[Ips-dsgr] ASWFC Daily Report - 20 April 26 issued 2330 UT on 20 Apr 2026 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Tue Apr 21 09:30:47 AEST 2026
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/20 APRIL 2026
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 20 APRIL AND FORECAST FOR 21 APRIL - 23 APRIL
STATUS INDICATORS SOL:GREEN MAG:GREEN ION: GREEN
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 20 Apr: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Apr: 105/54
1B. SOLAR FORECAST
21 Apr 22 Apr 23 Apr
Activity R0 R0 R0
Fadeouts None expected None expected None expected
10.7cm/SSN 110/60 120/72 120/72
COMMENT: Solar activity on UT day 20-Apr was R0, with no solar
flares. There are currently two numbered sunspot regions on the
solar disk. Active region (AR) 4415 (S18W89, alpha) is no longer
visible but appeared stable, and 4419 (N15W22, beta) went through
a brief growth phase following by decay. Solar activity is expected
to be R0 over 21-23 Apr.
No CMEs were observed on UT day 20-Apr.
S0 solar radiation storm conditions were observed on UT day 20-Apr.
S0 solar radiation storm conditions are expected over 21-23 Apr.
The solar wind environment on UT day 20-Apr continued to be elevated
due to the effects of a coronal hole. The solar wind speed ranged
from 400 to near 550 km/s. The peak total interplanetary field
strength (IMF, Bt) was 10 nT and the north-south IMF component
range (Bz) was +5 to -8 nT. Periods of southward Bz were observed
from 0555-1010 UT and again at 1535-1900 UT. The solar wind environment
is expected to remain elevated on UT day 21-Apr before beginning
to decline to near background levels.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 20 Apr: G0
Estimated Indices 20 Apr : A K
Australian Region 14 12333442
Cocos Island 11 12222441
Darwin 14 12333442
Townsville 13 22333342
Learmonth 19 12333552
Alice Springs 13 12333342
Gingin 19 11243552
Canberra 12 12323342
Kennaook Cape Grim 14 02333442
Hobart 14 02333442
Estimated Antarctic Regional K Indices 20 Apr :
Macquarie Island 28 01554552
Casey 14 13322352
Mawson 74 12433965
Observed Regional daily pc3 Indices 20 Apr :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 11 (Quiet)
Canberra 11 (Quiet)
Hobart 36 (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 20 Apr : A
Fredericksburg 19
Planetary 26
Observed AFr/Ap Indices 19 Apr : A K
Fredericksburg 16
Planetary 23 4564 3322
2B. MAGNETIC FORECAST
Date Ap Conditions
21 Apr 15 G0, chance G1
22 Apr 12 G0
23 Apr 9 G0
COMMENT: On UT day 20-Apr geomagnetic conditions in the Australian
region were observed to be G0. Mostly G0-G1 geomagnetic conditions
were observed in the Antarctic region, although a period of G5
was registered at Mawson. Planetary conditions reached G1. Geomagnetic
activity is expected to be mostly G0 over 21-23 Apr, with a chance
for an isolated period of G1 on 21-Apr.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
20 Apr Normal-fair Normal-fair Normal-fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
21 Apr Normal-fair Normal-fair Normal-fair
22 Apr Normal Normal Normal-fair
23 Apr Normal Normal Normal
COMMENT: HF radio propagation on UT day 20-Apr was mildly degraded
throughout most of the day across the globe due to minor geomagnetic
activity. HF radio propagation is expected to remain mildly degraded
on 21-Apr, but likely to begin recovering to normal over 22-23
Apr.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
20 Apr 63
Observed Australian Regional MUFs
Cocos Island Region:
Near predicted monthly values during local day.
No data available during local night.
Niue Island Region:
Near predicted monthly values during local day.
Enhanced by 20% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Depressed by 25% during local night.
Southern Australian Region:
Mostly near predicted monthly values.
Antarctic Region (Casey/Davis/Mawson):
Near predicted monthly values 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
21 Apr 78 Near predicted monthly values to 10-15% depressed
22 Apr 85 Near predicted monthly values
23 Apr 90 Near predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) on UT day were near
predicted monthly values to 25% depressed. Spread-F was observed
in Hobart during local night and dawn hours. Sporadic-E was observed
in Niue, as well as a scintillation event from 0811-0829 UT.
Conditions in Brisbane were degraded. MUFs are expected to mostly
be near predicted values over 21-23 Apr, with some ongoing depressions
of 10-15% on 21-Apr.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 19 Apr
Daily Proton Fluence >1 MeV: 6.4E+05
Daily Proton Fluence >10 MeV: 1.7E+04
Daily Electron Fluence >2 MeV: 4.10E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 6%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B3.1
DSCOVR Satellite Solar Wind Day Averaged Data for 19 Apr
Speed: 489 km/sec Density: 3.2 p/cc Temp: 173000 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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