Summary and Forecast

Solar Summary

(last updated 20 May 2025 23:32 UT)

Activity 20 May: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 20 May: 118/70

Solar Forecast

(last updated 20 May 2025 23:32 UT)

21 May 22 May 23 May Activity R0-R1 R0-R1 R0-R1 Fadeouts Possible Possible Possible 10.7cm/SSN 118/70 120/72 120/72 COMMENT: Solar activity on UT day 20-May was at the R0 level, with several C-class flares observed. There are currently five numbered sunspot regions visible on the solar disk and two unnumbered regions. AR4087 (N17W21, beta) is the largest region on the disk and has shown decay in its trailer spots. Newly numbered AR4093 (S05E68, beta-gamma) recently rotated over the eastern limb and has shown recent decay in its trailer spots. An unnumbered region is visible near N18E55 (beta) and has exhibited spot development. A second unnumbered region recently appeared near S09E40 (alpha) and has shown mild growth. All other sunspot regions are either stable or in decay. Solar activity is expected to be at R0-R1 levels over 21-23 May. No Earth-directed CMEs have been observed. The solar wind speed on UT day 20-May increased, ranging from 450 to 590 km/s and is currently near 590 km/s. The peak total interplanetary magnetic field strength (IMF, Bt) was 11 nT and the north-south IMF component (Bz) range was -8 to +9 nT. The solar wind speed is expected to remain elevated over 21-23 May due to ongoing coronal hole high speed wind stream effects from a southern hemisphere coronal hole.

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