The Aurora Code

Aurora Codes. Are a set of abbreviations used to record and report auroral activity. Aurora code offers a quick and convenient means of recording the condition, qualifying symbol, structure, form, brightness and colour of a display:

Auroral  activity observed should be recorded using the code below on a report sheet drawn up in accordance with the sample provided below. The observer should enter a new line of data whenever the aurora is seen to change in form or activity. It may be necessary to fill in more than one line if more than one form is active at the same time. If in doubt, draw a sketch on which is written the necessary

                    Condition                                                                                                                           Qualifying Symbol

    Code       Definition                                                                                                           Code      Definition

q Quiet. No Movement m Multiple. Several groups of forms
a Active f Fragmentary. A part only of an auroral form
a1 Folding of Bands c Coronal. Rays converging
a2 Rapid Change of Shape of Lower Form Structure
a3 Rapid Horizontal Movement of Rays Code Definition       
a4 Forms fade quickly to be replaced by others H Homogeneous. Uniform in shape and intensity
p1 Pulsing. Rythmic change of form as a whole S Striated. Lines of brighter and darker light
p2  Flaming. Variations moving upwards R1 Rayed. Short Rays
p3 Flickering. Rapid irregular variations R2 Rayed. Medium Length Rays
p4 Streaming. Irregular horizontal variations in homogenious forms. R3 Rayed. Long Rays
Form Brightness
Code Definition Code Definition
   G    Glow. Brightness from horizon upwards. 1 Weak. Barely visible
A ARC. Uniformly curved arch of light. 2 Bright as moonlit cirrus cloud
RA Rayed ARC from which rays appear. 3 Bright as moonlit cumulus cloud
R Ray. A vertical shaf 4 Strong. Bright enough to cast shadow
B Band. Twisted ARC
V Veil. Indefinite
P Patch. Isolated “cloud ” of aurora.
N Undefined. Does not identify with other forms.
Colour
Code Definition
a Red Only in upper portion of form
b Red Lower Border only
c White Green or Yellow

d Red

e Red and Green

f Blue or Purple

                    Aurora code is used in the following format:  condition|qualifying|structure|form|brightness|colour

                     Example:   a3|cf|R|B|2|c

                    Is a fragment of white, green or yellow rayed band as bright as moonlit cirrus cloud, forming a
                    corona in the magnetic zenith. Confusion between corona (c) and colour class (c) is defined by
                    the columns in which the codeletters are ntered in the report forms

Auroral activity observed, should be recorded using the report sheet, and drawn up in accordance with the sample provided above. The observer should enter a new line of data whenever the aurora is seen to change in form or activity. It may be necessary to fill in more than one line if more than one form is active at the same time. If in doubt, draw a sketch on which is written the necessary data:

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