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Re: (meteorobs) Re:Question: Leonids 2003

Hi, Esko,


I don't know if you ever paid attention to the bolide peak in 1965.
Some radar observations indicated it was also rich in bright meteors
or fireballs. The mass distribution index may be as low as 1.5 (?).
While, i have never seen any information about the detailed source
of that event. Only Peter Jenniskens suggested that it was also caused
by so-called filament. As I understand, *filament* component was
on account of the liberation protection by the comet nucleus when both
the comet and the dust trail faced close encounters with big planets.

Jenniskens also estimated the total mass of filament, and concluded it's
10 to 100 times larger than the lost mass of the comet in a single return.
However, I'm still doubting something played important role above the
filament. I noted that every fireball event recently can be resovled and
explained simply by David Asher's method, i.e. numerical integration in
relative longer time scale. For instance, we observed a fairly spectacular
event of Leonids last year. This event was well confirmed by Japanese
radar observations. Trying numerical integration resulted a cross-section
of 18-rev. dust trail (ejected in 1400) encountered the earth at a precise
time with rE-rD=0.00002 AU=3000 km only. This is even smaller than
the radus of the earth. On the other hand, the population index at that time
was also much lower than the latter part of filament between the two
peaks. Unfortunately, as our poor observational conditions, the determined
value by us was not very responsible, although five different observers
made observations independently. Our result was the minimum r = 1.39
+/-0.08.

This is quite different from the the population index value several hours
later.
Between the European and American peaks, the value determined by IMO
was above 2.4.

BTW, There was an A&A paper by two people discussing the event in
1965 by radar technique, but I'm sorry for forgetting the authors. ;-<


Kind regards,
Huan


----- Original Message -----
From: "Lyytinen Esko" <Esko.Lyytinen@MINEDU.FI>
To: <meteorobs@atmob.org>
Sent: Wednesday, April 16, 2003 6:14 PM
Subject: RE: (meteorobs) Re:Question: Leonids 2003



Hi,

As I understad, the old meteoroids near the parent comet are more or
less confined to resonances, even though may be called 'filament'. For
example in my opinion the 1998 bolid outburst was caused by several
early releases of particles. The resonant particles from 1333, as
suggested by David and Rob (and the integration verified also by myself)
could not explain (in my opinion) the whole long lasting strong event. I
think that several returns around 800 AD were at least for a big part
responsible for this. And these particles were also in a similar type
resonance. This whole 'collection' may be called filament. It is however
expected to be mostly confined to the 2.4 year wide (one fifth of
Jupiter orbital period) resonant window.

Some particles can jump to adjacent windows and possibly trapped there
again in resonance. Also the parent comet itself was captured to the
present resonace roughly around 700AD. Before this, the comet 'passed
by' the different present windows and could leave there some matherial,
although (because of the required da0, to stay in the window) preferably
mostly (or only?) smaller matherial. The year 2003 is about two windows
'aside' from the primary window. Before 2001, I had modelled some old
particles to encounter several hours before the predicted storms, but I
think that I did see here in Finland in the local morning hours of Nov.
18, (roughly around 02UT, I recall), more of these (relatively bright
but not bolids like in 1998) than I would have expected. These may have
been in the resonant window adjacent to the 'primary window'. There
might again in 2003 appear more or less such surprises. Actually I think
it probable that something presently unmodelled will appear, but I also
think that a strong (if any) bolid shower will be unlike.

As to the modelling of years around different cometary returns, I have
got the impression that the bolid shower in 1998 was something even less
common than relatively strong storms. I am not quite sure about this
conclusion. I have paid more attention to this than to many other years.

Some level bolid showers are probably not rare, but to be as strong and
to last as long as in 1998 might be almost unique. The storm in 1799
probably was even stronger (in maximum) and at least in part from oldish
resonant matherial from several trails.
Then the recent 2001 Asian peak is expected to have consisted (besides
the 4-rev. strongest ZHR) from the 9, 10 11 and probably 12 rev. bright
meteors.

Esko


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