ARRL Propagation Bulletin ARLP039 (2009)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 25, 2009
To all radio amateurs 

ARLP039 Propagation de K7RA

This week we had a double-dose of good news.  Right at the time of
the Autumnal Equinox, on Tuesday, September 22, sunspot 1026, a new
Cycle 24 sunspot, came into view over the Sun's eastern horizon.  We
watched this emerge a week ago on the Sun's far side via the STEREO
project (see

STEREO is a fantastic tool, because it gives us all a live view of
nearly the whole Sun, and it displays very recent images.  It turns
out that images from each craft--the ahead (leading earth in its
orbit) and the behind (trailing earth in its orbit) satellite--are
updated approximately every 15 minutes!  No more guessing about
activity on the other side of the Sun, because we can see it live in
animated form based on real time data.

On that animated Sun display you can see there are longitude lines
every 30 degrees.  Since there are twelve of them, and a rotation of
the Sun takes approximately 27.5 days (it varies by latitude), then
on average it takes about .0764 days (1 hour, 50 minutes) for the
Sun's rotation to progress one degree longitude.  Therefore, when we
saw the sunspot at -120 degrees longitude, we could estimate that it
would take about 2.2917 days (2 days and 7 hours) for the spot to
reach the Sun's eastern horizon (at -90 degrees) and first become

On Monday the daily sunspot number was 11, then on Tuesday and
Wednesday a second Cycle 24 spot (number 1027) emerged in the Sun's
Northern Hemisphere.  Tuesday's daily sunspot number rose to 26,
then on Wednesday it was 31 as the area of the spots grew.  On
Thursday the sunspot number was 32.  From Monday to Tuesday the
total sunspot area increased by seven times, then on Wednesday it
doubled, then on Thursday rose about 29% over Wednesday's area.  You
can see the sunspot numbers, solar flux and sunspot area for each
day at,

Checking shows us
that geomagnetic indices are extremely quiet and stable, so I
suppose there are three pieces of great propagation news this week.
Both sunspots have moved into their maximum geo-effective position
(around zero degrees longitude, in the center of the solar disc as
viewed from Earth), led by sunspot 1027.

The current prediction from NOAA/USAF is for continued quiet
conditions today with a planetary A index of 5, then on Saturday
some unsettled conditions and a planetary A index of 12.  It drops
to 8 on Sunday, then back to 5 for the foreseeable future.  Solar
flux is expected to continue at about the same level through the
first few days of October.

Geophysical Institute Prague has a similar prediction for
geomagnetic values, quiet to unsettled September 25, unsettled
September 26, quiet to unsettled September 27, and quiet conditions
September 28 through October 1.

Ken Tata, K1KT of Warwick, Rhode Island (grid square FN41gs) reports
that the Fall 144 MHz Sprint saw some great activity along the East
Coast.  This is sponsored by the Southeastern VHF Society
( and lasted for just four hours, from 7:00 PM
to 11:00 PM local time, on Monday, September 21.

Ken wrote, "From Rhode Island the band was open from at least
central Virginia to southern Nova Scotia. Overall, signals were
stable with shallow, slow QSB. This was perhaps the most active 2
meter contest I've seen. At 8 PM local time it sounded like an HF

Tim Hickman, N3JON of Timonium (Baltimore area), Maryland said
"Propagation is up!" after he worked VK4MA long path on September 23
at 2137z.  Tim was running barefoot with a small 2-element multi
band beam, and received an S5 signal report.  Unfortunately, he
didn't say what band he was using, but I will bet it was 20 meters.

K4WY, KI4BXN and others tipped us off to a fascinating new story
about solar wind during the cycle minimum.  Dr. Sarah Gibson, lead
scientist on the study, found that solar wind may be much more
active during cycle minima than previously thought.  See the story
at,, and

This weekend is the CQ World Wide DX RTTY Contest, and FT5GA, the
Glorioso DXpedition will be active.

With the heightened solar activity, here are some rough propagation
estimates for the path to Glorioso Island this weekend, which is off
the East Coast of Africa, northwest of Madagascar.

From Chicago, best bet for 15 meters is 1600-2100z, 1600-2300z for
17 meters, 1930-0030 on 20 meters, 2130-0400z on 30 meters, 40
meters from 2230-0030z, and 80 meters from 2300-0300z.

From Cleveland, Ohio, check 15 meters 1500-2030z, 17 meters
1700-2230z, 20 meters 1900-0030z, 30 meters 2100-0400z, with a
possibly difficult period 0200-0230z, 40 meters 2200-0330z, and 80
meters 2300-0300z.

From Boston, 12 meters 1400-1830z, 15 meters 1200-2130z, with
signals gradually increasing over that period, 17 meters also
increasing signal strengths 1300-2300z, 20 meters 1730-0030z, with
increasing signal strengths, 30 meters 1900-0430z, with best chance
2130-0100z, 40 meters 2130-0330z, and 80 meters 2200-0230z.

From New York City, 12 meters 1430-1900z, 15 meters 1200-2130z, 17
meters 1330-2300z, 20 meters 1800-0030z, 30 meters 2200-0330z, 40
meters 2100-0400z, 80 meters 2230-0300z.

From Philadelphia, 12 meters 1430-1900z, 15 meters 1200-2200z, 17
meters 1330-2300z, 20 meters 2000-0030z, 30 meters 2200-0400z, 40
meters 2100-0400z, and 80 meters 2230-0330z.

From Atlanta, 15 meters 1500-2130z, 17 meters 1630-2300z, 20 meters
2000-0030z, 30 meters 2130-0400z, 40 meters 2230-0400z, and 80
meters 2330-0300z.

From Miami, 10 meters 1600-1730z, 12 meters 1500-1800z, 15 meters
1600-1930z, 17 meters 1630-2230z, 20 meters 2000-0030z, 30 meters
2130-0430z, 40 meters 2230-0330z, and 80 meters 2230-0300z.

Dallas, Texas, 15 meters 1430-2230z, 17 meters 1600-2330z, 20 meters
2100-0030z, 30 meters 2200-0430z, 40 meters 2330-0330z, 80 meters

Omaha, Nebraska, 15 meters 1630-2100z, 17 meters 1530-2330z, 20
meters 2000-0030z, 30 meters 2200-0400z, 40 meters 2300-0330z, 80
meters 0000-0230z.

Phoenix, Arizona 12 meters 1900-2100z, 15 meters 1530-2300z, 17
meters 1400-0000z, 20 meters 2130-0030z and around 0330z, 30 meters
0000-0330z, 40 meters 0000-0300z, 80 meters 0100-0230z.

Denver, Colorado, 15 meters 1630-2200z, 17 meters 1500-0000z, 20
meters 2000-0030z, 30 and 40 and 80 meters, 0000-0300z.

Salt Lake City, 15 meters 1730-2230z, 17 meters 1500-0000z, 20
meters 2000-0030z, 30 meters 2130-0330z, 40 meters 0030-0230z, 80
meters 0030-0230z.

From the middle of California, 15 meters 1730-2300z, 17 meters
1530-0000z, 20 meters 1430-0030z and also 0300-0400z, with dropouts
at 1600z and 2100z. 30 meters 2330-0330z, 40 meters 0130-0300z, 80
meters 0130-0230z.

From Seattle, 15 meters 1930-2230z, 17 meters 1700-2330z, 20 meters
1430-0300z, 30 meters 2100-0300z, 40 meters 0000-0230z.

From Hawaii, 10 meters 0330-0600z, 12 meters 0300-0700z, 15 meters
0230-0830z, 17 meters 1100-1230z, 20 meters 1230-1500z and
1730-1930z, 30 meters 1300-1800z, 40 meters 1330-1730z, 80 meters

On most of the above paths, signals gradually strengthen throughout
the given time period.

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 a detailed
explanation of the numbers used in this bulletin see,  An archive of past
propagation bulletins is at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for September 17 through 23 were 0, 0, 0, 0, 11, 26,
and 31 with a mean of 9.7.  10.7 cm flux was 69.1, 69, 70.5, 71.3,
71.9, 74.7, and 76.1 with a mean of 71.8.  Estimated planetary A
indices were 8, 3, 2, 4, 7, 4 and 2 with a mean of 4.3.  Estimated
mid-latitude A indices were 6, 2, 1, 3, 5, 2 and 1 with a mean of