[Ips-dsgr] ASWFC Daily Report - 21 September 25 issued 2330 UT on 21 Sep 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Mon Sep 22 09:30:49 AEST 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/21 SEPTEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 21 SEPTEMBER AND FORECAST FOR 22 SEPTEMBER - 24 SEPTEMBER
STATUS INDICATORS SOL:** YELLOW ** MAG:** YELLOW ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 21 Sep: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 21 Sep: 176/130
1B. SOLAR FORECAST
22 Sep 23 Sep 24 Sep
Activity R0, chance of R1 R0, chance of R1 R0, chance of R1
Fadeouts Possible Possible Possible
10.7cm/SSN 180/133 180/133 185/138
COMMENT: Solar activity on UT day 21-Sep was at R0. There are
currently ten numbered sunspot regions on the solar disk. Of
note, AR4217 (S14W14, beta-gamma) shows growth in both intermediates
and trailer spots and has produced a number of low level C class
flares over the UT day. AR4223 (S15W04 gamma) continues to show
some growth in its small spots but is becoming magnetically less
complex. AR4226 (S11E57 beta) has shown rapid growth in its trailer
spots. It appears beta complexity but it is hard to classify
noting its proximity to the eastern limb. Other solar regions
on the visible solar disk are either stable or in decay. AR4225
(N12E15, beta) has shown some growth and some decay in its small
spots south of the main spot. Solar activity is expected to be
R0,chance R1 over 22-24 Sep. A small solar filament centred around
S20W05-W10 appeared to disappear in GONG H-alpha imagery during
the interval 21/0400-0620UT. A large slowly erupting filament
on the high northeastern limb was visible late in the UT day.
No Earth-directed CMEs have been observed. No CME appeared to
be associated with the solar filament activity in the southern
solar quadrant. A narrow finger of plasma ejecta on the NW limb
was visible around 21/1813UT on GOES SUVI 304. The activity on
the northeast and northwest limbs appear to be associated with
northward non-Earth directed CME's just becoming visible in LASCO
C2. S0 solar radiation storm conditions were observed on UT day
21-Sep. S0 solar radiation storm conditions are expected over
22-24 Sep. A moderately sized isolated coronal hole is visible
in the northwestern solar hemisphere with centre at approximately
N25W25. The solar wind on UT day 21-Sep continued to slowly decline.
The solar wind speed ranged from 340 km/s to 290 km/s and is
currently at 300 km/s. The peak total interplanetary field strength
(IMF, Bt) was 7 nT and the north-south IMF component range (Bz)
was +5 to -4 nT. The solar wind is expected to be near background
levels through most of the day with a moderate increase in solar
wind speed expected from late 22-Sep due to the solar wind stream
from the coronal hole now west of the solar central meridian.
The US GOES geosynchronous satellite 2MeV energy electron detector
has remained elevated. 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 21 Sep: G0
Estimated Indices 21 Sep : A K
Australian Region 3 12201201
Cocos Island 2 12111100
Darwin 4 12202202
Townsville 6 22212212
Learmonth 5 22202202
Alice Springs 3 11202201
Gingin 4 22201211
Canberra 3 11201201
Kennaook Cape Grim 3 11201201
Hobart 3 11201211
Estimated Antarctic Regional K Indices 21 Sep :
Macquarie Island 1 00110100
Casey 8 23410211
Mawson 7 23201223
Observed Regional daily pc3 Indices 21 Sep :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 0 (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 21 Sep : A
Fredericksburg 8
Planetary 10
Observed AFr/Ap Indices 20 Sep : A K
Fredericksburg 5
Planetary 5 2221 1001
2B. MAGNETIC FORECAST
Date Ap Conditions
22 Sep 17 G0, chance of G1 late in the UT day.
23 Sep 20 G0-G1
24 Sep 13 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 21-Sep.
Periods of G1 geomagnetic activity are possible from late 22-Sep
and G0-G1 for 23-24 Sep due to a coronal hole wind stream.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
21 Sep Normal Normal Normal-fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
22 Sep Normal Normal-fair Fair
23 Sep Normal Normal-fair Fair
24 Sep Normal Normal Normal-fair
COMMENT: HF radio propagation conditions on UT day 21-Sep were
mostly normal. HF radio propagation conditions are expected to
be mostly normal on 22-Sep. HF conditions at middle to high latitudes
may become mildly degraded from late 22-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
21 Sep 114
Observed Australian Regional MUFs
Cocos Island Region:
No data available during local day.
No data available during local night.
Niue Island Region:
Near predicted monthly values during local day.
Enhanced by 25% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Enhanced by 20% during local night.
Southern Australian Region:
Enhanced by 15% during local day.
Enhanced by 20% during local night.
Enhanced by 25% after local dawn.
Antarctic Region (Casey/Davis/Mawson):
Near predicted monthly values 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
22 Sep 110 Near predicted monthly values
23 Sep 100 Near predicted monthly values
24 Sep 100 Near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) in the Australian
region on UT day 21-Sep were near predicted values to 25% enhanced.
Spread F was observed in Perth over local night. On 22-Sep HF
conditions are likely to be enhanced by 15% during the local
day then mildly degraded conditions may be experienced during
local night hours for the southern Australian region due to an
anticipated mild increase in geomagnetic activity from a coronal
hole wind stream. MUFs are expected to be near predicted values
over 22-24 Sep. Mildly degraded conditions are expected during
local night hours on 23-Sep. Isolated minor shortwave fadeouts
are possible.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 20 Sep
Daily Proton Fluence >1 MeV: 5.0E+06
Daily Proton Fluence >10 MeV: 1.6E+04
Daily Electron Fluence >2 MeV: 2.40E+08 (moderate fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability:17%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B9.4
DSCOVR Satellite Solar Wind Day Averaged Data for 20 Sep
Speed: 350 km/sec Density: 2.6 p/cc Temp: 36800 K Bz: 0 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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