Summary and Forecast

Solar Summary

(last updated 16 May 2026 23:30 UT)

Activity 16 May: R1 Flares Max Fadeout Freq. Sectors M1.9 1612UT possible lower South American/ Atlantic M1.9 1742UT possible lower South American/ Atlantic Observed 10.7 cm flux/Equivalent Sunspot Number for 16 May: 109/59

Solar Forecast

(last updated 16 May 2026 23:30 UT)

17 May 18 May 19 May Activity R0, chance of R1 R0, chance of R1 R0, chance of R1 Fadeouts Possible Possible Possible 10.7cm/SSN 105/54 106/55 110/60 COMMENT: Solar flare activity on UT day 16-May was at the R1 level due to an M1.9 flare at 16/1612UT and an M1.9 flare at 16/1742UT. There are currently three numbered sunspot regions visible on the solar disk and three unnumbered regions. AR4436 (N20W24, alpha) and AR4435 (N22W81, beta) were responsible for the first and second M-class flares of the day respectively. AR4436 appears stable, whilst AR4435 has rotated off the solar disk. AR4438 (N19W69, beta) is in decay. An unnumbered region has developed on the disk at around N05E28 and two unnumbered regions have rotated on to the disk at around N15E70 and N04E70 respectively. All three have beta magnetic complexity. Solar flare activity is expected to be at the R0 level over 17-19 May, with a chance of R1. S0 solar proton conditions were observed on UT day 16-May. S0 solar proton conditions are expected over 17-19 May. A north-directed CME is visible in SOHO imagery and STEREO-A imagery from 16/1648UT. This CME is associated with an eruption on the solar disk at around N17W16 from 16/1612UT, visible in SDO, GOES SUVI and H-Alpha imagery. Modelling of this CME suggests an impact with Earth on 18-May at around 1700UT +/- 10 hours. Several other CMEs were observed on 16-May, but none are considered geoeffective. The solar wind speed was elevated over the UT day 16-Mar, mostly ranging between 575 and 820 km/s interplanetary magnetic field strength (IMF, Bt) was 15 nT and the north-south IMF component (Bz) range was -8 to +8 nT. The solar wind speed is expected to remain elevated on 17-May. A further enhancement is expected on 18-May due to a CME first observed on 16-May. Elevated solar wind conditions are expected to persist over 19-May.

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