays. It typically appears as a narrow pinkish band visible south of a main display. The mechanisms that produce STEVEs are different from those that cause a regular aurora display.

Typically seen to the west from northern Scotland or slightly more towards the northwest as you head further south, STEVE is a short-lived phenomenon, easily missed as it appears detached from a main display. STEVE displays last about an hour before fading, so vigilant observations in the right direction at least every 15 minutes are needed to catch them.

GLOW (N) Similar to northern twilight; A faint glow may be an indication of impending auroral activity PATCHES (P) Isolated patches of auroral light. May appear as Homogenous Patches (HP) or Rayed Patches (RP) VEIL (V) Often appears as a background sheet of auroral light covering large areas of sky during bright and active displays HOMOGENOUS ARC (HA) An arc of uniform auroral light. Where the arc forms twists or kinks it becomes known as a Homogenous Band (HB) RAYED ARC (RA) Auroral arc with vertical columns of light. Folds or kinks may appear forming a Rayed Band (RB). Isolated Auroral Rays (RR) may sometimes be seen CORONA (C) Should auroral activity extend further south during a particularly active display, an auroral corona may appear overheadCommon auroral structural forms

The phenomenon called STEVE, photographed from an aircraft window, with the Zodiacal Light to the right of it

Aurora in West Sussex, June 2018. The rarity of sightings this far south makes them especially important to record