[SFDXA] ARLP016 Propagation de K7RA

Fri Apr 20 18:41:32 EDT 2012

ZCZC AP16
QST de W1AW
Propagation Forecast Bulletin 16  ARLP016
 From Tad Cook, K7RA
Seattle, WA  April 20, 2012
To all radio amateurs

SB PROP ARL ARLP016
ARLP016 Propagation de K7RA

As promised in the ARRL Letter, this week's bulletin features a report 
on recent solar activity and solar cycle progression from Carl 
Leuetzelschwab, K9LA.

Solar flux and sunspot numbers reached a short term low on April 8-11, 
but now are rising again.  For the past week, April 12-18, average daily 
sunspot numbers more than doubled compared to the previous seven days, 
rising more than 39 points to 71.7.  Average daily solar flux increased 
from 95.9 to 105.1.  On April 19, the day following this period, the 
daily sunspot number rose dramatically from 96 to 122, and so did solar 
flux values, from 121.5 to 137.8

Since April 10, eleven new sunspot groups emerged.  One each on April 
10-13, two on April 14, one on April 16 two on April 17 and one each on 
April 18-19.

Predicted Solar Flux for April 20-25 is 135, followed by 130 on April 
26-27, 105 on April 28, 100 on April 29-30, 95 on May 1-9, then rising 
to 100 on May 10-12 and 105 on May 13-18 and 110 on May 19-22.

Predicted planetary A index is 8, 5, 5, 7, 12, and 12 on April 20-25, 5 
on April 26-29, 8 on April 30, 5 on May 1-7, and 8, 12, 15 and 10 on May 
8-11, and 5 on May 12-20.

Alaska Dispatch ran an article with video on the solar flare mentioned 
in K9LA's report below.  See it at 
http://www.alaskadispatch.com/video/video-massive-eruption-suns-surface

German ham Toni Umlandt, DD3EO mentioned another resource in response to 
our mention in last week's bulletin ARLP015 of a public remotely 
controlled SDR radio receiver in Walla Walla, Washington that anyone can 
use via the internet.  He said to check http://www.websdr.org/ .  This 
lists 36 SDR receivers, and I think all of them can be used 
simultaneously by multiple users.

K9LA's report:

Monday, April 16 gave us moderate solar activity, which was due to an 
M1.7 X-ray flare from Region 1458 around 1745 UTC.  But since then, 
solar activity has continued at low levels.  The daily 10.7 cm solar 
flux is expected to slightly increase to around 120 during the next 
several days.  There is an extremely small chance of X-Class flares (1%) 
and a somewhat greater chance of M-Class flares (around 15%).

With solar activity continuing at low levels, the ascent of Cycle 
24 noticeably slowed in the past couple months.  For example, after a 
  monthly mean 10.7 cm solar flux peak in November 2011 of 153, the next 
three months saw ever-decreasing monthly means -- 141, 133, and 107 for 
December, January, and February, respectively.  March (last month) 
recovered a bit with a monthly mean of 115, but April so far appears to 
be headed for another low monthly mean (through April 18, the 10.7 cm 
solar flux monthly mean is hovering around 102).  As a side note, these 
up-and-downs in the monthly mean solar flux are typical of a solar cycle.

But these recent low monthly means have taken their toll on the smoothed 
10.7 cm solar flux.  Since early 2009, the smoothed 10.7 cm solar flux 
rose nicely.  The recent low monthly means have resulted in the smoothed 
value pretty much leveling off in the past two months at around 118.  
This smoothed value is borderline for good worldwide 10-Meter openings 
(especially East-West), so 10-Meters will be at the mercy of the 
day-to-day variation of the F2 region.

Does this mean we've reached Cycle 24's peak?  Not necessarily --  other 
Cycles have had similar slow-downs, but then the solar activity picked 
up again in terms of the monthly means to continue the increase of the 
smoothed value.  The monthly means during the next several months will 
be interesting to observe, and may give us an early clue as to how high 
Cycle 24 will ultimately go.

Regardless of what happens with Cycle 24, the time is now to get on the 
higher bands (especially 12-Meters and 10-Meters) to take advantage of 
F2 region propagation.  If Cycle 24 performs to the
nominal prediction from the Marshall Space Flight 
Center (http://solarscience.msfc.nasa.gov/predict.shtml), we're pretty 
much there -- and we're not likely to have much mid latitude 50 MHz F2
propagation during this solar cycle (but watch for sporadic E links to 
the equatorial ionosphere for Trans-Equatorial Propagation).  If Cycle 
24 performs more to the nominal prediction of the
International Space Environment 
Service (http://www.swpc.noaa.gov/SolarCycle/), then we should have 
somewhat better propagation on the higher bands in the next year or so.

If you would like to make a comment or have a tip for our readers, email 
the author at, k7ra at arrl.net <mailto:k7ra at arrl.net>.

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.  Find more 
good information and tutorials on propagation at 
http://myplace.frontier.com/~k9la/ <http://myplace.frontier.com/%7Ek9la/> .

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 April 12 through 18 were 50, 50, 65, 77, 86, 78, and 
96, with a mean of 71.7.  10.7 cm flux was 95.3, 97.7, 98.1, 101.7, 
107.9, 113.8 and 121.5, with a mean of 105.1.  Estimated planetary A 
indices were 13, 19, 9, 5, 5, 8, and 8, with a mean of 9.6.  Estimated 
mid-latitude A indices were 11, 13, 7, 5, 5, 8, and 7, with a mean of 8.
NNNN
/EX