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RE: (meteorobs) Re:Question: Leonids 2003




Hi Huan,

I have paid some attention to the bolide peak in 1965. We have made with
Markku Nissinen, quite wide integrations from old trails. We have gone
trough these only in part. My purpose has been to pay attention also to
the year 1965. There has now been quite along pause in this inspection.
I don't remember the relevant orbit numbers and dont have the data here
in my work, but I got the impression that something has or will be found
for the year 1965. I expect that I will come back to this, maybe soon
(within a week hopefully?), because you now raised this question.

As to the "filament", I think that this has been in a more wide use than
you describe. I recall that we used this also in the long-period paper,
even though this can not have much connection to comet nucleus
perturbations and also not to resonances.

I have earlier (several years ago) made some particle integrations that
took the nucleus graviational pertubations in to accout in the
computing. The parent comet has a nongravitational A2-parametr value
that lengthens its period at each revolution (quite small as compared to
the planetary effects on orbital period during the librations).

My purpose was to test, if this could in a way 'collect' a big number of
particles, that were originally ejected into orbit very close to the
parent comet, with an orbital period only very little longer than the
parent comet has (very small positive da0). The particles in a way try
avoid the parent. So I tested, if such meteoroids would be affected by
the parent comet, strong enough that a number of these were collected in
orbits that keep keep them close to the comet and will also have this
much (what the cometary A2 affects on it) increased (over the plenetry
effects) orbital period because of the parent nucleus perturbations.

I could not get this situation preserved even for a single particle, I
recall. Planetary pertubations (even though very much the same to these
particles than to the parent comet) were strong enough to disturb this.
I am not even sure, if this had worked without the planetary effects.
Besides this 'escaping' action, the nucleus effect near aphelion tends
to affect (increase for those behind the comet) the q values of this
kind particles, making these soon to have orbital paths different
enough.
I think that the graviational effects of the parent body (to the
meteoroids) are very minor quite soon after the ejection.

Esko

>>>

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,

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