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ARRL Propagation Bulletin ARLP016 (2016)

SB PROP @ ARL $ARLP016
ARLP016 Propagation de K7RA

ZCZC AP16
QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
From Tad Cook, K7RA
Seattle, WA  April 15, 2016
To all radio amateurs 

SB PROP ARL ARLP016
ARLP016 Propagation de K7RA

There was an upward bump in recent solar activity, with average
daily sunspot number for the April 7-13 period at 32 (compared to
19.1 for the previous seven days) and average daily solar flux
rising 23 points to 106.1.
 
Note that what we are seeing now is the occasional uptick in solar
activity as the sun continues its decline to solar minimum, perhaps
sometime around 2020.
 
Average daily planetary A index rose three points to 12.4, and
average daily mid-latitude A index from 7.6 to 8.3.
 
For the near term, predicted solar flux is 110 on April 15-17, 105
on April 18-19, 95 on April 20-22, 100 on April 23, 95 on April
24-29, 90 on April 30 through May 3, then 95, 100, 105, and 110 on
May 4-7, 112 on May 8-13, and 115 on May 14-17.  Solar flux then
drops below 100 on May 21 and beyond.
 
Predicted planetary A index is 12 on April 15, 8 on April 16-18, 12
on April 19, 8 on April 20, 5 on April 21-22, 12 on April 23, 10 on
April 24-25, 8 on April 26, 5 on April 27-28, then 20, 15 and 8 on
April 29 through May 1, 5 on May 2-3, then 12 and 8 on May 4-5, 5 on
May 6-7, 8 on May 8-9, then 18, 30 and 10 on May 10-12, then 5 on
May 13-16 and 8 on May 17-18.
 
Also on the subject of geomagnetism, we have two predictions from
Prague.
 
The first from the Institute of Geophysics of the Academy of
Sciences of the Czech Republic.  Tomas Beyer predicts for the short
term:
 
Geomagnetic activity forecast for the period April 15-21, 2016
 
Quiet:  Apr 19-21 
Unsettled:  Apr 15-18 
Active:  possible but unlikely Apr 17-18 
 
Geomagnetic activity summary: 
 
Maximum of geomagnetic activity has been recorded at Apr 12-13 when
the local K-index reached K=5.  The active conditions continued till
morning Apr 14, then turned to unsettled.
 
Next week, we expect at most quiet to unsettled conditions only with
possible active episode between Apr 17-18.  Nevertheless, it may be
only an isolated event.  Then, we expect return of quiet to
unsettled level.
 
From Petr Kolman, OK1MGW of the Czech Propagation Interest Group, he
predicts:
 
Geomagnetic activity forecast for the period April 15-May 11, 2016
 
Geomagnetic field will be: 
Quiet on April 21-22, May 6-7 
Mostly quiet on  April 17-18, 27-28, May 1-3, 8 
Quiet to unsettled on  April 15-16, 19-20, 25-26, May 11 
Quiet to active on April 23-24, 29-30, May 4-5, 9-10 
Active to disturbed on May (9-10) 
 
Amplifications of the solar wind from coronal holes are expected on
April 18-20, 23-24, 28-30, May 4-5, 8-11
 
Remarks:  Parenthesis means lower probability of activity
enhancement.
 
Recently KL7JT asked a question which we forwarded to K9LA.  Here is
a link to the exchange, which includes links to the images
referenced.  Just click Download This File at each link.
 
http://bit.ly/22z8pI0 
 
Here is an update on the NASA STEREO mission: 
 
http://go.nasa.gov/1IPQCIT 
 
And this link is to the STEREO tool itself: 
 
http://stereo.gsfc.nasa.gov/ 
 
Bill Liles, NQ6Z wrote about a QSO Today podcast (Number 081) he
heard:
 
"I am curious about one comment you made.  You were asked about
effect from solar or lunar eclipse and you answered no.
 
I agree with that answer re lunar eclipse.  I am wondering about the
reason for the answer with respect to solar eclipse.  During the
time of the eclipse over a patch of the ionosphere, which granted is
only a few minutes, the sun's radiation is blocked so one should see
recombination in the D layer and thus it will not be as absorptive
as during normal daytime.  Thus MF and low HF freqs should
experience nighttime propagation characteristics.
 
This effect, as far as I have found, was first observed in 1912.
Appleton also used this effect in the 1929s to help answer the
question of what causes the ionization by the sun, particles or
electromagnetic waves.
 
Solar eclipse effects have been the subject of many scholarly
reports and a few books using real data.
 
Thus my curiosity as to why your answer was no?  Were you meaning on
a more global scale?  As it seems true on a local scale.
 
BTW, ARRL and Scientific American did a study on this effect in the
1920s and one comment was that 75 meters behaved as if it was
nighttime."
 
The answer?  I was wrong.  In response, Bill sent a pdf about
effects on radio from a solar eclipse in 1999, which you can
download here:
 
http://bit.ly/1Wvrk7c 
 
For more information concerning radio propagation, see the ARRL
Technical Information Service at
http://arrl.org/propagation-of-rf-signals. For an explanation of the
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/.
 
My own archives of the NOAA/USAF daily 45 day forecast for solar
flux and planetary A index are in downloadable spreadsheet format at
http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .
 
Click on "Download this file" to download the archive, and ignore
the security warning about file format.  Pop-up blockers may
suppress the download.
 
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 7 through 13 were 26, 27, 29, 26, 41, 34,
and 41, with a mean of 32.  10.7 cm flux was 92.3, 98.3, 105.5,
110.6, 116.6, 111.3, and 108.2, with a mean of 106.1.  Estimated
planetary A indices were 17, 9, 3, 7, 6, 19, and 26, with a mean of
12.4. Estimated mid-latitude A indices were 10, 6, 3, 6, 5, 12, and
16, with a mean of 8.3.
NNNN
/EX