Register Account

Login Help

ARRL Propagation Bulletin ARLP005 (2013)

ARLP005 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 5  ARLP005
From Tad Cook, K7RA
Seattle, WA  February 1, 2013
To all radio amateurs 

ARLP005 Propagation de K7RA

Sunspot numbers and solar flux barely changed in the past week.
Average daily sunspot numbers were 55.7, down slightly from 56.4 the
previous week, and average daily solar flux was 98.7, down from
110.7. Geomagnetic conditions continued their quiet spell.

The most active day was Saturday, January 26, when both the
mid-latitude and planetary A index was 18, and Alaska's college A
index was 46.

The predicted solar flux is 100 for February 1, 105 on February 2-5,
110 on February 6-7, 120 and 125 on February 8-9, 120 on February
10-11, then 115, 110 and 105 on February 12-14, 110 on February
15-18, 105 on February 19-23, 95 on February 24-25, 110 on February
26, and 125 on February 27 through March 1. Flux values peak again
at 140 on March 3-4.

The predicted planetary A index is 5 on February 1, then 12, 18, 15
and 8 on February 2-5, 5 on February 6-8, 8 on February 9-10, 5 on
February 11-18, 8 on February 19, 5 on February 20-21, then 15, 10
and 8 on February 22-24, 5 on February 25 through March 7, and 8 on
March 8-9.

OK1HH believes we will see quiet conditions on February 1-3, quiet
to unsettled February 4, mostly quiet February 5, quiet to active
February 6, mostly quiet February 7, quiet to unsettled February 8,
quiet to active February 9-10, quiet to unsettled February 11,
mostly quiet February 12, quiet to active February 13-14, active to
disturbed February 15, quiet to unsettled February 16, quiet on
February 17-21, active to disturbed February 22, quiet to unsettled
February 23 and quiet February 24.

Regular readers know we've been tracking a three-month moving
average of sunspot numbers for several years now. The average daily
sunspot number for the three calendar months ending January 31 was
82.8, better than last month, but nothing like the numbers we saw
over a year ago in fall 2011.

The three-month averages for the past year, the months ending in
February 2012 through January 2013 were 83.3, 73.7, 71.2, 87.3,
91.5, 96.5, 91.9, 89.9, 81.2, 82.3, 74.4 and 82.8.

The one month average sunspot number for January was 98.9, the
highest monthly average since May and July of last year.

Not much news in reports from readers this week, but N8II of West
Virginia reported last Friday, January 25, "Today was pretty decent
considering the now double digit SFI and K of 2. I worked RC4HAA on
15 meter CW who was S6-9, and 12 meters opened well to Europe from
1400-1440Z. I got in on the tail end of it with QSOs with SV3, HB9,
OM0 and G4.

"Last night at 0200Z I caught T6LG in Afghanistan on 80 CW for a new
band/country. He was about S3-S6 and not hearing the USA stations
calling him that well (about 10 callers when I was there)."

Glenn Axelrod, N6INM/9 in Mundelein, Illinois wrote: "Are SFI and
conditions going to improve by the Spring/Summer? Are we ever going
to see numbers again like in '58 in my lifetime? I am 48 years old."

By SFI, Glenn means solar flux index. We have no way of knowing when
this cycle will peak, or even if it may have already peaked, but
peaks of solar cycles become easier to predict later in the first
part (the upswing) of any cycle.

Until recently experts predicted this cycle would probably peak in
Spring of 2013, which begins in less than seven weeks. But later
predictions moved it out to Fall of 2013, with slightly lower
numbers. We had a period of higher solar activity in November and
December of 2011, which led some to believe that perhaps the cycle
had peaked early. Others believe we may see a double-peak in this
cycle, as we have in some earlier solar cycles.

But we should see seasonal improvements in HF conditions in the
Spring and again in the Fall.  By seasonal, I mean that even if we
saw no change in solar activity, just due to the season and position
of the Sun relative to us, we see better conditions on the higher
frequencies in Spring and Fall than we tend to see in Summer and

In September through December 2011 the monthly averages of daily
sunspot numbers were 106.4, 123.6, 133.1 and 106.4. The previous
four months (May through August) saw averages of 61.5, 55.5, 67.2
and 66, so the final third of 2011 showed a dramatic jump in
activity. But the next year the numbers dropped back again. The
average daily sunspot number for all of 2012 was 82.3. The average
for all of 2011 was only 29.9, so that jump at the end of the year
was exciting, and convinced many of us that the cycle was starting
to really ramp up. The January 2013 average was a little less than

There is a hypothesis which posits that we may see a grand minimum,
decades of depressed sunspot numbers, but of course that cannot be
proven by observation in the next decade or two. I hope it isn't
true. I hope we see future activity which is strong and surprises
everyone, but I wouldn't count on it. I was licensed during the low
point between Cycle 19 (the biggest in history) and Cycle 20, and
along with many others have been wishing for decades to see another
like Cycle 19. But Cycle 19 turned out to be a rarity. But just like
Cycle 19 surprised many people, I hope we can be surprised again.

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 January 24 through 30 were 60, 44, 55, 60, 52,
63, and 56, with a mean of 55.7. 10.7 cm flux was 103.4, 100.5,
99.4, 97.7, 97.6, 95.4, and 96.6, with a mean of 98.7. Estimated
planetary A indices were 1, 6, 18, 6, 4, 2, and 2, with a mean of
5.6. Estimated mid-latitude A indices were 1, 7, 18, 5, 3, 2, and 2,
with a mean of 5.4.


Instragram     Facebook     Twitter     YouTube     LinkedIn