Daily Report

(last updated 21 Apr 2025 23:30 UT)

SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT ISSUED AT 2330UT/21 APRIL 2025 FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE SUMMARY FOR 21 APRIL AND FORECAST FOR 22 APRIL - 24 APRIL STATUS INDICATORS SOL:** YELLOW ** MAG:** YELLOW ** ION: ** YELLOW ** ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx ----------------------------------------------------------- 1A. SOLAR SUMMARY Activity 21 Apr: R1 Flares Max Fadeout Freq. Sectors M1.9 1837UT possible lower East Pacific/ North American Observed 10.7 cm flux/Equivalent Sunspot Number for 21 Apr: 163/117 1B. SOLAR FORECAST 22 Apr 23 Apr 24 Apr Activity R0-R1 R0-R1 R0-R1 Fadeouts Possible Possible Possible 10.7cm/SSN 163/117 160/114 160/114 COMMENT: Solar activity on UT day 21-Apr was R1, with an isolated M1.9 solar flare from AR4062 (S03W16, beta). There are currently seven numbered sunspot regions on the solar disk. All sunspots are currently stable, with none showing any significant growth in th e past day. Solar activity is expected to be R0-R1 over 22-24 Apr. No Earth directed CMEs have been observed in the past 24 hours, although several non-Earth directed CMEs were observed from a region on the western solar limb. 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 on UT day 21-Apr was mildly disturbed, possibly due to a co-rotating interaction region ahead of the large coronal hole in the southern solar hemisphere, or else the arrival of this coronal hole. The peak total interplanetary field strength (IMF, Bt) was 18 nT and the north-south IMF component range (Bz) was +10 to -13 nT. The solar wind speed showed a notable increase from 0600 UT onwards, and ranged from 420 to 735 km/s. The solar wind environment is expected to continue to be disturbed over 22-24 Apr due to the large coronal hole in the southern hemisphere. ----------------------------------------------------------- 2A. MAGNETIC SUMMARY Geomagnetic field for Australian Region 21 Apr: G0 Estimated Indices 21 Apr : A K Australian Region 18 33444332 Cocos Island 14 22434331 Darwin 19 33444333 Townsville 17 33444322 Learmonth 20 32454332 Alice Springs 17 33444232 Gingin 17 32444332 Canberra 16 33443322 Kennaook Cape Grim 17 33443332 Hobart 18 33443333 Estimated Antarctic Regional K Indices 21 Apr : Macquarie Island 37 33465553 Casey 19 44433333 Mawson 44 44544573 Observed Regional daily pc3 Indices 21 Apr : Darwin 4 (Quiet) Townsville 0 (Quiet) Learmonth 0 (Quiet) Alice Springs 0 (Quiet) Gingin 17 (Quiet) Canberra 19 (Quiet) Hobart 66 (Active) 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 28 Planetary 39 Observed AFr/Ap Indices 20 Apr : A K Fredericksburg 14 Planetary 0 ---- ---- 2B. MAGNETIC FORECAST Date Ap Conditions 22 Apr 20 G1-G2 23 Apr 25 G1-G2 24 Apr 25 G1-G2 COMMENT: ASWFC Geomagnetic Warning 33 was issued on 18 April and is current for 21-22 Apr. G0 geomagnetic conditions were observed in the Australian region on UT day 21-Apr. G0-G3 geomagnetic conditions were observed in the Antarctic region, and G0-G1 geomagnetic conditions were observed on the planetary scale. G1-G2 geomagnetic conditions are expected over 22-24 Apr due to a large coronal hole in the southern solar hemisphere. This feature has already connected to Earth with strong solar wind speeds and is expected to remain connected with Earth for several days. ----------------------------------------------------------- 3A. GLOBAL HF PROPAGATION SUMMARY Latitude Band Date Low Middle High 21 Apr Normal-fair Normal-fair Fair-poor PCA Event : No event. 3B. GLOBAL HF PROPAGATION FORECAST Latitude Band Date Low Middle High 22 Apr Normal-fair Fair Fair-poor 23 Apr Normal-fair Fair Fair-poor 24 Apr Normal-fair Fair Fair-poor COMMENT: On UT day 21-Apr HF radio propagation conditions were normal to fair in the first half of the day, then degradations began setting in by the latter half to all latitudes. HF radio propagation conditions are expected to be degraded over 22-24 Apr, particularly during local night hours and particularly for high latitudes. The cause for the degradations is a large coronal hole in the southern solar hemisphere. ----------------------------------------------------------- 4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY Date T index 21 Apr 105 Observed Australian Regional MUFs Cocos Island Region: Near predicted monthly values. 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. Depressed by 15% during local night. Southern Australian Region: Near predicted monthly values during local day. Depressed by 20% during local night. Antarctic Region (Casey/Davis/Mawson): Depressed by 15% 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 22 Apr 100 10 to 20% below predicted monthly values 23 Apr 90 15 to 25% below predicted monthly values 24 Apr 85 15 to 25% below predicted monthly values COMMENT: Maximum usable frequencies (MUFs) in the Australian region on UT day 21-Apr were near predicted values to 20% depressed. Sporadic-E was observed in the Cocos Islands during local night hours. MUFs are expected to be depressed 10-25% over 22-24 Apr due to coronal hole activity. Spread-F is expected over local night hours. ----------------------------------------------------------- 5. SPACE ENVIRONMENT SUMMARY GOES satellite data for 20 Apr Daily Proton Fluence >1 MeV: 3.1E+05 Daily Proton Fluence >10 MeV: 1.5E+04 Daily Electron Fluence >2 MeV: 2.30E+07 (normal fluence) Electron Fluence Daily Deep Dielectric Discharge Probability: 4% Fluence (flux accumulation over 24hrs)/ cm2-ster-day. X-ray background: C1.0 DSCOVR Satellite Solar Wind Day Averaged Data for 20 Apr Speed: 394 km/sec Density: 5.9 p/cc Temp: 87600 K Bz: 1 nT (Courtesy Space Weather Prediction Center, Boulder USA) -----------------------------------------------------------