Register Account

Login Help

ARRL Propagation Bulletin ARLP001 (2012)

ARLP001 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 1  ARLP001
From Tad Cook, K7RA
Seattle, WA  January 6, 2012
To all radio amateurs 

ARLP001 Propagation de K7RA

Reports of good conditions continue, although sunspot activity
declined a bit.  Average daily sunspot numbers for December 29
through January 4 declined nearly 20 points (when compared to the
previous seven days) to 88.1.  Average daily solar flux was off 6.4
points to 143.1.

88.1 is the lowest reported weekly sunspot number average since
Propagation Forecast Bulletin ARLP035 from 18 weeks ago.

As expected, last week's report of 80.1 as the average daily sunspot
number for all of 2011 was correct.  The additional sunspot numbers
from December 30-31 did not change it, but we just had to verify.

In a preview for this bulletin in Thursday's ARRL Letter, I
indicated a problem with the planetary A index numbers we are
getting from NOAA.  I made an inquiry, and heard from Mike Husler of
NOAA/SWPC.  NOAA is no longer getting planetary A and K index data
from the USAF, but is now doing their own estimates. But their
estimates seemed to be too low, so they have changed their method
for calculating planetary A and K indices.

Mike Husler wrote, "A comparison of our new real-time Kp estimate
with the official values for October-December showed that we were
tending to estimate too low. In order to improve the situation we
reran the fits between stations' Ks (as they would be derived using
our real-time algorithm) and official Kp to get an updated table of
conversion coefficients. The new values have been deployed as of 4
January 2012 at 1500Z.

"For 10/19/2011-12/15/2011 we found the following improvement in
performance of the estimate compared to the official values: Kp Mean
absolute error decreases from 0.44 to 0.24.  Average bias improves
from -0.41 to 0.00

"Ap Mean absolute error decreases from 1.93 to 0.98.  Average bias
improves from -1.69 to -0.34.

"You should generally see somewhat higher Kp and Ap values than you
have been seeing previously. The values from 10/1/2011 forward are
NOAA Kp values with the correction stated above and the values prior
to that are from the USAF Kp."

They are currently going back and correcting data for the last few
months of 2011. I do not know what he meant by ''official values,''
but I suspect that since the Ap and Kp values are called estimates,
that there is some other longer term method for determining
"official values."

Mike also wrote, "Here is a web page for general information about
the Kp and Ap indices from the official source:


"Here is a link to the data files that are updated twice per month.
I recommend people use these data if they need something that is for
previous months:


A new solar cycle prediction was released on January 3, revised
slightly lower from the prediction released less than three weeks
before, on December 16.

The key phrase from the December 16 prediction: "We find a starting
time of October 2008 with minimum occurring in December 2008 and
maximum of about 99 in February of 2013."  This was changed in the
January 3 prediction to: "We find a starting time of October 2008
with minimum occurring in November 2008 and maximum of about 96 in
February of 2013."

The latest version is at: .

The Washington Post recently ran a blog post on space weather events
of 2011.  Read it at  Look for the

We received 6 meter reports from Jon Jones, N0JK.  On December 30 he
wrote: "Great Es on 6M yesterday 12/29.  Open most of the afternoon
and evening for many parts of the USA. And Es links from W4, W5 and
W8 to E51 and ZL. K5N was a Grid DXpedition active yesterday from
the line from two rare grids, DM90/DL99. The Es allowed them to give
many ops two really rare new grids. I logged them at 0403 UTC 12/30
on my indoor dipole. They were in to my location only about 7

On January 5, Jon wrote: "The 6 Meter band really came alive last
week. Major long lasting Es openings on Dec. 30, 31 and Jan. 1. New
Years Eve worked NP4A FK68 on double hop Es. Jan. 1 strong short Es
to ND, MN, WY, etc. Noted spots by stations in W4, W5 to VK, ZL on
Es links New Years Eve."

Thanks, Jon.

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 Find more good
information and tutorials on propagation at

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 December 29 through January 4 were 105, 104, 68,
61, 83, 95, and 101, with a mean of 88.1. 10.7 cm flux was 147.1,
141.1, 132.9, 130, 134.7, 134.6, and 136.2, with a mean of 136.7.
Estimated planetary A indices were 7, 6, 4, 4, 5, 7, and 3, with a
mean of 5.1. Estimated mid-latitude A indices were 7, 5, 5, 4, 4, 9,
and 3, with a mean of 5.3.


Instragram     Facebook     Twitter     YouTube     LinkedIn