[Ips-dsgr] ASWFC Daily Report - 20 September 25 issued 2330 UT on 20 Sep 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Sun Sep 21 09:30:48 AEST 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/20 SEPTEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 20 SEPTEMBER AND FORECAST FOR 21 SEPTEMBER - 23 SEPTEMBER
STATUS INDICATORS SOL:** YELLOW ** MAG:** YELLOW ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 20 Sep: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Sep: 166/120
1B. SOLAR FORECAST
21 Sep 22 Sep 23 Sep
Activity R0,chance R1 R0,chance R1 R0,chance R1
Fadeouts Possible Possible Possible
10.7cm/SSN 165/119 170/124 170/124
COMMENT: Solar activity on UT day 20-Sep was at R0. Solar regions
on the visible solar disk are small to medium in size. Of the
more notable regions solar region AR4223 (S15E10, gamma) which
consists of a number of smaller spots, shows continued growth
in its leader spots and exhibits some magnetic complexity. Solar
region AR4225 (N12E28, beta) is slightly growing, with penumbral
development south of its main spot where an area of very small
magnetic complexity may be developing. Solar region AR4220 (S18W38,
beta) trailer spots have declined and appear to be spreading
out and breaking up, with a rapid decline in trailer spot umbral
area. Solar region AR4216 (N11W37, alpha) continues to decay
and produced isolated low level C class flares. There are currently
ten numbered sunspot regions on the solar disk. Other solar regions
on the visible solar disk are small and are either stable or
in decay. Solar activity is expected to be R0,chance R1 over
21-23 Sep. A solar filament centred ar S25E60 was active and
appeared to slowly partial disappear in GONG H-alpha imagery
during the interval 20/0440-0930UT. No Earth-directed CMEs have
been observed up to 20/2024UT. No CME appeared to be associated
with the solar filament activity in the southeast solar quadrant.
S0 solar radiation storm conditions were observed on UT day 20-Sep.
S0 solar radiation storm conditions are expected over 21-23 Sep.
A moderately sized isolated coronal hole is visible in the northern
solar hemisphere just west of the solar central meridian with
centre solar latitude at approximately N25. The solar wind on
UT day 20-Sep continued to slowly decline. The solar wind speed
ranged from 390 km/s to 340 km/s and is currently at 340 km/s.
The peak total interplanetary field strength (IMF, Bt) was 3
nT and the north-south IMF component range (Bz) was +3 to -3
nT. The magnitude of the IMF has been very small. The solar wind
is expected to be near background levels over on 21-Sep. A moderate
increase in solar wind speed is expected from late 22-Sep due
to the solar wind stream from the coronal hole now just west
of the solar central meridian. Old solar region AR4197 appears
to have returned as minor region AR4227. The US GOES geosynchronous
satellite 2MeV energy electron detector has been elevated over
16-20 Sep. An elevated 2MeV electron flux is statistically associated
with an increased risk of geosynchronous satellite anomalies.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 20 Sep: G0
Estimated Indices 20 Sep : A K
Australian Region 1 11110001
Cocos Island 1 11200000
Darwin 2 21110002
Townsville 2 21110011
Learmonth 2 12100001
Alice Springs 2 21100001
Gingin 1 11100001
Canberra 1 11110000
Kennaook Cape Grim 2 11210001
Hobart 2 10210001
Estimated Antarctic Regional K Indices 20 Sep :
Macquarie Island 1 00210000
Casey 6 32330001
Mawson 12 23330005
Observed Regional daily pc3 Indices 20 Sep :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 6 (Quiet)
Canberra 0 (Quiet)
Hobart 0 (Quiet)
Pc3 pulsations are high frequency (10-45 second period) variations
of the Earths magnetic field. Daily pc3-indices are the daily sum
of 20 minute pc3-indices for that station and have been shown to be
well correlated with rejection of high resolution aeromagnetic
survey flight-line data.
NOTE: Indices may have been generated from data obtained in
cooperation with the following organisations: Geoscience Australia,
University of Newcastle Space Physics Group, Australian Government
Antarctic Division and International Center for Space Weather
Science and Education, Japan.
Estimated AFr/Ap Indices 20 Sep : A
Fredericksburg 5
Planetary 5
Observed AFr/Ap Indices 19 Sep : A K
Fredericksburg 7
Planetary 3 1111 2011
2B. MAGNETIC FORECAST
Date Ap Conditions
21 Sep 5 G0
22 Sep 17 G0, G1 periods late in UT day
23 Sep 20 G0-G1
COMMENT: ASWFC Geomagnetic Warning 70 was issued on 19 September
and is current for 22-23 Sep. G0 geomagnetic conditions were
observed in the Australian and Antarctic regions on UT day 20-Sep.
G0 geomagnetic conditions are expected on 21-Sep. Periods of
G1 geomagnetic activity are possible from late 22-Sep and on
23-Sep due to a coronal hole wind stream.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
20 Sep Normal Normal Fair-normal
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
21 Sep Normal Normal Normal
22 Sep Normal Normal-fair Normal-Fair
23 Sep Normal Fair-normal Fair
COMMENT: HF radio propagation conditions on UT day 20-Sep were
mostly normal. HF radio propagation conditions are expected to
be mostly normal on 21-Sep. HF conditions at middle to high latitudes
may become mildly degraded from late 22-23 Sep in association
with a mild increase in geomagnetic activity from a coronal hole
wind stream. Isolated minor shortwave fadeouts are possible.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
20 Sep 107
Observed Australian Regional MUFs
Cocos Island Region:
No data available.
Niue Island Region:
Near predicted monthly values during local day.
Enhanced by 30% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Enhanced by 15-50% during local night.
Southern Australian Region:
Mostly near predicted monthly values.
Enhanced by 25% after local dawn.
Antarctic Region (Casey/Davis/Mawson):
Enhanced by 15% over the UT day.
Monthly T index:
Month T index
Aug 96
Sep 92
Oct 90
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
21 Sep 100 Near predicted monthly values
22 Sep 100 Near predicted monthly values
23 Sep 100 Near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) in the Australian
region on UT day 20-Sep were near predicted values to 50% enhanced,
with enhancements of 50% observed at Darwin during local night
hours. Other northern Australian region sites were enhanced by
15% during the local night. MUFs are expected to be near predicted
values over 21-23 Sep. Mildly degraded HF conditions may be experienced
during local night hours for the southern Australian region during
22-23 Sep, due to an anticipated mild increase in geomagnetic
activity from a coronal hole wind stream. Isolated minor shortwave
fadeouts are possible.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 19 Sep
Daily Proton Fluence >1 MeV: 1.6E+06
Daily Proton Fluence >10 MeV: 1.6E+04
Daily Electron Fluence >2 MeV: 2.90E+08 (moderate fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability:18%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: C1.1
DSCOVR Satellite Solar Wind Day Averaged Data for 19 Sep
Speed: 454 km/sec Density: 0.6 p/cc Temp: 56600 K Bz: 1 nT
(Courtesy Space Weather Prediction Center, Boulder USA)
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Australian Space Weather Forecasting Centre
Bureau of Meteorology
ASWFC at bom.gov.au
www.bom.gov.au | www.sws.bom.gov.au
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