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Leonid MAC

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What is the occasion all about?


In 1999, we saw the first meteor storm of the space age. Even now, the societal and physical effects of meteor storms remain unclear. Will a particularly intense meteor storm cause satellites to malfunction some time in the future? What chemical reactions will occur as the meteors incinerate? Might cometary debris have influenced the development of life on Earth?

The current episode of Leonid storms is a unique chance to study these issues. The figures show how the showers have manifested itself in the past years and how our understanding has gradually improved with new observations.

1998 logo 1998 dust trail pattern 1998 zhr curve
1999 logo 1999 dust trail pattern 1999 zhr curve
2000 logo 2000 dust trail pattern 2000 zhr curve
2001 logo 2001 dust trail pattern 2001 zhr curve
2002 logo 2002 dust trial pattern 2002 zhr curve

The graphs in the middle are a map of where the dust is located, according to calculations by David Asher of Armaugh Observatory. Each colorfull elipse is the point where a trail of dust, from one of comet 55P/Tempel-Tuttle's returns to the Sun, crosses the Earth's orbital plane. The blue trails are the onces closest to Earth's orbit. Those are detected as Leonid showers. The year of origin of each trail is marked. The path of Earth is shown as an orange line.

The observed Leonid shower rates in the years 1998, 1999 and 2000 during Leonid MAC missions and from data gathered by the International Meteor Organisation are shown on the right. The rates are in unit of "Zenith Hourly Rate", the count of meteors seen by a visual observer when the sky conditions are ideal and the shower radiant is in the zenith. The horizontal axis shows the time in hours since November 18 at 0h UT of a given year. The graphs for 2001 and 2002 are predicted rates by one of several dust models, in particular that of Esko Lyytinen and Tom Van Flandern (which is sort of in the middle of predicted levels of activity). Note that the encounter with each blue trail resulted in a peak of Leonid shower activity.

Each encounter is unique and provides important information about the exact location of the dust trails and the dust properties of different ages. From precise measurements, Leonid MAC PI Dr. Peter Jenniskens derived such properties as the meteoroids density, how much dust is ejected by the comet in each return. More information here.

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