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(meteorobs) sporadics
Lew, you wrote
> But what are folks various fews on exactly where these modes (peaks) in
> annual sporadic activity occur? And is it generally agreed upon that it's a
> smooth sine curve (or roughly) throughout the year, or is there more
> character to the curve?
According to radar data it's roughly a sine curve with maximum in
October-December and minimum in March to June. However, my visual impression is
that the maximum is September-October and the minimum, February-March. Another
article by Simek (1995) only distinguishes winter and summer sporadics and
investigates their diurnal variation. Note that the curve is reversed for the
southern hemisphere, since the sporadic activity is related to the elevation of
the apex, and high apex on the northern is a low apex on the southern
hemisphere. The apex is at its lowest position on March 21, and at its highest
position on September 23, so these dates would be the geometrical minimum and
maximum, but other sources also seem to play a role. Moreover, while in February
nights are long, and you can 'see' the apex getting very high in the sky until
about 6 local time, you will not be able to 'see' it that high in April despite
the same declination because of shorter nights. The same happens with high rates
in favour of October rather than of August. Hence, the average sporadic rates
should be expected to be higher in February. My own visual impression is that
the diurnal change of sporadic rates is much larger in February than in
September. Evening hours in February are extremely slow, though the morning can
be really fun. In September the change is much less obvious, many sporadics are
seen all night.
Rainer
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