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 
lectromagnetic 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, htt
://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@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 htt
://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

)\/(ark

Always Mount a Scratch Monkey

... There's no Betty Rubble in Flintstones Chewable Vitamins.
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