[Ips-dsgr] ASWFC Daily Report - 17 December 25 issued 2330 UT on 17 Dec 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Thu Dec 18 10:30:49 AEDT 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/17 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 17 DECEMBER AND FORECAST FOR 18 DECEMBER - 20 DECEMBER
STATUS INDICATORS SOL:GREEN MAG:** YELLOW ** ION: ** YELLOW **
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 17 Dec: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 17 Dec: 119/71
1B. SOLAR FORECAST
18 Dec 19 Dec 20 Dec
Activity R0 R0 R0
Fadeouts None expected None expected None expected
10.7cm/SSN 118/70 115/66 110/60
COMMENT: Solar activity on UT day 17-Dec was R0, with no significant
solar flares. Overall the on disk solar regions are all relatively
small. Solar region AR4307 (S15W71, beta) produced isolated low
level C class flares and has shown minor growth as it approaches
the south west solar limb. Solar region AR4311 (N07E07, beta)
is growing. There are currently four numbered sunspot regions
on the solar disk and a new unnumbered small region has rotated
onto the solar disk over the northeast limb. Other regions are
stable or in decay. A large erupting solar prominence was observed
on the northern solar limb in GOES 304 imagery from 17/0133UT.
Solar activity is expected to be R0 over 18-20 Dec. No Earth
directed CMEs were observed on UT day 17-Dec. A wide angle north
directed (out of the ecliptic plane) CME was observed in LASCO
C2 from 17/0200UT in association with the northern solar limb
prominence eruption. A smaller northeast directed CME was also
observed during the activity. S0 solar radiation storm conditions
were observed on UT day 17-Dec. S0 solar radiation storm conditions
are expected over 18-20 Dec. On UT day 17-Dec the solar wind
speed was strong to very strong with an increasing trend due
to a coronal hole wind stream, ranging from 548-648km/s and is
currently at 648 km/s. The maximum total interplanetary field
strength (IMF, Bt) was 8 nT and the north-south IMF component
range (Bz) was +6 to -5 nT. The IMF Bz component fluctuated mildly
southward during the UT day. The solar wind speed is expected
to remain elevated for today.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 17 Dec: G0
Estimated Indices 17 Dec : A K
Australian Region 11 32223233
Cocos Island 11 22223333
Darwin 11 32223233
Townsville 10 32223223
Learmonth 14 32234333
Alice Springs 9 22223223
Gingin 14 32234333
Canberra 11 23323223
Kennaook Cape Grim 14 33323333
Hobart 13 33323233
Estimated Antarctic Regional K Indices 17 Dec :
Macquarie Island 17 33325323
Casey 48 57644344
Mawson 44 34544566
Observed Regional daily pc3 Indices 17 Dec :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 38 (Quiet to unsettled)
Canberra 53 (Unsettled)
Hobart 64 (Active)
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 17 Dec : A
Fredericksburg 10
Planetary 14
Observed AFr/Ap Indices 16 Dec : A K
Fredericksburg 6
Planetary 12 3322 2332
2B. MAGNETIC FORECAST
Date Ap Conditions
18 Dec 20 G0-G1
19 Dec 15 G0, chance G1
20 Dec 8 G0
COMMENT: ASWFC Geomagnetic Warning 100 was issued on 15 December
and is current for 17-18 Dec. G0 geomagnetic conditions were
observed in the Australian region on UT day 17-Dec. G1-G3 geomagnetic
conditions were observed in the Antarctic region. G0-G1 conditions
are expected on 18-Dec due to a coronal hole wind stream. G0,
chance G1 geomagnetic conditions are expected on 19-Dec.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
17 Dec Normal Normal Fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
18 Dec Normal Fair Fair
19 Dec Normal Fair-normal Fair
20 Dec Normal Normal Normal-fair
COMMENT: HF radio propagation conditions on UT day 17-Dec were
fair to normal. HF radio propagation conditions are expected
to be fair on 18-Dec and fair to normal on 19 Dec. Conditions
are expected to be normal on 20-Dec.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
17 Dec 82
Observed Australian Regional MUFs
Cocos Island Region:
Near predicted monthly values.
Niue Island Region:
Near predicted monthly values.
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
Nov 103
Dec 89
Jan 89
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
18 Dec 60 Depressed 15 to 20%/near predicted monthly values
19 Dec 75 Depressed 10 to 15%/near predicted monthly values
20 Dec 90 Near predicted monthly values
COMMENT: ASWFC HF Communications Warning 123 was issued on 17
December and is current for 18 Dec only. Maximum usable frequencies
(MUFs) in the Australian region on UT day 17-Dec were near predicted
values. Sporadic E was observed during the local day. MUFs are
expected to be 15-20% depressed to near predicted values for
18-Dec, 10-15% depressed on 19-Dec and near predicted monthly
values on 20-Dec. Mildly degraded HF conditions are possible
during local night hours 18-19 Dec.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 16 Dec
Daily Proton Fluence >1 MeV: 1.2E+06
Daily Proton Fluence >10 MeV: 1.5E+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: B5.0
DSCOVR Satellite Solar Wind Day Averaged Data for 16 Dec
Speed: 583 km/sec Density: 1.7 p/cc Temp: 334000 K Bz: 4 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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