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ARRL Propagation Bulletin ARLP017 (2015)

ARLP017 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 24, 2015
To all radio amateurs 

ARLP017 Propagation de K7RA

Solar activity perked up this week, with average daily sunspot
numbers rising from 65.6 in the previous seven days to 120.9 in the
April 16-22 period.

Average daily solar flux increased from 132.5 to 150.4 over the same

The day with the most geomagnetic activity was April 16, when the
mid-latitude A index was 28, planetary A index was 43, and the high
latitude college A index in Alaska was 57. These are high numbers!

Predicted solar flux for the near term is 135 and 130 on April
24-25, 125 on April 26 through May 1, 130 on May 2-5, 135 and 140 on
May 6-7, 145 on May 8-9, 140 on May 10, 135 on May 11-16 and then a
jump to 150 on May 17-18 before declining to 125 on May 23.

Predicted planetary A index is 8 and 12 on April 24-25, 8 on April
26-27, 10 on April 28, 8 on April 29 through May 2, 5 on May 3-5, 8
on May 6-8, 5 on May 9-11, then 8, 15, 20, 12, 8 and 12 on May
12-17, and 5 on May 18-19.

From April 16-22 there was one new sunspot region appearing each
day, except for April 21 when there were two.

If you check the solar flux prediction archive at
(click on "Download This File") you can see how dramatically the
prediction for the next few days changed recently. The forecasters
pulled back on their estimates for higher solar flux.

F.K. Janda, OK1HH sent his weekly geomagnetic prediction, and he
sees quiet to active conditions April 24, active to disturbed April
25, quiet on April 26, quiet to active April 27, quiet to unsettled
April 28, disturbed April 29, active to disturbed April 30 through
May 1, quiet to active May 2, mostly quiet May 3-6, active to
disturbed May 7-8, quiet to active May 9, mostly quiet May 10, quiet
on May 11, active to disturbed May 12, disturbed May 13-14, quiet to
active May 15, quiet to active May 16-18, and mostly quiet May

OK1HH says that increases in solar wind are mostly unpredictable,
but he expects increases on April 24, May 3-5, May 15-18, and May

On Sunday, April 19 Jeff Hartley, N8II of Shepherdstown, West
Virginia wrote: "The high solar wind essentially closed 15M and up
for a couple of days late last week except for SA, back to near
normal now. I easily worked HS0ZCW on 12M SSB today at 1517Z and a
few loud southern EU. 10 never really opened to EU, but EA8DAZ was
S9+20 dB."

On April 23, Jon Jones, N0JK of Kansas wrote: "10 meters was good to
the South Pacific the afternoon of April 23. FW5JJ was quite loud to
the Midwest USA around 2200z on 28.029 MHz. I worked him with 50
watts while parked from my mobile. K index was 0.

"Last Saturday April 18 there was strong early season sporadic-E on
6 meters. I worked W7GJ MT and KE8FD UT around 2145z on 50 MHz via
Es.  K7TNT WY had a 'pipeline' to CE2AWW for 2 hours. No copy on
CE2AWW in KS.  I had to work Saturday night shift, but saw many
people spotted FK8CP via Es link to TEP that evening."

Thanks, Jon.

I believe his 10 meter mobile antenna is one of those shortened CB
whips on the roof of his car.

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

Archives of the NOAA/USAF daily 45 day forecast for solar flux and
planetary A index are at
. Click on "Download this file" to download the archive and view in
spreadsheet format.

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 April 16 through 22 were 85, 93, 114, 142, 125,
153, and 134, with a mean of 120.9. 10.7 cm flux was 150.2, 149.6,
147.6, 151.7, 149.6, 153.8, and 150.3, with a mean of 150.4.
Estimated planetary A indices were 43, 25, 13, 9, 10, 22, and 11,
with a mean of 19. Estimated mid-latitude A indices were 28, 20, 10,
9, 9, 18, and 9, with a mean of 14.7.


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