When the deep purple falls (APOD 2009 February 1)
Posted: Sun Feb 01, 2009 11:56 am
http://apod.nasa.gov/apod/ap090201.html
<<Explanation: Higher than highest communications tower, higher than highest mountain, higher than highest airplane, lies the realm of the aurora. Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from energetic electrons and protons striking molecules in the Earth's atmosphere. Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles. This particularly rare purple auroral corona occurred in 2004 high above Harstad, Norway.>>
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http://en.wikipedia.org/wiki/Aurora_(astronomy)
<<Most aurorae are green and red emissions from atomic oxygen. Molecular nitrogen and nitrogen ions produce some low level red and very high blue/violet aurorae. The light blue and green colors are produced by ionic nitrogen and the neutral nitrogen gives off the red and purple color with the rippled edges. Different gases interacting with the upper atmosphere will produce different colors, caused by the different compounds of oxygen and nitrogen. The level of solar wind activity from the Sun can also influence the color of the aurorae.>>
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http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line
Kármán line
<<The Kármán line lies at an altitude of 100 km (62.1 miles) above the Earth's sea level, and is commonly used to define the boundary between the Earth's atmosphere and outer space. The line was named after Theodore von Kármán, a Hungarian-American engineer and physicist who was active primarily in the fields of aeronautics. He first calculated that around this altitude the Earth's atmosphere becomes too thin for aeronautical purposes (because any vehicle at this altitude would have to travel faster than orbital velocity in order to derive sufficient aerodynamic lift from the atmosphere to support itself). Also, there is an abrupt increase in atmospheric temperature and interaction with solar radiation.
Although the United States does not officially define a "boundary of space", the U.S. definition of an astronaut, which is still held today, is a person who has flown above 80 km (50 miles) above mean sea level. In 2006, three veteran NASA X-15 pilots were retroactively (two posthumously) awarded their astronaut wings, as they had flown between 90 and 108 km in the 1960s, but at the time had not been recognized as astronauts.>>
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<<Explanation: Higher than highest communications tower, higher than highest mountain, higher than highest airplane, lies the realm of the aurora. Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from energetic electrons and protons striking molecules in the Earth's atmosphere. Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles. This particularly rare purple auroral corona occurred in 2004 high above Harstad, Norway.>>
-------------------------------------
http://en.wikipedia.org/wiki/Aurora_(astronomy)
<<Most aurorae are green and red emissions from atomic oxygen. Molecular nitrogen and nitrogen ions produce some low level red and very high blue/violet aurorae. The light blue and green colors are produced by ionic nitrogen and the neutral nitrogen gives off the red and purple color with the rippled edges. Different gases interacting with the upper atmosphere will produce different colors, caused by the different compounds of oxygen and nitrogen. The level of solar wind activity from the Sun can also influence the color of the aurorae.>>
-------------------------------------
http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line
Kármán line
<<The Kármán line lies at an altitude of 100 km (62.1 miles) above the Earth's sea level, and is commonly used to define the boundary between the Earth's atmosphere and outer space. The line was named after Theodore von Kármán, a Hungarian-American engineer and physicist who was active primarily in the fields of aeronautics. He first calculated that around this altitude the Earth's atmosphere becomes too thin for aeronautical purposes (because any vehicle at this altitude would have to travel faster than orbital velocity in order to derive sufficient aerodynamic lift from the atmosphere to support itself). Also, there is an abrupt increase in atmospheric temperature and interaction with solar radiation.
Although the United States does not officially define a "boundary of space", the U.S. definition of an astronaut, which is still held today, is a person who has flown above 80 km (50 miles) above mean sea level. In 2006, three veteran NASA X-15 pilots were retroactively (two posthumously) awarded their astronaut wings, as they had flown between 90 and 108 km in the 1960s, but at the time had not been recognized as astronauts.>>
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