[Ips-dsgr] ASWFC Daily Report - 21 December 25 issued 2330 UT on 21 Dec 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Mon Dec 22 10:30:51 AEDT 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/21 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 21 DECEMBER AND FORECAST FOR 22 DECEMBER - 24 DECEMBER
STATUS INDICATORS SOL:** YELLOW ** MAG:** RED ** ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 21 Dec: R1
Flares Max Fadeout Freq. Sectors
M1.3 1827UT possible lower East Pacific/
North American
Observed 10.7 cm flux/Equivalent Sunspot Number for 21 Dec: 124/77
1B. SOLAR FORECAST
22 Dec 23 Dec 24 Dec
Activity R0-R1 R0-R1 R0-R1
Fadeouts Possible Possible Possible
10.7cm/SSN 130/84 135/89 140/94
COMMENT: Solar activity was at the R1 level on UT day 21-Dec,
with an M1.3 flare observed at 21/1827UT, originating from Active
Region (AR) 4316 (S07E27, beta-gamma). This region has increased
in size and magnetic complexity over the last 24 hours. It is
one of four regions on the visible solar disk. AR4311 (N04W55,
alpha) also exhibited growth, before decaying late in the UT
day. Active Region 4317 (N13E66, beta) continues to rotate from
the eastern limb, with additional nearby spots also rotating
into view. All other regions appear stable. Solar activity is
expected to be at R0-R1 over the period 22-24 Dec, given the
past flare activity of AR4316. S0 solar radiation storm conditions
were observed over the past 24 hours, with the proton flux remaining
at background values. S0 conditions are forecast to continue
over the period 22-24 Dec. No Earth-directed Coronal Mass Ejections
have been observed over the past UT day with available coronograph
imagery. Solar wind speeds increased over 21-Dec as Earth connected
with a coronal hole high-speed wind stream, increasing from 380-420
km/s early in the UT day to reach 620-660 km/s by 21/0900UT.
An additional small increase in wind speed was observed at 21/2000UT,
with speeds now ranging between 680-720 km/s. An increase in
the interplanetary magnetic field strength (IMF, Bt) accompanied
the increase in wind speed, and peaked at 15 nT. The north-south
component (Bz) ranged from -12 to +9 nT over this period, with
periods of extended southward Bz between 21/0515-0615UT and 21/1250-1450UT.
The solar wind speed is forecast to remain very strong over 22-23
Dec, before decreasing on 24-Dec as the ongoing effects of the
coronal hole high speed wind stream wane.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 21 Dec: G0
Estimated Indices 21 Dec : A K
Australian Region 18 23344334
Cocos Island 13 22333333
Darwin 20 33334335
Townsville 19 33344334
Learmonth 19 33344334
Alice Springs 17 23344333
Gingin 15 32334333
Canberra 18 23434334
Kennaook Cape Grim 20 23444334
Hobart 23 24444434
Estimated Antarctic Regional K Indices 21 Dec :
Macquarie Island 31 23356543
Casey 47 47644444
Mawson 64 55546567
Observed Regional daily pc3 Indices 21 Dec :
Darwin 13 (Quiet)
Townsville 7 (Quiet)
Learmonth 6 (Quiet)
Alice Springs 5 (Quiet)
Gingin 37 (Quiet to unsettled)
Canberra 35 (Quiet to unsettled)
Hobart 65 (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 21 Dec : A
Fredericksburg 16
Planetary 21
Observed AFr/Ap Indices 20 Dec : A K
Fredericksburg 4
Planetary 6 2111 2223
2B. MAGNETIC FORECAST
Date Ap Conditions
22 Dec 28 G0-G1
23 Dec 28 G0-G1
24 Dec 16 G0, chance G1
COMMENT: ASWFC Geomagnetic Warning 101 was issued on 21 December
and is current for 21-23 Dec. G0 geomagnetic conditions were
observed in the Australian region for UT day 21-Dec, with a period
of G1 observed in Darwin late in the UT day. Periods of G1-G3
geomagnetic activity were observed in the Antarctic region, with
G1 conditions reported over the same time period at the planetary
level due to connection with a trans-equatorial coronal hole
high-speed wind stream. G0-G1 geomagnetic conditions are expected
on 22-23 Dec, due to ongoing high speed wind stream effects.
These conditions will ease to G0, chance G1 on 24-Dec as this
coronal hole moves beyond a geoeffective position.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
21 Dec Normal-fair Normal-fair Normal-fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
22 Dec Fair-normal Fair-normal Fair
23 Dec Fair-normal Fair-normal Fair
24 Dec Normal-fair Normal-fair Fair-normal
COMMENT: HF radio propagation conditions on UT day 21-Dec were
Normal-Fair, with some mild depressions in the European and North
American regions during local night hours. MUFs in the European
region were up to 15% below predicted values during local night
hours over this period. Some depressions were seen in the Australian
and Asian regions during the local morning hours. These degradations
are expected to continue on 22-23 Dec, due to ongoing coronal
hole high-speed wind stream effects, before recovering on 24-Dec.
Shortwave fadeouts are possible.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
21 Dec 122
Observed Australian Regional MUFs
Cocos Island Region:
Near predicted monthly values during local day.
Enhanced by 30% during local night.
Niue Island Region:
Depressed by 20% during local day.
Near predicted monthly values during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Enhanced by 35% during local night.
Depressed by 25% after local dawn.
Southern Australian Region:
Mostly near predicted monthly values.
Depressed by 20% 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
22 Dec 70 15 to 20% below predicted monthly values
23 Dec 70 15 to 20% below predicted monthly values
24 Dec 90 Near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) were mostly near predicted
values during UT day 21-Dec, with some enhancements observed
during local night hours in the Northern Australian region, and
20-25% depressions observed during local morning across the northern
and southern Australian regions. Low frequency sporadic-E was
observed, particularly in the Brisbane, Townsville, and Perth
regions. Spread F was also observed in Hobart during local night
hours. MUFs are forecast to be 15-20% depressed on 22-23 Dec
due to ongoing high-speed wind stream effects from an equatorial
coronal hole. These conditions are expected to improve towards
monthly predicted values over 24-Dec as high speed wind stream
effects subside. Sporadic-E during local night hours may also
be observed. Shortwave fadeouts are possible.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 20 Dec
Daily Proton Fluence >1 MeV: 2.5E+06
Daily Proton Fluence >10 MeV: 1.5E+04
Daily Electron Fluence >2 MeV: 2.30E+08 (moderate fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability:16%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B6.5
DSCOVR Satellite Solar Wind Day Averaged Data for 20 Dec
Speed: 442 km/sec Density: 7.6 p/cc Temp: 51200 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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