Daily Report

(last updated 16 Apr 2026 23:30 UT)

SUBJ: ASWFC DAILY SOLAR AND GEOPHYSICAL REPORT ISSUED AT 2330UT/16 APRIL 2026 FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE SUMMARY FOR 16 APRIL AND FORECAST FOR 17 APRIL - 19 APRIL STATUS INDICATORS SOL:GREEN MAG:** YELLOW ** ION: ** YELLOW ** ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx ----------------------------------------------------------- 1A. SOLAR SUMMARY Activity 16 Apr: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 16 Apr: 108/58 1B. SOLAR FORECAST 17 Apr 18 Apr 19 Apr Activity R0 R0 R0 Fadeouts None expected None expected None expected 10.7cm/SSN 110/60 110/60 108/58 COMMENT: Solar flare activity was at the R0 level during UT day 16-Apr. Solar region AR4419 (N13E31, beta-gamma) has continued to slowly develop and produced several low level C1 flares in the past 24 hours and this medium sized region is currently the largest of the on disk regions. Smaller solar region AR4416 (N19W67, beta) is decaying as it approaches the northwest solar limb. Solar region AR4415 (S18W34, alpha) is a stable monopole. There are currently three numbered regions on the visible solar disk. A new small solar region may soon rotate onto the solar disk at solar latitude N13. Solar flare activity is forecast to be at the R0 level over 17-19 Apr, with a slight chance of an isolated R1 flare from AR4419. S0 solar radiation storm conditions were observed on 16-Apr. S0 solar radiation storm conditions are expected for 17-19 Apr. No Earth directed CMEs have been observed. A westward CME was observed from 15/2348UT and is considered a far side event. A large isolated coronal hole is located across the solar central meridian. The solar wind speed on UT day 16-Apr was light and steady and ranged from 343 to 319 km/s and is currently at 334 km/s. The peak total interplanetary magnetic field strength (IMF, Bt) was 7 nT and the north-south IMF component (Bz) ranged between -4 and +4 nT. A very weak partial shock signature was observed in some of the solar wind parameters at 16/0254UT. An increase in the solar wind speed is expected from late 17-Apr and on 18-Apr from the large coronal hole now crossing the solar central meridian, with possible moderate southward fluctuations of the IMF Bz component prior to and during the Earth's entry into the high speed wind stream. ----------------------------------------------------------- 2A. MAGNETIC SUMMARY Geomagnetic field for Australian Region 16 Apr: G0 Estimated Indices 16 Apr : A K Australian Region 1 01000011 Cocos Island 1 11100010 Darwin 2 12100012 Townsville 2 12000012 Learmonth 1 11000010 Alice Springs 1 01000011 Gingin 1 01000020 Canberra 1 01000011 Kennaook Cape Grim 0 00000010 Hobart 0 00000010 Estimated Antarctic Regional K Indices 16 Apr : Macquarie Island 0 00000000 Casey 5 13310020 Mawson 4 02210032 Observed Regional daily pc3 Indices 16 Apr : Darwin 0 (Quiet) Townsville 0 (Quiet) Learmonth 0 (Quiet) Alice Springs 0 (Quiet) Gingin 0 (Quiet) Canberra 2 (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 16 Apr : A Fredericksburg 4 Planetary 4 Observed AFr/Ap Indices 15 Apr : A K Fredericksburg 3 Planetary 4 1111 1212 2B. MAGNETIC FORECAST Date Ap Conditions 17 Apr 18 G0, then G1 18 Apr 30 G1, chance G2 19 Apr 25 G1, chance G2 COMMENT: ASWFC Geomagnetic Warning 28 was issued on 15 April and is current for 17-19 Apr. G0 geomagnetic conditions were observed in the Australian and Antarctic regions on UT day 16-Apr. G0 geomagnetic conditions are expected for most of 17-Apr. A coronal hole wind stream is expected to increase geomagnetic activity possibly to G1 from late 17-Apr with G1, chance G2 conditions expected on 18-19 Apr. ----------------------------------------------------------- 3A. GLOBAL HF PROPAGATION SUMMARY Latitude Band Date Low Middle High 16 Apr Normal Normal Fair-normal PCA Event : No event. 3B. GLOBAL HF PROPAGATION FORECAST Latitude Band Date Low Middle High 17 Apr Normal Normal-fair Fair 18 Apr Normal Fair Fair-poor 19 Apr Normal Fair Fair-poor COMMENT: Global HF radio propagation conditions were fair to normal on 16-Apr. Ionospheric scintillation was observed at Niue during the interval 16/0833-0848UT. Fair to normal HF conditions are expected 17-Apr with degraded conditions expected for middle to high latitudes from 18-Apr due to anticipated geomagnetic activity from a coronal hole wind stream. ----------------------------------------------------------- 4A. AUSTRALIAN REGION IONOSPHERIC SUMMARY Date T index 16 Apr 60 Observed Australian Regional MUFs Cocos Island Region: Enhanced by 20% during local day. Depressed by 35% during local night. Niue Island Region: Near predicted monthly values. Northern Australian Region: Near predicted monthly values during local day. Depressed by 30% during local night. Southern Australian Region: Depressed by 15% during local day. Near predicted monthly values during local night. 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 17 Apr 70 Depressed 10 to 15%/near predicted monthly values 18 Apr 45 Depressed 20 to 30%/near predicted monthly values 19 Apr 30 Depressed 20 to 30%/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 16-Apr were depressed 30% to near predicted monthly values. Depressions of up to 30% were observed during local night hours in the northern Australian region. The recent ionospheric depressions are not associated with geomagnetic activity. Southern Australian region MUFs are expected to be 15% depressed to near predicted monthly values on 17-Apr. Degraded HF conditions may be experienced for the southern Australian region from 18-Apr in association with anticipated geomagnetic activity induced by a coronal hole wind stream. ----------------------------------------------------------- 5. SPACE ENVIRONMENT SUMMARY GOES satellite data for 15 Apr Daily Proton Fluence >1 MeV: 5.6E+05 Daily Proton Fluence >10 MeV: 1.8E+04 Daily Electron Fluence >2 MeV: 1.10E+08 (moderate fluence) Electron Fluence Daily Deep Dielectric Discharge Probability:11% Fluence (flux accumulation over 24hrs)/ cm2-ster-day. X-ray background: B3.0 DSCOVR Satellite Solar Wind Day Averaged Data for 15 Apr Speed: 348 km/sec Density: 3.4 p/cc Temp: 38800 K Bz: 0 nT (Courtesy Space Weather Prediction Center, Boulder USA) -----------------------------------------------------------