Australis is a luminous glow in the night sky of the Southern
Hemisphere, most commonly in the polar region over Antarctica.
It has a great variability in brightness, from a feeble glow to
a brilliant display of many colours. And it can transform from
quiet arcs stretching from horizon to horizon to a sky filled
with spectacular, dancing rays and bands. It is analogous to the
Aurora Borealis in the Northern Hemisphere.
of these "southern lights" was first suggested in Europe
in 1733 by de Mairan, in the first textbook published that was
devoted to the aurora. They were confirmed by Captain James Cook,
who observed the phenomenon during his voyage of discovery to
Australia in Endeavor in 1770. During his subsequent expedition
to the Antarctic in Resolution (1772-75), he and his crew
had several sightings. He then coined the term Aurora Australis,
and compared its colours and motions to those of the Aurora Borealis
that they had viewed over Sweden. Subsequent voyages of Antarctic
exploration pushed farther south and reports of auroras became
common in ship's logssuch as in 1831 from John Biscoe, captain
of the ship Tula, when surrounded by icebergs at the Antarctic
the same time, nearly the whole night the Aurora Australis showed
the most brilliant appearance, at times rolling itself over our
heads in a beautiful column, then as suddenly forming itself as
the unrolled fringe of a curtain, and again suddenly shooting
to the form of a serpent and at times appearing not many yards
above us; it was decidedly transacted in our own atmosphere, and
was without exception the grandest phenomenon of nature of its
kind I have ever witnessed"
The Aurora Australis occurs
well to the south of inhabited regions and only very major ones
expand equatorward sufficiently to be seen over such continents
as Australia (and there only a very few times a year). One of
the earliest reported from Australia was by Francis Abbott in
"On August 29, 1859 there appeared a most brilliant Aurora
Australis extending from the W. through the S. to the Eastern
part of the horizon in one continued arc of about 190 degrees
and shooting up to the zenith.The phenomenon had for thirty
minutes a most magnificent appearance, the bands (i.e. rays)
being in complete repose formed a truncated cone of glory, the
apex of which, if projected, would have terminated in the zenith.
A second display of the Aurora appeared on the night of 2nd
September following, equally brilliant and extensive, but less
transitory, and with this difference, that from Sunset the whole
of the southern sky was of deep ruby colour
From 12 to 1 o'clock on the morning of the 3rd the Aurora broke
out into flickering streamers and corruscations, as brilliant,
and with as much diversity of colour as on the 29th of August,
forming in the zenith a well defined corona, which shortly after
became diffused and then dispersed."
These two auroras were
also seen in North America, Jamaica, Rome, and Athens and are
on the list of historical great auroras. The latter one was also
viewed and sketched from Melbourne.
sent expeditions to the Antarctic in the early part of the twentieth
century. One was the British National Antarctic Expedition of
1901-04. On this, Robert Falcon Scott and his party were forced
to establish winter quarters on Ross Island, near McMurdo Sound.
Many sightings of auroras were made from there. Douglas Mawson,
a member of Ernest Shackleton's British Antarctic Expedition of
1907-09, recorded very detailed observations of the aurora. He
continued these scientific studies during his 1911-14 Australasian
distribution of the aurora in the Southern Hemisphere was first
reported by Boller in 1898, based on some 780 nights during which
auroras were observed. There were several later efforts to map
the southern auroral zone but it was not until the International
Geophysical Year (IGY) during 1957-58 that more observational
data allowed Feldstein to produce much improved maps of both auroral
zones. His southern map showed that this auroral zone roughly
encircled Antarctica, well poleward of the southern continents.
And that the percentage of nights that one would expect to see
overhead auroras in major capital cities there was very low (Hobart,
3, Sydney or Auckland 1, Capetown 0.5, Buenos Aires .01). It is
not surprising that observations and studies of the Aurora Australis
in early times were scanty, compared to the much more extensive
studies of the Aurora Borealis, which in contrast occurred over
many populated areas.
Australis generated several legends and beliefs among early natives
of Australia and New Zealand, even though it occurred usually
well to the south of them and perhaps was not an integral part
of their culture. The auroras they saw were usually red, so they
quite naturally associated them with glowing fires. The Maori
of New Zealand believed that some of their ancestors had journeyed
far south by canoe and become trapped in ice. Their descendants
in that inhospitable zone sometimes lit huge bonfires signaling
their kinsmen in hope of being rescued. They thought aurora was
a reflection of these great fires in the night sky as Tahu-nui-a-Rangi
(Great Glowing of the Sky).
people in Northern Australia viewed the aurora as the feast fires
of the Oola-pikka folkghostly beings who sometimes spoke
to the people through these auroral flames. Only the elders dared
look at the lights and interpret their messages. Those in the
south explained auroras as the campfires of spirits, flickering
over Kangaroo Island off the south coast of Australia. Among the
Kurnai people of southeast Australia the aurora needed no interpretation:
it was an unequivocal and terrifying warning from the Mungan Ngour,
the "Great Man" and a sign of his wrath. The Kurnai
would run about trying to fend it off, and shouting at it to go
It had been
long recognized that the southern and northern lights had some
similarity and that the magnetic field of the Earth exerted some
influence over them. There was some evidence that auroral displays
occurred simultaneously in both hemispheres. A literature study
about 1865 revealed that of 34 displays seen in the Southern Hemisphere,
there were 23 coincident with auroras reported in North America.
Photographs taken in 1968 from coordinated aircraft flying over
Alaska and south of New Zealand showed auroras that were near
identical and, in fact, mirror-images of each other. More detailed
studies with spacecraft imagers have since established that the
two auroras are conjugate (occurring on both ends of the same
magnetic field line). Comparisons of such joint images show some
small differences in detail (intensities and form), explained
as due to irregularities in the geomagnetic field. So, the southern
and northern lights can be considered integral parts of a global
phenomenon. Comments on the aurora that follow can therefore apply
equally to either the southern or the northern lights.
As for general
characteristics, the aurora varies in brightness from a faint
glow at quiet times to a brightness approaching that of the full
moon during active periods. It is a permanent optical feature
of the upper atmosphere, appearing in each hemisphere as an oval
about 100 km or more above the earth. Its position varies with
geomagnetic activity. During moderate activity the aurora is located
about 23 degrees from each magnetic pole on the night side of
the Earth and about 15 degrees on the dayside. During magnetically
quiet times the oval shrinks poleward by as much as 5 degrees,
significantly reducing the size of the polar cap, that region
poleward of the aurora. The South Magnetic Pole is near Vostok
Station, Antarctica, and the southern "auroral oval",
the zone of most frequent auroral occurrence, roughly encircles
the Antarctic Continent. It is only during very major disturbances
that the southern lights move sufficiently equatorward to be seen
over continents such as Australia.
auroral displays have been recorded through history as far back
as 500 BC, it has been through concerted international efforts,
such as the IGY, and succeeding in situ balloon, rocket,
and satellite investigations that most understanding of the phenomenon
has emerged. The aurora is caused by particles, mainly electrons,
bombarding the upper atmosphere gases. Its visible spectrum consists
mainly of emissions from excited oxygen atoms (green and red emissions)
and nitrogen molecules (violet and pink). The variation in colour
seen in different displays is due to differing depths of penetration
into the atmosphere by the bombarding electrons.
spectrum extends over a wide frequency range extending from x-rays
to radio emissions. Some major emissions are in the extreme ultraviolet
region and are absorbed by the atmosphere, but can be detected
from above by spacecraft imagers. Orbiting satellites such as
the Dynamics Explorer, Viking, Polar, and Image have been used
routinely since 1981 to photograph the aurora globally, even in
the presence of full sunlight. They have verified that the aurora
is a permanent optical feature, consisting of two full haloes
encircling the earth. Viewed around this "24-hour oval"
there are typically quiet arcs in the evening sector, dynamic
brighter auroras in the midnight sector, diffuse auroral remnants
in the morning sector and faint, red aurora through the noon sector.
The IGY prompted
the establishment of many Antarctic bases in the 1950s, many of
which have had active research programs, including auroral studies.
At the Australian Mawson station and the Japanese Syowa station,
aurora can be seen on practically every clear night. They are
about 25 degrees from the South Magnetic Pole. Amundsen-Scott
Station at the South Geographic Pole, established in 1956, is
just poleward of the center of the auroral zone, but an ideal
location for studies of auroras near midday - aided by several
months of 24-hour darkness each year.
1996-2003 went from solar minimum (~1996) to solar maximum (~
2002) and the observations and photographs of Robert Schwarz,
a scientist then at Amundsen-Scott Station, illustrate how auroral
activity and poleward expansion increase with solar activity during
the 11-year sunspot cycle. They are in agreement with the more
extensive evidence from the Northern Hemisphere.
is controlled to a major degree by solar activity and the solar
wind, that continuous stream of electrons and protons emanating
from the sun. Major auroras are due to Coronal Mass Ejections
(CMEs) from the sun, while auroral substorms are usually triggered
by changes in the solar wind. Auroral substorms occur periodically
and typically last for about 3 hours. The first sign is a sudden
brightening of the quiet auroral arc in the midnight sector. This
brightening spreads westward along the auroral oval, then the
aurora expands poleward (termed the expansive phase). During this
time the aurora is most active and colourful, with draperies,
transient rays and rapidly moving arcs. The aurora then fades
and recedes to lower latitudes and is replaced by fainter patches,
often pulsating. This recovery phase lasts for up to 2 hours.
expanding down to low latitudes and lasting up to 2 days occur
very occasionally, and have been marvelled at through the ages.
They are marked by their near global extent, their long duration
and by their brightness and vivid colour. As they expand to lower
latitudes they usually exhibit a deep red colour. Global power
inputs via particle precipitation have been estimated as high
as 1000 gigawatts during the peak of such auroras. They tend to
occur around or following the peak of the 11-year cycle of solar
sunspot activity (but can occur any time). While there may be
something special causing these very unusual auroras, so far it
appears they are just "bigger" than the usual substorms
and not greatly different.
One of the
great auroras of the past century occurred on March 13-14, 1989,
with sightings reported from Argentina, Britain, and over much
of North America. Satellites recorded images of greatly expanded
auroras over both southern and northern latitudes. That aurora
lasted more than 30 hours and caused a major power disruption
along the American eastern seaboard. Another aurora approaching
the same magnitude was on April 6-7, 2000. It was seen in South
Africa, north of Capetown, a bright red glow lasting for three
hours. It was also viewed over much of Europe and throughout North
One last example was the great Aurora Australis seen on March
30-31, 2001. As reported in detail by the Royal Astronomical Society
of New Zealand, it was visible over much of New Zealand and Southern
Australia through the whole night and was often red in colour.
There were Aurora Borealis sightings at the same time over much
of North America and across Norway.
It is noteworthy
that for the latter two auroras there was a full array of spacecraft
in orbit and it was possible to trace their full evolution from
beginning to end. SOHO observed the solar CMEs, which caused them.
The progress of the clouds and the solar wind streaming earthward
were monitored by the ACE and WIND satellites, and the auroras
resulting some 2-3 days later (the sun-earth transit time) were
recorded by several satellites.
It is difficult
to get auroral observations from the ground in both hemispheres
simultaneously, due to the asymmetry of seasons. The best opportunities
are around the equinoxes, when there are similar day and night
conditions in both auroral zones. Fortunately, auroral activity
is somewhat greater through the spring and autumn seasons due
to increased magnetic activity, which adds to the chances of joint
observations. Major displays of Aurora Australis were reported
by viewers in New Zealand and Australia on May 4, 1998, October
24 and November 4, 2001, October 23, 2003, and November 7, 2004.
of the auroral zones there are often auroras, referred to as "polar
auroras". They were first noted by early Antarctic (and Arctic)
explorers. They are of similar origin to lower latitude auroras
but are somewhat different in appearance and character. They occur
under quiet magnetic conditions when auroral oval activity is
minimal. They consist of very narrow arcs, usually faint and colourless,
and they are always aligned along the Sun-Earth line. They usually
are seen to split off the poleward edge of the auroral oval and
drift across the polar cap, or to linger for hours depending on
the state of the solar wind.
now a general understanding of auroral phenomena, but some questions
still remain and these are now being addressed by several countries
in on-going research on the Aurora Australis in Antarctica, at
over 20 stations located around the continent. This work has been
recently extended with the addition of several remote automated
geophysical observatories on the continent, and with an array
of auroral radars that cover much of the southern auroral zone.
So, while historically much of the knowledge about auroras came
from observations of the Aurora Borealis, the Aurora Australis
has captured its proper share of attention during the past half-century
with the establishment and operation of the Antarctic research
Antarctic: Definitions and Boundaries; Auroral Substorm; Australasian
Antarctic Expedition (1911-14); Biscoe, John; British Antarctic
(Nimrod) Expedition (1907-09); British National Antarctic
(Discovery) Expedition (1901-04); Cook, James; International
Geophysical Year; Magnetic Field; Mawson, Douglas; Ross Island;
Scott, Robert Falcon; Shackleton, Ernest; Solar Wind; South Pole;
and Further Reading
Background to the Aurora Australis, Kingston, Tasmania:
Commonwealth of Australia (ANARE Report 135), 1990.
and Fred Jacka. Distribution of auroras in the Southern Hemisphere,
II: nightly probability of overhead aurora. Australian Journal
of Physics 15 (2): 261-272, 1962.
and I.L. Thomas. The southern auroral oval. Australian Journal
of Physics 24: 97-202, 1971.
and Alv Egeland, The northern lights: their heritage and science.
Translated by James Anderson. Oslo: Grondahl og Drewers Forlag
Majestic lights: the Aurora in science, history and the arts.
Washington, DC: American Geophysical Union, 1980.
Douglas. The last continent. London: Jarrold Publishers,
Aurora: the mysterious northern lights. Vancouver: Greystone
Robert. Polarlichter. Nordendstr. 58, 8080 Munchen, Germany,
C. The polar aurora. Oxford: The Clarendon Press, 1955
Jones, A. Historical review of great auroras. Canadian Journal
of Physics 70: 479-487, 1992.
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