Topband: 27 days rotation

[by way of Bill Tippett <btippett@alum.mit.edu>]

Subject: Topband: 27 days rotation
From: "Thomas Damboldt" <Thomas.Damboldt at T-Online.de>
Date: 01 Mar 2007 15:35 GMT

Hi topbanders and others,

of course it is the solar rotation as the solar radiation
causes the ionosphere and its changes. The moon with its tidal
effects is probably negligible but nevertheless attracts man's
attention because the lunar month is very close to the solar
rotation period. The solar rotation speed is different at
different solar latitudes (differential rotation) as the sun
is made of gas and does not rotate like a rigid body. An
average of 27 days for the repeat-interval on the earth is
good enough, as the real repeat interval varies due to the
speed of fields/particles causing the reaction in the earth's
ionosphere/atmosphere. There is never a 1:1 repeat of
propagation conditions after 27 days, but it is the best
indication we have until we know exactly the sources causing
day-to-day variations in HF- and particularly in
topband-propagation effects. And we are very far from knowing
them.......

73
Thomas, DJ5DT