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ARRL Propagation Bulletin ARLP024 (2015)

ARLP024 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 24  ARLP024
From Tad Cook, K7RA
Seattle, WA  June 12, 2015
To all radio amateurs 

ARLP024 Propagation de K7RA

Solar activity strengthened during the past week. Average daily
sunspot numbers increased from 34.3 to 112.4, and average daily
solar flux rose from 97.8 to 131.4. The middle latitude A index for
June 10-11 can only be guessed, due to some sort of outage depriving
us of K-index data over a 27 hour period. The outage began sometime
after 1200 UTC June 9 and ended sometime before 1800 UTC June 10.

June 8 was the day with the most geomagnetic upset, when the
planetary A index rose to 33.

Predicted planetary A index for the near term is 20, 15 and 16 on
June 12-14, then 10, 8 and 6 on June 15-17, then 5 on June 18
through July 3. We then see another active period on July 4-9 when
the predicted A index is 8, 20, 28, 20, 10 and 8, followed by 6, 5
and 8 on July 10-12, and 5 on July 13 and beyond.

At 0202 UTC on June 10 the Australian Space Forecast Centre
predicted increased geomagnetic activity on June 12 due to a coronal
mass ejection.

They issued a second warning at 0336 UTC predicting a glancing blow
at Earth early in the UTC day on June 12.

Predicted solar flux for the near term is 140 on June 12-13, then
135, 130, 125, 120 and 115 on June 14-18, 120 on June 19-26, 115 on
June 27, and 120 on June 28-29. The forecast then shows solar flux
rising to 145 on July 5-7 before settling back to 120 after July 12.

Petr Kolman, OK1MGW of the Czech Propagation Interest Group gives us
a geomagnetic forecast this week. He expects mostly quiet conditions
on June 12, quiet on June 13, active to disturbed on June 14, quiet
to active June 15-16, quiet June 17-21, quiet to unsettled June
22-25, quiet to active June 26-27, quiet on June 28-30, mostly quiet
July 1-2, quiet to unsettled July 3, active to disturbed July 4,
quiet to active July 5, and quiet to unsettled July 6-8.

He expects an increase in solar wind on June 14-15 and July 4-5.

OK1MGW has been writing these weekly forecasts with OK1HH since

David P. Moore sent us a link to an article titled "New Tool Could
Predict Large Solar Storms More Than 24-hours in Advance."

There were no reports from readers this week.

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

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 the file format.

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 June 4 through June 10 were 80, 105, 129, 136,
122, 110, and 105, with a mean of 112.4. 10.7 cm flux was 118, 126,
132.7, 137.3, 134.2, 136.5, and 131.4, with a mean of 131.4.
Estimated planetary A indices were 3, 3, 5, 7, 33, 13, and 12, with
a mean of 10.9. Estimated mid-latitude A indices were 4, 4, 7, 8,
22, 12, and 11, with a mean of 9.7.