Register Account

Login Help

ARRL Propagation Bulletin ARLP007 (2023)

ARLP007 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7RA
Seattle, WA  February 17, 2023
To all radio amateurs 

ARLP007 Propagation de K7RA

At 0725 UTC on February 15 the Australian Space Weather Forecasting
Centre issued a geomagnetic disturbance warning: "A CME impact
occurred around 2200 UTC on February 14. Bz has been southward for
the majority of time since impact and there is a chance of G1
geomagnetic conditions."

Bz is the north-south direction of the Interplanetary Magnetic Field

They predicted a disturbance for February 15-16.

They issued a new warning on February 17 at 0206 UTC:

"A partial halo CME observed on 15-Feb is due to impact Earth's
magnetosphere late on 17-Feb or early 18-Feb UTC. G1 geomagnetic
conditions are expected on 18-Feb, with a slight chance of G2.


For the latest geomagnetic conditions, I prefer this source:

More on the IMF:

Many sunspots appeared over this reporting week (February 9-15) with
three new sunspot groups on February 9, one more on February 10, two
more on February 11, another on February 12 and three more on
February 13. Finally, there was one more yesterday, Thursday,
February 16.

Recent sunspot images:

That one is for February 12. To see February 13, just change the
12feb23 string to 13feb23, and so on, for any other date.

Average daily sunspot numbers increased from 95.1 to 182.4, and
average daily solar flux from 155.9 to 196.4.

Geomagnetic activity also rose, with average daily planetary A index
going from 11.7 to 13.7, and middle latitude numbers from 7.6 to

The most active days were at the beginning and end of the week, with
planetary A index at 21 on February 9 and 29 on February 15. On
those two days the college A index at Fairbanks, Alaska was 33 and
46. The quietest day was Monday, February 13 when the planetary A
index was 4.

The outlook for the next month seems modest, with predicted solar
flux at 155, 160, 155, 145 and 135 on February 17-21, 125 on
February 22-23, 130 on February 24-26, 140 on February 27 to March
1, 145 on March 2-3, then 150, 155 and 165 on March 4-6, 180 on
March 7-13, 170 on March 14-15, 160 on March 16-18, and 150 on March
19, 140 on March 20-21, and 135 on March 22-25.

Predicted planetary A index is 22, 30, 12, 8 and 12 on February
17-21, 10 on February 22-24, then 5, 5 and 8 on February 25-27,
another 5, 5, and 8 on February 28 through March 2, then 5, 5 and 16
on March 3-5, then 18, 15 and 8 on March 6-8, and 5 on March 9-20,
then 10 on March 21-23, and 5, 5 and 8 on March 24-26, and another
5, 5 and 8 on March 27-29.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - February 16, 2023, from F.K. Janda, OK1HH.

"On February 11, we observed a seemingly dangerous sunspot group
AR3217, whose magnetic field had a beta-gamma-delta configuration,
in which large flares are often observed, up to X-class flares
accompanied by CMEs. This is what we saw at 1548 UTC, while extreme
UV radiation ionized the upper part of the Earth's atmosphere.
Direct result was the Dellinger effect, which disrupted shortwave
communications over all of South America.

"But this particular eruption did not create a CME. Another
explosion did. Five hours before the X eruption, a magnetic filament
appeared in the northern hemisphere of the Sun, which spewed a CME
into space. Thereafter we were expecting an Earth impact on
Valentine's Day, February 14. This was a fairly accurate prediction
because the Earth's intervention occurred just one day later, on
February 15. It was not a direct hit, only a weak G1 class
geomagnetic storm developed.

"On February 15 a magnetic filament eruption near the solar equator
and another CME heading towards Earth was observed. We can expect an
arrival on February 17-18, again as a weak G1 class geomagnetic
storm, perhaps intensifying to a mild G2 class storm on February 18.
Further we can expect to see more M-class solar flares in the next
few days. Also, an X-class flare is not out of the question. In
addition, the AR3226 sunspot group with an unstable magnetic field,
is directly facing the Earth."

Impossible but dramatic solar image: warns:

"GEOMAGNETIC STORM WATCH: Photographers, warm up your cameras. A CME
is heading for Earth, and it could spark an unusually good display
of Northern Lights when it arrives on Feb. 17-18. NOAA forecasters
say that moderate G2-class geomagnetic storms are possible. During
such storms, auroras have been seen in the USA as far south as,
e.g., New York and Idaho."

From the Western Washington DX Club email list:

WT8P posted at 1855 UTC on February 16:

"6M FT8 open to central and SA At 1845 UTC, LU9AEA (Argentina) and
TG9AJR (Guatemala) on FT8, 50.313 MHz."

W7YED posted at 1939 UTC, February 16:

"I was able to pick up 5 new ones on 6m in the space of about 20
minutes.  Nice opening!

"TI, CX, CE, LU, TG were all between +3 and -18."

A story about "vicious solar storms":

Aurora on Valentine's Day:

A video last week from Dr. Tamitha Skov, WX6SWW:

This weekend is the CW portion of the ARRL International DX Contest.
For details see: .

Send your tips, reports, observations, questions and comments to When reporting observations, don't forget to tell us
which mode you were operating.

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service 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 .

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for February 9 through 15, 2023 were 150, 190, 209,
197, 185, 206, and 140, with a mean of 182.4. 10.7 cm flux was
214.9, 207.8, 209.5, 199.7, 189.2, 179.7, and 173.7, with a mean of
196.4. Estimated planetary A indices were 21, 16, 11, 7, 4, 8, and
29, with a mean of 13.7. Middle latitude A index was 16, 12, 10, 5,
3, 6, and 23, with a mean of 10.7.


Instragram     Facebook     Twitter     YouTube     LinkedIn