[HCDX] NW7US Propagation Update: 5-XII-2003

[Tomas NW7US <nw7us@xxxxxxxxxxx>]

Howdy, Folks.

This weekend is quite active on the Amateur Radio bands.  The 
ARRL 160-Meter Contest starts at 2200 on 5-XII-2003 UTC to 1600, 
7-XII-2003 UTC, while the PSK Death Match starts at 0000, 
6-XII-2003 and runs until 2400 7-XII-2003 on 80, 40, 20, 15, 10, 
and 6 meters.  The TARA RTTY Melee runs from 0000 to 2400 on 
6-XII-2003 on 80, 40, 20, 15, and 10 meters.  There's also the 
TOPS Activity 80m Contest, which starts at 1800 on 6-XII-2003 and 
runs to 1800 on 7-XII-2003 in CW only on 80 meters.  Finally, 
there's the QRP ARCI Holiday Spirits Homebrew Sprint that runs 
from 2000 to 2400 on 7-XII-2003 in CW mode only on 160, 80, 40, 
20, 15, and 10 meters.

What is the propagation outlook on the High Frequency (HF) bands 
during this weekend?

Earlier, today (5-XII-2003 UTC), between 0100 and 0300, a weak 
shock wave was detected that indicated the arrival of the 
glancing blow from the coronal mass ejection from the prominence 
eruption on 2-XII-2003.  The geomagnetic field activity increased 
to minor storm levels with a planetary K index reaching 6.  Since, 
the geomagnetic field activity is remaining at the active (Kp of 
5) level.  After about 1200 UTC, the solar wind speed further 
increased, and the interplanetary magnetic field has remained 
moderately to strongly southward in its orientation.  This will 
continue to keep the geomagnetic field active to somewhat stormy.

There has been no clear influence of the small coronal hole that 
is now situated moving closer to the western limb of the sun.  
However, another large coronal hole is moving into a position 
that will directly increase the solar wind speed and therefore 
possibly influence the geomagnetic activity starting today.  This 
coronal hole, originally numbered CH66 and now numbered CH71 by 
Jan Alvestad, was geo-effective in previous 27-day solar cycles.  
The leading edge of the coronal hole is now at the central 
meridian.  Soon, the solar wind speed will become even stronger, 
with the possibility of strongly negative (southward) 
interplanetary field orientation as this coronal hole moves fully 
into a geo-effective position.  

The geomagnetic field is expected to be quiet to active on 
6-XII-2003, increasing to minor storm levels, off and on, from 
7-XII-2003 through 15-XII-2003.  This will cause the highest HF 
bands to become degraded and unreliable.  At the same time, we 
don't expect much flare activity, so the middle to low HF bands 
will be in fair to good condition.

That means that conditions on HF this weekend will be fair to 
good for most of the contests and for general HF activity, except 
on the highest bands.  Long distance low frequency HF, below 
2 MHz, propagation along east-west paths over high and upper 
middle latitudes will remain poor, while propagation along long 
distance north-south paths will be fair.  Above 2 MHz, to about 
18 MHz, should be fair to good over most low- to mid-latitude 
paths, but somewhat degraded over the polar paths.  Frequencies 
above 18 MHz will be degraded, with at least a fifteen-percent 
depression of normal maximum usable frequencies.

I will continue to monitor space weather and propagation 
conditions, reporting updates at http://prop.hfradio.org/ - the 
NW7US Live Propagation Center.

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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