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Propagation Forecast Bulletin #29 de K7RA:

from W1AW Bulletin via the ARRL on July 20, 2018
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Propagation Forecast Bulletin #29 de K7RA:

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:

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

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 6.1.

Source: W1AW Bulletin via the ARRL.

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