[CQ-Contest] Chance of Geomagnetic Storm

NW7US, Tomas nw7us at hfradio.org
Thu Jul 22 16:59:54 EDT 2004


Over the last week or so, we've been seeing very nice solar activity.   
Solar activity has been strong, with the 10.7-cm Flux reading a high of  
175.  Last night between 6 PM and midnight, from my location, I heard many  
20 meter QSO's between the West Coast and Europe and other areas of the  
world.  On Shortwave, I heard strong DX openings on higher frequencies,  
longer into the night.

Quite a number of flares, including a series of X-class as well as M-class  
flares have occurred over the last week or so.  Most of them did not have  
any significant, associated coronal mass ejections.  However, the few that  
occurred have caused us solar weather watchers to be on alert.  So far,  
the elevated solar wind speed and pressure have not had too great of an  
affect on the Earth's geomagnetic field activity, since the Interplanetary  
Magnetic Field (IMF) orientation (Bz) was oriented in such a way as to not  
cause disturbance.

However, as of the time of writing this NW7US Propagation Bulletin, at  
2030Z, 22 July 2004, the IMF is moderately oriented southward, and has  
been now for a long period of time (since approx. 1330Z), and has steadily  
increased in its southward orientation (the Bz component has steadily  
become more negative).  This will cause the geomagnetic field to become  
highly active, possibly even stormy.

I am now predicting that we will see K index reading of at least 5,  
possibly 6, through this evening.  This will degrade HF communications.   
The cause is the high-speed solar wind (currently near 700 km/s), and the  
long-duration southward orientation of the IMF, from a passing CME.

In addition, I detect possibly two coronal holes rotating into the center  
of the Sun.  They are each located off of the Sun's equator, but due to  
their proximity and apparent size, they could cause long-duration  
enhancement of the solar wind, causing a lengthy period of continued  
geomagnetic activity from active to stormy levels, over the course of next  

I will update you as conditions warrant.

73 de Tomas, NW7US (AARØJA/AAAØWA)

: 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/ :
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