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ARRL Propagation Bulletin ARLP020 (2013)

ARLP020 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA
Seattle, WA  May 17, 2013
To all radio amateurs 

ARLP020 Propagation de K7RA

This is, after all, the peak of the current solar cycle, or close to
it, so no surprise that solar indices are up. But based on past
solar cycles, many of us expected more. The latest forecast predicts
a peak for this cycle in Fall 2013, but of course that will be
determined afterward, and based on a long running average of sunspot
numbers. So don't miss this one. Don't wait until a year after the
peak, then lament not being on back when. Today may have the best
Spring propagation for a long time.

The past week saw average daily sunspot numbers increase by more
than 34 points to 156.1. Average daily solar flux was up by nearly
three points to 140.1. On Wednesday, May 15 the daily sunspot number
was 186, the highest number since January 6-7, when the sunspot
numbers were 186 and 196.

Predicted solar flux for the near term is 145 on May 17-18, 140 on
May 19, 135 on May 20, 130 on May 21, 125 on May 22, 120 on May
23-24, 160 on May 25, 170 on May 26, 160 on May 27-28, 155 on May
29-30, 150 on May 31, 155 on June 1, 160 on June 2-3, 155 on June 4,
150 on June 5, and 145 on June 6-8.

Predicted planetary A index is 15 on May 17, 8 on May 18-19, 5 on
May 20, 8 on May 21, 15 on May 22, 12 on May 23, 8 on May 24, 5 on
May 25-27, 15 and 10 on May 28-29, 5 on May 30 through June 8, 8 on
June 9, and 5 on June 10 and 12 on June 11.

Http:// reports this morning (May 17) that a CME may
strike Earth today from an X1 flare two days ago, but it is expected
to be a glancing blow instead of a direct hit. NOAA predicts a 40%
chance of polar geomagnetic storms. This is from sunspot group 1478,
which should be pointing directly at Earth in a few days. ZDnet ran
a story on this today:

Http:// ran a mid-week piece on sunspot group 1478,
complete with video and cinematic score:

OK1HH predicts quiet to active geomagnetic conditions May 17-18,
mostly quiet May 19, quiet on May 20, mostly quiet May 21, active to
disturbed May 22, quiet to active May 23-24, mostly quiet May 25-26,
quiet May 27, quiet to active May 28, active to disturbed May 29,
quiet to unsettled May 30, mostly quiet May 31 and June 1, quiet to
unsettled June 2-3, mostly quiet June 4, and quiet on June 5-8.

David Moore sends along a link to a video from Phil Plait's Bad
Astronomy blog on This one shows time-lapse
photography of aurora from Northern Michigan:

This is a pretty high bandwidth HD video, so if you have an average
broadband connection, you may want to turn off the audio and walk
away from the computer for a while and let the buffer load up on
data, then run the video from the beginning.

Phil Plait's commentary on the video is well worth reading, and you
can find it on if you select "Health and Science"
across the top, then page down to "Time Lapse Video."

There are a couple of space weather pages on Facebook of interest to
hams. You will have to sign up for Facebook to read these, but it is
free and painless. Check out

Check out, an
interesting and useful page found just by fooling around with a
popular web search engine. Search about one-fifth down the page for
"Solar Flux Index and Sunspots." You'll see an interesting plot
correlating proton flux, solar flux and sunspot number.

Today (May 17) at 0915 UTC the
site issued this alert: "There was a huge eruption on the Sun
observed with class M3.21." At 0952 UTC their website said "In the
past two hours there was a big solar flare with a class of M3.21."

Lee Gordy, W4KUT of Cartersville, Georgia sent this report about
what he was up to over the past few days, along with a propagation
query about solar flares and HF blackouts: "I participated in a
GEMA/FEMA/Homeland Security exercise at Stone Mountain, Georgia this
week. I was with Paulding County EMA/ARES. There were a couple dozen
EMA, Fire & Rescue, LEO and National Guard MCVs gathered from all
over the state for the four day event."

My guess is an MCV must be a Mobile Command or Communications
Vehicle, and of course a LEO is a Law Enforcement Officer. I think
EMA must be an Emergency Management Agency.

The exercise was Monday through Thursday, May 13-16.

Lee continues, "We were tasked with many activities, including
checking-in to the statewide Georgia ARES HF net (80 and 40 meters)
every hour, from 0900 through 1700 local, May 14-15, using CW, Voice
(LSB), and PSK31.

"ARES played a big part in the exercise.

"The HF conditions were, according to local propagation experts,
supposed to be a total HF blackout. But we had no problem on 80 and
40 meters. What happened?

"There was supposed to be a black-out due to CME or some kind of
disturbance. Our take?  Ol' Sol cannot be tamed!  Much less

"Our station (WX4PCA Paulding County ARES), observed no anomalies on
80 or 40 meters during the entire period from Monday May 13 through
Thursday May 16. Go figure."

Thanks, Lee! I believe the blackout predictions were based on worst
case scenarios in which solar flares could have a big effect if they
were aimed squarely at Earth, but they weren't.

If you check the archives for those days at (check the upper right, and dial in
your date) you will see plenty of coverage regarding solar flares,
but all were around the eastern limb of the Sun, none really
geoeffective toward Earth. But check the mid-latitude indices (on
the left side) at and
you don't see a lot of activity. Plus, Georgia is way down south,
and not subject to the disturbances common at higher latitudes. For
example, here in Seattle I am at 47.7 degrees north latitude, but
the entire state of Georgia sits between 30.7 and 35 degrees north

Jon Jones, N0JK of Lawrence, Kansas wrote: "Every dog has his day. I
worked LU9EHF FF95 in Argentina on 50.130 MHz with 59 signals at
2159 UTC May 10. My antenna was a dipole in the attic over the
garage, the radio a 100 watt FT-897.

"I was watching our two grand children while the XYL was out on
errands. I checked the radio and DXscape from time to time in
between entertaining them. At 2145 UTC K0HA EN10 spotted LU9EHF on
50.130. I tuned to .130 not expecting to hear anything, but heard
some weak Spanish accented SSB on frequency. It was LU9EHF. He
worked a W8 then suddenly got much louder. Very loud, way over S-9.
He worked N0LWF EN10wm in Nebraska at 2157 UTC. I waited anxiously
for them to finish their QSO. LU9EHF went QRZ, I dropped my call in.
Bam! Luis came right back and we exchanged reports. LU9EHF is in
FF95, 8,914 km away.

"I recorded parts of LU9EHF's QSOs with K9KU EN61 and WF0N EM28
after I signed with him. Luis was so loud the speaker on the radio
was distorting. Larry, N0LL EM09 spotted LU9EHF at 2220 and K0GU
DN70 at 2248 UTC. I suspect a fairly high wave angle to the Es link
given the strength of LU9EHF's signal on the dipole. Perhaps chordal
hop Es to TEP link?  It was one of the more remarkable things I have
heard on 6 meters.

"Let Hercules himself do what he may, the cat will mew and the dog
will have his day." Spoken by Hamlet in William Shakespeare, The
Tragedy of Hamlet, Prince of Denmark. Act V, Scene 1, page 13.

See for DXscape, mentioned by N0JK.

If you would like to make a comment or have a tip for our readers,
email the author at,

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

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for May 9 through 15 were 154, 149, 145, 173, 144,
142, and 186, with a mean of 156.1. 10.7 cm flux was 128.4, 124.8,
136.6, 147.3, 150.3, 147.9, and 145.6, with a mean of 140.1.
Estimated planetary A indices were 5, 5, 4, 5, 6, 8, and 9, with a
mean of 6. Estimated mid-latitude A indices were 4, 4, 4, 6, 6, 7,
and 10, with a mean of 5.9.


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