is a sprite?
A sprite is a very brief, luminous glow that occurs in the middle atmosphere.
Sprites often start around 45 miles high (in the mesosphere) and extend
upwards to the edge of the ionosphere (around 55-60 miles) and sometimes
downwards into the stratosphere below (to as low as 15-20 miles). They are
primarily red in color, except for some bluish tinge in the downward extending
When were sprites discovered?
Human beings have probably noticed red sprites out of the corner of their
eye since they first began roaming the Earth. Since 1886, scientists have
periodically reported in scientific journals that they thought they had
seen something they did not understand high above thunderstorms. Yet the
discovery can be traced to 6 July 1989 when University of Minnesota
Physics Professor John R. Winckler was testing a low-light video camera
for an upcoming research rocket flight. On playing back the tape, he and
his graduate students, Robert Franz and Robert Nemzek, were astounded to
find two fields of video showing two giant columns of light towering high
above distant thunderstorms in northern Minnesota. They were quick to realize
this accident might actually explain over a century of unexplained
visual reports of strange lights above thunderstorms.
long does a sprite last?
Sprites are very brief. The portion of the event that might be visible
to the naked eye often lasts less than one hundredth of a second. When
using a night vision camera, they are visible for longer periods,
but rarely more than one tenth of a second. GO
big is a sprite?
Huge! Aside from stretching vertically for as much as 45 miles, the sprite
can often be tens of miles across. Often sprite events comprise a series
of individual sprites that occur in clusters stretching 50 miles or more
across the sky. The entire volume of atmosphere enveloped by a sprite
can cover thousands of cubic miles.
Lightning. Sprites are the result of extremely powerful lightning discharges
sometimes occurring within thunderstorms. They are almost always triggered
by a powerful positive cloud-to-ground (CG) flash which lowers massive
amounts of electrical charge to the Earth. This momentarily increases
the electric field in the middle atmosphere beyond the point of dielectric
breakdown. In other words, a giant spark occurs, usually starting
around 45 miles above the ground. Electrical streamers then race both
downwards and upwards from that point. Though sprites may look rather
solid in many images, when viewed through telescopes, many
sprites are actually composed of networks of thin channels of electrical
streamers. Only a very small percentage (<10%) of positive CGs actually
produce sprites, and then, only in certain storms.
sprites connect with the clouds below?
Good question. At least from the low-light camera images obtained to date,
it does not appear that the downward extending tendrils actually reach
the tops of thunderstorms below. But the brilliant glow from the parent
lightning discharge in the cloud makes it difficult to tell for sure.
It is important to note that sprites do NOT shoot up from the cloud. The
luminous structure actually starts many miles above the storm which contains
the parent lightning discharge, and extends both upwards and downwards.
It is possible that some tendrils may extend all the way back down to
the cloud, but scientists are still working to prove this. GO
gives sprites their color?
Current thinking is that sprites result when free electrons in the thin
atmosphere are accelerated by the sudden change in electric field strength
caused by the parent lightning discharge far below. When the electrons
slam into molecules of nitrogen, they cause the nitrogen to glow. Certain
energies result in primarily red optical emissions, but in the lower part
of the sprite, blue colors can also be seen. The process is not all that
dissimilar from the aurora, where the energetic particles are supplied
by the solar wind. Oxygen also is activated in the aurora, accounting
in part for the green and white colors that also occur in that phenomenon.
Some humans see sprites as white or green in color, but that is a result
of the inability of the human eye to distinguish colors at such low intensities.
did the sprite get its name?
When people first began reporting sprites, initially from naked eye observations,
and then in 1989 on video tape, no one really knew what to call them.
Rocket lightning, flachenblitz, upward lightning, cloud-to-stratosphere,
and even cloud-to-space lightning were just a few of the names used. This
started getting very confusing very fast, especially as no one knew if
the phenomenon was actually lightning (as opposed to be being a result
of lightning), whether it was connected to the clouds, which way it went,
and whether it reached into space. Thus, early on, scientists
realized that a name was needed that was descriptive of the phenomenon,
but did not imply that we understood the physics before we did. "Sprites
are mythical, fleeting, and playful creatures that appear in mythology
and Shakespearean plays. The name was first suggested by Prof. David Sentman
of the University of Alaska-Fairbanks in 1994, and it stuck. As new transient
luminous events (TLEs) above thunderstorms were discovered, they were
given names in the same vein: elves, trolls, gnomes, pixies and blue jets
(which just named themselves because they looked just like...blue jets.)
shapes do sprites take?
Like snowflakes, no two sprites are alike. Early on, scientists were rather
bewildered by the amazing variety of shapes they were seeing in their
TV monitors. Soon they started attempting to classify them by shape, and
terms like carrot sprites, angel sprites, broccoli sprites and A-bombs
emerged. Tall, skinny sprites, now usually called columniform sprites
(or c-sprites) were initially called diet sprites (who said scientists
dont have a sense of humor!) GO
you see a red sprite with the naked eye?
The majority of sprites are probably just a bit too fast and too dim to
be easily seen by the naked eye. But given the right conditions, one can
visually observe the brighter sprites. (See our section on how to watch
for sprites.) It is difficult, though not impossible, to capture a sprite
on a consumer camcorder. If you can add a night scope attachment,
your chances of capturing one on tape go way up.
do scientists detect sprites?
Sprites and related phenomena can be detected in a variety of ways. Aside
from the naked eye, low-light cameras and sensitive optical sensors are
the main instruments used to detect sprites. One can also detect sprites,
or more properly the radio emissions from their parent lightning, by using
extremely low frequency (ELF) and very low frequency (VLF) radio receivers.
sprites make thunder?
There is growing evidence that sprites - or their parent lightning - may
produce sound waves at extremely low frequencies (around 1 Hertz). Below
the range of human hearing, these infrasound waves can be picked up by
special receivers at ranges of hundreds if not thousands of miles away.
While not thunder in the usual sense of the word, these infrasound emissions
are the acoustic signature of the processes which produce sprites.
should I call if I see a sprite?
Dont call 9-1-1. They have far too much to do. But if you do spot
something strange in or near a thunderstorm, please go to the www.Sky-Fire.TV
site to report your sightings. If you have images or video, even better,
because physical evidence beats visual observations every time. Most of
the findings about sprites, jets, elves and upward lightning have stemmed
from amateur or inadvertent observations. Expect the unexpected, and you
may not be disappointed.
And please...no UFO
sightings (a least of the little green men kind). GO
have sprites been observed?
Sprites have now been observed over much of the world, with the exception
of the Arctic and Antarctic regions where thunderstorms are almost non-existent.
The High Plains of the United States probably have some of the highest
sprite rates due to frequent, large nocturnal thunderstorms during spring
and summer. But sprites are likely to be common above storms in northwestern
Mexico, Argentina and southern Brazil and central Africa. Sprites have
been photographed over Europe, Japan, Peru, China and Australia, to name
is the connection between the Space Shuttle Columbia and sprites?
Shortly after Prof. John Winckler observed sprites from the ground in
1989, NASA officials realized that they had been using similar low-light
cameras on the Space Shuttle to take pictures of lightning and other events.
A review of the payload bay video cameras flown from 1989 to 1991, found
at least 18 examples of what appear to be sprites. Then in 2003, the first
Israeli astronaut, Ilan Ramon, flew on the STS-107 mission with optical
equipment designed to make detailed, calibrated images of sprites. Within
several days of launch, successful images of sprites (and elves) were
sent back to Earth for further analysis.
sprites pay a role in the loss of the Space Shuttle Columbia?
Shortly after the tragic loss of the Shuttle Columbia on 1 February 2003,
wild rumors began to fly that the Shuttle was brought down by a sprite.
This was fueled by reports of a picture taken by an amateur astronomer
in San Francisco purporting to show some sort of lightning-like
bolt striking or emanating from the orbiter as it flew over the
California coastline. As of this writing, NASA has not released the image
for external scientific review. But neither the description of the image
nor the weather conditions at the time suggested that a classic sprite
could have been involved. If the image does not turn out to be simply
an optical illusion, then the possibility of some as yet unknown electrical
phenomenon at the base of the ionosphere will have to be investigated.
are the major layers of the atmosphere?
Earths atmosphere is proportionately thinner than the skin on an
onion. And like the onion, it comes in several layers. The lowest layer
is called the troposphere. Rarely more than 10 miles deep, it contains
almost all of Earths weather systems. The next layer is the stratosphere,
where temperatures slowly increase with height, producing stable conditions.
It is also home to much of the planets shield of ozone. This gas
absorbs most of the harmful ultraviolet radiation streaming in from the
sun. At about 30 miles the stratosphere gives way to the mesosphere. This
layer is where many incoming meteors burn up, leaving fiery trails across
the night sky. Higher yet is the hot thermosphere, where most aurora are
found. The outermost layer is called the exosphere which gradually merges
into space, which as we have come to learn, isnt quite
as empty as once thought. The ionosphere, a region of electrically charged
particles, is considered more a part of the thermosphere, and it, too,
surrounds the planet like a shell. GO
is an elve?
The elve was first theoretically predicted by scientists at Stanford University
in the early 1990s and then observationally confirmed by imagers on the
Space Shuttle and the ground (by Tohoku University scientists) several
years thereafter. The elve results from an especially powerful electromagnetic
radiation pulse (EMP) that emanates from certain lightning discharges.
As the energy passes upwards through the base of the ionosphere it causes
the gases to briefly glow. Though as bright as a sprite, the elve only
lasts for less than a thousandth of a second. This makes elves virtually
impossible to see with the naked eye. They are most likely red in color,
and if you could see them, they would look like giant expanding doughnuts.
They occur at a height of around 60-65 miles, and can expand outward to
several hundred miles in diameter.
is a blue jet?
The blue jet was caught, again quite by accident, on low-light cameras
from the University of Alaska-Fairbanks onboard a NASA research jet in
1994. The jets appear to spurt upwards from cloud tops at speeds of 50-100
miles per second, reaching heights of up to 25 miles before fading. They
last generally less than a quarter of a second, but it is possible to
perceive their upward motion with the unaided eye. While generated by
storms with high lightning rates, unlike red sprites, blue jets do not
appear to be related to specific cloud-to-ground lightning discharges.
They also appear more likely to occur near the highest portion of intense
thunderstorm cells, such as those which produce tornadoes and severe weather.
you see blue jets with the naked eye?
Yes. At least the brighter ones. They emerge from the tops of intense
thunderstorm clouds that are highly electrically active. They are a pale
blue in color, and often appear as grainy, upward shooting blobs or cones
of light leaving a trail behind. It is best to be within 100 or so miles
of the storm as blue light does not transmit well through the atmosphere.
A moonless night in a rural area away from city lights, and a dark adapted
eye will help in spotting the elusive blue jet.
is an upward superbolt?
We are beginning to think that true upward lightning may well
exist. Regular lightning flashes can sometimes jump outside the parent
cloud, and rarely extend a short distance (less than a mile) above storm
tops. But a growing number of reports describe brilliant white channels
extending upwards many tens of thousands of feet above storm tops. They
resemble ordinary lightning channels, but also appear to last much longer,
up to one or two seconds, and do not flicker. They also seem to grow upward
out of the cloud, and upon reaching their maximum height, the entire channel
dims away. They may well occur above the tops of explosively growing clouds.
They often occur every few minutes, and episodes can last for a half hour
or more. Thus, they may not be too hard to photograph. See our sprite
picture gallery for some examples. GO
there sprites on other planets?
This is an interesting question for which we do not yet have an answer.
But it is fairly clear that lightning-like discharges occur in the atmosphere
of Jupiter. Thus the possibility of sprites above Jupiter's swirling clouds
must be considered. Time will tell.
science discovered everything in the middle atmosphere?
Scientists, sometimes only half jokingly, call parts of the middle atmosphere
the ignorosphere. For a long time it was ignored simply because
of the difficulty in obtaining information from this region. It is too
high to be sampled by aircraft and balloons. It is too low to be sampled
by satellites. Research rockets can whiz through and grab some data, but
only for a few minutes. Remote sensing tools like video and radars do
help at lot, but nothing beats getting actual measurements in situ, a
phrase borrowed from the Latin that scientists like to use. The discovery
of sprites, elves, blue jets and other "creatures" in this region
suggest there may be all manner of phenomena occurring here about which
we know little, or perhaps even nothing - yet.
Do sprites affect the ozone
Another good question. Ozone is created in the middle atmosphere as a
result of the bombardment of atmospheric oxygen by energetic particles
from the sun. This creates a special form of oxygen, with three O atoms
instead of two. Ozone is essential to shield life below from the very
harmful ultraviolet rays of the sun. Sprites also deposit energy into
the middle atmosphere. But it is not yet clear just what energy they release
and exactly how it may affect the chemistry of this region. Advanced chemical
models have been applied which suggest that sprites do produce chemical
changes, some of which could lead to ozone production.
airline pilots seen sprites?
Yes. For many years, along with blue jets and other strange sights. But
commercial pilots have to pass annual physical exams. And for a long time,
no one dared tell stories about these strange lights less
the reports be misinterpreted as an indication the pilot wasnt quite
right in the head. But during the 1970s and 1980s, reports were
gradually, and quietly, collected from a number of pilots, that in retrospect
make it clear they were seeing sprites and jets during night flights from
their excellent vantage point of the cockpit. GO
I make a great scientific discovery?
Yes. We are far from knowing all there is about the physical world about
us. But science is not just a matter of coming up with some wild idea.
Science is a very deliberate and serious process. To be a scientist, one
must follow the scientific method. Science is the process of creating
knowledge, first by making observations or theoretical calculations, and
then proposing a hypothesis. Other scientists then strive to find pieces
of evidence to prove - or disprove - the notion. Science is forever proposing
ideas, and then promptly tearing them down, only to replace them with
even more complete hypotheses which explain the physical world. It is
critical to know what other scientists have learned so that each new observation
can be related to what is known, or not known, about the physical world.
And the more you know about science, the greater the likelihood that you
may realize the great importance of some strange and unexpected observation.
Rather than shrugging your shoulders and saying, What the heck was
that? you may realize your sighting fills in a big blank in the
scientific puzzle matrix
in other words, you understand the relevance
of your discovery.
Science is NOT about
ego or current belief or politics. It is about truth. A scientist can
have an idea, a hypothesis as we put it. The idea might be right, it might
not. A true scientist tells the community, Hey, I have an idea.
What do you think? Other scientists will gladly tell him or her,
You are on the right track, or Youre all wet,
and here are the reasons why. It is a process of give and take. Listening
and learning. Science deals with observations. Hard FACTS. This give and
take is long, arduous, and sometime bruising to egos. But the ultimate
goal is to find one thing - the truth as best we can know it.
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