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ARRL Propagation Bulletin ARLP020 (2015)

ARLP020 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA
Seattle, WA  May 15, 2015
To all radio amateurs 

ARLP020 Propagation de K7RA

This week our quiet Sun came alive, and now the visible solar disc
is crowded with sunspots. On Monday, May 11 the SESC daily sunspot
number rose to 188. That is the highest sunspot number since January
30, when it was 193. Prior to that we have to go back to November
17, 2013 to find a higher sunspot number. It was 282 on that day,
which was way over on the other side of the peak in cycle 24, which
happened around February and March of 2014.

The average daily sunspot number increased 86 points from the
previous week to 146.9 for the current period, May 7-13. Over the
same periods the average daily solar flux rose from 115.4 to 156.3.

At 2324 UTC on May 12, the Australian Space Forecast Centre issued a
geomagnetic warning: "Increased geomagnetic activity expected due to
high speed coronal hole wind stream for 13 May 2015."

Indeed, the prediction was correct, and the planetary A index for
May 13 was 45, while the college A index reached 63.

The predicted planetary A index is 12, 10, 20 and 15 on May 15-18,
then 5 on May 19-28, 8 on May 29-30, 5 on May 31, then 8, 15 and 10
on June 1-3, 5 on June 4-6, 12 on June 7, 25 on June 8-9, and 12 and
8 on June 10-11.

Predicted solar flux is 140 on May 15-16, then 135, 125, 115 and 105
on May 17-20, then 100, 105 and 115 on May 21-23, 110 on May 24-27,
115 on May 28, 120 on May 29-31, 130 on June 1, 140 on June 2-4,
then peaking at 160 for the near term on June 9.

The OK1HH geomagnetic activity forecast sees quiet to active
conditions May 15-17, active to disturbed May 18, quiet to unsettled
May 19, quiet May 20-23, mostly quiet May 24, quiet to unsettled May
25, quiet May 26-27, mostly quiet May 28, quiet to unsettled May 29,
quiet to active May 30, quiet to unsettled May 31, active to
disturbed June 1, mostly quiet June 2-4, quiet June 5-6, quiet to
active June 7, active to disturbed June 8-9, and disturbed June 10.

The NASA Solar Cycle Prediction remains the same, but yesterday the
date was updated from January 14 to May 14, 2015 at . That is all that
changed. There is no new forecast.

The Washington Post weather blog ran this article about sunspot

Dave Pedersen, PJ4VHF/N7BHC reports a 2 meter CW reception on
Bonaire of the D4C/B beacon at Cape Verde via tropospheric ducting.
Bonaire is just north of Venezuela in the Caribbean and Cape Verde
is off the coast of Africa, west of Senegal, a distance of 2,917

This was on May 6, 2015 at 0100-0230 UTC on 144.436 MHz, using a
Kenwood TS-2000 and two 13 element Yagis at the receive site. The
beacon on the other end runs 20 watts. Dave reports the reception
was verified by Andre, HB9DUR, the beacon operator.

Dave also sent an audio/video file showing the receiver, and the CW
signal is clearly heard. I posted it at and
you should click on "Download This File."

Dave writes, "Fred NP2X and I were alerted by the Hepburn maps that
tropospheric cutting looked promising last week. We started
listening on 2m from the previous Saturday, May 2. The previous week
had seen many days of very good ducting all across the eastern
Caribbean with LP4 repeaters pinning the S meters here on Bonaire
for several days. Jamaica came in 60 over 9 on Saturday evening but
there were no stations on the repeater. We have experienced high
winds for the last 2 weeks here on Bonaire, gusting over 35 mph for
many days. I had parked my VHF array pointing west for minimum wind
resistance. Tuesday evening I was doing some paperwork in the shack,
and rotated the beams back east at 9pm local (0100 UTC) to prepare
for listening all night. To my amazement, I started copying CW while
the beam was still 30 degrees off the D4C bearing."

Nice job, Dave, and thanks for that excellent report.

Jeff, N8II reports that conditions were excellent on 15 meters on
Saturday, May 9 into Central and West Asia at 1400-1500 UTC during
the CQ M Russian contest.

Tomas Hood, NW7US sent a report and a link to a video of the X2.7
flare on May 5. Tomas wrote, "An impulsive, major solar flare
reaching X2.7 erupted at 22:05 UTC (5:05 p.m. CDT) and ended at
22:15 UTC, peaking at 22:11 UTC. This is the most intense flare so
far, in year 2015.

"A video compilation of this magnitude X2.7 solar flare, 'Sun
Unleashes Most Powerful Flare of 2015 (as of May 5),' may be viewed

"This X2.7-level flare produced a level R3 (Strong) shortwave radio
blackout on the sunlit side of Earth, which was over the Pacific

"A coronal mass ejection was associated with this flare. The flare
originated in Sunspot Active Region NOAA 2339.

"In addition, the flare produced a two-minute radio burst, heard as
a roar of static from shortwave receivers on Pacific isles and
western parts of North America. A radio burst of this kind is
generally short-lived, but can cause interference for radar, GPS,
and satellite communications."

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 in downloadable spreadsheet format at and .

Click on "Download this file" to download the archive and ignore the
security warning about the file 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 May 7 through 13 were 131, 134, 136, 134, 188,
170, and 135, with a mean of 146.9. 10.7 cm flux was 146.6, 149.8,
154.5, 159.9, 163, 163.2, and 157, with a mean of 156.3. Estimated
planetary A indices were 6, 6, 7, 11, 15, 15, and 45, with a mean of
15. Estimated mid-latitude A indices were 6, 7, 8, 12, 15, 16, and
25, with a mean of 12.7.