SB PROP @ ARL $ARLP031

ARLP031 Propagation de K7RA

ZCZC AP31

QST de W1AW

Propagation Forecast Bulletin 31 ARLP031

From Tad Cook, K7RA

Seattle, WA August 2, 2013

To all radio amateurs

SB PROP ARL ARLP031

ARLP031 Propagation de K7RA

The weekly averages of daily sunspot numbers and solar flux barely

changed at all compared to the previous week. Average daily sunspot

numbers went from 73.4 to 79.6, while average daily solar flux

decreased from 110.6 to 109.7.

The weak peak of this solar cycle continues. We are moving toward

the fall season, which is always seasonally better than summer for

HF propagation. Let's hope for a rise in solar activity to

complement the seasonal change.

The latest prediction from NOAA/USAF for the near term has solar

flux at 115 on August 2-3, 110 on August 4-6, then 115, 120 and 115

on August 7-9, 105 on August 10-12, 100 on August 13, 105 on August

14-18, 100 on August 19-24, and 125 on August 25. Flux values hit a

minimum around 100 on September 3-4, and rise to a peak of 135 on

September 11-12.

Expected planetary A index is 8, 12 and 8 on August 2-4, 5 on August

5-8, 8 on August 9-10, 5 on August 11-20, then 10, 15 and 10 on

August 21-23, 5 on August 24-26, 10 on August 27, 15 on August

28-31, 8 on September 1, and 5 after September 1.

Petr Kolman, OK1MGW presents a weekly geomagnetic prediction from

the Czech Propagation Interest Group. He predicts active to

disturbed conditions for today, August 2, quiet to active August 3,

quiet to unsettled August 4, mostly quiet August 5, quiet to

unsettled August 6-7, mostly quiet August 8-11, quiet August 12-13,

quiet to active August 14-15, quiet to unsettled August 16-18,

mostly quiet August 19-20, quiet to active August 21-22, and mostly

quiet August 23-24. Petr says that growth in the solar wind may

cause remarkable changes to the magnetosphere and ionosphere on

August 2-3 and 14-16.

NASA released their monthly solar cycle prediction, and there is no

change from last month. You can read it at

http://solarscience.msfc.nasa.gov/predict.shtml.

At the beginning of each month we take a look at the latest numbers

from our 3-month moving average of daily sunspot numbers. We do not

see any upward trend. We see two peaks, one toward the end of 2011

and another smaller peak this spring. In 2011, the 3 month periods

centered on October and November had average daily sunspot numbers

of 118.8 and 118.6. This spring the 3-month periods centered on

April and May had averages at 106.4 each. Could these be the

double-peaks of solar activity that some have predicted for this

sunspot cycle?

The 3-month moving averages of daily sunspot numbers centered on

January through June 2013 were 73.6, 80.7, 85.2, 106.4, 106.4, and

97.5. Just to clarify, the 3-month period centered on June includes

sunspot numbers for all of the 92 days from May 1 through July 31.

The sum is 8,970. Divide that total by 92, and the result is

exactly 97.5.

Jon Pollock, K0ZN of DeSoto, Kansas reported 17 meter observations

in last week's bulletin ARLP030, and this week has another report.

He wrote, "I won't keep reporting this, but I thought this was again

instructive since I am seeing this so frequently lately. On Friday,

July 26 I was up late and again decided to give 17 meters a try at

Midnight CST. Again 17 meters was very quiet, no signals at all.

i.e. 'Dead'. Except that I heard some weak thunderstorm crashes in

the background. My experience has been that often when you hear

that, the QRN source is a long way away. I called CQ about five

times (400 watts CW into a ground mounted vertical with a large

radial system) and VK7CW in Burnie, Tasmania came back (now about

12:15 AM CST) with a nice signal, about S-6. He was running 100

watts to a hexbeam. We ended up having a rag chew, and ours were

the only signals either one of us could hear on the band over a

9,380 mile path from Eastern Kansas. Again, 17 meters is more often

than not open when it seems dead, often for long haul contacts."

Rick Lindquist, WW1ME sent a link to yet another article about the

current solar cycle being the weakest in one-hundred years. It also

mentions a July meeting of the American Astronomical Society Solar

Physics Division, which was in Bozeman, Montana. You can read the

article at

http://www.universetoday.com/103803/solar-cycle-24-on-track-to-be-the-weakest-in-100-years/.

The American Astronomical Society promises to have downloadable

presentation files from the meeting, but nothing yet. They will be

posted at http://solar.physics.montana.edu/SPD/SPD2013/.

For more information concerning radio propagation, see the ARRL

Technical Information Service at

http://arrl.org/propagation-of-rf-signals. For an explanation of

the numbers used in this bulletin, see

http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of

past propagation bulletins is at

http://arrl.org/w1aw-bulletins-archive-propagation. More good

information and tutorials on propagation are at http://k9la.us/.

Monthly propagation charts between four USA regions and twelve

overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL

bulletins are at http://arrl.org/bulletins.

Sunspot numbers for July 25 through 31 were 71, 58, 64, 68, 97, 105,

and 94, with a mean of 79.6. 10.7 cm flux was 106.9, 109.5, 107.9,

109.4, 112.1, 113.1, and 108.7, with a mean of 109.7. Estimated

planetary A indices were 11, 14, 11, 7, 6, 6, and 5, with a mean of

8.6. Estimated mid-latitude A indices were 10, 23, 10, 8, 7, 6, and

5, with a mean of 9.9.

NNNN

/EX