[SFDXA] ARLP012 Propagation de K7RA

Fri Mar 18 13:02:26 EDT 2016

SB PROP @ ARL $ARLP012
ARLP012 Propagation de K7RA

ZCZC AP12
QST de W1AW
Propagation Forecast Bulletin 12  ARLP012
 From Tad Cook, K7RA
Seattle, WA  March 18, 2016
To all radio amateurs

SB PROP ARL ARLP012
ARLP012 Propagation de K7RA

Solar indicators were lower this week, while geomagnetic indicators were 
higher.

Compared to the previous seven days, average daily sunspot numbers in 
our reporting week (March 10-16) were down 12.7 points to 51.7, and 
average daily solar flux was down 3.2 points to 93.6. Average planetary 
A index was up 2.8 points to 15.7, and average mid-latitude A index 
increased from 8.6 to 12.

The latest forecast has a predicted solar flux of 95 on March 18-19, 90 
on March 20, 85 on March 21-24, 90 on March 25, 95 on March 26-28, 100 
on March 29-31, 95 on April 1-9, 93 on April 10, 90 on April 11-15, 95 
on April 16-17, and 90 on April 18-19. Flux values then rise to 100 on 
April 25-27.

Predicted planetary A index is 16, 8, 6 and 5 on March 18-21, then 6, 8 
and 10 on March 22-24, 5 on March 25-31, then 8, 30, 25 and 8 on April 
1-4, and 5 on April 5-6. Planetary A index rises to 25 on April 11 and 
30 on April 29.

Petr Kolman, OK1MGW predicts geomagnetic conditions will be mostly quiet 
on March 18-19, quiet on March 20-21, mostly quiet March 22, quiet to 
unsettled March 23-24, quiet on March 25-26, quiet to unsettled March 
27, quiet to active March 28-29, quiet to unsettled March 30, mostly 
quiet March 31 to April 1, active to disturbed April 2-3 (although the 
forecast is uncertain for these two days), quiet to active April 4, 
quiet to unsettled April 5-6, quiet to active April 7-8, mostly quiet 
April 9, active to disturbed April 10-12 and quiet to unsettled on April 13.

Petr expects an increase on solar wind from coronal holes on March 23-24 
(although like the April 2-3 forecast, this is uncertain) March 27-29, 
April 1-4, April 7-8, and April 10-12.

Tomas Hood, NW7US asked that this message be posted in the current 
propagation bulletin:

"Tad, would you share this?

"Tomas, NW7US, has posted a new, breathtakingly beautiful video of our 
Sun, at https://www.youtube.com/watch?v=HgP0e1VHBxc .  This 
high-definition video shows the Sun in the 171-angstrom wavelength of 
extreme ultraviolet light. It covers a time period of January 2, 2015 to 
January 28, 2016 at a cadence of one frame every hour, or 24 frames per 
day. This time-lapse is repeated with narration by solar scientist 
Nicholeen Viall and contains close-ups and annotations.

"The Sun is always changing and NASA's Solar Dynamics Observatory is 
always watching. Launched on Feb. 11, 2010, SDO keeps a 24-hour eye on 
the entire disk of the Sun, with a prime view of the graceful dance of 
solar material coursing through the Sun's atmosphere, the corona. SDO's 
sixth year in orbit was no exception.

"SDO's Atmospheric Imaging Assembly (AIA) captures a shot of the Sun 
every 12 seconds in 10 different wavelengths. The images shown here are 
based on a wavelength of 171 angstroms, which is in the extreme 
ultraviolet range and shows solar material at around 600,000 Kelvin 
(about 1 million degrees F). In this wavelength it is easy to see the 
Sun's 25-day rotation.

"During the course of the video, the Sun subtly increases and decreases 
in apparent size. This is because the distance between the SDO 
spacecraft and the Sun varies over time. The image is, however, 
remarkably consistent and stable despite the fact that SDO orbits Earth 
at 6,876 miles per hour and the Earth orbits the Sun at 67,062 miles per 
hour.

"Scientists study these images to better understand the complex 
electromagnetic system causing the constant movement on the Sun, which 
can ultimately have an effect closer to Earth, too: Flares and another 
type of solar explosion called coronal mass ejections can sometimes 
disrupt technology in space. Moreover, studying our closest star is one 
way of learning about other stars in the galaxy. NASA's Goddard Space 
Flight Center in Greenbelt, Maryland built, operates, and manages the 
SDO spacecraft for NASA's Science Mission Directorate in Washington, D.C."

Jim Wilson, K5ND of Grapevine, Texas wrote on March 15:

"Just thought I'd mention a very fun tropo opening this morning between 
Texas and the Southeast. It was my first experience with this and I 
wrote about it at, 
http://www.k5nd.net/2016/03/tropospheric-ducting-march-2016/ ."

Thanks, Jim.

This weekend the Vernal Equinox occurs at 0430 UTC on Sunday, March 20. 
Now there is more energy from the Sun impacting the ionosphere in the 
Northern Hemisphere, and this should enhance HF propagation.

Toward the end of last week's propagation forecast bulletin, 
http://www.arrl.org/w1aw-bulletins-archive/ARLP011/2016 , we posted a 
question from Steve Shorey, G3ZPS and a reference to a K9LA resource. 
K9LA responded this week: "My article doesn't say much about what 
actually happens in the atmosphere when the K index spikes up - it just 
shows that the ionization can be enhanced, and we have a model that 
could help show what's happening real-time.

"What happens is the energy from geomagnetic activity results in waves 
propagating through the atmosphere, and that rearranges the major F2 
region players - atomic oxygen for electron production and molecular 
nitrogen/oxygen for electron depletion."

If you would like to make a comment or have a tip for our readers, email 
the author at k7ra at arrl.net <mailto:k7ra at 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 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 March 10 through 16 were 61, 48, 56, 43, 57, 44, and 
53, with a mean of 51.7. 10.7 cm flux was 95, 94.2, 95, 92.6, 93.4, 
94.1, and 91, with a mean of 93.6. Estimated planetary A indices were 
10, 23, 13, 4, 14, 24, and 22, with a mean of 15.7. Estimated 
mid-latitude A indices were 7, 21, 11, 4, 11, 17, and 13, with a mean of 12.
NNNN
/EX
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