Ground
Shuttle Space
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Polar
tri-spectral imaging:
The aurora can be observed from space at wavelengths other than visible. Each wavelength regime has advantages and disadvantages.
Most of the energy in the auroral light is in visible wavelengths, so highest resolution images can be obtained. However, the sunlit Earth seen from space is about a million times brigheter than the aurora, so extreme care must be taken not to point a camera by accident at the sunlit Earth. During the summertime, much of the auroral oval is sunlit, so visible imaging is very restricted during this period.
Auroral light in ultraviolet wavelengths is used for imaging the entire auroral oval even in the sunlit portion. Scattered sunlight from the atmosphere is about as bright as the aurora, so the entire auroral oval can be seen from space if it is not too badly contaminated with sunlight. In addition, a camera will not burn out if pointed at the sunlit Earth.
The electrons producing the aurora also emit X-rays. An X-ray detector is totally blind to sunlight, so it can easily look at the entire auroral oval independent of season. The X-rays from the auroral region pertain to the higher energy electrons that dominantly produce the auroral light at visible and ultraviolet wavelengths. Thus X-ray measurements provide additional information about the electron precipitation. Unfortunately, the number of X-rays produced is small, so the sensitivity, or spatial resolution, of an X-ray detector is much poorer than a visible-light imager of the aurora. -
The auroral oval:
From Dynamics Explorer.
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Conjugate
Dynamics Explorer halos over poles:
Known as the auroral arowns.
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Stormer
height profile:
Statistical distribution of 12,330 height measurements of the northern lights derived by Stormer and his colleagues. The vertical scale gives the height in kilometers, and the horizontal scale gives the number of measurements.
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Web development: Theresa
Valentine
Last updated: 7/26/00
