ARRL

ARRL Propagation Bulletin ARLP021 (2002)

SB PROP @ ARL $ARLP021
ARLP021 Propagation de K7VVV

ZCZC AP21
QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7VVV
Seattle, WA  May 24, 2002
To all radio amateurs 

SB PROP ARL ARLP021
ARLP021 Propagation de K7VVV

Sunspot counts and solar flux reached a short-term minimum late last
week, but both seem to be on the rise again.  Average daily sunspot
numbers were down nearly 35 points from last week, and average solar
flux was down eight points.  Predicted solar flux for this weekend
is 175 for Friday and 170 for both Saturday and Sunday.  Flux values
are expected to rise to around 190 by month's end.

Geomagnetic disturbances are the bigger news this week, with a
geomagnetic storm on Thursday, May 23, caused by a series of three
coronal mass ejections on the previous day.  Planetary A index was
54 on Thursday, and planetary K index reached seven over two 3-hour
periods.  This means generally lousy HF radio conditions with
enhanced absorption, especially at higher latitudes.

Several sunspot groups in view have potential for more fireworks.
Currently the predicted A index for Friday through Sunday is 30, 15
and 10.  The high A and K values don't look good if they persist
during this weekend's CQ Worldwide WPX CW Contest, but if there are
no more coronal mass ejections or flares, the bands could recover.
As this was being written on Thursday evening the planetary K index
had dropped to three and so had the mid-latitude K index, as
reported by WWV.

NW7US sent along a tip for propagation watchers who have WAP enabled
wireless devices.  Point your WAP device toward
http://wap.hfradio.org/ .  A normal web browser will get redirected
to http://hfradio.org/ , but a cell phone will see WML instead of
HTML providing solar and geomagnetic information.

KB6HCN recently sent along a URL to a nice image of the sun.  See
http://antwrp.gsfc.nasa.gov/apod/ap020508.html , and for a larger
image click on the photo and go to
http://antwrp.gsfc.nasa.gov/apod/image/0205/sun2_trace_big.jpg .

Sunspot numbers for May 16 through 22 were 120, 134, 140, 155, 171,
185, and 217, with a mean of 160.3. 10.7 cm flux was 158.4, 157.1,
163, 170.9, 171.3, 185.9, and 181.1, with a mean of 169.7.
Estimated planetary A indices were 12, 10, 15, 18, 14, 14, and 14,
with a mean of 13.9.
NNNN
/EX