[Ips-dsgr] ASWFC Daily Report - 21 September 26 issued 2330 UT on 21 Sep 2026 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Tue Sep 22 09:30:52 AEST 2026
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/21 SEPTEMBER 2026
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 21 SEPTEMBER AND FORECAST FOR 22 SEPTEMBER - 24 SEPTEMBER
STATUS INDICATORS SOL:GREEN MAG:** YELLOW ** ION: ** YELLOW **
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: 104/53
1B. SOLAR FORECAST
22 Sep 23 Sep 24 Sep
Activity R0, chance R1 R0, chance R1 R0, chance R1
Fadeouts None expected None expected None expected
10.7cm/SSN 105/54 105/54 100/48
COMMENT: Solar flare activity was at the R0 level on the 21-Sep.
Solar flare activity is forecast at the R0 level, with a chance
of R1 over 22-24 Sep. Active Region (AR) 4534 (N07W15, beta)
has been dynamic in nature, with sunspot decay followed by later
growth in the UT day. The past 24 hours has also seen the development
of AR 4536 (S03E03, beta), 4537 (N07W10, beta) and 4538 (N12W08,
beta). AR 4532 has now decayed. All other sunspots are stable.
Solar radiation storm conditions were at the S0 level on the 21-Sep,
with the solar proton flux consistent with background levels.
S0 solar radiation storm conditions are forecast over 22-24 Sep.
No Earth-directed coronal mass ejections (CMEs) were observed
over the past UT day. The solar wind environment was stable ranging
from 315-370 km/s. The interplanetary magnetic field strength
(IMF, Bt) was stable over the UT day, peaking at 5 nT. The north-south
component (Bz) ranged between -4 and +3 nT over the same period.
The solar wind speed is expected to remain at background levels
over most of the 22-Sep, before rising late in UT day, as the
Earth begins to connect with a coronal hole high speed wind stream.
The solar wind speed will continue to rise on the 23-Sep due to this
high speed wind stream, remaining elevated throughout the 24-Sep.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 21 Sep: G0
Estimated Indices 21 Sep : A K
Australian Region 1 11000001
Cocos Island 0 11000000
Darwin 2 21100002
Townsville 2 21000011
Learmonth 1 21000001
Alice Springs 1 11000001
Gingin 1 20000001
Canberra 0 10000001
Kennaook Cape Grim 1 11000001
Hobart 1 11000001
Estimated Antarctic Regional K Indices 21 Sep :
Casey 7 33310102
Mawson 11 32000135
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)
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 3
Planetary 3
Observed AFr/Ap Indices 20 Sep : A K
Fredericksburg 6
Planetary 6 2321 1001
2B. MAGNETIC FORECAST
Date Ap Conditions
22 Sep 4 G0
23 Sep 24 G1
24 Sep 24 G1
COMMENT: Geomagnetic conditions in the Australian region were
at the G0 level over the 21-Sep, with G0 conditions also recorded
at the planetary scale. G0 conditions were reported in the Antarctic
region, except for one period of G1 in Mawson. G0 conditions
are forecast on the 22-Sep, with G1 forecast on 23-24 Sep due to
high speed wind stream effects and the solar equinox.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
21 Sep Normal Normal Normal
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
22 Sep Normal Normal Normal
23 Sep Normal Normal-fair Fair
24 Sep Normal Normal-fair Fair
COMMENT: Global high-frequency (HF) radio propagation conditions
on 21-Sep were mostly normal. Global HF propagation conditions
are forecast to be mostly normal on the 22-Sep, with mild degradations
expected on 23-24 Sep due to forecast geomagnetic activity.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
21 Sep 65
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.
Depressed by 15% during local night.
Northern Australian Region:
Near predicted monthly values.
Southern Australian Region:
Near predicted monthly values.
Antarctic Region (Casey/Davis/Mawson):
Near predicted monthly values over the UT day.
Monthly T index:
Month T index
Aug 66
Sep 62
Oct 60
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
22 Sep 60 Near predicted monthly values
23 Sep 40 Depressed 15%/near predicted monthly values
24 Sep 40 Depressed 15%/near predicted monthly values
COMMENT: Maximum Usable Frequencies (MUFs) in the Australian
region were mostly near predicted monthly values over UT day
21-Sep, with depressions of 15% observed at Niue Island during
local night. Mild spread-F was observed at Perth and Canberra.
MUFs are forecast to near predicted monthly values on the 22-Sep
and depressed by up to 15% over 23-24 Sep due to forecast geomagnetic
activity.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 20 Sep
Daily Proton Fluence >1 MeV: 3.6E+05
Daily Proton Fluence >10 MeV: 2.0E+04
Daily Electron Fluence >2 MeV: 2.90E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 5%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B2.8
Solar Wind Day Averaged Data for 20 Sep
Speed: 399 km/sec Density: 2.1 p/cc Temp: 86700 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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