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ARRL Propagation Bulletin ARLP022 (2012)

ARLP022 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 22  ARLP022
From Tad Cook, K7RA
Seattle, WA  June 1, 2012
To all radio amateurs 

ARLP022 Propagation de K7RA

Average daily sunspot numbers sank more than 28 points this week
(nearly 26%) to 81.9. Average daily solar flux declined more than 16
points to 111.6. This is for the seven days of May 24-30, and is
compared to the previous seven days, May 17-23.

No new sunspots appeared over the five days of May 26-30, but on May
31, three new sunspot groups appeared. One day earlier the sunspot
number was 78, while the total relative sunspot area was 400. On May
31 those numbers dropped to 73 and 330, even with the new spots.

On May 30, sunspot groups 1486, 1488, 1490 and 1492 were in place.
By May 31, 1486 and 1488 disappeared, and new sunspot groups 1493,
1494 and 1495 emerged. But the total area of all visible spots was
less than the day before.

You can track the fading of sunspot groups and the emergence of new
ones at The
dates shown are always for the new UTC day, the one following the
day for which the data is shown. So the report marked June 1 is
actually displaying data gathered on May 31.

In this report the area for each sunspot group is listed, and this
is expressed in millionths of a solar hemisphere.  The total sunspot
area for the day, along with the sunspot number, is displayed along
with solar flux resolved to whole numbers at

The short term outlook is revised from the one given in yesterday's
ARRL Letter, with solar flux peaking around 125 on June 2-7, hitting
a minimum of 105 on June 27-28, then peaking at 120 on July 1-12.

The latest prediction has solar flux at 120 on June 1, 125 on June
2-7, 120 on June 8-15, 115 on June 16-18, 110 on June 19-26, and
105, 105, 110 and 115 on June 27-30, then 120 on July 1-12.

Predicted planetary A index is 5 on June 1-2, then 10, 15, 18, 15
and 10 on June 3-7, 5 on June 8-11, 8 on June 12-13, 5 on June
14-17, and 15, 12 and 8 on June 18-20, and 5 on June 21-25.

With the start of a new month, we can revisit our moving averages
for sunspot numbers. We've been observing a three-month moving
average, based on whole calendar months, so the latest average is
for March, April and May 2012. About a month ago we were reporting
for the months of February, March and April. It is a simple
arithmetic - with an accent on the third, rather than second
syllable - average, with a total of all sunspot numbers divided by
the number of days in the period.

So over September 1 through November 30, 2011, there were 91 days
and the sum of all daily sunspot numbers for that period was 10,808,
yielding an average daily sunspot number of 118.8 when the sunspot
number total is divided by the number of days.  The next period
covered October 1 through December 31, 2011, with a total sum of all
daily sunspot numbers of 10,913 divided by 92 days, giving us an
average daily sunspot number of 118.6. That period in Fall 2011 had
the highest sunspot numbers seen so far in Cycle 24.

The three month moving averages of daily sunspot numbers for the
three month periods ending January 2010 through May 2012 were 15,
22.4, 25.7, 22.3, 18.5, 16.4, 20.4, 23.2, 28.9, 33, 35.6, 31, 30.1,
35.3, 55.7, 72.3, 74.4, 65.9, 61.5, 63, 79.6, 98.6, 118.8, 118.6,
110, 83.3, 73.7, 71.2, and 87.3. As you can see, the numbers are up
slightly over the past few months.

The monthly average sunspot numbers for February through May 2012
are 50.1, 78, 84.5 and 99.4.

Go to
to read an article on Ground Level Enhancements, or GLE, a rare
event in which a sudden rise in neutrons coincides with an energetic
solar flare or coronal mass ejection. A GLE detected on May 17 was
the first GLE of the current solar cycle.

Dave Blood, W1AFC of Oberlin, Ohio had some comments on WA8MEA's
recent query on LUF and MUF. Dave wrote, "MUF is affected by solar
UV light mostly and therefore is governed by the daily solar flux
levels. The LUF, as mentioned, is set by daytime absorption in the
D-region at about 100 km heights (hence by the number of radio wave
passes through it (up and down) and the number of ionospheric hops
supported by the F-region at 300 km heights). The absorption is
altered by the instantaneous X-ray radiation from the Sun and this
can vary up and down highly during solar flare activity. Radio
'Blackout' conditions occur when the absorption is so high that the
LUF exceeds MUF for any propagation path distance for long periods
from 20 minutes to several hours."

Dave worked for Raytheon for several decades on over-the-horizon
radar from 1960-1992. Dave has been a ham for 60 years.

Rick McCurdy, WA1GTP is in FN31si in Ivoryton, Connecticut.  He
wrote, "On May 23 at 1550 UTC I received RADAR on 432.100, first
time in years!  Heading was WSW from (Essex) New London/New Haven
CT area. Very few openings on 6 meters but April 30 worked short E
skip to VE2DLC, FN58rk, 527 miles. Also Florida openings May 24, not
much else."

We received another geomagnetic forecast from F.K. Janda, OK1HH.  He
predicts quiet to active conditions on June 1, quiet on June 2,
quiet to unsettled June 3-4, quiet to active June 5, active June
6-7, quiet to active June 8-9, quiet to unsettled June 10, quiet
June 11-12, quiet to active June 13, mostly quiet June 14, quiet to
unsettled June 15-16, quiet to active June 17, mostly quiet June 18,
active June 19, and quiet to unsettled June 20-21.

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 May 24 through 30 were 96, 86, 70, 83, 87, 73,
and 78, with a mean of 81.9. 10.7 cm flux was 115.5, 117.2, 110,
110.7, 110.3, 106.3 and 111, with a mean of 111.6. Estimated
planetary A indices were 8, 6, 4, 4, 6, 6, and 6, with a mean of
5.7. Estimated mid-latitude A indices were 11, 8, 5, 3, 3, 5, and 5,
with a mean of 5.7.


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