(meteorobs) Earth-grazer definition question

[Robert Lunsford]

Leo and All,

An earthgrazer can start near the radiant. In fact some of the most memorable earthgrazers I have seen started near the radiant and shot nearly the entire length of the sky. 

I believe this term came to being during the 1990's when the Leonids started getting some more attention. Observers would go out early and would report seeing very long Leonids. Someone offered an explanation of what they were seeing but there was no name for it. Someone then coined the term earthgrazer for these meteors. The original meaning was a meteor that struck the earth's atmosphere at such an angle that it only penetrated the upper fringes of the mesosphere. This increased the duration of the meteor as well as the length. There was no mention if the meteor left the atmosphere. There were also no limitations on path length.

My own definition for an earthgrazer is a meteor that appears when its radiant lies near the horizon. This circumstance will produce long meteors that last for several seconds due to the fact that they skim the upper atmosphere without penetrating very deeply into the mesosphere. 

I agree with Chris that whether an earthgrazer leaves the atmosphere or not is unimportant. The meteor can still skim the atmosphere and totally disintegrate. It will create a long meteor as seen from the surface. 

As for elevation, the upper limit is difficult to define. Through my studies I have found the lower limit to be 8 degrees, which I found surprising. I would have guessed that it would be closer to the horizon. So go ahead and watch the Geminids as soon as it becomes dark. Even if the radiant lies below the horizon so should be able to see some action. One of my most memorable collection of earthgrazers occurred during a Geminid max from the Mojave Desert just as it became dark. Most of the earthgrazers were shooting low in the sky to the north or southeast, but several shot straight overhead. None of them were negative magnitudes but the long trails and long duration's were most impressive! BTW, the 1994 Aurigid outburst was all earthgrazers as seen from southern California.

Robert Lunsford

---- LEO STACHOWICZ <l.stachowicz at btinternet.com> wrote: 
> I'm afraid I can't answer, but I do have a related question that has been on my mind: For the purposes of observation, if we are talking about sporadics (or if the shower is unknown), how many degrees of sky does a meteor have to travel before it can be called an earth-grazer? Also, in the case of a known shower member, how far from the radiant does the meteor have to start to be called an earth-grazer?
> Clear skies,Leo
>  
> 
> 
>     On Thursday, 19 November 2015, 23:21, Thomas Ashcraft <ashcraft at heliotown.com> wrote:
>  
> 
>    Definition of an earth-grazing fireball from wiki:
>  https://en.wikipedia.org/wiki/Earth-grazing_fireball
>  
>  " An Earth-grazing fireball (or Earth-grazer)[2] is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again."
>  
>  Does an earth-grazer have to leave earth's atmosphere to be called an earth-grazer?  Can it skim and ablate or burn up entirely and still be termed an earth-grazer?
>  
>  Thanks in advance.
>  
>  Thomas
>  
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