MattEU wrote:cheers mate
good old google books and plasma-universe.com ! Basic space plasma physics by Wolfgang Baumjohann and Rudolf A. Treumann
this toing and froing of the near-earth plasma jet where 10% of the solar winds energy sneaking into the earths atmosphere trigger the auroras and oscillates earths magnetic compasses.
the amazing thing about spacequakes is that their signature is very similar to earthquakes. they not only release the same amount of energy, have the same signature but also they occur over the same timeframe! if everything in the electric universe is scalable are we seeing what might cause earthquakes or is it that the release energy signature of these events is similar in an electric universe?
Earth's "plasma fountain", showing oxygen, helium, and hydrogen ions which gush into space from regions near the Earth's poles. The faint yellow area shown above the north pole represents gas lost from Earth into space; the green area is the aurora borealis, where plasma energy pours back into the atmosphere
Plasma - wiki
Above: A schematic diagram of Earth's magnetosphere. Earth is the circle near the middle and the plasma tail is denoted in yellow.
February 19, 2003: They hover on the edge of space. Thin, wispy clouds, glowing electric blue. Some scientists think they're seeded by space dust. Others suspect they're a telltale sign of global warming.
They're called noctilucent or "night-shining" clouds (NLCs). And whatever causes them, they're lovely.
"Over the past few weeks we've been enjoying outstanding views of these clouds above the southern hemisphere," said space station astronaut Don Pettit during a NASA TV broadcast last month. "We routinely see them when we're flying over Australia and the tip of South America."
Sky watchers on Earth have seen them, too, glowing in the night sky after sunset, although the view from Earth-orbit is better. Pettit estimated the height of the noctilucent clouds he saw at 80 to 100 km ... "literally on the fringes of space."
"Noctilucent clouds are a relatively new phenomenon," says Gary Thomas, a professor at the University of Colorado who studies NLCs. "They were first seen in 1885" about two years after the powerful eruption of Krakatoa hurled plumes of volcanic ash as much as 80 km high in Earth's atmosphere.
Ash from the Indonesian volcano caused such splendid sunsets worldwide that evening sky watching became a popular past time. One sky watcher in particular, a German named T.W. Backhouse who is often credited with the discovery of noctilucent clouds, noticed something odd. He stayed outside after the sun had set and, on some nights, saw wispy filaments glowing electric blue against the black sky. Scientists of the day figured they were some curious manifestation of volcanic ash.
Eventually the ash settled and the vivid sunsets of Krakatoa faded. Yet the noctilucent clouds remained. "It's puzzling," says Thomas. "Noctilucent clouds have not only persisted, but also spread." A century ago the clouds were confined to latitudes above 50o; you had to go to places like Scandinavia, Russia and Britain to see them. In recent years they have been sighted as far south as Utah and Colorado.
Above: Noctilucent clouds over Finland. The orange hues near the horizon are ordinary sunset colors, notes Gary Thomas. NLCs, on the other hand, are usually "luminous blue-white or sometimes just pale white," he says. Image credit Pekka Parviainen.
Astronaut Don Pettit is a long-time noctilucent cloud-watcher. As a staff scientist at the Los Alamos National Laboratory between 1984 and 1996, he studied noctilucent clouds seeded by high-flying sounding rockets. "Seeing these kinds of clouds [from space] ... is certainly a joy for us on the ISS," he said on NASA TV.
"Although NLCs look like they're in space," continues Thomas, "they're really inside Earth's atmosphere, in a layer called the mesosphere ranging from 50 to 85 km high." The mesosphere is not only very cold (-125 C), but also very dry--"one hundred million times dryer than air from the Sahara desert." Nevertheless, NLCs are made of water. The clouds consist of tiny ice crystals about the size of particles in cigarette smoke.
How ice crystals form in the arid mesosphere is the essential mystery of noctilucent clouds.
Ice crystals in clouds need two things to grow: water molecules and something for those molecules to stick to--dust, for example. Water gathering on dust to form droplets or ice crystals is a process called nucleation. It happens all the time in ordinary clouds.
Left: Another noctilucent cloud seen from the ISS. Earth's horizon has been deliberately overexposed to reveal the faint cloudtops. "That little diaphanous line you see paralleling Earth's horizon is an NLC," said Pettit. Photo credit: Don Pettit and NASA TV.
Ordinary clouds, which are close to Earth, get their dust from sources like desert wind storms. It's hard to waft wind-blown dust all the way up to the mesosphere, however. "Krakatoa may have seeded the mesosphere with dust in 1883, but that doesn't explain the clouds we see now," notes Thomas. "Perhaps the source is space itself," he speculates. Every day Earth sweeps up tons of meteoroids--tiny bits of debris from comets and asteroids. Most are just the right size to seed noctilucent clouds.
The source of water vapor is less controversial. "Upwelling winds in the summertime carry water vapor from the moist lower atmosphere toward the mesosphere," says Thomas. This is why NLCs appear during summer.
One reason for the recent spread of noctilucent clouds might be global warming. "Extreme cold is required to form ice in a dry environment like the mesosphere," says Thomas. Ironically, global warming helps. While greenhouse gases warm Earth's surface, they actually lower temperatures in the high atmosphere. Thomas notes that noctilucent clouds were first spotted during the Industrial Revolution--a time of rising greenhouse gas production.
Above: The optimum viewing geometry for noctilucent clouds. Sunlight scattered by tiny ice crystals in NLCs is what gives the clouds their characteristic blue color. [more]
Are NLCs a thermometer for climate change? A telltale sign of meteoroids? Or both? "So much about these clouds is speculative," says Thomas.
A NASA spacecraft scheduled for launch in 2006 will provide some answers. The Aeronomy of Ice in the Mesosphere satellite, or AIM for short, will orbit Earth at an altitude of 550 km. Although it's a small satellite, says Thomas, there are many sensors on board. AIM will take wide angle photos of NLCs, measure their temperatures and chemical abundances, monitor dusty aerosols, and count meteoroids raining down on Earth. "For the first time we'll be able to monitor all the crucial factors at once."
Meanwhile, all we can do is wait ... and watch. There's never been a better time to see noctilucent clouds. "During the summer months, look west perhaps 30 minutes to an hour after sunset when the Sun has dipped 6o to 16o below the horizon," advises Thomas. If you see luminous blue-white tendrils spreading across the sky, you've probably spotted an NLC. Observing sites north of 40o latitude are favored.
One more thing: don't forget your camera. According to astronaut Don Pettit, "you can never have too many pictures of noctilucent clouds."
Editor's note: Astronaut Don Pettit's remarks and his pictures of NLCs that appear in this story were first broadcast on NASA TV in January 2003.
Credits & Contacts
Author: Dr. Tony Phillips
Responsible NASA official: John M. Horack Production Editor: Dr. Tony Phillips
Curator: Bryan Walls
Media Relations: Steve Roy
The Science and Technology Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities
"A NASA spacecraft scheduled for launch in 2006 will provide some answers. The Aeronomy of Ice in the Mesosphere satellite, or AIM for short, will orbit Earth at an altitude of 550 km. Although it's a small satellite, says Thomas, there are many sensors on board. AIM will take wide angle photos of NLCs, measure their temperatures and chemical abundances, monitor dusty aerosols, and count meteoroids raining down on Earth. "For the first time we'll be able to monitor all the crucial factors at once."
mharratsc wrote:They studiously avoid ANY mention of space weather phenomena- even though they are talking about 'clouds' in the mesospheric shell...
"If you wanted to see these clouds from the surface of Mars, you would probably have to wait until after sunset" says Franck Montmessin, a SPICAM scientist with Service d'Aeronomie du CNRS, Verrières-le-Buisson, France, and lead author of the results. This is because the clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds, on Earth. These occur at 80 kilometres altitude above our planet, where the density of the atmosphere is similar to that of Mars’ at 35 kilometres. The newly discovered Martian clouds therefore occur in a much more rarefied atmospheric location.
At 90–100 kilometres above the Martian surface, the temperature is just –193° Celsius. This means that the clouds are unlikely to be made of water. "We observe the clouds in super-cold conditions where the main atmospheric component CO2 (carbon dioxide), cools below its condensation point. From that we infer that they are made of carbon dioxide," says Montmessin.
But how do these clouds form? SPICAM has revealed the answer by finding a previously unknown population of minuscule dust grains above 60 kilometres in the Martian atmosphere. The grains are just one hundred nanometres across (a nanometre is one thousand-millionth of a metre).
They are likely to be the 'nucleation centres' around which crystals of carbon dioxide form to make clouds. They are either microscopic chippings from the rocks on the surface on Mars that have been blown to extreme altitudes by the winds, or they are the debris from meteors that have burnt up in the Martian atmosphere.
Naval Research Laboratory, June 21, 2010
A team of scientists from the Naval Research Laboratory and George Mason University reports that the Earth's upper atmosphere has recently experienced the lowest density in 43 years. The team has published its findings in a paper entitled "Record-low thermospheric density during the 2008 solar minimum" that appeared in Geophysical Research Letters in June 2010.
The team of Dr. John Emmert and Dr. Judith Lean from NRL's Space Science Division and Dr. Michael Picone from George Mason University were studying the Earth's upper atmosphere between 200 and 600 km altitude. Although the air density at these altitudes is only about one-billionth of that at the Earth's surface, it provides sufficient drag on Low Earth Orbit (LEO) objects to cause their eventual reentry. "An operational consequence of this important new finding is that LEO satellites, including debris, may remain in orbit longer than expected," explains Emmert.
To describe their results, the researchers pointed out that the air density at orbital altitudes is ultimately linked to the temperature of the upper atmosphere. A hotter upper atmosphere will expand in vertical extent and increase the air density at a given altitude. The two major factors that control upper atmosphere temperatures are heating via absorption of ultraviolet (UV) radiation from the Sun, and cooling via CO2 infrared emission.
The Sun was unusually quiet during the prolonged solar minimum of 2007-2009, and the research team found that the associated reduction in solar UV heating can partly explain the reduction in density. Increasing concentrations of CO2 near the Earth's surface are likely making their way into the upper atmosphere and are thus increasing the upper atmosphere cooling efficiency. However, it is not yet clear whether the combination of reduced solar UV heating and enhanced CO2 cooling can fully account for the occurrence of the anomalously low thermospheric density, and the researchers suggested that changes in upper atmospheric chemistry and composition may have also contributed to the record-low density.
Naval Research Laboratory/George Mason University Team Observes Record-Low Densities in Upper Atmosphere
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