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ARRL Propagation Bulletin ARLP017 (2016)

ARLP017 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 22, 2016
To all radio amateurs 

ARLP017 Propagation de K7RA

Over the past reporting week, April 14-20, average daily sunspot
numbers rose from 32 to 40, while average daily solar flux declined
from 106.1 to 100.8.

Average daily planetary A index declined from 12.4 to 10.9, but
average daily mid-latitude A index rose slightly from 8.3 to 8.9.

The mid-latitude A index uses 3-hour data from a magnetometer at
Fredericksburg, Virginia, and the planetary numbers are derived from
readings at Sitka, Alaska; Meanook, AB, Canada; Ottawa ON, Canada;
Fredericksburg, Virginia; Hartland, UK; Wingst, Germany; Niemegk,
Germany; and Canberra, Australia. An example of a magnetic
observatory is the one in Alberta, Canada at Meanook. See for a photo and

We continue to see weak sunspot groups. There was a new one on April
13, another on April 16 and another on April 20.

The latest (Thursday, April 21, 2016) prediction has solar flux
values at 75 on April 22, 80 on April 23-28, then 88 and 98 on April
29-30, 95 on May 1-2, 100 on May 3-5, 95 on May 6, 98 on May 7-12,
92 on May 13-14, 102 on May 15-16, 95 on May 17-18, 97 on May 19-20
and 95 on May 21-26.

Predicted planetary A index is 5, 16 and 12 on April 21-23, 10 on
April 25-26, then 8, 5, 20, 15 and 8 on April 27 through May 1, 5 on
May 2-3, 12 on May 4, 5 on May 5-8, then 18, 25, 20, 8 and 5 on May
9-13, 12 on May 14-16, 8 on May 17, 5 on May 18-19, then 10 and 12
on May 20-21, and 10 on May 22-23. The planetary A index then rises
to 20 on May 26, and back to 5 for six of the seven days ending the
45 day forecast period.

F.K. Janda, OK1HH sends us the following geomagnetic activity
forecast for the period April 22-May 18, 2016.

"The geomagnetic field will be:

Quiet on April 27, May 7, 12, 16-18
Mostly quiet on April 22, 28, May 1, 3, 6, 13, 15
Quiet to unsettled on April 25-26, May 2, 4, 8
Quiet to active on April 24, 29, May 9, 11, 14
Active to disturbed on April 23, 30, May 5, 10

Increased solar wind is expected on April 23-26, 29-30, May 4-5,
10-11, 14."

Dick Bingham, W7WKR sent a link for a balloon flight (unmanned, or
maybe "unpersoned") using amateur radio with WSPR on 20 and 30
meters, providing telemetry and position data. See .  Dig deep, there is a lot of fascinating
data there. Note the circuitous route the balloon took.

David Moore sent a link to some SDO images at,
.  Pay no attention to the subsequent "NASA Flat Earth Cover-Up" video
which may follow.

Tomas Hood, NW7US would like to share this with us:

"Take a front-seat view of the Sun in this 30-minute ultra-high
definition movie in which NASA SDO gives us a stunning look at our
nearest star.

"This movie provides a 30-minute window to the Sun as seen by NASA's
Solar Dynamics Observatory (SDO), which measures the irradiance of
the Sun that produces the ionosphere. SDO also measures the sources
of that radiation and how they evolve.

"Charged particles are created in our atmosphere by the intense
X-rays produced by a solar flare. The solar wind, a continuous
stream of plasma (charged particles), leaves the Sun and fills the
solar system with charged particles and magnetic field. There are
times when the Sun also releases billions of tons of plasma in what
are called coronal mass ejections. When these enormous clouds of
material or bright flashes of X-rays hit the Earth they change the
upper atmosphere. It is changes like these that make space weather

"Sit back and enjoy this half-hour 4k video of our Star:  -- NW7US"

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

My own 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 file format. Pop-up blockers may suppress
the download.

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 14 through 20 were 45, 69, 51, 35, 28, 28,
and 24, with a mean of 40. 10.7 cm flux was 111.1, 112.4, 113.2,
102.1, 94.6, 89.1, and 83.2, with a mean of 100.8. Estimated
planetary A indices were 23, 9, 12, 19, 5, 3, and 5, with a mean of
10.9. Estimated mid-latitude A indices were 14, 9, 8, 17, 7, 3, and
4, with a mean of 8.9.