| Aurorae Data |
| An aurora involves emitted electromagnetic radiation that results primarily from the
interaction of energetic, extra-atmospheric particles with the neutral gases of the
upper atmosphere. These emissions extend from the ultraviolet to the infrared. The
portion of the emitted electromagnetic radiation that is visible to the human eye
is referred to as the visual aurora. One visible aurora form, which indicates the
occurrence or non-occurrence of auroras without any reference to form or brightness,
is known as a visoplot. With geomagnetic latitude as ordinate and universal time as
abscissa, various symbols are used to indicate whether, at a certain location, an
aurora is observed or is estimated to be overhead, to the north, or to the south.
This is done for each of eight 45 degree geomagnetic longitude sectors. Magnetic activity
index values, KP, are given for 3-hour periods. Northern and southern hemisphere visoplots
for the IGY period are contained in volume 29 of the annals of the International Geophysical
Year. Another form that shows the auroral geometry and the geomagnetic latitude and
longitude of a display at each hour of universal time is the synoptic auroral map
on polar projection. By use of various symbols, these maps show the location of veils,
patches, arcs. rays and bands. Also given is the value of KP for that particular time.
These maps are available on microfilm from the National Geophysical Data Center or
World Data Center A, Boulder, for certain time periods. Northern hemisphere maps are
available for 1964, 1965, 1967 and 1968. Southern hemisphere maps can be obtained
for the years 1964 and 1965. A similar form for displaying auroral data from the US
and Canada is the North American map. This type of map is not on polar projection,
but it does indicate the locations and forms of observed aurora. A large number of
these maps are held at NGDC Boulder and the available time periods can be obtained
upon inquiry. "Observers’ reports are also available in digital form.Aurora is electromagnetic
radiation emitted primarily from the interaction of energetic, extra-atmospheric particles
with the neutral gases of the upper atmosphere. These emissions extend from the ultraviolet
to the infrared. The portion of the emitted electromagnetic radiation that is visible
to the human eye is referred to as the visual aurora. The visible aurora are due primarily
to the interaction of energetic particles with the oxygen and nitrogen gases of the
upper atmosphere. The important emissions in the visible region are the discrete green
(5577A) and red (6300-6364A) lines of atomic oxygen and the molecular bands of ionized
molecular nitrogen in the blue and neutral molecular nitrogen in the red regions of
the spectrum.
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