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Re: (meteorobs) Two question regarding meteor rates?
>Is the seasonal variation, in the sporadic meteor-rate, thought to be
>related to a real variation in none-shower meteoroid distribution along
>the Earth's orbit? Or is it simply an extension of the same mechanism
>that causes the diurnal variation - extended to include the Earth's
>tilt? I guess I could work the answer out, if I knew how sporadic meteor
>rates in the northern and southern hemispheres varied with time.
Hello David!!
I'm sure some people on this list know a lot more about this topic than I
do. I hope they will correct my errors :-)
If Earth's tilt were the only mechanism involved, I guess we would expect
the seasonal variation in the southern hemisphere to "mirror" the activity
in the northern hemisphere... However, this is not the case! My memory
tells me that a graph in IMO's "Handbook for visual meteor observers" shows
this. Unfortunately I don't have a copy.
In fact, the sporadic "sources" (Helion, Antihelion, Northern Apex,
Southern Apex and the mysterious Toroïdal sources) seem to vary quite a lot
over the year! Apex and Antihelion are quite calm in the first half, but
very active in the second half of the year! Why? I don't know :-) ...but
there is an obvious link with comets! Antihelion particles all have low
incilination, prograde eccentric orbits, wich are essentially identical to
short-period comets. Apex particles have orbits similar to long-period comets.
Jones&Brown have written excellent articles on this topic, some of wich are
available through NASA's ADS (I can look up references if you want). These
studies are all based on radar observations, wich is obviously the best
possible data to do this. I recently tried to show sporadic source
variation as well using IMO's VMDB, but the results I obtained were rather
poor.
By the way: some time ago I discovered an interesting graph through Google:
http://www.asdot itb.ac.id/~ferry/Articles/MeteorFenomena/image5.gif
I do not understand the language of the originating webpage (
http://www.asdot itb.ac.id/~ferry/Articles/MeteorFenomena/MeteorFenomena.html
), but the graph seems to illustrate the effect of the seasonal variation
on the daily variation! This is very interesting material for people who
are trying to understand sporadic variation!
Kind regards,
Geert Barentsen
PS: It's very fun and informative to play with the data in the VMDB!! I
recommend it to everyone!
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