[Ips-dsgr] ASWFC Daily Report - 18 April 26 issued 2330 UT on 18 Apr 2026 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Sun Apr 19 09:30:50 AEST 2026
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/18 APRIL 2026
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 18 APRIL AND FORECAST FOR 19 APRIL - 21 APRIL
STATUS INDICATORS SOL:GREEN MAG:** RED ** ION: ** YELLOW **
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 18 Apr: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 18 Apr: 106/55
1B. SOLAR FORECAST
19 Apr 20 Apr 21 Apr
Activity R0 R0 R0
Fadeouts None expected None expected None expected
10.7cm/SSN 105/54 105/54 110/60
COMMENT: Solar flare activity was at the R0 level on UT day 18-Apr,
with no M-class or greater flares observed. There are currently
two active regions on the visible solar disk, with Active Region
(AR) 4419 (N13E02, beta) being the largest and most magnetically
complex. Both this region, and AR 4415 (S18W62, alpha) have remained
stable over the past 24 hours. Solar flare activity is forecast
to remain at the R0 level through 19-21 Apr. S0 solar proton
conditions were observed throughout UT day 18-Apr, with solar
proton flux consistent with background levels. S0 solar proton
conditions are expected over 19-21 Apr. No geoeffective coronal
mass ejections (CMEs) were observed over the last 24 hours. A
filament eruption, visible in GONG Halpha imaging, was observed
centred on S28E28 at 18/0732UT. A low-velocity, south-east-directed
CME was subsequently observed in SOHO/LASCO imagery from 18/0848UT.
The CME was modelled to pass ahead and below Earth, so is not
considered geoeffective. The solar wind speed on UT day 18-Apr
was initially light, ranging from 330-370 km/s early in the UT
day. A subsequent increase in the solar wind speed and temperature,
and decrease in the solar wind density at 18/0125UT signified
a connection to a coronal hole high speed wind stream. The solar
wind speed continued to increase, reaching a maximum of approximately
600 km/s, and is currently ranging between 520 and 560 km/s.
The interplanetary magnetic field strength (IMF, Bt) also rose
after the connection to the high speed wind stream, peaking at
18 nT, with the north-south component (Bz) ranging between -14
and +14 nT over the UT day. An extended period of southward Bz
was also recorded between 18/0308-0714UT. The solar wind is expected
to remain elevated over 19-20 Apr due to ongoing effects of this
high speed wind stream, before starting to decline by 21-Apr.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 18 Apr: G2
Estimated Indices 18 Apr : A K
Australian Region 20 24543332
Cocos Island 14 23343331
Darwin 18 34443323
Townsville 16 24443322
Learmonth 19 33543332
Alice Springs 19 24543322
Gingin 24 33544442
Canberra 16 23543222
Kennaook Cape Grim 24 24643332
Hobart 24 24643332
Estimated Antarctic Regional K Indices 18 Apr :
Macquarie Island 35 25664431
Casey 16 34443222
Mawson 27 44533354
Observed Regional daily pc3 Indices 18 Apr :
Darwin 2 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 8 (Quiet)
Canberra 18 (Quiet)
Hobart 52 (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 18 Apr : A
Fredericksburg 25
Planetary 38
Observed AFr/Ap Indices 17 Apr : A K
Fredericksburg 3
Planetary 4 1101 012-
2B. MAGNETIC FORECAST
Date Ap Conditions
19 Apr 25 G1, chance of G2
20 Apr 20 G0-G1
21 Apr 15 G0
COMMENT: ASWFC Geomagnetic Warning 28 was issued on 15 April
and is current for 17-19 Apr. Geomagnetic conditions in the Australian
region reached G1 on UT day 18-Apr, following Earth's connection
to a coronal hole high speed wind stream. A period of G2 was
observed in Hobart and Cape Grim, with G2 conditions also reported
at Macquarie Island. G2 geomagnetic conditions were also recorded
at the planetary level. G1 geomagnetic conditions, with a chance
of G2, are forecast for 19-Apr due to the ongoing effects of
this high speed wind stream. These conditions will decline to
G0-G1 geomagnetic conditions on 20-Apr, and to G0 on 21-Apr,
as the effects of this high speed wind stream begin to subside.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
18 Apr Fair-normal Fair-normal Fair-normal
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
19 Apr Fair Fair Fair
20 Apr Fair-normal Fair-normal Fair
21 Apr Normal-fair Normal-fair Fair-normal
COMMENT: Global Ionospheric conditions were fair to normal over
UT day 18-Apr, with some degradations in the North American and
European regions following the onset of geomagnetic activity.
Ionospheric conditions are expected to become fair on 19-Apr
due to the ongoing geomagnetic activity. Conditions will then
begin to improve over 20-21 Apr as the geomagnetic activity begins
to ease.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
18 Apr 90
Observed Australian Regional MUFs
Cocos Island Region:
Near predicted monthly values during local day.
Depressed by 30% during local night.
Niue Island Region:
Near predicted monthly values during local day.
Enhanced by 30% during local night.
Northern Australian Region:
Near predicted monthly values.
Southern Australian Region:
Near predicted monthly values during local day.
Enhanced by 15% during local night.
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
19 Apr 55 Depressed 10 to 20%/near predicted monthly values
20 Apr 65 Depressed 10 to 15%/near predicted monthly values
21 Apr 75 Near predicted monthly values
COMMENT: ASWFC Preliminary HF Communications Warning 36 was issued
on 16 April and is current for 18-20 Apr. Maximum Usable Frequencies
(MUFs) in the Australian region were largely near predicted values
on 18-Apr, with some enhancements seen at Niue Island and the
Southern Australian region. Spread-F was observed in Hobart and
Niue Island, with a scintillation event also reported between
18/0811-0830UT at Niue Island. MUFs are expected to become depressed
by 10-20% on 19-20 Apr due to ongoing geomagnetic activity, before
beginning to recover to near predicted monthly values on 21-Apr.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 17 Apr
Daily Proton Fluence >1 MeV: 1.8E+06
Daily Proton Fluence >10 MeV: 1.7E+04
Daily Electron Fluence >2 MeV: 1.00E+08 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability:10%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B3.4
DSCOVR Satellite Solar Wind Day Averaged Data for 17 Apr
Speed: 328 km/sec Density: 4.8 p/cc Temp: 39200 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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