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ARRL Propagation Bulletin ARLP032 (1998)

ARLP032 Propagation de K7VVV

Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7VVV
Seattle, WA  August 7, 1998
To all radio amateurs

ARLP032 Propagation de K7VVV

Solar activity was up a bit for the month of July after being flat
for several months.  Average solar flux took a jump earlier in the
year, from 93.4 for both January and February to 109.1 for March,
108.3 for April, 106.7 for May and 108.5 for June.  Average solar
flux for July was 114.1.  A year ago the average solar flux for
July, 1997 was 71.4.

Toward the end of each of the past few weeks there has been a great
geomagnetic disturbance on Thursday or Friday, and this week is no
exception.  July 16 saw a planetary A index of 37, it was also 37 on
July 23, it was 33 on July 31. On August 6 it was all the way up to
69, indicating a severe storm.  The cause of this latest upset was
probably a well placed coronal hole or mass ejection, and the
excitement should continue for a few days, along with very high
solar flux.  Flux values on Thursday were 138.3, and solar flux is
expected to climb over the next few days, Friday through Sunday, to
145, 150 and 150.  The last time the solar flux reached 150 was over
five years ago on March 11, 1993.

The planetary A index for the same three days is predicted to be 30,
18 and 10, so HF conditions could be really good by the end of the
weekend.  Don't forget that when conditions are bad on HF due to
geomagnetic storming, auroral skip could be causing great excitement
on VHF.

NASA released some encouraging news about the SOHO spacecraft this
week after finally establishing radio contact on Monday.  Although
it is doubtful whether SOHO will ever again be a rich source of
solar data, the NASA Deep Space Network has been able to
consistently track the craft over the past few days as it sends 10
second carrier bursts in response to NASA commands.

Sunspot Numbers for July 30 through August 5 were 69, 107, 74, 121,
112, 80 and 85 with a mean of 92.6.  10.7 cm flux was 114.8, 113.7,
112.1, 109.6, 108.5, 115.8 and 126.8, with a mean of 114.5, and
estimated planetary A indices were 12, 33, 15, 8, 6, 9, and 9, with
a mean of 13.1.

Here are some path projections for the European CW DX Contest this
weekend, using some optimistic numbers for Sunday.

From Boston to Europe, 80 meters looks good from 2330-0500z, peaking
around 0200-0330z.  Check 40 meters from 2200-0630z, peaking from
0030-0400z.  20 meters looks good around the clock, with the best
period from 2200-0230z and the worst around 0800- 0900z.  Check 15
meters 1300-2300z.

For Miami, 80 meters looks good 0000-0500z, 40 meters 2330-0600z, 20
meters 1900-0230z, 0400-0700z, and around 1030-1200z.  Check 15
meters around 1300-2330z, with best conditions around 1700-2200z.

From Nashville, TN, check 80 meters 0030-0430z, 40 meters 2345-
0600z, 20 meters 1930-0200z, and 15 meters with some chance of
opening during daylight hours.

From Utah 80 looks good 0245-0400z, 40 from 0200-0530z, 20 from
2030-0800z (with best conditions around 0100-0200z and 0430-0530z)
and 15 around 2030-2200z.

From Los Angeles check 80 around 0330z, 40 around 0230-0530z, 20
around 2200-0800z and 15 around 0630-0700z.


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