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ARRL Propagation Bulletin ARLP041 (2017)

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 13, 2017
To all radio amateurs 

ARLP041 Propagation de K7RA

At 0326 UTC on October 12 the Australian Space Forecast Centre
issued a Geomagnetic Disturbance Warning:

"The high speed streams associated with a recurrent positive
polarity Northern hemisphere coronal hole are expected to persist
for a few days. If the Bz component of the IMF turned strongly
southward for prolonged periods, earth could experience Minor Storm
conditions on 13 October."

"Increased geomagnetic activity expected due to a coronal hole high
speed wind stream for 13 October 2017."

Earlier reported, "A hole in the Sun's atmosphere
is spewing solar wind toward Earth, and this is sparking bright
auroras around the poles on October 11. At the time of this alert, a
G1-class geomagnetic storm is underway. NOAA forecasters estimate a
70 percent chance of continued storms at high latitudes on October
12 and 13 as Earth moves deeper into the solar wind stream. Visit for pictures and updated forecasts."

There were no sunspots visible on October 8 through 12, and the last
new sunspot to appear was September 25, which was still visible on
October 7, but not since then.

Average daily sunspot numbers for the past week (October 5-11)
dropped from 32.6 the previous seven days to 8.4. Average daily
solar flux declined from 87.9 to 76.8. Geomagnetic activity also
dropped but is now increasing. Average daily planetary A index went
from 16.3 to 8.9, and average mid-latitude A index went from 12.7 to

Predicted solar flux is 70 on October 13-17, then 72 on October
18-19, 80 on October 20-31, 76 on November 1-5, 74 on November 6-14,
76 on November 15, and 80 on November 16-26.

Predicted planetary A index is 35, 25, 20, 10, and 8  on October
13-17, 12 on October 18-19, 5 on October 20-23, then 35 and 45 on
October 24-25, 15 on October 26-27, then 10 and 8 on October 28-29,
5 on October 30-31, then 8 and 10 on November 1-2, 5 on November
3-5, then 8, 25, 30, 36, 28, 16 and 8 on November 6-12, 5 on
November 13-19, then 35 and 45 on November 20-21, 15 on November
22-23, then 10, 8 and 5 on November 24-26.

Geomagnetic activity forecast for the period October 13 to November
8, 2017 from F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on October and November-irregularly
Mostly quiet on October and November-irregularly
Quiet to unsettled October (18-22, 24,) 28-29, (30-31,) November (1-2, 4-6)
Quiet to active on October 13-16, (17, 23,) 26-27, November 3, 7
Active to disturbed on October 25, November 8

"Amplifications of the solar wind, mostly from coronal holes, are
expected on October 12-17, (18, 22, 24,) 25-26, November 7-12

- Amplifications of the solar wind-prediction is less reliable at
- Parenthesis means lower probability of activity enhancement and/or
lower reliability of prediction.
- Beware of paraskavedekatriafobia tomorrow: "

I normally would not include a link to a heavy metal recording, but
this is what OK1HH sent. Paraskavedekatriafobia refers to a fear, or
phobia, of Friday the thirteenth, which is today of course.

Here is a new video from Dr. Tamitha Skov, Space Weather Woman:

I understand Dr. Skov is studying for the amateur radio exam.

Here is a report from N8II in West Virginia, sent in on October 9:

"There were quite decent conditions over the weekend; OH0Z Aland
Island was S9 on 15M SSB both Saturday and Sunday. Despite a flux of
72 today, I heard northern Sweden on 15 CW and worked several
Ukraine stations on 15 CW with good signals in the 1400z hour along
with others farther west in Czech Republic, Bulgaria, Germany,
England, Spain and France. 15 has been open well to EU almost every
day in the past 2 weeks! I worked the CA QSO party and 20 was
excellent well into the evening Saturday (open past 0045z). 15 was
very good into CA from 1600-2000z Saturday with southern CA
noticeably favored on Sunday until around 1900z. Starting at 2007z I
worked 6 southern CA stations on 10 CW all less than S9, some weak.
N4PN in Macon, GA reported over 100 CA QSOs on 10 in the party!"

On October 6, Bil Paul, KD6JUI of Dixon, California sent this:

"After having had a rough time over the past several months getting
out on HF from my kayak and 10 watts, yesterday (Thursday, October
5) I was operating on 17m and 20m SSB while on the water and easily
got out using my end-fed half-wave wire vertical (cut for 20m).
Without much difficulty got out as far as the East Coast. Even had
an XE2 from lower Baja California break into a QSO to tell me I was
5/9 down there.

"The solar flux, I think, was 85 -- enough to make quite a

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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 October 5 through 11, 2017 were 26, 22, 11, 0,
0, 0, and 0, with a mean of 8.4. 10.7 cm flux was 84.7, 84.1, 79.6,
76.7, 72.3, 70.9, and 69.6, with a mean of 76.8. Estimated planetary
A indices were 7, 9, 5, 4, 3, 4, and 30, with a mean of 8.9.
Estimated mid-latitude A indices were 6, 6, 5, 3, 2, 13, and 21,
with a mean of 8.


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