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Re: (meteorobs) NASA News articles

In a message dated 6/25/99 1:36:19 AM Eastern Daylight Time, 
rmn@aaocbn.aaodot gov.au writes:

<< The reason there has been no storm under such conditions in the last 200
 years is because the situation has never occurred in the last 200 years
 where the Earth was close to either the comet or dust trail orbits.
 As the dust trail theory is the only one that successfully fits the times
 and intensities of storms, one could consider what it implies for storms
 should the Earth pass just behind the comet. >>

That statement concerning the apparent lack of any storms with the Earth 
arriving at the node of 55P/Tempel-Tuttle at less than 299 days can be 
attributed to an article that I wrote for WGN in 1998.  It indeed takes into 
account the six most recent Leonid cycles going back 200 years (to 1799).  
However, this general rule of no possible storm while the Earth is less than 
299 days removed from the comet node might be able to be stretched for a much 
longer span backwards in time.    

In a footnote (#4) in another upcoming article that I have submitted to WGN 
for possible publication, I note that:

"In separate lists of past Leonid storms compiled by Donald K. Yeomans and 
John W. Mason, eleven post-perihelion storms were concurrently identified 
dating back to AD 902 (902, 1002, 1202, 1238, 1533, 1601, 1833, 1866, 1868 
and 1966).  In only one case -- 1533 -- did a storm occur with the Earth 
trailing the parent comet by less than 299 days, the value in this particular 
case being 229.7 days.  The C-E (the minimum distance between the orbit of 
comet 55P/Tempel-Tuttle and the Earth) for 1533 was -0.0065 AU.  For these 
eleven storms, the "Earth at node" averaged value works out to be 623.4 days 
and the average C-E is -0.0067 AU.  Not included here are the 1965 Leonids, 
which was identified by Yeomans and Mason as a storm but since has been shown 
to have been merely a shower."

I should note that the above are based on historical and not dynamical 
findings.  

Certainly, it would be interesting to examine the dynamical conditions 
surrounding the one standout situation of 1533.  On the other hand, it has 
also been my contention that the descriptions of Leonid activity recorded 
prior to 1799 are highly subjective in regard to determining what could be 
classified as a "storm" versus a "shower."  This is why in my 1998 WGN 
contribution, that I only chose the most reliable samplings for just the past 
two centuries.  

In fact, since last November, I have been wondering that had the spectacular 
bevy of fireballs recorded in 1998 occurred in the years, 1498 or 998, would 
the existing chronicles from those years (chiefly from the Orient) given us 
impression that what took place was also a storm as opposed to a shower 
(albeit a brilliant one at that)?    

-- joe rao  
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