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ARRL Propagation Bulletin ARLP022 (2017)

ARLP022 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 22  ARLP022
From Tad Cook, K7RA
Seattle, WA  June 2, 2017
To all radio amateurs 

ARLP022 Propagation de K7RA

At 2336 UTC on June 1, the Australian Space Weather Forecast Centre
issued a Geomagnetic Disturbance Warning for June 2:

"The solar wind is expected to be influenced by a High Speed Solar
Wind Stream over the next 1 or 2 days. The source of this stream is
a small coronal hole centered over the equator. Geomagnetic activity
may reach active levels." June 2 geomagnetic conditions are expected
to be unsettled to active.

A new video from Dr. Tamitha Skov can be seen at:

Average daily sunspot number for the recent reporting week (May
25-31) was down from 31.7 to 15.6, compared to the previous seven
days. There were no sunspots on Tuesday, May 30, but on May 31
sunspot region 2661 appeared, and the sunspot number was 11, the
lowest non-zero sunspot number possible, due to the arcane method
for counting sunspots. 10 is assigned for every sunspot group, and 1
for each spot within that group. So a sunspot number of 11 means
there was one sunspot region or group, with only one sunspot.

At 0112 UTC on June 2, issued this alert regarding
sunspot 2661:

"ACTIVE SUNSPOT: On June 1st, a small but surprisingly active
sunspot rotated over the Sun's eastern limb. In less than 24 hours,
it has unleashed nearly a dozen C-class solar flares and hurled a
pair of CMEs into space -- an impressive display of fireworks. So
far, none of the explosions have targeted Earth, but this could
change in the days ahead as the active region rotates toward our
planet. Visit for more information and updates."

On June 1 the sunspot number rose from 11 to 18, which means the
number of sunspots increased from 1 to 8. The total area of the
sunspots doubled over those two days.

Average daily solar flux increased from 74.1 to 77.2.

Average planetary A index increased from 11 to 13.3, and average
mid-latitude A index went from 11.7 to 10.6.

Predicted solar flux is 77 on June 2-3, 78 on June 4-8, 75 on June
9-10, 78 on June 11, 80 on June 12-21, 75 on June 22-23, 72, 78 and
72 on June 24-26, 70 on June 27 through July 5, 75 on July 6-7, 78
on July 8 and 80 on July 9-16.

Predicted planetary A index is 10, 15, and 8 on June 2-4, 5 on June
5-9, 10 and 12 on June 10-11, 8 on June 12-13, then 10, 12, 25 and
10 on June 14-17, 8 on June 18-19, 5 on June 20-24, 12 on June 25, 5
on June 26 to July 6, then 10 and 12 on July 7-8, 8 on July 9-10,
then 10, 12, 25, and 10 on July 11-14 and 8 on July 15-16.

F.K. Janda, OK1HH sent this:

"Geomagnetic activity forecast for the period June 2-28, 2017

"Geomagnetic field will be:
Quiet on June 2, 7, 9, 20-21, 27-28
Mostly quiet on June 17, 19
Quiet to unsettled June 5-6, 14, 18, 22, 26
Quiet to active on June 3-4, 8, 10, 12-13, 23, 25
Active to disturbed on June 11, (15), 16, 24

"Amplifications of the solar wind from coronal holes are expected on
June (3, 5-6,) 12-19, 26-27

"Remark: - Parenthesis means lower probability of activity
enhancement and/or lower reliability of prediction.

"Note: as I will be sailing along the Bata channel next week, the
next geomagnetic activity forecast will be issued up to the second
week, i.e. on June 15.

"F.K. Janda, OK1HH"

The latest forecast from USAF Space Weather Squadron for ARRL Field
Day weekend (June 24-25) has solar flux on June 23-25 at 75, 72 and
78 and predicted planetary A index at 5, 5, and 12.

Both the planetary A index forecast and solar flux prediction for
Field Day weekend has not changed since May 29.

On Sunday, May 28 during the CW weekend of the CQ World Wide WPX
contest there was a large geomagnetic disturbance. Planetary A index
was 51, and the High Latitude College A index (Fairbanks, Alaska)
was 84. Those are both huge numbers.

I received two reports of enhanced 10, 15 and 20 meter propagation
on Sunday. The first was from Ken Miller, K6CTW of Rancho Cucamonga,

"Had an interesting experience last night during the CQ WPX CW
contest. 15 and 20 Meters appeared to be wide open (according to the
spotting sites) between 0440 and 0540 UTC during a major geomagnetic
storm. Normally when spots appear at times or during conditions that
do not favor simple antennas and low power, it has not been worth it
to even check it out. However, I did turn on the rig and was able to
work Indonesia (YE1K), New Zealand (ZM1A), Japan (JF3BFS) and the
Marianas Islands/Tinian (NH0J) with only the 40 watts to a
window-line fed inverted V. I'll bet lots of others had the same
wonderful experience.

"Be great to find out how this happened because isn't it a given
that major geomagnetic storms totally disrupt the higher bands?"

I decided to run this by Carl Luetzelschwab, K9LA. His response:

"BTW, Ken was the 'Tonight Show' guy with Chip K7JA in the 'texting
vs. Morse code' competition - dah dit, dit, dit dah, dah!

"This is an excellent example of how we take a very complicated
process (the effect of a geomagnetic storm on the ionosphere) and
try to simplify it with one general statement.

"Ken's observations during CQ WPX CW on 15m and 20m simply tell us
that this statement isn't 100% true. Yes, in general, the high
latitude F2 region is adversely affected by elevated K indices.  But
the low latitude F2 region can be enhanced. And the mid latitude F2
region could be anywhere in between depending on where we are in the
geomagnetic storm. His paths to YB, ZL and KH0 are relatively
low/mid latitude paths from his California QTH, and suggest what
happened was an enhancement (or at least no change) for a short
period of time. The JA QSO gets to the highest latitude (about 50
degrees north geographic), but apparently it wasn't affected too
much for some of the time.

"Attached is a prediction from SWPC's STORM model
for August 5 and 6 of 2011 based on the geomagnetic storm at that
time." [Unfortunately this attachment is an image that K9LA saved
back in 2011 from that same URL, and is not available there or
anywhere else. If you want a copy, email me at with
the subject "K9LA attachment from ARLP022" -K7RA]

"This model integrates the last eleven Kp indices (actually the last
eleven a-sub-p indices, which are the linear equivalents of the Kp
index) to predict what the F2 region is doing compared to the quiet
F2 region. Note that all latitudes of the northern hemisphere and
the high latitudes of the southern hemisphere were predicted to be
adversely impacted, while the mid latitudes of the southern
hemisphere were predicted to be kind of a wash and the low latitudes
of the southern hemisphere were predicted to be somewhat enhanced.
Ionosonde data generally confirms this, but even the STORM model may
not capture the very short-term dynamics of the entire real-world

"The bottom line is a major geomagnetic storm doesn't necessarily
totally disrupt the higher bands throughout the entire worldwide
ionosphere. Two corollaries are that a single K index (as used by
W6ELProp and ICEPAC) is inadequate to explain the entire real-world
ionosphere under disturbed conditions, and even using the STORM
model may not predict the short-term changes.

"These short-term events are why we don't have a daily model of even
the quiet ionosphere - our understanding is statistical in nature
over a month's time frame."

Tim Goeppinger, N6GP of Tustin, California sent this note concerning
this very same event:

"The West Coast had an interesting opening to Japan and Guam on 10
meters around 0400z on May 28 during the CQ WPX Contest. I recorded
some audio and made this YouTube video about these unusual
conditions: "

Carl, K9LA also commented on Tim's report:

"That 10m opening in your other e-mail looks like it was about the
same time as Ken's observations on 20m and 15m. Always keep your
ears open during a geomagnetic storm - you may be surprised.

"Right now we're off to Seaside, OR for Sea-Pac. Back Sunday
evening.  I'll probably take a closer look at the 10m comments after
we get back."

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
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 25 through 31, 2017 were 19, 22, 21, 20, 16,
0, and 11, with a mean of 15.6. 10.7 cm flux was 76.1, 80.2, 81.9,
78.8, 75.8, 73.7, and 74.1, with a mean of 77.2. Estimated planetary
A indices were 4, 3, 14, 51, 10, 7, and 4, with a mean of 13.3.
Estimated mid-latitude A indices were 4, 3, 14, 32, 10, 6, and 5,
with a mean of 10.6.


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