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/ :
: Associate Member of Propagation Studies Committee of RSGB :
: US Army Miltary Affiliate Radio Service (MARS) SMD AAA0WA :
: 122.93W 47.67N / Brinnon, Washington USA CN87 CW/SSB/DIGI :
: Website/software/database design http://newwebmakers.com/ :
: 10x56526, FISTS 7055, FISTS NW 57, Lighthouse Society 144 :
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