Fw: [CVCC] Fw: HAMFEST AND DX DINNER

[rsmorris]

----- Original Message ----- 
From: <Thomas.Ogburn at lfg.com>


Bob,

Could you forward this to the CVCC mailist? Due to recent corporate
email changes I can no longer access the QTH.net mailing list.

Thanks.

Tom


Date posted: 2006-08-24

U.S. Plan to Protect Satellites Could Knock Out HF Communications
RF Report has described the danger to orbiting satellites from coronal
mass ejections from the sun and geomagnetic storms in previous articles.
High altitude nuclear explosions (HANEs) have also been found to cause
satellite failures. The operational lifetime of orbiting satellites is
shortened when high-energy electrons are trapped in the earth's Van
Allen radiation belt. As the number of satellite orbiting the earth has
increased, so have efforts to protect them from HANEs and unusual
natural events such as large geomagnetic storms. These efforts, referred
to as Radiation Belt Remediation (RBR), work by precipitating
high-energy electrons from the natural or HANE-induced radiation belts
into the upper atmosphere.


One of the proposed RBR techniques would probably involve use of a
constellation of approximately 10 satellites transmitting very low
frequency (VLF) waves to dump electrons from the HANE-induced radiation
belt. However, this intense energized particle precipitation would lead
to large ionization changes in the ionosphere, disrupting HF
communications.


The effect of RBR systems on the atmosphere and HF communications is
outlined in the paper The atmospheric implications of radiation belt
remediation by C.J. Rodger and his team at the Department of Physics,
University of Otago, Dunedin, New Zealand. The paper contains detailed
models of atmospheric and HF propagation changes from both satellite and
ground based RBR systems using VLF transmitter. Charts also show the
effects of varying the duration of the VLF transmissions.


Obviously there is great interest in protecting satellites, especially
those used for strategic communications and navigation. Since HF
communications are used for long-range communication with aircraft and
also to link many isolated communities in the Pacific, disrupting HF
communications for several days could also cause problems. The paper
discusses the trade offs between the length and nature of RBR operations
and disruption of HF communications.



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