[CQ-Contest] NW7US Propagation Update: 18-XII-2003

Tomas NW7US nw7us at hfradio.org
Thu Dec 18 00:35:20 EST 2003

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Hello, Radio Enthusiast!

The very large coronal hole that has kept the geomagnetic field 
at active to minor storm levels is no longer in view. This is 
giving us a nice period of quiet geomagnetic activity, with the 
result being that we are seeing propagation that is more normal 
over most of the paths around the world.

A smaller coronal hole is currently near the central solar 
meridian and is expected to lead to minor geomagnetic storm 
conditions from Sunday, 21-XII-2003 onwards. Between now and 
then, it is expected that the 10.7-cm flux will climb a bit, 
perhaps as high as 130, while the planetary A index (Ap) should 
remain at or below 10.  From 21-XII-2003 onward, the flux will 
gradually fall to about 100, with some elevation of the Ap index 
as the geomagnetic field becomes active again due to that coronal 

After 31-XII-2003, we.ll see conditions become a bit rougher, 
again. However, this is due to the coronal hole that we.re seeing, 
not because of any major flare. Between today and the first of the 
New Year, there is only a slim chance of any moderate flare, while 
there will be a good number of minor small flares (B- and C-class 
flares). There is also a small chance for a proton event from mid 
to late December. This might make over-the-pole propagation a bit 

At the time of writing this bulletin, the solar wind speed is at 
about 400 km per second, which is a normal speed, with only a slight 
southerly orientation of the interplanetary magnetic field.  As of 
17-XII-2003, the sunspot count is 92, and the 10.7-cm flux is 118.  
The Ap is 10, and the Kp (planetary K index) is 3.

This translates to some very good conditions for the High 
Frequencies (HF). Expected MUFs are normal, rather than depressed 
as we.ve seen for the last couple of weeks. The season is great for 
worldwide DX on HF, and this period between now and the New Year 
will offer great conditions for most of the time. The highest 
frequencies will have some long-range F-layer openings (since the 
flux will be above 100), but they will be short. Lower frequencies 
will propagate much better over most paths.

Come by and check out the online Propagation and Radio (SWL and 
Amateur) discussion forum, where a group of us are discussing the 
science and current events of space weather and propagation: 

In addition, you can always get the latest live space weather and 
propagation information at http://prop.hfradio.org -- or with a 
WAP phone, at http://wap.hfradio.org/

Happy Dxing!

73 de Tomas, NW7US (AAR0JA/AAM0EWA)
: Propagation Editor for CQ, CQ VHF, and Popular Communications :
: Quarterly Propagation Columnist for Monitoring Times Magazine :
: Creator of live propagation center - http://prop.hfradio.org/ :
: Member, US Army Miltary Affiliate Radio Service (MARS) AAR0JA :
: 122.93W 47.67N / Brinnon, Washington USA - CN87 - CW/SSB/DIGI :
: Washington State MARS Emergency Operations Officer -- AAM0EWA :
: 10x56526, FISTS 7055, FISTS NW 57,  AR Lighthouse Society 144 :

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