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Dynamics of Leonid dust trails (the cause of storms) Armagh Observatory, Northern Ireland

Summary: Dynamics of Leonid dust trails (the cause of storms)
D.J. Asher
Armagh Observatory, Northern Ireland
(Last revised 2000 February 7)
Although the background level of meteors from the Leonid stream is not
especially high, within the stream are dense, narrow trails of meteoroids and
dust, the debris of Comet 55P/Tempel-Tuttle. These trails are similar to those
discovered by the Infra-Red Astronomical Satellite in the orbits of other peri-
odic comets. When the Earth encounters a trail, a meteor outburst or storm
occurs. Two qualitatively di erent kinds of trail are present in the Leonid
stream. `Normal' trails, up to a few centuries old, form simply because me-
teoroid particles of slightly smaller and larger orbital periods than the comet
gradually stretch ahead of and behind the comet. The number density of par-
ticles is much higher at the centre of these trails than elsewhere in the Leonid
stream. Therefore the Earth's passages close to the centre of these trails are
associated with the highest Zenithal Hourly Rate storms. Trails of the second
kind form as a result of resonant dynamical behaviour over more than a few
centuries. Although the overall number densities of meteoroid particles in reso-
nant trails are smaller than in normal trails, the resonant trails are rich in larger
particles. This meant that the 1998 outburst had much lower ZHR than the


Source: Armagh Observatory


Collections: Physics