[Ips-hf-warning] IPS HF COMMS WARNING

[rwc]

SUBJ: IPS PRELIMINARY HF RADIO COMMUNICATIONS WARNING 03/78
ISSUED AT 28/2219Z OCTOBER 2003
BY THE AUSTRALIAN SPACE FORECAST CENTRE.

A MAJOR FLARE WITH BRIGHT/FAST SOLAR MASS EJECTION WAS 
OBSERVED OVERNIGHT.

HF CONDITIONS ARE EXPECTED TO BE INITIALLY GOOD FOR
FIRST HALF UT DAY ON 29 OCT.  DEGRADED/DEPRESSED HF 
PROPAGATION CONDITIONS EXPECTED FROM SECOND HALF 29 
OCTOBER AND STRONG DEPRESSION LIKELY AFTER LOCAL 
DAWN 30 OCTOBER 2003.

IF COMMS DIFFICULTIES EXPERIENCED TRY A LOWER FREQUENCY BAND
A MORE DETAILED HF WARNING WILL FOLLOW IF DEPRESSIONS EVENTUATE.

HIGH LATITUDE/POLAR COMMUNICATORS:
TRANSPOLAR HF CIRCUITS CURRENTLY UNUSABLE DUE TO INTENSE SOLAR
PROTON EVENT FOLLOWING MAJOR FLARE, CAUSING POLAR CAP
ABSORPTION.

Note that Preliminary Warning number 77 is a fail to eventuate,
due to weaker than expected geomagnetic activity overnight,
following weak shock arrivals. However, this more recent solar event 
was very large and clearly Earth directed and therefore 
has a much greater chance of causing an ionospheric storm.
_____________________________________________________________



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