Summary and Forecast

Solar Summary

(last updated 18 Oct 2026 23:46 UT)

Activity 18 Oct: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 18 Oct: 137/91

Solar Forecast

(last updated 18 Oct 2026 23:46 UT)

19 Oct 20 Oct 21 Oct Activity R0-R1 R0, chance of R1 R0, chance of R1 Fadeouts Possible None expected None expected 10.7cm/SSN 135/89 135/89 125/78 COMMENT: Solar flare activity was at the R0 level on UT day 18-Oct, with no significant flares observed. There are currently four active sunspot regions on the visible disk, with Active Region (AR) 4551 (S15W46, beta-gamma) being the largest. This region has exhibited some minor spot evolution over the previous UT day, and has remained mostly stable. Recently numbered region 4559 (S21W41, beta) has appeared on the disk over the past 24 hours, but has started to decay. Region 4557 (N08W11, beta) has also exhibited mild decay over the same period. A new region, numbered 4560, has appeared at N15E15, exhibiting a beta magnetic classification. Solar flare activity is forecast to be at the R0-R1 level over 19-Oct, declining to R0 with a chance of R1 over 20-21 Oct as these large sunspot regions continue to show signs of decay. S0 solar radiation storm conditions were observed on 18-Oct, with the proton flux at background levels. S0 solar radiation storm conditions are forecast over 19-21 Oct. No geoeffective coronal mass ejections were observed over the previous UT day in available coronagraph imagery. A large filament centred on N05W50 has shown signs of evolution over the previous UT day, which will continue to be monitored. The solar wind environment trended toward ambient conditions over UT day 18-Oct. The solar wind speed began the UT day at 500-520 km/s, declining to range between 400 and 420 km/s over the past 6 hours. The interplanetary magnetic field strength (IMF, Bt) was largely stable throughout the UT day, peaking at 7 nT, with the north-south component (Bz) ranging between -5 and +5 nT. The solar wind speed is forecast to continue to trend toward ambient conditions over most of 19-Oct, before rising late in the UT day due to Earth's connection to a coronal hole high speed wind stream. The solar wind speed is expected to continue to rise over 20-Oct due to this high speed wind stream, and remain elevated on 21-Oct.

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