[Ips-dsgr] ASWFC Daily Report - 20 December 25 issued 2330 UT on 20 Dec 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Sun Dec 21 10:30:51 AEDT 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/20 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 20 DECEMBER AND FORECAST FOR 21 DECEMBER - 23 DECEMBER
STATUS INDICATORS SOL:** YELLOW ** MAG:** RED ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 20 Dec: R1
Flares Max Fadeout Freq. Sectors
M1.0 0753UT possible lower Mid East/Indian
Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Dec: 120/72
1B. SOLAR FORECAST
21 Dec 22 Dec 23 Dec
Activity R0, chance R1 R0, chance R1 R0, chance R1
Fadeouts Possible Possible Possible
10.7cm/SSN 120/72 120/72 125/78
COMMENT: Solar activity reached the R1 level on UT day 20-Dec,
with an M1.0 flare observed at 20/0753UT from newly numbered
Active Region 4315 (N21E49, beta). This region is one of six
numbered regions on the visible solar disk and showed growth
over the past 24 hours, with Active Regions 4311 (N04W41, beta)
and 4314 (N25E35, beta) also showing growth during this period.
The largest region on the solar disk, AR4312 (N25E36, alpha),
appeared stable. Two new Active Regions appeared on the disk
during the last UT day. The first, numbered 4316, appeared at
S07E41, and appears to have beta magnetic classification. The
second region, AR4317, has rotated onto the front side of the
disk at N13E74, with its magnetic classification affected by
limb foreshortening. Solar activity is expected to be at R0 with
a chance of R1 over the period 21-23 Dec, given the growth of
several active regions on the Sun. S0 solar radiation storm conditions
were observed throughout 20-Dec, and are forecast to continue
at the S0 level over the period 21-23 Dec. Two Coronal Mass Ejections
were observed in the last 24 hours, both of which were not considered
geoeffective. The solar wind speed has decreased over the past
UT day, dropping from 460-490 km/s early in the UT day to 390-420
km/s currently. The interplanetary magnetic field strength (IMF,
Bt) peaked at 6 nT during this time, with the North-South component
(Bz) ranging between -3 and +4 nT. The solar wind speed is expected
to trend towards background across much of 21-Dec, until the
Earth connects with a trans-equatorial coronal hole late in the
UT day. The solar wind speed will then increase due to these
high speed wind stream effects.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 20 Dec: G0
Estimated Indices 20 Dec : A K
Australian Region 5 11212122
Cocos Island 3 11112111
Darwin 6 11212123
Townsville 5 21112122
Learmonth 5 11212222
Alice Springs 5 11212122
Gingin 5 11212221
Canberra 4 11112112
Kennaook Cape Grim 4 11212112
Hobart 4 11212112
Estimated Antarctic Regional K Indices 20 Dec :
Macquarie Island 4 10003212
Casey 15 44423222
Mawson 17 42424333
Observed Regional daily pc3 Indices 20 Dec :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 0 (Quiet)
Canberra 19 (Quiet)
Hobart 6 (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 20 Dec : A
Fredericksburg 6
Planetary 6
Observed AFr/Ap Indices 19 Dec : A K
Fredericksburg 4
Planetary 6 2211 1222
2B. MAGNETIC FORECAST
Date Ap Conditions
21 Dec 12 G0, chance G1
22 Dec 28 G0-G1
23 Dec 28 G0-G1
COMMENT: G0 geomagnetic conditions were observed across the Australian
and Antarctic regions throughout UT day 20-Dec. G0 geomagnetic
conditions were also observed at the planetary scale. G0 conditions,
with a chance of G1, are expected on 21-Dec, with a high speed
wind stream from an equatorial coronal hole expected to connect
with the Earth late on UT day 21-Dec. G0-G1 conditions are then
expected during 22-23 Dec due to these wind stream effects.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
20 Dec Normal Normal Normal-fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
21 Dec Normal Normal Normal-fair
22 Dec Fair Fair Fair-poor
23 Dec Fair Fair Fair-poor
COMMENT: HF radio propagation conditions on UT day 20-Dec were
Normal-Fair, with Fair conditions observed during daylight hours
across the European and Asian regions. These conditions trended
towards Fair-Poor in some northern polar regions. Some degradations
were also seen during local night hours in the North and Central
American regions. Conditions are expected to remain Normal on
21-Dec, with degradations expected during 22-23 Dec due to coronal
hole high-speed wind stream effects. Minor shortwave fadeouts
are possible.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
20 Dec 99
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
21 Dec 95 Near predicted monthly values
22 Dec 70 Depressed 10 to 15%/near predicted monthly values
23 Dec 70 Depressed 10 to 15%/near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) were largely near
predicted values across the entire Australian region during UT
day 20-Dec. Low frequency sporadic-E was observed during local
night hours, particularly in Brisbane. MUFs are forecast to be
near monthly predicted values throughout 21 Dec, declining to
10–15% below predicted values on 22-23 Dec as high-speed wind
stream effects from an equatorial coronal hole commence. Sporadic-E
during local night hours may also be observed. Minor shortwave
fadeouts are possible.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 19 Dec
Daily Proton Fluence >1 MeV: 5.1E+05
Daily Proton Fluence >10 MeV: 1.5E+04
Daily Electron Fluence >2 MeV: 1.10E+08 (moderate fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability:11%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B5.9
DSCOVR Satellite Solar Wind Day Averaged Data for 19 Dec
Speed: 534 km/sec Density: 1.2 p/cc Temp: 155000 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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