[Ips-dsgr] ASWFC Daily Report - 21 April 26 issued 2330 UT on 21 Apr 2026 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Wed Apr 22 09:30:43 AEST 2026
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/21 APRIL 2026
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 21 APRIL AND FORECAST FOR 22 APRIL - 24 APRIL
STATUS INDICATORS SOL:** YELLOW ** MAG:GREEN ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 21 Apr: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 21 Apr: 112/63
1B. SOLAR FORECAST
22 Apr 23 Apr 24 Apr
Activity R0, chance R1 R0, chance R1 R0, chance R1
Fadeouts Possible Possible Possible
10.7cm/SSN 115/66 120/72 120/72
COMMENT: Solar activity on UT day 21-Apr was R0, with no solar
flares. There are currently three numbered sunspot regions on
the solar disk. Active region (AR) 4419 (N15W36, beta) remained
mostly stable, although a new region has begun to grow underneath
it. New region AR 4420 (N16E52, beta) showed fast growth and
produced a number of C-class flares. All other sunspots are either
stable or in decay. Solar activity is expected to be R0, chance
R1 over 22-24 Apr.
A CME was observed from 0312 UT associated with a filament liftoff from
0209 UT in the north. This CME is not expected to impact the Earth. No other
front-side CMEs were observed in available imagery.
S0 solar radiation storm conditions were observed on UT day 21-Apr.
S0 solar radiation storm conditions are expected over 22-24 Apr.
The solar wind environment on UT
day 21-Apr was mildly disturbed due to ongoing coronal hole effects.
The solar wind speed ranged from near 450 to 580 km/s. The peak
total interplanetary field strength (IMF, Bt) was 8 nT and the
north-south IMF component range was +5 to -6 nT. The solar wind
environment is expected to return to background conditions on
22-Apr and remain so over 23-24 Apr.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 21 Apr: G0
Estimated Indices 21 Apr : A K
Australian Region 12 33123431
Cocos Island 9 31123420
Darwin 12 32223432
Townsville 12 33123422
Learmonth 19 43224532
Alice Springs 12 33123431
Gingin 18 42224532
Canberra 10 23123421
Kennaook Cape Grim 16 33133531
Hobart 14 33124432
Estimated Antarctic Regional K Indices 21 Apr :
Macquarie Island 23 34245531
Casey 17 34423432
Mawson 53 65424666
Observed Regional daily pc3 Indices 21 Apr :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 4 (Quiet)
Canberra 4 (Quiet)
Hobart 34 (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 21 Apr : A
Fredericksburg 14
Planetary 19
Observed AFr/Ap Indices 20 Apr : A K
Fredericksburg 13
Planetary 24 1244 3554
2B. MAGNETIC FORECAST
Date Ap Conditions
22 Apr 14 G0
23 Apr 10 G0
24 Apr 8 G0
COMMENT: G0 geomagnetic conditions were observed in the Australian
region on UT day 21-Apr. G0-G2 geomagnetic conditions were observed
in the Antarctic region. The planetary region reached G1 geomagnetic
conditions. G0 geomagnetic conditions are expected over 22-24
Apr.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
21 Apr Fair Fair Fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
22 Apr Normal-fair Normal-fair Fair
23 Apr Normal Normal-fair Normal-fair
24 Apr Normal Normal Normal
COMMENT: HF radio propagation conditions on UT day 21-Apr were
degraded for most of the globe in response to brief periods of
geomagnetic activity. HF radio propagation conditions on UT day
22-Apr may be mildly degraded, although expected to recover.
Conditions are expected to be normal over 23-24 Apr.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
21 Apr 34
Observed Australian Regional MUFs
Cocos Island Region:
No data available during local day.
No data available during local night.
Niue Island Region:
Near predicted monthly values during local day.
Depressed by 25% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Depressed by 35% during local night.
Southern Australian Region:
Depressed by 40% during local day.
Depressed by 40% during local night.
Antarctic Region (Casey/Davis/Mawson):
Depressed by 25% over the UT day.
Monthly T index:
Month T index
Mar 92
Apr 83
May 81
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
22 Apr 65 Near predicted monthly values to 10-20% depressed
23 Apr 85 Near predicted monthly values to 10-15% depressed
24 Apr 100 Near predicted monthly values
COMMENT: Maximum usable frequencies on UT day 21-Apr were near
predicted monthly values to 40% depressed. Sites along the east
coast of Australia were degraded during local night hours, with
strong spread-F, sporadic-E and weak signals. MUFs are expected
to begin recovering on 22-Apr, although depressions of 10-20%
are still possible at local dawn hours. This may continue into
23-Apr, before returning to normal on 24-Apr.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 20 Apr
Daily Proton Fluence >1 MeV: 1.3E+06
Daily Proton Fluence >10 MeV: 1.8E+04
Daily Electron Fluence >2 MeV: 3.70E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 5%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B3.4
DSCOVR Satellite Solar Wind Day Averaged Data for 20 Apr
Speed: 487 km/sec Density: 3.5 p/cc Temp: 172000 K Bz: -3 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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