(meteorobs) Hypervelocity meteors

[GeoZay at aol.com]

>> Hello  list,

before reading this article I thought that meteors at v>73km/s  were 
uncommon. What do you know/think about this topic?<<
 
Hello...not sure if this will make it to the list or not, since I usually  
have trouble making posts there. However, for your personal knowledge, below is  
a paragraph that I extracted from my guide book that I wrote about ten years 
ago  on this topic. It's not much, but might give you a little insight. 
Oh...the  guidebook is called "Zay's Meteor Observing Guidebook". It was 
unpublished, but  there's over 100 photocopies floating around worldwide somewhere. :O) 
It was  mainly a collection of notes that I made for myself in my own words of  
understanding about meteor observing. This made it easier for me  to refer to 
something later if I came down with a brain fart or something.  Anyhow, hope 
this paragraph helps you some.
George Zay

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"Since  the earth could be plowing into meteors coming from the opposite 
direction on  the apex side, expect to see mostly fast meteors in the morning hours
…namely  between midnight and noon. You can also expect to see the slowest 
meteors  occurring between noon and midnight and centered around 6 p.m. This is 
because  they have to catch up with the earth. Whatever speed they are 
traveling at, they  have to go just a little faster to overtake the earth. When this 
happens, you  can subtract the earth’s speed from the meteor’s speed and add 
the pull of  earth’s gravity.  What is left is  the apparent speed of a slow 
meteor. What this boils down to is that the slowest  geocentric velocity a 
meteor can have while in a solar orbit is 11 km/s (7 mps).  Visually a meteor at 
this speed looks as if it’s crawling along. The fastest  geocentric velocity a 
meteor can have while in solar orbit is 72 km/s (45 mps).  Visually a meteor 
at this speed appears to be a very fast streak.  From a 1948 - 1950 Canadian 
Radio  survey, it has been learned that less than 1 percent of all meteors were  
traveling faster than the established 72 km/s solar speed limit. Of these 
that  were traveling at apparent hyperbolic speeds, none were traveling faster 
than 80  km/s. As the survey noted, this excessive solar speed is within the 
realms of  being measurement errors. But in recent years, additional research has 
been done  that indicates the Canadian survey was relatively accurate. The 
Christchurch  (New Zealand) meteor radar AMOR(Advanced Meteor Orbit Radar) has 
also yielded  about 1% of meteoroids having an atmospheric speed in excess of 
100 km/s. In  addition, the Ulysses space probe dust detector has in 1994, 
discovered  interstellar grains in the outer solar system at about 5 AU, having 
hyperbolic  trajectories. This mean it’s traveling too fast to stay in orbit 
around the  sun."



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