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ARRL Propagation Bulletin ARLP040 (2012)

ARLP040 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7RA
Seattle, WA  October 5, 2012
To all radio amateurs 

ARLP040 Propagation de K7RA

A coronal mass ejection (CME) hit Earth on September 30, triggering
a jump in geomagnetic indices.  The planetary A index on October 1
was 31, and the K index went as high as 7, making aurora visible
across the northern tier of the United States. Strange, but the
northern latitude college A index was 23 (near Fairbanks, Alaska),
about the same as the mid-latitude index, which was 21, in
Fredericksburg, Virginia. During a geomagnetic disturbance it is
common to see indices go much higher in the far-northern latitudes.

Average daily sunspot numbers declined 8.3 points to 73, and average
daily solar flux was off exactly one point, to 128.7.

The latest prediction from NOAA/USAF has solar flux on October 5-6
at 110, 105 on October 7, 100 on October 8-11, 115 on October 12-13,
120 on October 14-15, 130 on October 16, 140 on October 17-18, and
then 145 and 150 on October 19-20. The same forecast has solar flux
rebounding to 150 on November 16, after reaching a minimum of 110 on
November 4-5.

The predicted planetary A index is 5 on October 5-8, 10 and 8 on
October 9-10, 5 on October 11-14, then 8, 12 and 10 on October
15-17, 5 on October 18-25, 10 on October 26, 5 on October 27-28, and
reaching a peak of 15 on October 29.

Now from F.K. Janda, OK1HH comes his geomagnetic forecast. October 5
expect quiet to active conditions, quiet October 6-8, mostly quiet
October 9, quiet October 10, mostly quiet October 11, quiet to
unsettled October 12-14, mostly quiet October 15, active to
disturbed October 16, mostly quiet October 17, quiet to unsettled
October 18, quiet October 19-20, mostly quiet October 21, quiet
October 22-23, quiet to unsettled October 24, and back to quiet
again on October 25-27.

In September we saw a slight decline in sunspot averages. Monthly
averages of daily sunspot numbers for April through September 2012
were 84.5, 99.4, 90.1, 99.6, 85.8 and 84.

Three-month moving averages of daily sunspot numbers, for 3-month
periods ending February through September 2012 were 83.3, 73.7,
71.2, 87.3, 91.5, 96.5, 91.9 and 89.9. So the last number, 89.9, was
an average of daily sunspot numbers for all of July, August and
September, and the number prior to that, 91.9, was for the months of
June, July and August.

In 6 meter news, Floyd Chowning, K5LA of El Paso, Texas wrote, "I
have been seeing many spots on the DX cluster where stations are
working from Africa to Europe earlier in the day our time. So
decided to start listening and finally heard a DX station."  He
copied the beacon CE3AA/B in Santiago at 2122z on October 4 on
50.0293 MHz. That distance is nearly 5,100 miles.

Jon Jones, N0JK says there was "a fairly impressive aurora" on
October 1, and KF6A in Alma, Michigan copied the N0LL 6-meter beacon
in Smith Center, Kansas at 0442z on that day on 50.0776 MHz. The
distance was 770 miles, and the direction from the beacon toward the
receiving station was 66.6 degrees, or roughly east-northeast.

Jon also wrote, "The next day (or later the same day, UTC)
conditions were good on 24 MHz to 3D2C Conway Reef. They were very
loud to Kansas around 2030 UTC on October 1. I was able to work them
with my mobile set up. With the good but not high solar flux, 24 MHz
has often been a good band for DXing, better than 10 or 15 meters.
Signals from 3D2C were not nearly as loud on 10 meters when I

The NASA solar cycle prediction was revised slightly since last
month. You may recall that the predicted peak was moved recently
from Spring to Fall 2013, and now the predicted peak has gone down
one point, from a smoothed sunspot number of 76 to 75. Read it at

Larry Godek, W0OGH in Gilbert, Arizona reported October 1: "Saturday
and Sunday both the RTTY portions were overloaded with activity.
Couldn't believe the number and signal strength of stations. Even 40
Saturday night was something I've not heard in many years. On SSB,
10 meters in particular, it sounded like the days of AM when
stations were overlapping. Amazingly there were very few, maybe half
dozen that I heard ragchewing between 28.6 and 29.0 MHz. Almost
everything else was below 28.6. Even had good AM activity above 29.0
as some of the locals were talking about the QSOs they had in that
segment of the band.

"10 FM through the KQ2H repeater had European stations till after
lunch time here in the west. Only heard one or two other stations
from the US, all of it was foreign. Even 29.640 had lots of traffic
although nothing like 29.620.

"I didn't check anything on the WSPR modes but it would have been
interesting to see how the high SFI and A index affected them as
well. You could tell by late Sunday afternoon that things had
changed as the noise level came way up almost like the Summer
afternoons. Previous to this past 3 days the band noise has been
almost nil. Had to turn the gain on the K3 way up on 10 as I thought
no noise, weak signals but that wasn't the case at all.

"I'd suspect the stations who were active this past weekend will be
talking about this opening as it truly brought back memories of the
good times when the bands were full of activity with great signals."

The day before, September 30, Larry wrote, "WOW! The RTTY guys must
have thought they died and went to heaven! RTTY sigs on 15 meters
alone occupied 70 KHz of the band and a lot of excellent quality DX
signals as well. 10 was really nice also but didn't spend much time
there as I was busy down on the low part of the band. Worked 5 new
countries on 10 FM and more on the CW and SSB modes. Lets hope this
is an indication of what's left of this cycle. I could certainly use
some extra oxygen on days like this when my heart gets a cardiac
workout from the excitement of hot bands! Whoever is responsible,
keep up the good work. Makes being retired a lot more fun as I may
only get one more of these cycles to play in."

Herb Lacey, W3HL of Cary, North Carolina noted that there seem to be
more sunspots south of the Sun's equator than north. I responded
that this seems to be true lately, but when I looked in the archives over the past year, there
didn't seem to be more sunspots in the southern hemisphere. K9LA was
consulted, and said that asymmetry in the north-south distribution
of sunspots is common. He referred to butterfly diagrams of solar
cycles, and you can see them at,

As each solar cycle progresses, sunspots emerge closer to the
equator. K9LA drew our attention to Cycle 20, around 1970. You can
see a weighting toward the northern hemisphere. The previous cycle,
around 1960, Cycle 19, also seems to favor northern spots, and Cycle
22 around 1990 seems to favor southern sunspots.

K9LA doesn't know of any explanation for the asymmetry, and notes it
is probably tied to plasma flow in the Sun.

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 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 September 27 through October 3 were 97, 77, 70,
95, 59, 55, and 58, with a mean of 73. 10.7 cm flux was 133.2,
137.8, 136, 135.6, 128.1, 118.2, and 111.7, with a mean of 128.7.
Estimated planetary A indices were 5, 2, 4, 10, 31, 5, and 5, with a
mean of 8.9. Estimated mid-latitude A indices were 3, 2, 4, 9, 21,
5, and 5, with a mean of 7.


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