On Predicting the Time of Leonid Storms

R. H. McNaught.
First published in The Astronomer, 1999 March.

Extended abstract

The use of the orbit of 55P/Tempel-Tuttle in predicting Leonid storms is discussed and rejected in favour of dust trail calculations. Asher (1999) has calculated the perturbations to the individual dust trails from ejection from the comet for three revolutions or more prior to any potential encounter. These calculations confirm the encounter circumstances given by Kondrat'eva et al. (1997), but with ten times better resolution in the node of the dust trails. All observed storms correlate closely with the Earth's passage within about 0.001 AU from a dust trail. It is shown that the time of encounter with Asher's dust trails very closely represent the observed times of maxima given in Brown (1999) for all six storms (ZHR>1000) of the last 200 years. Asher's dust trails indicate that the Leonid maxima in the next two years will occur at:

with an uncertainty of +/- 90 minutes and possibly as small as +/- 10 minutes. The uncertainty is based on the close correspondence between the time of encounter of the dust trails and the time of observed storms in the last 200 years.

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