[Prev][Next][Index][Thread]

RE: (meteorobs) What I think I know (and don't know) ...



I try to give a short comment to Gregg. 

Even if the ejection of particles were uneven (near perihelion) with
possible gaps, these patterns will not be left as such in the orbit. The
meteoroid size particles will follow quite close the same path as the parent
comet at the return of release. (The comet dust-tail and the "connection"
between meteoroid size particles may be filled with with different size
dust, too small to be visible as meteors.) It is the resulting orbital
period (determined by ejection speed/radiation pressure) of particles that
will determine the position of the particles at the next returns (with
perturbations affecting). There are only minimal effects as to where exactly
the particles were ejected (as long as this is near perihelion).

(
If considerable normal to motion ejection speeds are present (not applicable
to our model, except maybe in special cases (like possibly cometary
outbursts having happened)), there will be some "convergence" effects at the
next returns that affect the main peak "sharpness" (and also maximum ZHR
with good hits), and has connection to exactly where the meteoroids were
ejected. As far as I know, this effect has not (much) been considered in the
litteratude and more consideration would be out of topic here.
)

Esko

>From: Gregg Lawrence

>Yes there have been some rather interesting replies to this problem.  
>However, let us look at the most basic precept, namely the release of dust 
>from a comets nucleus.  When we look at a come in passing, we can usually 
>see two basic tails.  The type I or ion tail is directly influenced by
solar 
>radiation and pressure.  Less obvious is the radiation pressure or solar 
>influence on the type II tail or the dust tail.  If we examine photos of
the 
>coma area where it flows into the tail, sometimes we can see no transition,

>such as with Comet Arend-Roland 1957III (C/1956R1).  It is obvious that 
>there is a large quantity of dust, since the better photos clearly show the

>anti-tail.  Comet Seki-Lines 1962 III (C/1962 C1)also shows no transition.

>We can follow the dust tail all the way into the coma, with no separation.

>Yet we can also detect what appears to be areas of irregular dust 
>deposition.  Halley's comet is also an example of where there has been 
>uneven deposition of dust.  So was comets West 1976 VI (C/1975 V1), 
>Brorsen-Metcalf 19898X (23P/1989 N1), and many others.  So if the dust is 
>being ejected by the nucleus in and irregular fashion then we can expect 
>areas of concentrated dust to be follow the comet in a similar and related 
>orbit. During an apparition of a comet, if there should be a tail 
>disconnection event (DE), it is quite possible that the may also influence 
>the dust tail.  So in either case we should see areas of greatere and
lesser 
>concentration of dust all throughout the orbit of a comet.  Over time,
these 
>areas will spread out a little due to gravitational perturbations, which 
>might explain why some years we see showers and some we don't.
>
>Cheers,
>Gregg
>
>rigel_ori@hotmail.com
>at OCS.
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html