No subject

A index value of 5 for all three days. This seems to be their
default predicted value for low activity. I've never seen them issue
a prediction for an A index value below 5, even though since the
first of the year the planetary A index has been below this value on
January 1-12, 15, 21-24, 28-31, February 1, 3-6, 9-12, 15, 18,
24-25, 27, March 4-8, 10 and 13.

Their forecast was revised on March 12, when the values changed to
10, 5 and 5. That changed to 12, 5 and 5 on March 13-14, and on
March 15, the forecast for March 16-18 was 12, 39 and 20. So two
days prior to the event, they predicted 39 for March 17, which is
not bad.

What did OK1HH predict for those dates?  On February 28 the
prediction was quiet to unsettled on March 16, and mostly quiet
March 17-18. The March 7 prediction was quiet to unsettled on March
16-17 and quiet March 18. The March 14 prediction was quiet to
unsettled March 16-17 and mostly quiet March 18, echoing the
prediction from two weeks prior. Of course, the U.S. government
source has the advantage of releasing a new prediction every day.

Spaceweather.com issued an alert about the event on Friday, March 15
at 2355 UTC. The message titled "Geomagnetic Storm Warning" said, "A
magnetic eruption on the Sun during the early hours of March 15th
hurled a coronal mass ejection (CME) directly toward Earth.  NOAA
forecasters estimate a 70% chance of polar geomagnetic storms when
the CME arrives on March 17th."

Jack Kelley, K4WY of Fairfax Station, Virginia had an unusual
experience on a seemingly dead band on Sunday. He wrote, "I had some
interesting propagation in the wake of the CME last weekend.  After
checking the bands (160-10) the sole station I found was 5T0JL at S9
on 30 meters - we worked each other easily - and after listening to
Jean's following QSOs I found he was working W6s almost exclusively.
Again no other signal, anywhere. So how did this occur? The path was
assumed to be east-west, and in darkness, but all the W6 QSOs
stumped me, particularly after the worst of the CME effects. A
similar scenario happened with 6V7S later that same evening as he
plowed through the extremely high QRN."

This was Sunday night local time, 0130-0200z Monday. We ran this by
Carl Luetzelschwab, K9LA, who indicated that the path through low
latitudes was the key to success.

He wrote, "The effects from elevated K indices due to a CME include
modification to the worldwide F2 region ionization. Generally the
mid and high latitudes see a depletion of electrons, whereas low
latitudes aren't affected too much (or even see an enhancement)."

He ran some numbers using the Space Weather Prediction Center STORM
model, and said, "In both hemispheres the F2 region ionization was
depleted significantly around 0200 UTC on 18 March. But the
ionization at low latitudes in both hemispheres fared much better.

"Additionally, was there perhaps some 'spotlight' propagation going
on? Could be. The ionosphere is very dynamic, especially under
disturbed conditions."

The day after the big blast, the New York Times ran an interesting
article on solar flares and possible effects on the power grid,
satellites and communications. Check it out at
http://www.nytimes.com/interactive/2013/03/19/science/space/0319-solar.html
and don't forget to click on the link, "Related Article," which
takes you here:
http://www.nytimes.com/2013/03/19/science/space/on-the-watch-for-a-solar-storm.html.

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

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. Find more good
information and tutorials on propagation at
http://myplace.frontier.com/~k9la/.

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 14 through 20 were 133, 105, 90, 126, 116,
68, and 70, with a mean of 101.1. 10.7 cm flux was 122.8, 123.1,
126, 125.7, 117.6, 110.4, and 107.6, with a mean of 119. Estimated
planetary A indices were 5, 6, 10, 46, 7, 5, and 9, with a mean of
12.6. Estimated mid-latitude A indices were 4, 5, 8, 32, 6, 4, and
7, with a mean of 9.4.
NNNN
/EX