Disclaimer: The following material is being kept online for archival purposes.
Although accurate at the time of publication, it is no longer being updated. The page may contain broken links or outdated information, and parts may not function in current web browsers.
What? -- does it look like
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.
Dynamics Explorer halos over poles:
Known as the auroral arowns.
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
Last updated: 7/26/00
Above is background material for archival reference only.