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(meteorobs) Re: Two question regarding meteor rates?



David and All,

This is indeed feasible for sporadic meteors with radiants on or near the
ecliptic such as the antihelion and apex sources. My recent studies have
indicated that these sources provide only a small fraction of the overall
sporadic production. For all the other true sporadics, they are independent
of the altitude of the ecliptic. Therefore it seems that the area traversed
by the Earth during the second half of the year is truly more populated with
meteoric debris thus producing a higher rate of sporadic activity. Keay and
Ellyett (1969) have produced a graph that shows the sporadic peaks for the
Southern Hemisphere occurs in July while in the Northern Hemisphere is
occurs over the entire last quarter of the year. This graph is reproduced on
page 112 of the IMO's Visual Handbook Second Edition, which is unfortunately
out of print.

I hope this helps!

Bob Lunsford




----- Original Message ----- 
From: "David Entwistle" <david@d-entwistle.fsnet.codot uk>
To: <meteorobs@atmob.org>
Sent: Tuesday, April 27, 2004 11:45 AM
Subject: Re: (meteorobs) Two question regarding meteor rates?


> In message <003c01c42c2e$a75b1ae0$9600000a@HAL>, Marco Langbroek
> <marco.langbroek@wanadoodot nl> writes
> >
> >> The ITU-R recommendation P.843.1, which covers meteor burst
propagation,
> >> suggests a northern hemisphere sporadic rate for August, which is four
> >> times the February rate. This presumably covers both day-time and
night-
> >> time activity. They don't provide any reference for this conclusion and
> >> it could simply be incorrect.
> >
> >There are a number of significant streams in this part of the years,
> >including some daylight sources. Perhaps these contribute.
> >
>
> I'm wondering if you were to assume a constant meteoroid distribution,
> but combine the effects of the daily diurnal variation, with its 06:00
> peak and 18:00 trough, with the annual variation due to the height of
> the ecliptic, you will indeed get the variation described in the ITU
> document. This will peak, when the daily 06:00 peak coincides with the
> ecliptics maximum height during that day. This will reflect the maximum
> sporadic meteor rate, when considered meteors throughout the whole day.
>
> However, when you only consider the visible night-time rates, you need
> to combine the above factors, but only over a limited part of each day.
> As the night time period is essentially half of the diurnal trough and
> half diurnal peak, the above effect is largely removed and the result
> will be quite a different distribution - that described in Jennnisken's
> report cited - largely resulting from the height of the ecliptic.
>
> Does this seem feasible?
>
> -- 
> David Entwistle
>
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