[CQ-Contest] Heads up - poor propagation ahead...

[nw7us at hfradio.org]

NW7US Propagation Bulletin
07 February 2005

Propagation today (07-II-2005) has turned poor on many HF circuits, due to  
a fast solar wind originating in a large coronal hole.  This coronal hole  
is located in the northern hemisphere of the visible solar disk, and is in  
position to continue influencing Space Weather around the Earth through  
the 9th.

Minor aurora at high latitudes, with possible short bursts at the higher  
range of the mid-latitudes, is possible through the 9th.  The current IMF  
orientation is not favorable for strong aurora, and the dynamic pressure  
of the solar wind is not high.  Even though the solar wind speed is over  
600 km/s at the moment due to the high-speed wind from this coronal hole,  
there is only minor aurora (Au level is 8).

This has elevated the Kp index to a current level of 6 (as of this  
bulletin, 0700 UTC 08-II-2005).  For the later part of 07 February, the Kp  
has been at or above 4.  This is causing a moderate depression of the  
critical frequencies that can be propagated via the ionosphere for a given  
radio signal path.  So, if you normally communicate on 5 MHz, the critical  
frequency could be lowered to as low as 3 MHz.  Signal levels will be  
weaker, due to the weakening of the ionosphere in general.

I am forecasting the next 24 hours to continue being rough for short-skip  
propagation (i.e., state-wide).  This is due to the weakening and lowering  
of the critical frequencies useful for short-skip propagation.   
Intra-state HF comms will be workable, though not optimal.

I am further forecasting the next 48 hours to be variable in terms of  
reliable communications for state-wide and regional paths.  There are  
returning sunspot groups that may bring a series of moderate flares.  Any  
moderate to strong flare could trigger coronal mass ejections, causing  
geomagnetic storms such as we saw several weeks ago.

73 de Tomas, NW7US (AAR0JA/AAA0WA)

: Propagation Editor for CQ, CQ VHF, Popular Communications :
: Creator; live propagation center http://prop.hfradio.org/ :
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