Summary and Forecast

Solar Summary

(last updated 17 Dec 2025 23:30 UT)

Activity 17 Dec: R0 Flares: none. Observed 10.7 cm flux/Equivalent Sunspot Number for 17 Dec: 119/71

Solar Forecast

(last updated 17 Dec 2025 23:30 UT)

18 Dec 19 Dec 20 Dec Activity R0 R0 R0 Fadeouts None expected None expected None expected 10.7cm/SSN 118/70 115/66 110/60 COMMENT: Solar activity on UT day 17-Dec was R0, with no significant solar flares. Overall the on disk solar regions are all relatively small. Solar region AR4307 (S15W71, beta) produced isolated low level C class flares and has shown minor growth as it approaches the south west solar limb. Solar region AR4311 (N07E07, beta) is growing. There are currently four numbered sunspot regions on the solar disk and a new unnumbered small region has rotated onto the solar disk over the northeast limb. Other regions are stable or in decay. A large erupting solar prominence was observed on the northern solar limb in GOES 304 imagery from 17/0133UT. Solar activity is expected to be R0 over 18-20 Dec. No Earth directed CMEs were observed on UT day 17-Dec. A wide angle north directed (out of the ecliptic plane) CME was observed in LASCO C2 from 17/0200UT in association with the northern solar limb prominence eruption. A smaller northeast directed CME was also observed during the activity. S0 solar radiation storm conditions were observed on UT day 17-Dec. S0 solar radiation storm conditions are expected over 18-20 Dec. On UT day 17-Dec the solar wind speed was strong to very strong with an increasing trend due to a coronal hole wind stream, ranging from 548-648km/s and is currently at 648 km/s. The maximum total interplanetary field strength (IMF, Bt) was 8 nT and the north-south IMF component range (Bz) was +6 to -5 nT. The IMF Bz component fluctuated mildly southward during the UT day. The solar wind speed is expected to remain elevated for today.

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