Daily Report

(last updated 20 Sep 2025 23:30 UT)

SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT ISSUED AT 2330UT/20 SEPTEMBER 2025 FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE SUMMARY FOR 20 SEPTEMBER AND FORECAST FOR 21 SEPTEMBER - 23 SEPTEMBER STATUS INDICATORS SOL:** YELLOW ** MAG:** YELLOW ** ION: GREEN ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx ----------------------------------------------------------- 1A. SOLAR SUMMARY Activity 20 Sep: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Sep: 166/120 1B. SOLAR FORECAST 21 Sep 22 Sep 23 Sep Activity R0,chance R1 R0,chance R1 R0,chance R1 Fadeouts Possible Possible Possible 10.7cm/SSN 165/119 170/124 170/124 COMMENT: Solar activity on UT day 20-Sep was at R0. Solar regions on the visible solar disk are small to medium in size. Of the more notable regions solar region AR4223 (S15E10, gamma) which consists of a number of smaller spots, shows continued growth in its leader spots and exhibits some magnetic complexity. Solar region AR4225 (N12E28, beta) is slightly growing, with penumbral development south of its main spot where an area of very small magnetic complexity may be developing. Solar region AR4220 (S18W38, beta) trailer spots have declined and appear to be spreading out and breaking up, with a rapid decline in trailer spot umbral area. Solar region AR4216 (N11W37, alpha) continues to decay and produced isolated low level C class flares. There are currently ten numbered sunspot regions on the solar disk. Other solar regions on the visible solar disk are small and are either stable or in decay. Solar activity is expected to be R0,chance R1 over 21-23 Sep. A solar filament centred ar S25E60 was active and appeared to slowly partial disappear in GONG H-alpha imagery during the interval 20/0440-0930UT. No Earth-directed CMEs have been observed up to 20/2024UT. No CME appeared to be associated with the solar filament activity in the southeast solar quadrant. S0 solar radiation storm conditions were observed on UT day 20-Sep. S0 solar radiation storm conditions are expected over 21-23 Sep. A moderately sized isolated coronal hole is visible in the northern solar hemisphere just west of the solar central meridian with centre solar latitude at approximately N25. The solar wind on UT day 20-Sep continued to slowly decline. The solar wind speed ranged from 390 km/s to 340 km/s and is currently at 340 km/s. The peak total interplanetary field strength (IMF, Bt) was 3 nT and the north-south IMF component range (Bz) was +3 to -3 nT. The magnitude of the IMF has been very small. The solar wind is expected to be near background levels over on 21-Sep. A moderate increase in solar wind speed is expected from late 22-Sep due to the solar wind stream from the coronal hole now just west of the solar central meridian. Old solar region AR4197 appears to have returned as minor region AR4227. The US GOES geosynchronous satellite 2MeV energy electron detector has been elevated over 16-20 Sep. An elevated 2MeV electron flux is statistically associated with an increased risk of geosynchronous satellite anomalies. ----------------------------------------------------------- 2A. MAGNETIC SUMMARY Geomagnetic field for Australian Region 20 Sep: G0 Estimated Indices 20 Sep : A K Australian Region 1 11110001 Cocos Island 1 11200000 Darwin 2 21110002 Townsville 2 21110011 Learmonth 2 12100001 Alice Springs 2 21100001 Gingin 1 11100001 Canberra 1 11110000 Kennaook Cape Grim 2 11210001 Hobart 2 10210001 Estimated Antarctic Regional K Indices 20 Sep : Macquarie Island 1 00210000 Casey 6 32330001 Mawson 12 23330005 Observed Regional daily pc3 Indices 20 Sep : Darwin 0 (Quiet) Townsville 0 (Quiet) Learmonth 0 (Quiet) Alice Springs 0 (Quiet) Gingin 6 (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 Sep : A Fredericksburg 5 Planetary 5 Observed AFr/Ap Indices 19 Sep : A K Fredericksburg 7 Planetary 3 1111 2011 2B. MAGNETIC FORECAST Date Ap Conditions 21 Sep 5 G0 22 Sep 17 G0, G1 periods late in UT day 23 Sep 20 G0-G1 COMMENT: ASWFC Geomagnetic Warning 70 was issued on 19 September and is current for 22-23 Sep. G0 geomagnetic conditions were observed in the Australian and Antarctic regions on UT day 20-Sep. G0 geomagnetic conditions are expected on 21-Sep. Periods of G1 geomagnetic activity are possible from late 22-Sep and on 23-Sep due to a coronal hole wind stream. ----------------------------------------------------------- 3A. GLOBAL HF PROPAGATION SUMMARY Latitude Band Date Low Middle High 20 Sep Normal Normal Fair-normal PCA Event : No event. 3B. GLOBAL HF PROPAGATION FORECAST Latitude Band Date Low Middle High 21 Sep Normal Normal Normal 22 Sep Normal Normal-fair Normal-Fair 23 Sep Normal Fair-normal Fair COMMENT: HF radio propagation conditions on UT day 20-Sep were mostly normal. HF radio propagation conditions are expected to be mostly normal on 21-Sep. HF conditions at middle to high latitudes may become mildly degraded from late 22-23 Sep in association with a mild increase in geomagnetic activity from a coronal hole wind stream. Isolated minor shortwave fadeouts are possible. ----------------------------------------------------------- 4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY Date T index 20 Sep 107 Observed Australian Regional MUFs Cocos Island Region: No data available. Niue Island Region: Near predicted monthly values during local day. Enhanced by 30% during local night. Northern Australian Region: Near predicted monthly values during local day. Enhanced by 15-50% during local night. Southern Australian Region: Mostly near predicted monthly values. Enhanced by 25% after local dawn. Antarctic Region (Casey/Davis/Mawson): Enhanced by 15% over the UT day. Monthly T index: Month T index Aug 96 Sep 92 Oct 90 4B. AUSTRALIAN REGION IONOSPHERIC FORECAST Date T index MUFs 21 Sep 100 Near predicted monthly values 22 Sep 100 Near predicted monthly values 23 Sep 100 Near predicted monthly values COMMENT: Maximum usable frequencies (MUFs) in the Australian region on UT day 20-Sep were near predicted values to 50% enhanced, with enhancements of 50% observed at Darwin during local night hours. Other northern Australian region sites were enhanced by 15% during the local night. MUFs are expected to be near predicted values over 21-23 Sep. Mildly degraded HF conditions may be experienced during local night hours for the southern Australian region during 22-23 Sep, due to an anticipated mild increase in geomagnetic activity from a coronal hole wind stream. Isolated minor shortwave fadeouts are possible. ----------------------------------------------------------- 5. SPACE ENVIRONMENT SUMMARY GOES satellite data for 19 Sep Daily Proton Fluence >1 MeV: 1.6E+06 Daily Proton Fluence >10 MeV: 1.6E+04 Daily Electron Fluence >2 MeV: 2.90E+08 (moderate fluence) Electron Fluence Daily Deep Dielectric Discharge Probability:18% Fluence (flux accumulation over 24hrs)/ cm2-ster-day. X-ray background: C1.1 DSCOVR Satellite Solar Wind Day Averaged Data for 19 Sep Speed: 454 km/sec Density: 0.6 p/cc Temp: 56600 K Bz: 1 nT (Courtesy Space Weather Prediction Center, Boulder USA) -----------------------------------------------------------