[CQ-Contest] NW7US Propagation Bulletin 2030 UTC 17-I-2005

[nw7us at hfradio.org]

NW7US Propagation Update
17 January 2005 - 2030 UTC

The latest long-duration flare from active solar region 720 (the flare  
measured X3.8 and X4.1, officially recorded as X3.8 at 0659 UTC  
17-I-2005), which took 2 hours to reach maximum, and had a long decay as  
well, unleashed such an intense amount of plasma, proton, and energy burst  
that many sensing equipment (satellites like ACE) have become unreliable  
and unusable.  The solar wind speed exceeded 800 km/s, and the  
interplanetary magnetic field orientation was observed pointing southward,  
until the sensors 'shut down' under the influence of the proton  
bombardment.  So, we don't really know how high the wind speed has been  
since, nor do we really know how the IMF is oriented.

What we know is that we are under a full onslaught of a proton storm.  We  
are under the influence of a very strong solar wind.  Massive amounts of  
plasma and a solar particle cloud is passing as the result of the coronal  
mass ejection from the X2-class flare of a few days ago.  The planetary K  
index (Kp) has reached the level of 7 - a real geomagnetic storm.

The CME-triggered storm will continue for at least the next 12 to 24  
hours.  But, with the arrival of what looks like a medium-sized coronal  
hole, as well as the arrival of a new coronal mass ejection on 18 January  
2005, we are expecting the geomagnetic storm to increase to severe storm  
levels on the 18th.

The X3.8 flare unleashed a very fast coronal mass ejection.  This one is  
faster than the last two by over 300 km/s.  It was measured at 1567 km/s,  
and was directed toward Earth.  This means that it will arrive here  
sometime on 18 January 2005.  This one is big.  The long-duration of this  
event indicates a possibly very large cloud ejected over a longer period  
than the last two ejections.  Again, that translates to a severe  
geomagnetic storm.  Since the current strong (S3) radiation storm is  
expected to continue for several more days, we cannot be sure if the  
sensors will give us indication of when the shock wave arrives.  Reports  
will therefore be spotty.

Active region 720 has been amazingly eventful.  Five large solar flares  
produced moderate (R2) to strong (R3) radio blackouts since 15 January.   
HF radio communications on the sunlit hemisphere of Earth experienced  
significant signal degradation during these solar flares, and the area  
around eastern Africa was totally shut down.

Active Region 720 is a large and complex sunspot cluster. Further major  
eruptions are possible from this region before it rotates around the  
visible solar disk on 22 January.  Continued radio blackouts, geomagnetic  
storms, and solar radiation storms will impact MW, HF, VHF  
communications.  Aurora is a sure bet.

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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