Daily Report

(last updated 17 Oct 2025 23:30 UT)

SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT ISSUED AT 2330UT/17 OCTOBER 2025 FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE SUMMARY FOR 17 OCTOBER AND FORECAST FOR 18 OCTOBER - 20 OCTOBER STATUS INDICATORS SOL:** RED ** MAG:** YELLOW ** ION: GREEN ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx ----------------------------------------------------------- 1A. SOLAR SUMMARY Activity 17 Oct: R1 Flares Max Fadeout Freq. Sectors M1.0 16/2319UT possible lower West Pacific M1.5 0128UT possible lower West Pacific M1.1 1245UT possible lower European M1.0 1432UT possible lower South American/ Atlantic M1.3 1633UT possible lower South American/ Atlantic M1.1 1903UT possible lower East Pacific/ North American Observed 10.7 cm flux/Equivalent Sunspot Number for 17 Oct: 164/118 1B. SOLAR FORECAST 18 Oct 19 Oct 20 Oct Activity R1-R2 R1-R2 R1-R2 Fadeouts Probable Probable Probable 10.7cm/SSN 165/119 155/109 160/114 COMMENT: Solar activity on UT day 17-Oct was at the R1 level due to several M-class flares, the largest of which was an M1.5 flare at 17/0128UT produced by AR4246 (N24W79, beta-gamma). There are currently eight numbered sunspot regions visible on the solar disk. AR4246 is the most magnetically complex region on the disk. This region appears to be decaying and will soon rotate over the western limb. AR4252 (S13W04, beta) has shown recent growth in its trailer spots. AR4256 (S16E55, beta) has exhibited growth in its leader spots. Newly numbered AR4257 (S08E76, beta) recently rotated over the eastern limb and appears stable. All other sunspot regions are either stable or in decay. Solar activity is expected to be at R1-R2 levels over 18-20 Oct. S0 solar proton conditions were observed on UT day 17-Oct. S0 solar proton conditions are expected over 18-20 Oct, with a chance of S1. Several CMEs were observed, but none are considered geoeffective. The solar wind speed on UT day 17-Oct mildly declined, ranging from 375 to 415 km/s and is currently near 390 km/s. The peak total interplanetary magnetic field strength (IMF, Bt) was 14 nT and the north-south IMF component (Bz) range was -9 to +11 nT. A mild step increase was observed in the IMF, Bt parameter at 17/0933UT, potentially indicative of a CME arrival, however no increase was observed in the solar wind speed. The solar wind speed is expected to remain near background levels on 18-Oct, then increase over 19-20 Oct due to coronal hole high speed wind stream effects from an equatorial coronal hole. ----------------------------------------------------------- 2A. MAGNETIC SUMMARY Geomagnetic field for Australian Region 17 Oct: G0 Estimated Indices 17 Oct : A K Australian Region 9 21233322 Cocos Island 8 11233321 Darwin 12 32233323 Townsville 11 21243322 Learmonth 11 22243322 Alice Springs 9 21233322 Gingin 10 31233321 Canberra 8 21332222 Kennaook Cape Grim 10 21343212 Hobart 8 21332221 Estimated Antarctic Regional K Indices 17 Oct : Macquarie Island 13 10453211 Casey 13 33343222 Mawson 11 23333311 Observed Regional daily pc3 Indices 17 Oct : Darwin 0 (Quiet) Townsville 0 (Quiet) Learmonth 0 (Quiet) Alice Springs 0 (Quiet) Gingin 16 (Quiet) Canberra 15 (Quiet) Hobart 31 (Quiet to 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 17 Oct : A Fredericksburg 13 Planetary 16 Observed AFr/Ap Indices 16 Oct : A K Fredericksburg 3 Planetary 4 1121 1012 2B. MAGNETIC FORECAST Date Ap Conditions 18 Oct 18 G0-G1 19 Oct 19 G0-G1 20 Oct 14 G0, chance of G1 COMMENT: ASWFC Geomagnetic Warning 81 was issued on 17 October and is current for 17-19 Oct. G0 geomagnetic conditions were observed in the Australian region on UT day 17-Oct. Mostly G0 geomagnetic conditions were observed in the Antarctic region, with an isolated period of G1 observed at Macquarie Island. G0-G1 geomagnetic conditions are expected on 18-Oct due to the current elevated IMF conditions. G0-G1 geomagnetic conditions are expected on 19-Oct, declining to G0, with a chance of G1 on 20-Oct due to coronal hole high speed wind stream effects from an equatorial coronal hole. ----------------------------------------------------------- 3A. GLOBAL HF PROPAGATION SUMMARY Latitude Band Date Low Middle High 17 Oct Normal Normal Normal-fair PCA Event : No event. 3B. GLOBAL HF PROPAGATION FORECAST Latitude Band Date Low Middle High 18 Oct Normal Normal-fair Fair 19 Oct Normal Normal-fair Fair 20 Oct Normal Normal Normal-fair COMMENT: HF radio propagation conditions on UT day 17-Oct were mostly normal. Normal to fair HF conditions are expected over 18-19 Oct. Mostly normal HF conditions are expected on 20-Oct. Shortwave fadeouts are probable. ----------------------------------------------------------- 4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY Date T index 17 Oct 105 Observed Australian Regional MUFs Cocos Island Region: Enhanced by 30% during local day. Near predicted monthly values during local night. Niue Island Region: Near predicted monthly values. Northern Australian Region: Near predicted monthly values during local day. Enhanced by 15% during local night. Southern Australian Region: Near predicted monthly values during local day. Enhanced by 20% during local night. Antarctic Region (Casey/Davis/Mawson): Near predicted monthly values over the UT day. Monthly T index: Month T index Sep 109 Oct 89 Nov 89 4B. AUSTRALIAN REGION IONOSPHERIC FORECAST Date T index MUFs 18 Oct 105 Near to 15% above predicted monthly values 19 Oct 100 Near predicted monthly values 20 Oct 100 Near predicted monthly values COMMENT: Maximum usable frequencies (MUFs) in the Australian region on UT day 17-Oct were near predicted monthly values to 20% enhanced. MUFs are expected to be near predicted monthly values to 15% enhanced on 18-Oct and near predicted monthly values over 19-20 Oct. Shortwave fadeouts are probable. ----------------------------------------------------------- 5. SPACE ENVIRONMENT SUMMARY GOES satellite data for 16 Oct Daily Proton Fluence >1 MeV: 1.6E+06 Daily Proton Fluence >10 MeV: 1.7E+04 Daily Electron Fluence >2 MeV: 1.40E+08 (moderate fluence) Electron Fluence Daily Deep Dielectric Discharge Probability:13% Fluence (flux accumulation over 24hrs)/ cm2-ster-day. X-ray background: C2.1 DSCOVR Satellite Solar Wind Day Averaged Data for 16 Oct Speed: 429 km/sec Density: 3.2 p/cc Temp: 46800 K Bz: 1 nT (Courtesy Space Weather Prediction Center, Boulder USA) -----------------------------------------------------------