(meteorobs) Question about radiant drift

[Bamm Gabriana]

Hello David,

Thanks a lot! I think this is just what I wanted. Where can I read 
about this? Where can I get the formulas and where can I get the 
values unique to each shower?

I'll be away for a week, please cc any response to my email address 
since I may not catch it in the list (I read the messages on the web 
through yahoo).

Clear Skies
Bamm

--- In meteorobs at yahoogroups.com, David Entwistle <david at d...> wrote:
> In message <ca18ok+v2c5 at e...>, bgarcing <bgarcing at y...>
> writes
> >
> >What are the factors that affect these? And how to compute these 
> >factors using elements unique to each stream? Thanks and clear 
skies.
> >
> >Bamm
> 
> Hello Bamm,
> 
> I don't have an answer for you, but I think I know what needs to
> considered to arrive at an answer. My mathematics is a bit rusty, 
but
> with a bit of help we should be able to work through it.
> 
> The position of the meteor shower radiant is dependant on the 
relative
> velocity between the Earth and the shower meteoroids. This in turn 
is
> determined by calculating the vector sum of the Earth's heliocentric
> velocity (both speed and direction) and the meteoroids heliocentric
> velocity (both speed and direction). there may be small correction
> required for the Earth's attraction, but we'll ignore that.
> 
> McKinley [1] puts it as follows:
> 
> (quote>
> 
> 'The Earth's velocity is directed along the apex of the Earth's 
way. A
> meteor moving with a heliocentric velocity Vh from a radiant 
located at
> an angular distance c from the apex will have  a resultant 
geocentric
> velocity Vg given by
> 
> Vg**2 = = Vh**2 + Ve**2 + 2 * Vh * Ve * cos(b)
> 
> and the radiant will appear to be shifted to an angular distance c 
from
> the apex where 
> 
> sin c = (Vh * sin(b)) / Vg
> 
> <end quote>
> 
> That explains how to calculate the radiant position from the 
component
> velocities, but we'll need to work backwards, from the radiant to 
find
> the component velocities. Apply the factors causing the drift and 
then
> put them through the above equations again. 
> 
> The radiant drift will be caused by changes in either the 
meteoroid's,
> or the Earth's velocity. The meteoroids velocity may vary somewhat, 
but
> I'd expect the variation in the Earth's velocity and particularly
> variation in its direction, which will be dominant. It is the 
direction
> of the Earth's way (apex) which will move along the ecliptic by
> approximately 1 degree a day. 
> 
> [1] Meteor Science and Engineering - D W R McKinley
> -- 
> David Entwistle
> 
> _______________________________________________
> Mailing list meteorobs
> meteorobs at m...
> http://lists.meteorobs.org/mailman/listinfo/meteorobs