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

Re: (meteorobs) NASA News articles

Hi -- I wanted to thank both Joe Rao and Rob McNaught for their informative
comments on the Leonids.

I have a question for Joe:  Joe, in your 1998 Sky & Telescope article on
the Leonids there is a 2 dimensional scatter plot with "Distance of the
comet's orbit from Earth" on one axis and "Distance between comet's and
Earth's arrival time at node" on the other.  It appears to show that there
were seven Leonid apparitions dating back to 934 when the Earth arrived at
the node less than 299 days after the comet.  Of those, only 1965 and 1533
were major showers, and none rose to the level of "storm."  

Am I reading this plot correctly?

Regards, Tony Phillips

At 12:42 AM 6/26/99 EDT, Skywayinc@aol.com wrote:
>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  
>
>
====================================================
Dr. Tony Phillips        phillips@spacesciences.com

VISIT     http://www.SpaceWeather.com  
          http://www.StarTrails.com
          http://www.SouthPole.com

To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html
References: