[Ips-dsgr] ASWFC Daily Report - 20 April 25 issued 2333 UT on 20 Apr 2025 [SEC=OFFICIAL]
Australian Space Weather Forecasting Centre
aswfc at bom.gov.au
Mon Apr 21 09:33:22 AEST 2025
SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT
ISSUED AT 2330UT/20 APRIL 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
SUMMARY FOR 20 APRIL AND FORECAST FOR 21 APRIL - 23 APRIL
STATUS INDICATORS SOL:** YELLOW ** MAG:** YELLOW ** ION: ** YELLOW **
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx
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1A. SOLAR SUMMARY
Activity 20 Apr: R1
Flares Max Fadeout Freq. Sectors
M1.0 1211UT possible lower European
Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Apr: 156/110
1B. SOLAR FORECAST
21 Apr 22 Apr 23 Apr
Activity R0-R1 R0-R1 R0-R1
Fadeouts Possible Possible Possible
10.7cm/SSN 160/114 165/119 165/119
COMMENT: Solar activity on UT day 20-Apr was R1 due to an M1
flare from the southeast solar limb. A new smaller sized region
has rotated over the southeast solar limb and is yet to be numbered.
This region is the presumed source of yesterday's M4 flare. Of
the more notable existing on disk regions, AR4062 (S04E04, beta)
continues to decay and AR4064 (N10E22, beta) has been mostly
stable with some decline in intermediate spots. Small region
AR4063 (N05W42, beta) is decaying and produced a C4.3 flare at
20/1718UT. There are currently seven numbered sunspots on the
solar disk and one unnumbered region. Other regions are small.
No region has rotated over the northeast limb at solar latitude
N15. The active solar filament at S05W40 remains on disk though
has changed shape considerably over the last two days. A large
coronal hole is visible in the southern solar hemisphere and
is transiting the solar central meridian. Taking into account
the current solar B angle of -5 degrees, which tilts up the southern
solar pole, much of the area of this large coronal hole is still
at a reasonably high solar latitude. As this hole rotates across
the solar disk it's area now appears to extend further to the
southeast. Solar activity is expected to be R0-R1 on 21-23 Apr.
Isolated R1 flare activity is possible from the new solar region
in the southeast solar quadrant. S0 solar radiation storm conditions
were observed on 20-Apr. S0 solar radiation storm conditions
are expected over 21-23 Apr. No Earth directed CMEs were observed.
Non Earth directed minor CMEs were observed to the southeast
in LASCO C2 from 20/0924UT and to the southwest in STEREO-A from
20/1509UT. The solar wind speed was steady and ranged from 380
to 420 km/s and is currently at 400 km/s. The peak total interplanetary
field strength (IMF, Bt) was 13 nT and the north-south IMF component
range was +8 to -9 nT. The IMF Bt and solar wind density became
gradually increased after 20/1730UT. The cause of this IMF and
density enhancement is unclear. The solar wind speed remained
relatively constant during this period. The IMF Bz briefly fluctuated
southward during the interval 20/1800-1900UT. The solar wind
speed is expected to increase to moderate to strong during 21-22
Apr due to a wind stream from the southern hemisphere coronal
hole. The solar wind may then stay elevated for 3-4 days.
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2A. MAGNETIC SUMMARY
Geomagnetic field for Australian Region 20 Apr: G0
Estimated Indices 20 Apr : A K
Australian Region 6 32211022
Cocos Island 4 22210022
Darwin 7 32211132
Townsville 6 32211122
Learmonth 7 41211122
Alice Springs 5 32211021
Gingin 8 32211033
Canberra 4 21211022
Kennaook Cape Grim 5 21212022
Hobart 5 22212022
Estimated Antarctic Regional K Indices 20 Apr :
Macquarie Island 9 32134011
Casey 12 34421122
Mawson 21 63322134
Observed Regional daily pc3 Indices 20 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 20 Apr : A
Fredericksburg 14
Planetary 14
Observed AFr/Ap Indices 19 Apr : A K
Fredericksburg 18
Planetary 18 4343 3324
2B. MAGNETIC FORECAST
Date Ap Conditions
21 Apr 16 G0, G1 possible late in UT day
22 Apr 25 G1, chance G2
23 Apr 25 G1, chance G2
COMMENT: ASWFC Geomagnetic Warning 33 was issued on 18 April
and is current for 21-22 Apr. G0 geomagnetic activity was observed
in the Australian region on UT day 20-Apr. In the Antarctic region
G0 conditions were observed at Macquarie Island and Casey, with
an isolated G2 period were at Macquarie Island. A single period
of planetary G1 conditions were observed early in the UT day.
G0-G1, chance G2 conditions expected during 21-23 Apr due to
the anticipated Earth entry into a coronal hole wind stream.
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3A. GLOBAL HF PROPAGATION SUMMARY
Latitude Band
Date Low Middle High
20 Apr Normal Fair-normal Fair-normal
PCA Event : No event.
3B. GLOBAL HF PROPAGATION FORECAST
Latitude Band
Date Low Middle High
21 Apr Normal Normal-fair Fair
22 Apr Normal Normal-fair Fair
23 Apr Normal Normal-fair Fair
COMMENT: On UT day 20-Apr degraded HF conditions were fair to
normal. HF radio propagation conditions are expected to become
fair from late 21-Apr to 23 Apr for middle to high latitudes
due to expected geomagnetic activity from a coronal hole wind
stream.
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4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY
Date T index
20 Apr 103
Observed Australian Regional MUFs
Cocos Island Region:
Enhanced by 35% during local day.
Near predicted monthly values during local night.
Niue Island Region:
Near predicted monthly values during local day.
Depressed by 20% during local night.
Northern Australian Region:
Near predicted monthly values during local day.
Enhanced by 20% during local night.
Southern Australian Region:
Near predicted monthly values during local day.
Hobart MUFs depressed 15-30%.
Depressed by 15-30% during local night.
Antarctic Region (Casey/Davis/Mawson):
Depressed by 30% over the UT day.
Monthly T index:
Month T index
Mar 126
Apr 115
May 113
4B. AUSTRALIAN REGION IONOSPHERIC FORECAST
Date T index MUFs
21 Apr 115 Near predicted monthly values
22 Apr 95 10 to 15% below predicted monthly values
23 Apr 85 10 to 20% below predicted monthly values
COMMENT: Maximum usable frequencies (MUFs) in the Australian
region on UT day 20-Apr were variable. Most southern region sites
during the local day were near predicted monthly values becoming
15-30% depressed during the local night hours. Hobart MUFs were
initially 30% depressed, slowly recovering during the local day,
then becoming depressed again during local night hours. Northern
Australian region sites were near predicted monthly values to
20% enhanced. Spread F was observed during local night hours
at Hobart and Canberra. MUFs for 21-Apr are expected to be generally
near predicted monthly values. Southern Australian regional MUFs
are expected to become depressed 10-20% at times over 22-23 Apr
due to anticipated geomagnetic activity induced by a coronal
hole wind stream.
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5. SPACE ENVIRONMENT SUMMARY
GOES satellite data for 19 Apr
Daily Proton Fluence >1 MeV: 2.6E+05
Daily Proton Fluence >10 MeV: 1.4E+04
Daily Electron Fluence >2 MeV: 1.40E+07 (normal fluence)
Electron Fluence Daily Deep Dielectric Discharge Probability: 3%
Fluence (flux accumulation over 24hrs)/ cm2-ster-day.
X-ray background: C1.0
DSCOVR Satellite Solar Wind Day Averaged Data for 19 Apr
Speed: 386 km/sec Density: 3.8 p/cc Temp: 63900 K Bz: -5 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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