SB PROP @ ARL $ARLP038

ARLP038 Propagation de K7RA

ZCZC AP38

QST de W1AW 

Propagation Forecast Bulletin 38  ARLP038

From Tad Cook, K7RA

Seattle, WA  September 19, 2014

To all radio amateurs

SB PROP ARL ARLP038

ARLP038 Propagation de K7RA

On September 11 and 12 two powerful CMEs hit Earth, producing a G3

class geomagnetic storm. The result was a planetary A index of 44 on

Friday, and during the final three hours of the UTC day (2:00 PM to

5:00 PM PDT) the planetary K index reached 7, which is very high.

Overall solar activity is down, with the average daily sunspot

number declining from 152 to 124.9 in the latest reporting period

(September 11-17). Average daily solar flux dropped from 155.8 to

139.8.

Predicted flux values have declined as well. As an example, the

daily 45 day forecast for solar flux on September 21 was 120 on

August 6-10, 125 on August 11-17, 135 on August 18 through September

7, 150 on September 8-12, 130 on September 13, 120 on September

14-15 and 115 on every day since.

Predicted solar flux is 120 on September 19, 115 on September 20-21,

110 on September 22-25, 115 on September 26, 120 on September 27-28,

130 on September 29, 135 on September 30 and October 1, 140 on

October 2, 145 on October 3-5, 150 on October 6-7, 145 on October

8-9. and 140 on October 10-12. Flux values then dip to 125 on

October 17, rise again slightly, then go down to 115 on October

21-23. After that solar flux values are expected to rise again,

perhaps to 150 by early November.

Predicted planetary A index is 5 on September 19-25, 15 on September

26-27, 12 on September 28-29, 10 on September 30, 5 on October 1-2,

8 on October 3-4, 5 on October 5, 10 on October 6-7, then quieting

down to 5 on October 8-11, then rising to 8, 10 and 8 on October

12-14, and quieting down to 5 again on October 15-21. The next

really active period is predicted to have a planetary A index of 20

on October 22.

Petr Kolman, OK1MGW of the Czech Propagation Interest Group believes

geomagnetic conditions should be quiet to unsettled on September

19-20, quiet on September 21, active to disturbed September 22-23

(although he is uncertain about this), quiet to unsettled September

24-26, quiet to active September 27-28, quiet to unsettled September

29 through October 3, quiet to active October 4-5, mostly quiet

October 6-9, quiet October 10-12. mostly quiet October 13-14, and

quiet to unsettled October 15.

Petr expects an increase in solar wind on September 22-23 (although

he is less than certain about this, just as in the geomagnetic

prediction for those two days), and also on September 26-29 and

October 3-4.

The Autumnal Equinox is just a short time away, in the early hours

of September 23 at 0229 UTC. This is Monday night in North America.

The equinox portends improved worldwide communications on the HF

bands. As an example, modeling propagation using W6ELprop and a

modest solar flux of 120, 20 meter signals between California and

Japan on the equinox run about 6 dB hotter in the early evening on

the West Coast than they would a month earlier.

Rich Zwirko, K1HTV of Amissville, Virginia (FM18ap) sent this report

about recent activity in the ARRL September VHF Contest last weekend

(September 13-15):

"The Wednesday, September 10 CME and X1.6 solar flare resulted in an

aurora which occurred on Friday evening, Sept. 12. Unfortunately,

this was the day before the ARRL VHF Contest. I managed to work

W1AW/1 and a couple of VEs on 6 meter CW via the buzz mode. On 2

meters I worked W9EWZ (EN52) and heard W9ZIH (EN51) and K9MRI (EN72)

via the auroral curtain. During the VHF contest, the first sign of

Es occurred just before 2030Z Saturday. A number of Florida stations

were worked plus stations in Cuba (CO3VR and CO3JA) and Mexico

(XE3/K5ENS). Just before 2200Z our Es opening to the south coupled

into the Florida-to-South America TEP. This resulted in K1HTV QSOs

with two LU stations in GF05 (LU9AEA and LU6DRV) and two stations in

GF15 (CX2TQ and CX9AU). By 2220Z Saturday the Es and TEP had

disappeared.

"As September VHF contests go, I would rate the overall conditions

to be above what is normally expected in the inland Mid-Atlantic

region. Normally the Summer Es conditions have gone, but the

Saturday Es opening, coupling to the TEP resulted in some

interesting QSOs.

"73, Rich - K1HTV"

Thanks, Rich!

I'll clarify a couple of terms, for readers who might be new. When

Rich refers to "Es" he is talking about E-layer propagation, which

can appear sporadically and propagate signals at 10, 6 and 2 meters

during certain seasons of the year, such as summer and again and

less often in December. Long distance HF propagation relies on the

higher and more predictable F-layer of the ionosphere.

TEP refers to Trans-Equatorial Propagation, or propagation in an

approximate north/south path across the equator. When we have a big

solar flare and geomagnetic storm such as the one last week,

sometimes on HF TEP is the only available propagation mode.

"Buzz mode" refers to auroral propagation, in which VHF stations aim

their antennas north toward the Aurora Borealis. The reflected

signals are distorted, hence the reference to "buzz."

Wikipedia has a pretty good description of sporadic-E propagation at

http://en.wikipedia.org/wiki/Sporadic_E_propagation , and K9LA has a

treatise on TEP at http://k9la.us/Trans-Equatorial_Propagation.pdf .

As mentioned every week at the end of this bulletin, K9LA has a

great web site devoted to propagation at http://k9la.us/ .

Http://www.spaceweather.com reports "No geomagnetic storm was in the

forecast for September 19, but a storm occurred anyway. Sky watchers

around the Arctic Circle saw the midnight sky turn green as

magnetometers registered an unexpected G1-class disturbance between

0300 and 0600 UTC. The source of the display was a fluctuation in

the interplanetary magnetic field (IMF). During the early hours of

September 19 the IMF tipped south, opening a crack in our planet's

magnetosphere. Solar wind poured in to fuel the storm."

The planetary K index was 4 at 0300 UTC and 5 at 0600 UTC. NOAA

forecasters estimated a 20% chance of more polar geomagnetic storms

overnight. See http://www.swpc.noaa.gov/ftpdir/latest/DGD.txt .

Dennis Condron, K0LGI of Marion, Iowa posted his observations about

last week's big flare, and you can read it here:

https://groups.google.com/forum/?fromgroups#!topic/radiometeors/cKA0M9bokRM

Dave Sublette, K4TO of Winchester, Kentucky pointed out that the

report from N0JK in last week's bulletin never mentioned what band

he was talking about. Later, after putting the bulletin to bed I

received an email from N0JK to let me know it was 6 meters.

If you would like to make a comment or have a tip for our readers,

email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL

Technical Information Service web page at

http://arrl.org/propagation-of-rf-signals. For an explanation of the

numbers used in this bulletin, see

http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past

propagation bulletins is at

http://arrl.org/w1aw-bulletins-archive-propagation. More good

information and tutorials on propagation are at http://k9la.us/.

Monthly propagation charts between four USA regions and twelve

overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL

bulletins are at http://arrl.org/bulletins.

Sunspot numbers for September 11 through 17 were 164, 157, 165, 120,

92, 85, and 91, with a mean of 124.9. 10.7 cm flux was 151.4, 152,

145.1, 139.3, 132.9, 133, and 125, with a mean of 139.8. Estimated

planetary A indices were 12, 44, 13, 3, 3, 7, and 6, with a mean of

12.6. Estimated mid-latitude A indices were 16, 35, 13, 3, 2, 7, and

4, with a mean of 11.4.

NNNN

/EX