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ARRL Propagation Bulletin ARLP029 (2018)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 20, 2018
To all radio amateurs 

ARLP029 Propagation de K7RA

Over three weeks of blank sun! reported 22
consecutive days with no sunspots as of Thursday, and there is
nothing to indicate when sunspots will return.

A few weeks ago I thought sunspots would return by now, based on
solar flux predictions.  If we look back to forecasts from less than
two weeks ago, such as this one, it shows predicted solar flux of 80
for July 17 to 19.

Here we can see that higher flux values seem to correlate with
increased sunspot activity:

But since the July 7 forecast shown above, predicted flux values
have been well below 80.

Over the past reporting week (July 12 to 18), the average of the
daily sunspot number was zero, same as the previous seven days.
Average daily solar flux changed only slightly from 71.5 to 71.8.

Average daily planetary A index declined from 7.3 to 6.4, while
average daily middle latitude A index shifted from 7.9 to 6.1.

The latest prediction (July 19) shows predicted solar flux at 70 on
July 20 to 26, 68 on July 27 to August 1, 70 on August 2, 72 on
August 3 to 18, 70 on August 19, 68 on August 20 to 28, 70 on August
29, and 72 on August 30 to September 2.

Will we see sunspots return during the August 3 to 18 period?
Maybe, but I am not betting on it.  But based only on predicted
solar flux, it seems more likely than between today and August 2.

Predicted planetary A index is 15, 8, 12, 20 and 8 on July 20 to 24,
5 on July 25 to August 5, 8 on August 6, 5 on August 7 to 11, then 8
on August 12, 5 on August 13 to 15, then 16, 8, 10, 18 and 8 on
August 16 to 20, and 5 on August 21 to September 2.

Geomagnetic activity forecast for the period July 20 to August 15,
2018 from OK1HH.

"Geomagnetic field will be:
Quiet on July 26 to 30, August 5, 11, 15
Quiet to unsettled on August 4, 6, 10, 14
Quiet to active on July 31, August 1, 3, 7 to 9, 12
Unsettled to active on July 20, 22, 24 and 25
Active to disturbed on July (21,) 23, August 2, (13)

Solar wind will intensify on July 20 to 23 (and August 7 to 11)

- Parenthesis means lower probability of activity enhancement.
- Configuration of active areas in the Sun is changing again, which
temporarily reduces the reliability of predictions."

Interesting article on plasma jets and related activity deep within
the sun:

Tamitha Skov says we are facing three more weeks of a spotless sun.

"Dear Tad,

With all the solar activity recently, it's hard to believe we have
gone three weeks with a spotless Sun.  Some scientists within the
community are even saying we have arrived at solar minimum.  Yet
despite this sad news, Space Weather remains far from quiet.  It
seems our Sun is finding ways of staying busy.

I too find myself busier than I expected as we reach solar minimum.
In fact, just this past week I was invited to do an interview on
Space Weather for CBS News.  It was an amazing experience to visit
the Los Angeles CBS studio, be wired up like a real news anchor, and
be broadcast live via satellite to a sister CBS station in
Minnesota.  Moments like this are becoming a larger part of this
amazing journey.  I am so grateful I get to share it with you.  I
promise to make available more behind the scenes footage of this
studio adventure in my Patreon project.

Speaking of, last week I promised I would give you a chance to offer
me voluntary feedback on the project before I begin pre-launch later
this month.  If you would like a sneak peek at the perks I am
offering, here is the link to the tiers I have created.  Feel free
to let me know what you think:

This week the forecast brings another chance for aurora, especially
at high latitudes.  This is due to some fast solar wind that might
bump us to near storm levels around Friday.  Afterwards, unsettled
conditions should linger throughout the weekend.  Radio propagation
will likely drop down to poor conditions by the beginning of next
week, but hopefully the solar storm will help give propagation a
boost on the night side of Earth, with auroral propagation possible.
The weak storm should also help improve GPS/GNSS reception at low
latitudes.  Like I said, it's a busy week!

Cheers, Tamitha"

Her latest video update:

For more information concerning radio propagation, see the ARRL
Technical Information Service 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 July 12 through 18, 2018 were 0, 0, 0, 0, 0, 0,
and 0, with a mean of 0.  10.7 cm flux was 72.1, 72.5, 72.3, 71.7,
71.9, 71.2, and 71.2, with a mean of 71.8.  Estimated planetary A
indices were 8, 6, 5, 4, 9, 9, and 4, with a mean of 6.4.  Estimated
mid-latitude A indices were 8, 6, 4, 4, 8, 9, and 4, with a mean of


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