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(meteorobs) A weak Ursids outburst possible in 2002


We have searched for possible encounters, this December, with old Ursids
trails left from the parent comet 8P/Tuttle.

The most promising trail appears to be the very old trail from the year
1090.

This trails is of course very strongly disrupted. According to the
modelling, meteoroids from this trails seem to have some clustering near
the Earth orbit at the correct time this December. Possible encounter
can be at two completely different sections of the trail, these making
further 'foldings'. Especially the one with larger da0, seems to consist
of a wide range of da0:s (could be divided further to at least three
sections).

Using the solar radiation pressure to cause the da0 in the modelling,
the encountering sections correspond the beta values of about 0.00041 or
0.00042 and 0.00059 to 0.00070
The smaller beta value has the most close encounter in the nominal
solution A2=0, but this situation is preserved only with quite a small
range of the A2-values near zero. At the higher beta values, it is the
"A2-effect", (negative values) that seems to bring the particles more
close to the Earth orbit.

The encounter with the smaller da0 is predicted at solar longitude
270.71 or 270.72 and the other at solar longitude 270.76 to 270.82. The
former is expected to contain brighter meteors. The peaks are expected
to merge into each other with a more or less gradual dimming of the
meteors.

We can't give any ZHR value and not even tell which one of the trail
sections will give the higher ZHR. The parent comet early motion
uncertainties grow quickly when we compare for example the returns
around 1100 to those near 1400. 
We can not be even certain of any apparent trail encounter, but do
expect that the encounters are strong enough to be detected and give ZHR
above the background. In 2000 the beta value was about 0.0011, so the
meteors are now expected to be generally brighter. Because of the full
moon this is an important factor.

The times are:
2002,12,22.79 or about 19:00UT, for the first section encounter
2002,12,22.86 or about 20:40UT, for the second section encounter


Esko Lyytinen
esko.lyytinen@luukku.com
Markku Nissinen
markku.nissinen@pp.inet.fi
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