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ARRL Propagation Bulletin ARLP040 (2019)

ARLP040 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7RA
Seattle, WA  October 4, 2019
To all radio amateurs 

ARLP040 Propagation de K7RA

A new sunspot from old Solar Cycle 24 appeared on Tuesday and
Wednesday of this week, then by Thursday was gone.

The sunspot number was 11 on both days, the minimum non-zero sunspot

Average daily solar flux rose only slightly from 67.3 to 67.6.
Geomagnetic indices were higher. Average planetary A index rose from
5.4 to 14.4, and average mid-latitude A index increased from 4.6 to

Predicted solar flux for the next 45 days is 68 on every day,
October 4 through November 17.

Over the same period predicted planetary A index is 8 on October
4-5, 5 on October 6-7, then 8, 10, 5, 5, 8 and 12 on October 8-13, 8
on October 14-15, 5 on October 16-20, then 12, 5 and 5 on October
21-23, then 18, 25, 12 and 10 on October 24-27, then 8, 8 and 12 on
October 28-30, and again 8, 8 and 12 on October 31 through November
2, then 5 on November 3-5, then 8, 5, 8, 10, 8 and 8 on November
6-11, 5 on November 12-16 and 12 on November 17.

Geomagnetic activity forecast for the period October 04-October 29,
2019 from F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on: October 8, 16-17, 29
Quiet to unsettled on: October 4-5, 7, 9, 20, 23
Quiet to active on: October 6, 10-11, 15, 18-19, 22, 27-28
Unsettled to active on: October (12-14,) 21, 26
Active to disturbed: October 24-25

"Solar wind will intensify on: September 27-30, October 1 (-4, 7-9,)
11 (-14,) 21-26.

"Parenthesis means lower probability of activity enhancement.  The
predictability of changes remains lower."

On October 2, Mike Schaffer, KA3JAW of Easton, PA wrote:

"To my surprise, due to its rarity, double-hop sporadic-E was active
on the 11 meter Citizens Band yesterday afternoon, Tuesday, October
1 from 12 noon to 2 pm eastern local time.

"Eight days past the Autumnal Equinox, and the unexpected happens
inside the northern wedge of the Bermuda Triangle, which is the
mid-point path over the Sargasso Sea in the western Atlantic Ocean.

"It (Es) turned on like a switch with no warning.

"The Es was being funneled in from Puerto Rico, Dominican Republic
in the northern Caribbean Sea.

"Dominican Republic is 1,567 air miles and Puerto Rico is 1,629 air
miles from my location.

"The typical maximum single-hop Es range is 1,400 miles. Both
exceeded this limit, thus this was a double-hop event that occurred.

"At 12:30 pm, readable with practically no difficulty (4), strength
at good signals (6).

"Backscatter was heard from Pennsylvania and New York states calling
stations at 1:19 pm."

Dr. Tamitha Skov, WX6SWW writes:

"Dear Tad,

"After spending far too long with a spotless Sun, our favorite star
finally brings some bright regions back into Earth-view. The
emergence of several of these, including one that has officially
been designated a sunspot (region 2749), has brought some much
needed smiles to many in this community-- including me. Already we
have had about 200 days without any sunspots this year, which is
about as deep as solar minimum gets. Is anyone as ready as I am for
a change?

"As for the forecast this week, we are expecting some fast solar
wind to hit over the next few days as a southern coronal hole
rotates through the Earth-strike zone. This could bring aurora to
high latitudes, possibly through the weekend, but aurora
photographers at mid-latitudes should expect shows to be sporadic
and elusive. As for emergency and amateur radio, this storm might
boost radio propagation a bit, especially on Earth's night side.
Improved trans-equatorial propagation might also occur near the gray
line (which means there might be some good radio contacts between
the northern and southern hemisphere during the dawn and dusk hours)
as these conditions will likely be enhanced by the weak solar storm.

"Of course, the increased solar activity this week may fizzle as
fast as it started. It's way too early to wish for big solar flares
from a yet-to-be-seen Solar Cycle 25. But the return of bright
regions on Earth's dayside is a nice gift. If nothing else, they
make for a colorful backdrop while we wait for the weather to

"Cheers, Tamitha"

Her latest video can be found at:

An update from SpaceRef:

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
numbers used in this bulletin, see

An archive of past propagation bulletins is at More good
information and tutorials on propagation are 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 26 through October 2, 2019 were 0, 0,
0, 0, 0, 11, and 11, with a mean of 3.1. 10.7 cm flux was 67.1,
66.4, 67.3, 67.4, 67.9, 68.7, and 68.3, with a mean of 67.6.
Estimated planetary A indices were 4, 21, 27, 13, 15, 13, and 8,
with a mean of 14.4. Middle latitude A index was 2, 15, 21, 10, 11,
11, and 7, with a mean of 11.


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