[Ips-dsgr] ASWFC Daily Report - 19 December 25 issued 2330 UT on 19 Dec 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Sat Dec 20 10:30:51 AEDT 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/19 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 19 DECEMBER AND FORECAST FOR 20 DECEMBER - 22 DECEMBER
STATUS INDICATORS SOL:GREEN MAG:** YELLOW ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 19 Dec: R1
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 19 Dec: 118/70
1B. SOLAR FORECAST
20 Dec 21 Dec 22 Dec
Activity R0 R0 R0
Fadeouts None expected None expected None expected
10.7cm/SSN 118/70 116/68 116/68
COMMENT: Solar activity was at the R1 level during the UT day
19-Dec, with a single M1.0 flare observed, originating from the
western limb. There are currently three numbered regions on the
visible solar disk, with Active Region (AR) 4312 (N19E46, alpha)
being the largest. It has remained stable over the last 24 hours,
with the other numbered active regions in decay. Two new regions
appeared on the disk during the last UT day. One region appeared
at N28E48, with beta magnetic classification, while another region
was visible at N23E65 and appears to have an alpha classification.
Solar activity is expected to remain at the R0 level over 20-22
Dec. S0 solar radiation storm conditions were observed over the
past 24 hours, with the proton flux consistent with background
values across the last UT day. Solar radiation storm conditions
are forecast to continue to be at the S0 level over the period
20-22 Dec. No new Coronal Mass Ejections were observed over the
past UT day. The solar wind speed has gradually declined over
the last 24 hours, as a coronal hole moves past a geoeffective
position. The solar wind declined from 580-610 km/s early in
the UT day and is currently ranging between 480-520 km/s. The
interplanetary magnetic field strength (IMF, Bt) peaked at 5
nT during 19-Dec, with the North-South component (Bz) ranging
between -5 and +4 nT. The solar wind speed is forecast to continue
declining over UT days 20-21 Dec, before an increase is expected
due to another coronal hole moving into a geoeffective position
by 22-Dec.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 19 Dec: G0
Estimated Indices 19 Dec : A K
Australian Region 5 22111222
Cocos Island 3 11110221
Darwin 5 22210222
Townsville 5 22111222
Learmonth 5 22111222
Alice Springs 5 22110222
Gingin 6 31111222
Canberra 4 21110122
Kennaook Cape Grim 5 22211112
Hobart 5 22211212
Estimated Antarctic Regional K Indices 19 Dec :
Macquarie Island 4 22101211
Casey 31 55642333
Mawson 22 44323354
Observed Regional daily pc3 Indices 19 Dec :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 2 (Quiet)
Canberra 11 (Quiet)
Hobart 25 (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 19 Dec : A
Fredericksburg 6
Planetary 7
Observed AFr/Ap Indices 18 Dec : A K
Fredericksburg 11
Planetary 17 4343 2333
2B. MAGNETIC FORECAST
Date Ap Conditions
20 Dec 6 G0
21 Dec 12 G0, chance G1
22 Dec 22 G0-G1
COMMENT: G0 geomagnetic conditions were observed across the entire
Australian region for UT day 19-Dec. Periods of G1-G2 geomagnetic
conditions were observed in the Antarctic region. G0 geomagnetic
conditions are expected on 20 Dec. G0 conditions, with a chance
of G1, are expected late on 21-Dec, as an equatorial coronal
hole is expected to connect with Earth. This will increase to
G0-G1 conditions on 22-Dec due to coronal hole high-speed wind
stream effects.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
19 Dec Normal-fair Normal-fair Normal-fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
20 Dec Normal Normal Normal-fair
21 Dec Normal Normal Normal-fair
22 Dec Fair-normal Fair-normal Fair
COMMENT: HF radio propagation conditions on UT day 19-Dec were
Normal-Fair, with Fair-Poor conditions observed towards the end
of the UT day across the European region. Some degradations were
also seen during local night hours in the North American and
Asian regions. Conditions are expected to be Normal during 20-21
Dec, with degradations expected from 22-Dec due to coronal hole
high-speed wind stream effects.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
19 Dec 91
Observed Australian Regional MUFs
Cocos Island Region:
Depressed by 40% during local day.
Depressed by 20% during local night.
Niue Island Region:
Mostly near predicted monthly values.
Enhanced by 20% after local dawn.
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
20 Dec 95 Near predicted monthly values
21 Dec 90 Near predicted monthly values
22 Dec 75 About 10-15% below predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) were largely near
predicted values during UT day 19-Dec, with the exception of
the Cocos Islands, where depressions of 20-40% were observed.
Low frequency sporadic-E was observed, with spread F also observed
in the southern Australian region during local night hours. MUFs
are forecast to be near monthly predicted values throughout 20-21
Dec, declining to be 10-15% depressed on 22-Dec as high-speed
wind stream effects from an equatorial coronal hole commence.
Sporadic-E during local night hours may also be observed.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 18 Dec
Daily Proton Fluence >1 MeV: 1.0E+06
Daily Proton Fluence >10 MeV: 1.5E+04
Daily Electron Fluence >2 MeV: 8.00E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 9%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B4.8
DSCOVR Satellite Solar Wind Day Averaged Data for 18 Dec
Speed: 625 km/sec Density: 1.4 p/cc Temp: 410000 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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