[Ips-dsgr] ASWFC Daily Report - 18 December 25 issued 2330 UT on 18 Dec 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Fri Dec 19 10:30:50 AEDT 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/18 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 18 DECEMBER AND FORECAST FOR 19 DECEMBER - 21 DECEMBER
STATUS INDICATORS SOL:GREEN MAG:** YELLOW ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 18 Dec: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 18 Dec: 116/68
1B. SOLAR FORECAST
19 Dec 20 Dec 21 Dec
Activity R0 R0 R0
Fadeouts None expected None expected None expected
10.7cm/SSN 115/66 110/60 110/60
COMMENT: Solar activity on UT day 18-Dec was R0, with current
on disk solar regions all small in size. Solar region AR4307
(S15W84, beta) and AR4305 (S24W82, beta) are rotating off disk
over the southwest solar limb. Region AR4311 (N04W11, beta) whilst
increasing in longitudinal extent the umbral area is declining
and is in overall slow decay. Region AR4308 (N08W20, alpha) has
almost completely decayed. New region AR4312 (N19E56, alpha)
is stable. Minor low level C class flaring was observed from
AR4307, AR4308 and AR4312. There are currently five numbered
sunspot regions on the solar disk. Other regions are stable or
in decay. Solar activity is expected to be R0 over 19-21 Dec.
A very small 5 degree long solar filament located at S15E60 erupted
during the interval 18/1538-1619UT. No Earth directed CMEs were
observed on UT day 18-Dec. A southwest CME was observed from
18/0400UT in LASCO C2 imagery. This CME could not be correlated
to the solar disk and CME analysis using LASCO and STEREO-A imagery
suggests a longitude of W120 degrees. No CME appeared associated
with the small filament eruption. S0 solar radiation storm conditions
were observed on UT day 18-Dec. S0 solar radiation storm conditions
are expected over 19-21 Dec. On UT day 18-Dec the solar wind
speed was strong with a declining trend due to a coronal hole
wind stream from a coronal hole now well west of the solar central
meridian. Solar wind speed ranged from 700-570 km/s and is currently
at 590 km/s. The maximum total interplanetary field strength
(IMF, Bt) was 7 nT and the north-south IMF component range (Bz)
was +5 to -6 nT. The IMF Bz component fluctuated mildly southward
during the first half of the UT day. The solar wind speed is
expected to remain elevated with a slow declining trend for today.
Another coronal hole is visible in the eastern solar hemisphere
at solar longitude E30. Solar wind 27 day recurrent patterns
suggest a broad period of elevated solar wind speed is possible
from mid 21-Dec to 27-Dec, with recurrent patterns more reliable
across previous solar rotations for the interval 23-24 Dec.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 18 Dec: G0
Estimated Indices 18 Dec : A K
Australian Region 11 32332322
Cocos Island 8 32222321
Darwin 10 32232322
Townsville 11 32332322
Learmonth 12 42332322
Alice Springs 11 32332322
Gingin 15 42332432
Canberra 12 32432322
Kennaook Cape Grim 15 32442422
Hobart 13 32442321
Estimated Antarctic Regional K Indices 18 Dec :
Macquarie Island 28 33563521
Casey 42 66643433
Mawson 44 54443665
Observed Regional daily pc3 Indices 18 Dec :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 2 (Quiet)
Alice Springs 0 (Quiet)
Gingin 38 (Quiet to unsettled)
Canberra 58 (Unsettled)
Hobart 22 (Quiet to unsettled)
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 18 Dec : A
Fredericksburg 14
Planetary 18
Observed AFr/Ap Indices 17 Dec : A K
Fredericksburg 10
Planetary 18 3332 3345
2B. MAGNETIC FORECAST
Date Ap Conditions
19 Dec 15 G0
20 Dec 8 G0
21 Dec 16 Mostly G0, G1 period possible at the end of the
UT day.
COMMENT: G0 geomagnetic conditions were observed in the Australian
region on UT day 18-Dec. Geomagnetic activity was mildly elevated
due to a coronal hole wind stream. G1-G2 geomagnetic conditions
were observed in the Antarctic region. Planetary geomagnetic
conditions briefly reached G1 for the last Kp period on 17-Dec
and were at G0 on 18-Dec. G0 conditions are expected for 19-20
Dec. Geomagnetic 27 day recurrence patterns suggest that G1 periods
are possible at times from late 21-Dec to 23-Dec, with the more
persistent pattern of geomagnetic activity for 23-Dec.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
18 Dec Normal Fair-normal Fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
19 Dec Normal Normal Fair-normal
20 Dec Normal Normal Normal
21 Dec Normal Normal Normal-fair
COMMENT: HF radio propagation conditions on UT day 18-Dec were
fair to normal. HF radio propagation conditions are expected
to be normal on for 19-21 Dec. Mildly degraded HF conditions
for middle to high latitudes may be experienced from 22-Dec.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
18 Dec 96
Observed Australian Regional MUFs
Cocos Island Region:
Mostly near predicted monthly values.
Niue Island Region:
Mostly near predicted monthly values.
Northern Australian Region:
Near predicted monthly values during local day.
Enhanced by 15% during local night.
15% depressed after local dawn.
Southern Australian Region:
Depressed 15% early in the UT day then
near predicted monthly values.
15% depressed after local dawn.
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
19 Dec 75 Depressed 10 to 15%/near predicted monthly values
20 Dec 85 Near predicted monthly values
21 Dec 85 Near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) in the Australian
region on UT day 18-Dec were 15% depressed to 15% enhanced. Sporadic
E was observed at times during the local day. MUFs are expected
to be initially 15% depressed then recovering on 19-Dec and near
predicted monthly values for 20-21 Dec. Mildly degraded HF conditions
may be experienced for the southern Australian region during
22-23 Dec in association with recurrent 27 day geomagnetic activity
patterns.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 17 Dec
Daily Proton Fluence >1 MeV: 8.4E+05
Daily Proton Fluence >10 MeV: 1.4E+04
Daily Electron Fluence >2 MeV: 4.00E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 6%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B6.4
DSCOVR Satellite Solar Wind Day Averaged Data for 17 Dec
Speed: 584 km/sec Density: 1.6 p/cc Temp: 228000 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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