Summary and Forecast

Solar Summary

(last updated 27 Sep 2026 23:30 UT)

Activity 27 Sep: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 27 Sep: 97/44

Solar Forecast

(last updated 27 Sep 2026 23:30 UT)

28 Sep 29 Sep 30 Sep Activity R0 R0 R0 Fadeouts None expected None expected None expected 10.7cm/SSN 98/45 100/48 105/54 COMMENT: Solar flare activity on UT day 27-Sep was at the R0 level, with only low-level C-class flares observed. There are currently five numbered sunspot regions visible on the solar disk. Active region (AR) 4533 (S13W27, beta) has returned after decaying on the 26-Sep, but remains on the precipice of decay. ARs 4534, 4537 and 4538 have all rotated off disk. AR 4536 (N03W77, alpha) will rotate of disk in the next 24 hours. AR4524 is due to return on the 29-Sep, if it has not yet decayed. It was previously responsible for low-level M-class flares. All other sunspot regions are either stable or in decay. Solar flare activity is expected to be at the R0 level over 28-30 Sep. Solar radiation storm conditions were at the S0 level on the 27-Sep, with the solar proton flux at background levels. S0 solar radiation storm conditions are forecast over 28-30 Sep. No Earth-directed coronal mass ejections (CMEs) were observed over the past UT day. The solar wind speed on UT day 27-Sep has gradually decreased as coronal hole high speed wind stream effects abate. Speeds ranged from 470 to 365 km/s, the latter being the current speed. The peak total interplanetary magnetic field strength (IMF, Bt) was 5 nT. The north-south component (Bz) ranged between -4 and +2 nT over the same period. Sustained periods of weak southward IMF were observed over most of the UT day. The solar wind speed is expected to continue its decline over the 28-Sep, before stabilising at typical levels.

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