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(meteorobs) grazer geometry
I will volunteer an explanation of the grazers.
Should I make a mistake, I would ask some of the more experienced observers here
to jump right in and correct any errors. Thanks
A grazing meteoroid particle encounters the
Earth's atmosphere at a angle of entry approaching zero degrees. This is because
the radiant source of the meteor stream is on the horizon (or near it) for the
particular location of the observer. Later, when the radiant is high overhead
the particles enter at a steep angle, encounter denser atmosphere quickly, and
burn up more quickly. Their path is short. Grazers are doing just that,
skimming along the thinnest part of the atmosphere, barely intruding and
therefore expend their mass over a longer burn path.
For those comfortable with geometry, the path is
tangential to the Earth's atmosphere at the point of entry.
The circumstances necessary to a tangential burn
are somewhat limiting and so grazers are fairly rare but their spectacular
nature makes it worth the long wait.
I have seen two grazing Perseids from south texas
and 8 Leonid grazers - 2 in 1998 and 6 in 2001.
I caught two of the Leonid grazers on film last
year but they are unspectacular on film. They resemble satellite images taken on
long exposures.
4 of the Leonids last year were horizon-to-horizon,
the rest ran about 120 degrees.
Hope this helps.
Tom
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