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RE: (meteorobs) Perseids storms predicted for 2029 (and other wil d stuff)



Hi,

I give here my comments to some points raised by Daniel.
On the talk Tom gave, I have only the information that I read from Daniel's
report.

>3. that one can predict the maximum ZHR value to expected when the
>Earth encounters such a trail without *any* knowledge of past
>storms, just from the above-mentioned model alone,

and

>4. that this approach has predicted the max. ZHR values of all
>Leonid storms and outbursts since 1999 with far higher precision
>than all attempts based on historical observations,

I expect some level misunderstanding here either from the receiving side, or
Tom trying to make too much of a simplified assertion.
The most inportant point is that, it is quite clear that different comets
release different amounts of meteoroids, and wihout observational
information on this there is no way to tell this.

Actually, almost all available (that I can deal with) data has been used for
the model. For example, although the (non regular) radiation pressure
effects can be studied and their presence predicted from theory, the actual
magnitude depends on meteoroid properties (size, shape, density, 'darkness',
thermal conductivity, ..) and can not be got information from anything else
than the observations.

I now remember to give my THANKS to the observers, of the vast amount of
observational data that you and others have gathered in the many thousands
(maybe up to millions) of hours, that we can now deal with!

>5. that the predictions of the max. ZHR values get even better
>(i.e. to within a few percent) of the observations when one
>assumes that the 'official' IMO values are too small by 30 to
>40% because too many bad observers are always added in,
>leading to an average value too low,

Comparing like this, does (seem to) give a better fit, and it is to be noted
that 'present day' standards observations have been in existence since a
short time. However, even those reduced values that Tom compared, are not
from one fixed model, because the model has been updated in the meantime,
adding at least the new observational data and making a quantiative
"A2-modeling" (or called also 'continuous acceleration' modeling). If all
these storms were postpredicted now (with this day model), we would get
values that are diffrent from those given then, althoug in part (NOT all)
this differing (development of the model) will be explained by different
present day (as compared to old data) observational 'standards' or
reductions, and cumulation of new data.

I have been thinking that a 1/2 (or 2/1) correctness of the predicted rate
is not bad, although of course I hope further improvement.

>6. that in 2002 there will be a storm with a ZHR of 3500 at
>4:10 UTC and another one with a ZHR of 2600 at 10:46 UTC on
>November 19 (these are the 'reduced' values, if I remember
>correctly),

These are our present predictions for the year 2002 (I didn't now check
these given timings in minute). 
Yes.., the younger trail is predicted to give slower rates. There would not
be a difference (in this way) within these but, because of two consistent
data points, I have assumed the 4-rev trail to be in general more weak than
the trails are typically. If this is a too quick conclusion, then the model
would predict higher (than given) rates from the 4-rev trail. Please, hope
this freely, in Americas :-)

What may seem more odd, is that the 7-rev storm is modeled as shorter in
duration than the 4-rev.
The "A2-effect" is very much case dependent. In general the effect of this
increases quickly with orbit numbers. This case, however seeme to be an
exception (in 2002, NOT in 2001).  This fact(?) also, in part, explains the
relatively high predicted rate from the 7-rev trail.
(These things go some way outside the topic of Tom's talk, but since I
started to write this, ..)

 
Let's see what the expected storms will be.
(Hopefulle this time preferably more strong than predicted, than less. I
think that this would make the observers more satisfied, (and would be more
willing to 'forgive' the erroros in predictions :) I didn't make an
underestimate because of this.

>9. that the Perseids will experience new strong outbursts
>from 2004 onwards and will reach storm level from 2029
>onwards.

I correct first the year (from whatever phese this error has arisen).
There should be 2028 instead of 2029.

Since these predictions are originally 'found' and studied by me, I tell the
following.
I expect in 2004 a short outburst of relatively dim meteors ( superimposed
over the yearly backgeound) that most probably does NOT increase into storm
level. The miss-distance is as much as about 0.0012 Au (I recall). I can not
give any specific value, but some level quess is a few hundred, so nothing
especiall, compared for example with the years 1992, 1993 (I recall). (Even
that 'quess' assumes a markedly stronger dust release then thet from the
Leonids parent comet.)

I do predict a genuine (relatively short in time) storm in 2028. I can not
give any more specific predicted rates. After my early finding and study of
this, I became somewhat uncertain, if the 'A2-effect' might disperse this.
Some further modeling seem to indicate that this wil not be the case.

The perihelion of the Perseid parent comet Swift-Tuttle, has been lowered
during the last few revolutions enoug for the Earth to encounter fresh
trails (in principle). However possible storms after some next returns have
not been tried to predict (yet).

After the parent comet return, the time period of storms to be able to
happen (if the amount of releseased dust is relatively big (as I expect),
otherwise there may be only strong outbursts), is about ten times longer
than with the Leonids (due to the bigger orbital period). But once, the
'window' is gone, there is quite a long time to wait the next window after
the next return of the parent comet. (Actually there most probably is not
any such exactly limited window.)

>Daniel Fischer, reporting from Albuquerque, New Mexico, USA
>..

Best wishes, Esko
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