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ARRL Propagation Bulletin ARLP017 (2017)

SB PROP @ ARL $ARLP017
ARLP017 Propagation de K7RA

ZCZC AP17
QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 28, 2017
To all radio amateurs 

SB PROP ARL ARLP017
ARLP017 Propagation de K7RA

Each of the average solar and geomagnetic indices rose last week
(April 20-26) over the previous seven days.

Average daily sunspot number rose from 8.6 to 35.7, and solar flux
rose from 76.5 to 81.4.

Average daily planetary A index went from 8 to 26.4, and average
daily mid-latitude A index from 6.3 to 18.4.

The day with the most geomagnetic activity was April 22 when the
planetary A index was 54. One the same date, Alaska's College A
index (near Fairbanks) was 86.

Predicted planetary A index is 8, 5 and 5 on April 28-30, then 14,
10, 8 and 10 on May 1-4, 15 on May 5-6, 8 on May 7-8, 5 on May 9-14,
8 and 15 on May 15-16, and then into a more active period at 30, 25,
45, 50 and 30 on May 17-21. Then 20 on May 22-24, then 15, 8, 5 and
20 on May 25-28, 10 on May 29-31, 15 on June 1-2, 8 on June 3-4, and
5 on June 5-9.

Predicted solar flux values are 79 on April 28-29, 78 on April 30
and May 1, 77 on May 2-4, 75 on May 5-14, 80 on May 15-18, 85 on May
19-24, 80 on May 25-28 and 75 on May 29 to June 10.

OK1HH sent us this geomagnetic activity forecast for the period
April 28 to May 24, 2017.

"Geomagnetic field will be:
Quiet on May 9-10, 12-13
Mostly quiet on April 30, May 7
Quiet to unsettled April 29, May 2, 4, 14, 21-24
Quiet to active on April 28, May 1, 3, 8, 11, 15-16, 19
Active to disturbed on May (5-6,) 17-18, 20

"Amplifications of the solar wind from coronal holes are expected on
April 28, May (1-5,) 6-8, (9-11,) 18-22

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

I thought I ran this last week, but apparently not:

https://www.youtube.com/watch?v=JR7D9zTygao

These always seem to come out after the bulletin is posted.

You might want to check this for more up-to-date videos from Dr.
Tamitha Skov:

https://www.youtube.com/user/SpWxfx/videos

Thanks to Don, N5DM for that tip.

If you would like to make a comment or have a tip for our readers,
email the author at k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at,
http://arrl.org/propagation-of-rf-signals. For an explanation of
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere.

An archive of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at http://k9la.us/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.

Sunspot numbers for April 20 through 26, 2017 were 26, 39, 29, 43,
41, 36, and 36, with a mean of 35.7. 10.7 cm flux was 80.7, 82.2,
83.6, 82.5, 80.2, 81.3, and 79.6, with a mean of 81.4. Estimated
planetary A indices were 30, 19, 54, 41, 20, 12, and 9, with a mean
of 26.4. Estimated mid-latitude A indices were 20, 11, 37, 24, 19,
10, and 8, with a mean of 18.4.
NNNN
/EX