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ARRL Propagation Bulletin ARLP012 (2016)

ARLP012 Propagation de K7RA

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

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 .  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, ."

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, , 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

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

My own 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 file format. Pop-up blockers may suppress
the download.

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 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.