Summary and Forecast

Solar Summary

(last updated 17 May 2026 23:30 UT)

Activity 17 May: R1 Flares Max Fadeout Freq. Sectors M1.4 0339UT possible lower E. Asia/Aust. Observed 10.7 cm flux/Equivalent Sunspot Number for 17 May: 104/53

Solar Forecast

(last updated 17 May 2026 23:30 UT)

18 May 19 May 20 May Activity R0, chance of R1 R0, chance of R1 R0, chance of R1 Fadeouts Possible Possible Possible 10.7cm/SSN 105/54 110/60 115/66 COMMENT: Solar flare activity on UT day 17-May was at the R1 level due to an M1.4 flare at 17/0339UT. There are currently six numbered sunspot regions visible on the solar disk. The one M-class flare of the day was produced by a region which has rotated off the western limb. There are no large or magnetically complex sunspot regions visible on the solar disk. AR4441 (N08E16, beta), AR4442 (S16E47, alpha) and AR4443 (S16E63, alpha) all showed spot development over the UT day. All other regions are stable. Solar flare activity is expected to be at the R0 level over 18-20 May, with a chance of R1. S0 solar radiation storm conditions were observed on UT day 17-May. S0 solar radiation storm conditions are expected over 18-20 May. No geoeffective CMEs were observed on 17-May. The solar wind speed declined over the UT day 17-May, mostly ranging between 540 and 730 km/s . The wind speed is currently at around 550 km/s. The peak total interplanetary magnetic field strength (IMF, Bt) was 5 nT and the north-south IMF component (Bz) range was -3 to +3 nT. The solar wind speed is expected to continue to decline on 18-May until the anticipated arrival of a CME first observed on 16-May causes an increase. A general decline in wind speed is expected over 19-20 May.

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