Summary and Forecast

Solar Summary

(last updated 28 Sep 2026 23:30 UT)

Activity 28 Sep: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 28 Sep: 95/41

Solar Forecast

(last updated 28 Sep 2026 23:30 UT)

29 Sep 30 Sep 01 Oct Activity R0 R0 R0 Fadeouts None expected None expected None expected 10.7cm/SSN 95/41 100/48 100/48 COMMENT: Solar flare activity on UT day 28-Sep was at the R0 level, with no significant flares observed. Active Region 4535 (N13W31, beta-gamma) is the only active sunspot region currently visible on the solar disk, and has shown decay over the previous 24 hours. Solar flare activity is forecast to remain at R0 over 29-Sep to 01-Oct. S0 solar radiation storm conditions were observed on 28-Sep, with the proton flux consistent with background values across the UT day. S0 solar radiation storm conditions are forecast over 29-Sep to 01-Oct. A filament eruption centred on N15W60 was observed from 28/1308UT in GOES/SUVI 304A imagery. A resultant low-velocity, west-directed coronal mass ejection (CME) was observed in SOHO/LASCO coronagraph imagery from 28/1436UT. Modelling of this event suggests that the bulk of this eruption will pass ahead and above the Earth. However, part of this event is expected to impact Earth, with a glancing CME arrival at Earth forecast on 01-Oct at 2300UT +/-10 hours. The solar wind environment continued to trend toward ambient conditions on 28-Sep, following a previous high speed wind stream. The solar wind speed slowly declined from 360 km/s early in the UT day to currently be at approximately 320 km/s. The interplanetary magnetic field strength (IMF, Bt) peaked at 4 nT, with the north-south component (Bz) ranging between -2 and +2 nT over the UT day. The solar wind speed is expected to remain at ambient levels over 29-30 Sep, with a rise expected at the end of UT day 01-Oct due to the glancing CME arrival.

Solar Activity levels are explained in the SWS Solar Terrestrial Glossary.