Satgen 513  Sunspots are Coming P2 by GM4IHJ  (BID SGEN513) 1999-01-23

Despite a reduction in Maximum Usable Frequency for HF propagation, of
late there has been a marked increase in polar auroral activity , over
and slightly north of Scotland. Still further north, satellite
RS12/13s 29.458 MHz downlink has suffered badly , particularly on
afternoon orbits going across the northern polar quadrant as seen from
Scotland. RS signals have often been very auroral, some hours before
auroral activity was noticable on terrestrial signals.

Usually the auroral signal is the only one present . The normal clear
tone morse beacon signal disappears, and is replaced by a steady 50 to
100 Hz band of noise, just above the frequency where the clear tone
signal would normally appear on an FFT display.

However, there are times when the auroral signal is both, varying in
frequency spread, and, unstable in frequency. Such that, an FFT
display shows broad frequency elements producing a sawtooth pattern
down the screen. A pattern which starts high in frequency and dopplers
steadily down for about 20 seconds , before jumping back abruptly, to
the original higher frequency , and begining to repeat the same
pattern. It is perhaps noteworthy that this pattern, new to this
author, appears at a time when the Harang Discontinuity in the auroral
circulation current is passing north of the listening station. ie
perhaps when the cross bar appears in what has been called the "THETA"
auroral circulation pattern ? Although at this time any connection
with the THETA pattern is purely conjectural. However one thing
certain , is that the sawtooth pattern in the signal during radio
aurora , is usually followed by a visual auroral display. 

All of which adds up to yet another new dimension of understanding
which is now available to stations equiped with FFT monitoring
facilities. With these facilities it is now possible to get very early
warning of the onset of radio aurora either via monitoring of VHF TV
station carriers in Northern Norway or Sweden. or by monitoring late
morning and early afternoon orbits of RS12/13 as it passes over these
same areas thereby "seeing" auroral conditions long before they become
evident by ordinary direct methods here in Scotland, and to anticipate
visual aurora 

PS. With what looks like a cruel blow to scientists and controllers
who only recently restored the SOHO Solar observation satellite to
life , after a control glitch. SOHO orbiting at Lagrange 1 gravity
stability point 1 million miles sunwards of earth, has now suffered a
gyro stabilization failure which may prove fatal. Satgen 505 recently
commented on this type of failure . Once upon a time satellite failure
was usually atributable to battery, or position keeping fuel
exhaustion. But as batteries improve and fuel lasts longer, these
complex stabilization gyros and inertial wheels are rapidly coming to
the top of the failure list .