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Re: Variation in sporadic rates
>>Evidence of the annual variation...
>
>Interesting you mentioned that, Mark! What other evidence is there for
this? >Has it been tied back into careful plotting studies, to confirm the
"sporadic"
>nature of all inputs? I'd guess an asymmetry of material around the Sun
would >be a pretty significant observation, particularly one that wasn't
related in >any way to planetary positions!
For those who may not have heard of this variation before, sporadic meteors
exhibit both a diurnal variation where more meteors occur before dawn than
after dusk and an annual variation where more occur in the second half of
the year.
Much of the proof of the annual variations come from radio observations,
those from Jodrell Bank coming to mind first. A while back, as an experimet,
I used ALPO data from 1994 and 1995 as a check of this variation. Both years
did show this tendency.
Diurnal variation is caused by the motion of the earth. For any observer
located at a point on the earth's surface, that observer will be facing the
direction the earth is traveling in its orbit near dawn, therefore meteors
will "collide" with the earth. At dusk, the observer is facing the opposite
direction, so for meteors to become visible, they must be at a velocity
sufficient enough to catch up with the earth. A well-used analogy is that of
snowflakes striking the windshield of a car. More will strike the front
windshield than the back.
mark