SB PROP @ ARL $ARLP033

ARLP033 Propagation de K7RA

ZCZC AP33

QST de W1AW

Propagation Forecast Bulletin 33 ARLP033

From Tad Cook, K7RA

Seattle, WA August 16, 2013

To all radio amateurs

SB PROP ARL ARLP033

ARLP033 Propagation de K7RA

Again this week, solar activity was unchanged, with average daily

sunspot numbers slipping from 85.4 to 85, and average daily solar

flux increasing 4.4 points to 111.7. Geomagnetic conditions were

stable.

The latest solar flux prediction from USAF/NOAA has flux values of

125 on August 16, 130 on August 17-18, 120 on August 19-20, 110 on

August 21-23, 105 on August 24, 110 on August 25-26, 115 on August

27-29, 110 on August 30, 105 on August 31 through September 6, then

110 and 115 on September 7-8 and 120 on September 9-11.

Predicted planetary A index is 12 and 8 on August 16-17, 5 on August

18-19, then 12 and 15 on August 20-21, 8 on August 22-23, 5 on

August 24-30, then 12, 15, and 10 on August 31 through September 2,

and 5 on September 3-7.

OK1HH issues his own weekly geomagnetic activity forecast, and he

sees mostly quiet geomagnetic conditions August 16-17, quiet to

active August 18, quiet on August 19, mostly quiet August 20, quiet

August 21, active to disturbed August 22, quiet to unsettled August

23, quiet to active August 24, quiet to unsettled August 25-28,

quiet August 29-30, active to disturbed September 1, quiet to

unsettled September 2, quiet on September 3-5, mostly quiet

September 6-8, active to disturbed September 9, quiet to active

September 10, and active to disturbed September 11. OK1HH says "a

positive storm phase" is expected August 22, and a growing solar

wind may cause remarkable changes in the magnetosphere and

ionosphere on August 16, and 21-22, and September 1-2, 6-7, and 11.

At 0318 UTC on August 16, the Australian Space Forecast Centre

issued a geomagnetic warning, saying a high speed wind stream is

spewing from a coronal hole. Unsettled to active geomagnetic levels

are expected today, August 16, and minor storm levels are possible.

Scientific American has a 60 second podcast explaining why the

changing magnetic polarity of the sun is nothing to worry about.

Listen at

http://www.scientificamerican.com/podcast/episode.cfm?id=solar-magnetic-field-flip-poses-no-13-08-15.

We get our solar flux data directly from the observatory in

Penticton, British Columbia where they measure and report the

numbers. It has been available at

ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_values/fluxtable.txt

but this week that server seemed unreachable. I poked around for

quite some time and finally found the same data in html rather than

plain text format at

http://www.spaceweather.ca/data-donnee/sol_flux/sx-5-flux-eng.php.

Al Kaiser, N1API of Meriden, Connecticut asked, "If you have two

flares at the same time from two different sunspot areas on the sun,

do they add up to give a bigger class of flare, or just end up as

one longer event?"

They are counted and rated separately. And if the flares are on

different areas of the sun, they are probably pointing in different

directions, so one or both might not affect earth.

Randy Crews, W7TJ of Spokane, Washington has long been fascinated by

the idea that the current solar cycle 24 may turn out to have two

peaks, like the last few cycles. He writes, "There have been

several predictions that cycle 24 might have a second peak. Well

maybe - maybe not. Cycle 21 had a definite single peak: November

of 1979. Cycle 22 had two peaks: September of 1989 and January of

1991. Cycle 23 also had two peaks: April/July of 2000 and December

of 2001. K9LA presented some interesting analysis regarding the

declining magnetic strength of sunspots since 1995 and especially

cycle 24." See

http://myplace.frontier.com/%7ek9la/Looking_Ahead_To_Solar_Cycle_25.pdf

Randy continues, "Anyone who brings up a NASA photo of sunspots

during Cycle 21-23 will see many large magnetically complex sunspots

vs. Cycle 24's 'freckles' of small magnetically simple spots. So we

MAY see a second peak IF the magnetic strength of the sunspots

holds, or better yet increases. If not, a second peak is doubtful,

and chances are the peak of activity has passed (as defined by the

average monthly solar flux and average monthly sunspot count). The

Sun is always full of surprises. During the CQWW Contest of October

2003 the solar flux punched up to 290!"

Ah, Randy, wouldn't that be nice to see again! In fact, your

current author's stewardship of this bulletin began in 1991, not

because of any particular expertise regarding astrophysics, but due

to a similar sudden burst of solar activity, which happened to

coincide with the former (and only other) author of this bulletin

becoming too ill to write (see http://oldqslcards.com/W1HDQ.pdf).

The event was Thursday, January 31, 1991 when the solar flux reached

357. Someone needed to write about this. I had no idea when I

alerted folks in Newington that it would be me.

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 August 8 through 14 were 90, 51, 76, 90, 85, 98,

and 105, with a mean of 85. 10.7 cm flux was 104.4, 103.6, 102.5,

110.4, 114.1, 122, and 125.2, with a mean of 111.7. Estimated

planetary A indices were 5, 9, 6, 6, 6, 9, and 10, with a mean of

7.3. Estimated mid-latitude A indices were 4, 11, 7, 7, 6, 9, and

9, with a mean of 7.6.

NNNN

/EX