[HCDX] NW7US Propagation Update: 11-XI-2003

[Tomas NW7US <nw7us@xxxxxxxxxxx>]

The large coronal hole that was predicted to move into
geoeffective position by 11-XI-2003 has indeed, affecting
the solar wind.  The solar wind has been elevated since
10-XI-2003, with a consistantly southward orientation (Bz
is negative) in the interplanetary magnetic field (IMF).
The solar wind stream is expected to continue at this
higher speed for the next few days, with a high possibility
that the IMF will remain orientated southward.  This will
cause the geomagnetic field to remain at least active, but
most likely at minor to major storm levels (at least a
G2-level geomagnetic storm, Kp levels between 4 and 7).

The Ap is expected to continue to rise, up to a possible 70,
during the next few days.  But, the 10.7-cm flux is also 
rising a bit, with 95, 98, and 100 expected from today, 
11-XI-2003, through 13-XI-2003.

There have been a series of B-class flares from the new
sunspots (498, 499, 500).  This has caused very minor
degradation of the middle HF bands in geographical areas
directly facing the sun.  Type-II radio emissions have
been recorded, as well, indicating minor coronal hole mass 
ejections (CME), further enhancing the solar wind stream.

As I write this, the first M-class flare peaked at 1351Z
11-XI-2003, at about M1.  It is unclear to me yet where
this flare came from.  It might have been from region
500, or, highly possible, from the now-returning sunspot
region 484 (we saw activity from this one several weeks
ago).  The possible return of large active regions that
contributed to the high activity of the last 3 weeks is
expected between 11-XI-2003 and 16-XI-2003, starting a
new surge of flaring activity for several weeks.  In the
meantime, the very large coronal hole should be the main
source of Earth disturbances.

Overall conditions, then, on HF will be poor to fair.  The
high geomagnetic activity for a period of many days will
degrade or even shut down polar and high-latitude paths,
while leaving mid- and low-latitude propagation paths only
marginal.  There will be exceptions to this across paths
of sunlight, due to the higher flux levels.  VHF conditions
could be enhanced due to the active aurora conditions and
elevated geomagnetic activity.

More at http://prop.hfradio.org/



73 de Tomas, NW7US (AAR0JA/AAM0EWA)
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