ARRL

ARRL Propagation Bulletin ARLP031 (2011)

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 5, 2011
To all radio amateurs 

SB PROP ARL ARLP031
ARLP031 Propagation de K7RA

Solar activity increased markedly this week, with the sunspot number
rising to 130 on Monday, August 1, the highest since a reading of
131 on April 14, 2011.  Average daily sunspot number more than
doubled this week compared to last, rising nearly 54 points to 99.3.
 
On Thursday I received a Significant Event Report from Rob
Steenburgh, KA8JBY, Space Weather Forecaster at NOAA Space Weather
Prediction Center:
 
"A trio of significant active regions produced a series of radio
blackout (solar flare) events in the past few days.  To date, three
radio blackouts reaching the R2 (Moderate) level have been observed.
Earth-directed coronal mass ejections have been associated with each
of the biggest radio blackout events on August 2-4.  Solar radiation
enhancements have also occurred in conjunction with each of these
events, with the solar radiation storm event threshold being
exceeded to reach the S1 (Minor) level in conjunction with the
August 4 event".
 
"Three coronal mass ejections (CMEs) are currently en route to
Earth, with the commencement of geomagnetic storming expected early
to mid-day on August 5 with the arrival of the CMEs associated with
the August 2-3 events.  The third of the string, seemingly the
fastest CME, may catch up with the first two in the next 12-18
hours, compressing the plasma and enhancing the embedded magnetic
field.  Storming levels are expected to attain G3 (Strong)
conditions.  The current Solar Radiation Storm may experience a kick
with the shocks, and attain S2 (Moderate) thresholds".
 
"Some level of geomagnetic disturbance is expected to continue
through August 7 as the series of CMEs affect the Earth.  Continued
activity is likely from these regions as they continue to rotate off
the visible solar disk over the next 7 days.  The Space Weather
Prediction Center will continue to monitor this event as it
unfolds".
 
Thanks, Rob!
 
A NASA video shows a couple of the CMEs.  Check
http://www.nasa.gov/mission_pages/sunearth/news/News080411-dblpunch.html.
 
The latest forecast on Thursday night has planetary A index for
August 5-9 at 50, 30, 20, 15, and 10, then 8 on August 10-12, then
5, 8, 10, 15, 12, 10 and 8 on August 13-19.  Solar flux predicted
for August 5 is 115, 110 on August 6-7, 100 and 95 on August 8-9,
then 85 on August 10-12, then 100 on August 13-16.
 
The planetary A index at 50 is quite high.
 
Geophysical Institute Prague predicts active conditions on August
5-7, unsettled to active August 8, quiet to unsettled August 9, and
quiet conditions August 10-11.
 
July is over, so let's look at some of the numbers.  The average
daily sunspot number for the month of July was 67.2, up from 55.5
for June.  The moving three month average of daily sunspot numbers
for May through July, centered on June was 61.5.  The 3-month moving
average centered on January through June was 35.3, 55.7, 72.3, 74.4,
65.9 and 61.5.
 
Vince Varnas, W7FA of Portland, Oregon wrote on July 30:  "For the
last week the ST0R DXpedition to South Sudan has had very weak
signal strength here in the Portland area, particularly at night on
the 17 meter band (18 MHz).  Generally they are S-3, at best".
 
"At 0209 UTC on July 30 there was a M9 solar flare from a big
sunspot.  At 0522 UTC I heard and worked the ST0R station on CW with
much, much louder signal strength, both directions.  (They were at
the noise or slightly above a few hours earlier.  When I worked them
on SSB on July 26 at 2303 UTC they were about S-4.)  They were S-8
to 9 on the S-meter.  The difference in signal strength between
'normal' and last night was about 30 db.  Since it is a scientific
fact that solar flares can and do enhance the reflectivity of the F
layer, my conclusion is that this is what produced the markedly
stronger signals from ST0R".
 
Thanks, Vince.
 
Sergej Ignatov, UZ2HZ of Kremenchug, Ukraine asked about a link to
the Penticton source for thrice-daily solar flux readings, as the
link he was using no longer works.  Yes, they changed servers again,
so the URL has changed.  Try
ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_values/fluxtable.txt
in your web browser.  The column you want is third from the right,
the observed flux values, and the local noon (2000z) readings.
Although readings are taken three times per day, the noon reading is
the official solar flux for the day, also shown at
http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt in whole number
resolution.
 
As geomagnetic conditions change over the next few days, you can
check http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt for the
planetary K index, updated every three hours.  You can also check
out http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html every day
after 2100z for an updated daily forecast of solar flux and
planetary A index.
 
Joe Molon, KA1PPV of Stamford, Connecticut writes:  "Well it
happened again.  Not much happening southbound but this time the
door to Europe was wide open.
 
I had heard about the M Class flare and decided to check up on solar
conditions because I knew it might get really good before it goes
into the toilet.  I saw a SF of 116 with an A Index of 3 and a K
Index of 1 and that is all I needed.
 
In one hour I logged IZ5RVG, DL2OCE, IC8TEM, IZ5MXA and EB5DZC.
 
Not that unusual for someone running 100W into a beam but, as usual,
I did it the hard way with 1.5 watts all on 20 meters.  Got 599 on
all except for the last when the noise crept up.
 
I was using my Small Wonder Labs PSK kit for 20m with 1.5W into a
Diamond BB7V 25 feet AGL.  The propagation Gods opened the gate and
I walked right through.  Wow!  It was great to get everyone that I
tried for.  That never happens in QRPland.  Good DX.  Yep!  It's
about time!  Now watch the power grid get knocked out tomorrow when
the CME shows up!"
 
Thanks, Joe!  Sounds like fun.
  
If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@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://mysite.ncnetwork.net/k9la/index.html.
 
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 28 through August 3 were 84, 88, 101, 128,
130, 98, and 66, with a mean of 99.3.  10.7 cm flux was 107.3,
111.7, 112.7, 118.6, 124.9, 121.6, and 119.9, with a mean of 116.7.
Estimated planetary A indices were 3, 5, 16, 8, 9, 3, and 3, with a
mean of 6.7.  Estimated mid-latitude A indices were 3, 3, 10, 7, 6,
3, and 3, with a mean of 5.
NNNN
/EX