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Topic: Auroral light

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	Polar Aurora
		An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights; in the Southern Hemisphere it is called the aurora australis.
		The location of the auroral oval is generally found between 60 and 70 degrees north and south latitude.
		Most of the auroral features are greenish yellow but sometimes the tall rays will turn red at their tops and along their lower edge.
	www.ebroadcast.com.au /lookup/encyclopedia/au/Auroral_light.html (1023 words)

	Alaska Office of Economic Development
		The great auroral displays are spectacular global events during which the Aurora spreads down from the polar regions to cover as much as two thirds of the earth's skies with bright, fast-moving masses of light, often deep red in color.
		The light is a glow from atoms and molecules in the earth's upper atmosphere.
		Auroral color depends on the type of atoms and molecules struck by the energetic particles, particularly electrons, that rain down along earth's magnetic field lines in the discharge process.
	www.dced.state.ak.us /oed/student_info/learn/northernlights.htm (1676 words)

	Northern Hemisphere Enlarged View (Site not responding. Last check: 2007-10-12)
		This plot shows the current extent and position of the auroral oval in the northern hemisphere, extrapolated from measurements taken during the most recent polar pass of the NOAA POES satellite.
		The statistical pattern depicting the auroral oval is appropriate to the auroral activity level determined from the power flux observed during the most recent polar satellite pass.
		The process to estimate the hemispheric power, and the level of auroral activity, involves using this normalization factor which takes into account how effective the satellite was in sampling the aurora during its transit over the polar region.
	www.sel.noaa.gov /pmap/pmapN.html (314 words)

	Classes of Auroral Light and Associated Precipitation
		At least two classes of auroral activity are associated with the medium energy plasmasheet particles in Figure 17.3 and 17.4.
		The second class is due to ``discrete auroral arcs'' which are typically bright, localized structures that are primarily (but not always) produced during the auroral brightenings that accompany magnetospheric substorms.
		Auroral displays associated with electrons and with protons are observed at Earth, having different spectral properties and typically different locations too.
	www.physics.usyd.edu.au /~cairns/teaching/lecture17/node3.html (795 words)

	Attiyah's Sun Theory - Bad Astronomy and Universe Today Forum
		A- Both the auroral light and all the light emissions received at Earth coming directly from the seen Sun's position in the sky show simultaneous variations with the geomagnetic activities and precipitation of the charged particles on the ionosphere.
		B- The intensity variations of the auroral brightness and light received at Earth coming directly from the Sun are directly proportional to the level of the geomagnetic activities and strength of the precipitation of the charged particles on the ionosphere.
		The Auroral Oval and Dome of the Skylight
	www.bautforum.com /showthread.php?t=46168 (5509 words)

	NOAA Home Page - Question of the Month (Site not responding. Last check: 2007-10-12)
		The particular colors we see in an auroral display depend on the specific atmospheric gas struck by energetic particles, and the energy level to which it is excited.
		Oxygen is responsible for two primary auroral colors: green-yellow wavelength of 557.7 nm is most common, while the deep red 630.0 nm light is seen less frequently.
		It should be noted that the auroral oval does not follow lines of equal latitude, so people on the East Coast of the United States have a higher likelihood of seeing aurora than those at the same latitude on the West Coast.
	www.noaa.gov /questions/question_030502.html (1697 words)

	Weather Elements: The Aurora
		The lights we call the aurora is produced by the interaction of the high-energy particles (usually electrons and hydrogen ions carried by the solar wind) with the oxygen and nitrogen atoms in the Earth's upper atmosphere.
		The particular colours we see in an auroral display depends on the specific atmospheric gas struck, its electrical state at the time of collision, and the energy of the extraterrestrial particle involved in the collision.
		Auroral rays are thin beams or shafts of auroral light that hang vertically above the observer.
	www.islandnet.com /~see/weather/elements/aurora.htm (1107 words)

	NASA - Auroras Dancing in the Night
		In a sense, auroras are the neon lights of the Earth's poles.
		The green light emitted from excited oxygen is centered around a wavelength of 558 nanometers, while the rarer red light is emitted around wavelengths in the 630 nanometer region.
		Auroral activity seems to be at its peak 180 degrees from the sun.
	www.nasa.gov /vision/universe/watchtheskies/aurora.html (942 words)

	BAA Aurora Section: The Aurora
		Sometimes there are patches of auroral light without distinct boundaries, in clear sky (so that it is not the effect of obscuring clouds) and well up from the horizon (so that it is not a glow).
		The intensity of auroral light is often too low to stimulate the colour-sensitive parts of the eye and auroral forms may have the grey-white appearance of cloud lit by weak moonlight But at higher intensities (or to a well dark adapted eye) aurora exhibits a variety of colours, mainly greens and deep reds.
		Interference filters passing the auroral emission colour green of 5577 angstroms may be used to search for auroral light in cloudy, moonlight, hazy or town lit conditions.
	www.britastro.org /aurora/theaurora.htm (1054 words)

	Solar Terrestrial Probes Dictionary
		The auroral altitude range is 80 to 1000 km, but typical auroras are 100 to 250 km above the ground; the color of the typical aurora is yellow-green, from a specific transitions of atomic oxygen.
		Auroral light from lower levels in the atmosphere is dominated by blue and red bands from spectral line of atomic oxygen.
		A sudden brightening (only rarely seen without special filters, isolating the red light of hydrogen) may be followed by the signatures of particle acceleration to high energies--x-rays, radio noise and often, a bit later, the arrival of high-energy ions from the Sun.
	stp.gsfc.nasa.gov /stp_program/stp_dictionary.htm (2717 words)

	Aurora (astronomy) Summary
		With the advent of spectroscopy in the nineteenth century, it became possible to examine what elements were responsible for producing auroral light, and developments in the twentieth century of the theory of atomic structure and the nature of solar activity and the Earth's magnetic field allowed scientists to understand the cause of aurorae.
		The Earth is constantly immersed in the solar wind, a rarefied flow of hot plasma (gas of free electrons and positive ions) emitted by the sun in all directions, a result of the million-degree heat of the sun's outermost layer, the solar corona.
		An auroral electrojet index (measured in nanotesla) is regularly derived from ground data, and serves as a general measure of auroral activity.
	www.bookrags.com /Aurora_(astronomy) (5112 words)

	The Basics of Auroral Emissions
		The auroral lights appear as time-varying bands and filaments of light, often of many different colours, often moving about the sky, often showing structures oriented in the vertical direction (qualitatively consistent with the orientation of magnetic field lines), and showing structures that are discrete (such as auroral arcs).
		Examples of the auroral lights can be found in Figures 15.6 and 15.11, as well as in Cravens' [1997] book, the paper of Carlson and Egeland [1995], and the web sites given to you at the end of Lecture 13.
		Auroral emissions are produced as a result of energetic electrons and protons from the solar wind and Earth's magnetosphere colliding with the constituents of Earth's upper atmosphere and ionosphere.
	www.physics.usyd.edu.au /~cairns/teaching/lecture17/node2.html (661 words)

	NORDLYS - Northern Lights
		Among the Eskimos in Greenland and northern Canada, the aurora was the realm of the dead, and when the lights changed rapidly, it meant that dead friends were trying to contact their living relatives.
		It was a common belief that the northern lights were the reflections in the sky of huge fires in the distant north, or that the mighty God himself lighted up the dark and cold parts of the world.
		One romantic conception found in Danish folklore is that these lights were due to a throng of swans flying so far to the north that they were caught in the ice.
	www.northern-lights.no /english/mythology/index.shtml (369 words)

	IMAGE Spacecraft Takes First Pictures of Electrified Gas Surrounding Earth
		The aurora, commonly known as the northern and southern lights, is a ghostly light show seen most often at high latitudes of Earth.
		The dance of lights that is visible from the ground is caused by electrons striking and lighting up the atmosphere much like electricity lights up a television screen.
		Light from the Earth's aurora occur principally in two oval-shaped bands lying between ~65 and 75 degrees magnetic latitude and centered on the northern (aurora borealis) and southern (aurora australis) magnetic poles.
	www.solarviews.com /eng/imagepr1.htm (930 words)

	Glossary
		The pattern or distribution of auroral light around Earth’s north and south magnetic poles.
		A Doppler shift in the spectrum of an astronomical object is commonly known as a redshift when the shift is towards longer wavelengths (the object is moving away) and as a blueshift when the shift is towards shorter wavelengths (the object is approaching).
		Auroral substorms are caused by powerful charged particles in the magnetotail.
	www.spaceweathercenter.org /swop/Glossary/1.html (2854 words)

	Jupiter Auroral Campaign (Site not responding. Last check: 2007-10-12)
		The aurora are curtains of light resulting from high energy electrons following the planet's magnetid field into the upper atmosphere, where collisions with atmospheric atoms and molecules produce the observed light.
		Auroral footprints can be seen in this image from Io (along the left hand limb), Ganymede (near the center just below the referenc oval), and Europa (just below and to the right of Ganymede's auroral footprint).
		The greenish-white light is produced bybi incident high energy charged particles colliding with oxygen atoms in the Earth's upper atmosphere, and the fainter red color seen at higher altitudes is a combination of collisions with nitrogen and hydrogen atoms.
	www.sprl.umich.edu /cassinihstjupiterflyby (954 words)

	SOUTHERN AURORAE I
		Such astounding eerie light is caused by applying a simple electrical current that collides with normal neutral atoms like oxygen and nitrogen in the upper atmosphere.
		This emitting light is under the same process that occurs in the everyday fluorescent light tube that you may have in your bathroom or perhaps outdoor for the backyard or shed.
		Although is was later shown that some aurorae appeared blue or purplish due sunlight shining on the upper rays during twilight, it was not the principal process of the auroral light.
	www.geocities.com /ariane1au/PageAurora001.htm (2928 words)

	auroras
		Auroral light is similar to light from color television.
		Auroral light is the from the air glowing as charged particles, particularly electrons, rain down along the Earth's magnetic field lines.
		Usually, if sun-earth conditions produce an auroral substorm, a diffuse patch of glowing sky will be seen first, followed by a discrete arc that brightens, perhaps a thousand-fold in a minute.
	earthsci.org /fossils/space/physics/aurora.htm (669 words)

	Aurora Page (Site not responding. Last check: 2007-10-12)
		Another is the flaming Aurora, where bursts of light appear at the base of the Auroral form and then rapidly move up and disappear at the top.
		Auroral brightness is rated on a scale of 0 to 4, 0 being a barely visible Aurora, and 4 being a very bright Aurora.
		The word Aurora Australis refers to the Aurora that occurs in the southern hemisphere (southern lights), whereas Aurora Borealis refers to the Aurora that occurs in the northern hemisphere (northern lights).
	ph99.bc.edu /grad/Tomek/Auroral_Homepage/Aurora.html (2372 words)

	Collisions and Emissions (Site not responding. Last check: 2007-10-12)
		Excited states are unstable, and atoms emit light of specific wavelengths as they decay back down to a stable configuration.
		Unlike sunlight, auroral light is not a continuous spectrum of wavelengths.
		Auroral emissions also result from chemical reactions that occur among the ionized and dissociated gases.
	deved.meted.ucar.edu /hao/aurora/txt/x_a_2_1.php (195 words)

	Colored by the atmosphere
		The highest part of the auroral curtain is red, the middle is greenish-white and the lower edge is pink.
		At the lower edge of the curtain, the density of molecules doesn't permit oxygen to emit light; the pinkish color comes from a combination of red and blue from nitrogen.
		Anders Jonas Ångstrom (1814-1874) was one of the first to discover the auroral spectrum and note its distinct differences from the sun's spectrum.
	www.gi.alaska.edu /asahi/color.htm (381 words)

	Aurora (astronomy) - Wikipedia, the free encyclopedia
		Light emitted by the Aurora tends to be dominated by emissions from atomic oxygen, resulting in a greenish glow (at a wavelength of 557.7 nm) and - especially at lower energy levels and at higher altitudes - the dark-red glow (at 630.0 nm of wavelength).
		established that the aurora appeared mainly in the "auroral zone", a ring-shaped region of with a radius of approximately 2500 km around the magnetic pole of the earth, not its geographic one.
		The northern lights are mentioned in the song "North to Alaska" sung by Johnny Horton.
	en.wikipedia.org /wiki/Auroral_light (5373 words)

	Coastline Aurora (Site not responding. Last check: 2007-10-12)
		The finding that auroral emissions are sometimes affected by the presence of a coastline offers a further challenge to our understanding of the phenomenon because it has been always assumed that these lights were completely controlled by processes in and above the Earth's upper atmosphere, and not occasionally by the surface sea and land masses.
		This intense auroral arc is aligned with the northern coast of Alaska and extends for a distance of 400 miles from Barrow eastward over Prudhoe Bay and on to Kaktovik.
		The intensity of the auroral light diminishes abruptly at the shoreline and remains relatively dim over the land.
	aurora.physics.uiowa.edu /coast.html (1031 words)

	05. Aurora
		I don't know whether this flashing aftereffect is well-known among those who study the auroral light (and I was in a location with a very dark night sky, no nearby human settlements), but I think I may have an explanation for it.
		My theory is that a recombination of electrons and protons (in one form or another) would spontaneously begin at some location, and the light emitted by this event would serve to trigger other, adjacent charged particle pairs to recombine, thus creating a fast-moving wave of recombination events and associated light.
		I should add these cascades of light were a great deal dimmer than the prior auroral displays, and they would require some truly exotic equipment to study in any systematic way.
	www.arachnoid.com /alaska2004/aurora.html (913 words)

	Auroral folklore [Oulu] (Site not responding. Last check: 2007-10-12)
		In some traditions, auroral rays were perceived as lights carried by the Valkyries as they rode the sky.
		In ancient Roman and Greek records, references may sometimes be found to 'chasmata' in the sky, the auroral arc structure being regarded in such instances as being the mouth of a celectial cave.
		Another romantic notion was that auroral light result from icebergs crashing together in the polar seas.
	www.oulu.fi /~spaceweb/textbook/aurora/folklore.html (596 words)

	ExploraTour - Looking at the World in a Different Light (Site not responding. Last check: 2007-10-12)
		The aurora is made of colorful and rapidly moving lights in the night sky.
		The lights are made in much the same way as the picture on your TV screen -- the atmosphere is like a giant picture tube.
		On Jupiter, the auroral light is mostly in the ultraviolet.
	www.windows.ucar.edu /cool_stuff/backup_imagemaps/Exploratour_1r.html (663 words)

	Auroral sounds
		Scientists of northern lights are just too busy with the ionosphere where the lights originate, the Earth mangetosphere where the charged particles that create aurora are accelerated, and the solar wind that drives the whole thing.
		To imagine how skies may look like when auroral sounds are heard you can watch a movie composed of pictures taken by the all-sky camera in Poker-Flat, Alaska.
		The auroral lights originate at heights from 60 to 400 km.
	members.tripod.com /~auroralsounds (1196 words)

	The Ashen Light
		Ashen Light is thought to be an airglow or auroral phenomenon by some /2,5/, and airglow and aurora are seen from orbiting spacecraft /6,7/.
		Another piece of evidence for the reality of the Ashen Light phenomenon is the fact that its occurrence correlates with a phenomenon that should not affect seeing conditions and of which the observers should have been completely unaware.
		The Ashen Light has many properties that one would expect for a phenomenon intrinsic to Venus rather than an artifact introduced by the observers, In particular, it appears that it has a local time of occurrence that is very similar to that of Venus lightning.
	www-ssc.igpp.ucla.edu /personnel/russell/papers/ashen (2942 words)

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