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ARRL Propagation Bulletin ARLP037 (2005)

ARLP037 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 37  ARLP037
From Tad Cook, K7RA
Seattle, WA  September 2, 2005
To all radio amateurs 

ARLP037 Propagation de K7RA

Geomagnetic activity was down quite a bit from last week, but solar
wind and a south-pointing Interplanetary Magnetic Field late
Wednesday left Earth vulnerable. The mid-latitude K-index reached 4,
and the planetary K index rose to 6. The IMF is from our Sun, and
the point where it contacts earth magnetic field is called the
magnetopause. Earth's magnetic field protects us from solar wind,
and the Earth's magnetic field at the magnetosphere usually points

But when the IMF points south, it is opposite Earth's magnetic
field, and the two link up. This carries energy from the Sun
directly into the Earth, and this can cause aurora and geomagnetic
instability. This is generally bad for HF radio propagation.

The IMF continues to point south on Thursday evening, and this could
leave Earth vulnerable to a coronal mass ejection erupting on the
Sun on Wednesday, August 31 at 2230z. The wind from this event is
traveling at about 3.36 million miles per hour, or 1500 km per

The predicted planetary A index for Friday through Monday, September
2-5 is 30, 25, 10 and 10. Sunspot numbers and solar flux should rise
slowly over the next week.

As September begins, we look forward to the Autumn equinox in the
Northern Hemisphere, always a better time for HF propagation. It is
also time to look at the average solar flux and sunspot numbers from
August, comparing them to previous months.

Average daily sunspot number in August was 65.6, down slightly from
68.7 in July. July average daily solar flux was 96.5, declining to
92.4 in August.

The average daily sunspot numbers for the months October 2004
through August 2005 were 77.9, 70.5, 34.7, 52, 45.4, 41, 41.5, 65.4,
59.8, 68.7 and 65.6. Average daily solar flux for the same months
was 106, 113.7, 95, 102.3, 97.2, 89.9, 85.9, 99.5, 93.7, 96.5 and

Peter Baskind, N4LI of Germantown, Tennessee (grid square EM55)
reported that on August 27 there was a great 6-meter opening in
which he worked stations around the eastern U.S. and Caribbean.
Most surprising was a 30 minute opening to Argentina with LU6DRV
(grid square GF05) peaking sometimes over S9, uncommon he says for
that far north.

I remembered this week that a ham I used to chat with on AMTOR in
the 1980s, W5KSI, Angelo Glorioso Jr., lived in New Orleans. I
emailed him and his son to inquire about their welfare, hoping they
evacuated early from the city before the storm. His son (Angelo III,
N5UXT) answered right back, said he was in Baton Rouge and his dad
was in Texas. He asked me to call his dad, who evacuated to Houston
on Sunday morning. I rang up Angelo, asked how he was doing, and he
said "Everything is gone," including the house he's lived in for 50
years and his mother's home. Angelo lived about 500 feet east of
Bayou Saint John, on Filmore Avenue, a mile south of Lake

The last they saw their home was around 10:00 AM Sunday morning when
Angelo and his wife began the 360 mile drive to the Bunker Hill
Village area of Houston via Interstate 10. Even though all of I-10
was switched for the evacuation to westbound traffic only, the
traffic crawled the whole way. Angelo and his wife drove nearly
non-stop until 4:30 PM Monday, an average speed of less than 12
miles per hour. Angelo told me he wakes up in the morning expecting
the nightmare to be over, and then it sinks in, that it really did
happen. But he is grateful he made it out of New Orleans safely with
his family.

Ed Bruette, N7NVP, the SM for Western Washington sent along some
non-ham frequencies to monitor for possible hurricane traffic. Of
course, these are outside the ham bands, and all we should do is
listen. All are in Upper Sideband. USN/USCG hurricane nets are on
7507 and 9380 KHz. American Red Cross also uses Upper Sideband for
disaster communications on 2802.4, 3171.4, 5136.4, 5141.4, 6859.5,
7550.5 and 7698.5 KHz. 7550.5 is the primary frequency. Hugh
Stegman, NV6H has put together a list of hurricane recovery
frequencies at,

I've been asked recently about any new sunspots from the next solar
cycle. The conventional wisdom is that sunspots with a new magnetic
polarity are actually from the next solar cycle. I talked to Bill
Murtagh of the NOAA Space Environment Center, and he said a recent
one was what he called a rogue sunspot group, or a "gnarly group."
In fact, spots with a magnetic polarity opposite to the prevalent
one appear from time to time throughout the solar cycle, and are a
good indicator for enhanced geomagnetic activity to come.

I called Bill to ask him about the sunspot cycle prediction tables
in the back of the Preliminary Report and Forecast, mentioned in
Propagation Bulletin ARLP033, from August 5. I was curious how these
are updated and when, and also noted that the prediction for solar
cycle minimum around the end of 2006 has not changed in several
years.  Bill said this estimate is still valid, but they should have
an update in April 2006 to be announced during Space Weather Week. A
panel of experts will meet to come up with an updated model for the
end of the current cycle.

Bill said that so far the prediction for the smoothed sunspot number
for the peak of the next cycle ranges from a pessimistic 50 maximum
to 150 maximum. By contrast, the famous cycle 19 from the late 1950s
had a smoothed peak of 201.3, and cycles 21 and 22 (the last two)
peaked at 164 and 158. The current cycle, 23, peaked at 120.8.

The tables I called Bill about can be seen in the back of a recent
issue of Preliminary Report and Forecast at, He said the
smoothed solar flux and sunspot numbers are averaged over a 13 month
period, so the most recent number that is not a prediction would be
six months ago.

The number shown for the current month would be the six predicted
months in the future combined with the previous six observed months.

If you would like to comment or have a tip, email the author at,

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
bulletins is found at,

Sunspot numbers for August 25 through 31 were 76, 57, 91, 99, 88, 68
and 48 with a mean of 75.3. 10.7 cm flux was 92.4, 93.2, 92.1, 89.8,
89.2, 86, and 84, with a mean of 89.5. Estimated planetary A indices
were 24, 11, 7, 7, 9, 4 and 36 with a mean of 14. Estimated
mid-latitude A indices were 18, 5, 4, 5, 5, 3 and 17, with a mean of


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