[Ips-dsgr] ASWFC Daily Report - 17 April 26 issued 2330 UT on 17 Apr 2026 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Sat Apr 18 09:30:43 AEST 2026
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/17 APRIL 2026
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 17 APRIL AND FORECAST FOR 18 APRIL - 20 APRIL
STATUS INDICATORS SOL:GREEN MAG:** RED ** ION: ** YELLOW **
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
-----------------------------------------------------------
1A. SOLAR SUMMARY
Activity 17 Apr: R0
Flares: none.
Observed 10.7 cm flux/Equivalent Sunspot Number for 17 Apr: 107/57
1B. SOLAR FORECAST
18 Apr 19 Apr 20 Apr
Activity R0, chance of R1 R0, chance of R1 R0, chance of R1
Fadeouts None expected None expected None expected
10.7cm/SSN 105/54 105/54 105/54
COMMENT: Solar flare activity during UT day 17-Apr was at the
R0 level, with a C4.1 flare from Active Region (AR) 4419 (N13E16,
beta), the largest observed over the last 24 hours. This region
is the largest and most magnetically complex of the three regions
currently on the visible solar disk, and has exhibited minor
growth and separation over the last UT day. The other two regions
remain stable. Solar flare activity is forecast to be at the
R0 level, with a chance of R1, over the period 18-20 Apr due
to the flare potential of AR 4419. S0 solar proton conditions
were observed throughout UT day 17-Apr, with the proton flux
remaining at background levels. S0 conditions are expected over
18-20 Apr. No geoeffective coronal mass ejections (CMEs) have
been observed over the last 24 hours. A low-velocity east-directed
CME was visible in STEREO-A coronagraph imagery from 17/0253UT.
This CME has been modelled to miss Earth. The solar wind speed
was light throughout UT day 17-Apr, broadly ranging between 300
and 350 km/s. The interplanetary magnetic field strength (IMF,
Bt) peaked at 12 nT during 17-Apr, with the north-south component
(Bz) ranging between -6 and +6 nT during this time. The solar
wind speed is expected to increase over 18-Apr as the Earth connects
with a coronal hole high speed stream. These elevated solar wind
conditions are likely to persist over 19-20 Apr.
-----------------------------------------------------------
2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 17 Apr: G0
Estimated Indices 17 Apr : A K
Australian Region 1 10000021
Cocos Island 2 11010021
Darwin 3 21100022
Townsville 2 11000022
Learmonth 2 10000031
Alice Springs 1 00000021
Gingin 1 01000021
Canberra 1 10000011
Kennaook Cape Grim 1 10000011
Hobart 0 00000011
Estimated Antarctic Regional K Indices 17 Apr :
Macquarie Island 0 00000010
Casey 3 12210011
Mawson 3 11100122
Observed Regional daily pc3 Indices 17 Apr :
Darwin 0 (Quiet)
Townsville 0 (Quiet)
Learmonth 0 (Quiet)
Alice Springs 0 (Quiet)
Gingin 0 (Quiet)
Canberra 0 (Quiet)
Hobart 0 (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 17 Apr : A
Fredericksburg 15
Planetary 20
Observed AFr/Ap Indices 16 Apr : A K
Fredericksburg 3
Planetary 3 1111 101-
2B. MAGNETIC FORECAST
Date Ap Conditions
18 Apr 30 G1, chance of G2
19 Apr 25 G1, chance of G2
20 Apr 20 G0-G1
COMMENT: ASWFC Geomagnetic Warning 28 was issued on 15 April
and is current for 17-19 Apr. G0 geomagnetic conditions were
recorded in the Australian region on 17-Apr, as well as being
observed in the Antarctic region, and at the planetary level.
G1 geomagnetic conditions, with a chance of G2, are forecast
for 18-19 Apr, due to the effects of a coronal hole high speed
wind stream that will connect with the Earth on 18-Apr. These
conditions will ease to G0-G1 on 20-Apr as these effects begin
to wane.
-----------------------------------------------------------
3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
17 Apr Fair-normal Fair-normal Fair
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
18 Apr Fair Fair Fair-poor
19 Apr Fair Fair Fair-poor
20 Apr Fair-normal Fair-normal Fair
COMMENT: Global ionospheric conditions were fair to normal on
UT day 17-Apr, with degradations observed mainly in high- and
low-latitude regions at different times of the UT day. Ionospheric
conditions are expected to weaken to fair levels over 18-19 Apr
due to coronal hole high speed wind stream effects. These will
begin to improve to fair to normal conditions on 20-Apr.
-----------------------------------------------------------
4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
17 Apr 66
Observed Australian Regional MUFs
Cocos Island Region:
Enhanced by 25% during local day.
Near predicted monthly values during local night.
Depressed by 20% after local dawn.
Niue Island Region:
Depressed by 15% during local day.
Depressed by 30% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Depressed by 25% during local night.
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
Mar 92
Apr 83
May 81
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
18 Apr 45 Depressed 20 to 30%/near predicted monthly values
19 Apr 55 Depressed 20 to 30%/near predicted monthly values
20 Apr 65 Depressed 10 to 15%/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 on UT day 17-Apr were mostly
near predicted monthly values. Depressions of up to 25% were
observed during local night hours in the Northern Australian
region, and up to 30% at Niue Island. MUF depressions of up to
20-30% are forecast over 18-19 Apr due to anticipated geomagnetic
activity induced by a coronal hole wind stream. These depressions
will begin to trend toward predicted monthly values on 20-Apr
as the effects of the high speed wind stream begin to subside.
-----------------------------------------------------------
5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 16 Apr
Daily Proton Fluence >1 MeV: 6.4E+05
Daily Proton Fluence >10 MeV: 1.7E+04
Daily Electron Fluence >2 MeV: 7.30E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 9%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: B3.6
DSCOVR Satellite Solar Wind Day Averaged Data for 16 Apr
Speed: 329 km/sec Density: 3.0 p/cc Temp: 47900 K Bz: 0 nT
(Courtesy Space Weather Prediction Center, Boulder USA)
-----------------------------------------------------------
Australian Space Weather Forecasting Centre
Bureau of Meteorology
ASWFC at bom.gov.au
www.bom.gov.au | www.sws.bom.gov.au
More information about the ips-dsgr
mailing list