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Re: (meteorobs) Re: NM1999Aug9/10 meteors dull
At 06:03 PM 1999-08-10 -0400, Norman McLeod wrote:
>At this point the Perseid max is 2.5 days away ; there still
>ought to be more Perseids on August 10 than this. I would have expected
>about 10/hour in a normal year. Now I'm concerned whether the max will
>continue at 2/3 normal strength this year, as it has done throughout the
>90's except for 1997. The peak is sharper and the hours straddling the peak
>have become poorer.
We radio amateurs have, for a number of years, noticed that the number of
radio-reflecting meteors appears to decrease during the few days prior to
the Perseids peak. I'm not certain whether that's still holding true as of
this morning; the number of reflections I heard on my daily 1130-1145 UTC
schedule on 144 MHz appeared to be about the same today as during most days
of last week. I did note that a few hams have seemed to think there was a
small increase in reflections on 50 MHz several hours ago (approximately 20
UTC); but that could just be because folks were listening for meteor
reflections due to the approaching peak, rather than an actual increase
over sporadic background. In any case, the "new" peak expected this year at
23 UTC could hardly come at a worst time of the day for we radio meteor
enthusiasts since the apparent meteor velocities will be compromised due to
entering the atmosphere over North America in the same direction as the
earth's rotation. I would expect this to cause very little increase in high
frequency radio meteor reflections such as 144 MHz and perhaps a
barely-noticeable increase in low-frequency reflections in the 50 MHz band.
I would expect the number of FM and TV broadcast reflections to range
somewhere in between. The higher the entering velocity, the higher the
frequency reflected and the higher the altitude at which the trail ionizes,
which increases the distances between a transmitter and receiver for a
given reflection.
Clear skies,
SteveH, K0XP
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