Summary and Forecast

Solar Summary

(last updated 20 Dec 2025 23:30 UT)

Activity 20 Dec: R1 Flares Max Fadeout Freq. Sectors M1.0 0753UT possible lower Mid East/Indian Observed 10.7 cm flux/Equivalent Sunspot Number for 20 Dec: 120/72

Solar Forecast

(last updated 20 Dec 2025 23:30 UT)

21 Dec 22 Dec 23 Dec Activity R0, chance R1 R0, chance R1 R0, chance R1 Fadeouts Possible Possible Possible 10.7cm/SSN 120/72 120/72 125/78 COMMENT: Solar activity reached the R1 level on UT day 20-Dec, with an M1.0 flare observed at 20/0753UT from newly numbered Active Region 4315 (N21E49, beta). This region is one of six numbered regions on the visible solar disk and showed growth over the past 24 hours, with Active Regions 4311 (N04W41, beta) and 4314 (N25E35, beta) also showing growth during this period. The largest region on the solar disk, AR4312 (N25E36, alpha), appeared stable. Two new Active Regions appeared on the disk during the last UT day. The first, numbered 4316, appeared at S07E41, and appears to have beta magnetic classification. The second region, AR4317, has rotated onto the front side of the disk at N13E74, with its magnetic classification affected by limb foreshortening. Solar activity is expected to be at R0 with a chance of R1 over the period 21-23 Dec, given the growth of several active regions on the Sun. S0 solar radiation storm conditions were observed throughout 20-Dec, and are forecast to continue at the S0 level over the period 21-23 Dec. Two Coronal Mass Ejections were observed in the last 24 hours, both of which were not considered geoeffective. The solar wind speed has decreased over the past UT day, dropping from 460-490 km/s early in the UT day to 390-420 km/s currently. The interplanetary magnetic field strength (IMF, Bt) peaked at 6 nT during this time, with the North-South component (Bz) ranging between -3 and +4 nT. The solar wind speed is expected to trend towards background across much of 21-Dec, until the Earth connects with a trans-equatorial coronal hole late in the UT day. The solar wind speed will then increase due to these high speed wind stream effects.

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