Solar activity increased to high levels. Along with several lesser C-class flares Region 226 (N19W16) produced an M6.8/Sf major flare (optical classification has some doubt due to the seeing conditions) at 20/1318 UTC. A Type II radio sweep (estimated shock velocity of 868 km/sec), Tenflare, and strong discrete radio busts accompanied the flare. This region has undergone little change from yesterday and retains it's beta-gamma-delta magnetic classification. Region 229 (N19W16) produced a near long duration M2.7/2n flare at 19/2153 UTC that had a Type II radio sweep with an estimated shock velocity of 668 km/sec. A Type IV radio sweep, Tenflare, and multiple discrete radio bursts were associated with the flare. SOHO/LASCO C2 and C3 imagery indicate a possible earth-bound CME as a result of this activity. Region 230 (S08E19) continues to show steady growth and was responsible for several minor C-class flares today. No new regions were numbered today.

Solar activity is expected to be at moderate levels. Regions 226, 229, and 230 all have the potential for M-class production. Region 226 remains capable of producing an isolated major flare.

The geomagnetic field was at quiet to minor storm levels. The elevated conditions are due to a geoeffective recurrent positive polarity coronal hole high speed stream. The greater than 10 MeV proton flux at geosynchronous orbit became elevated following the M2.7 event early in the period while the greater than 2 MeV electron flux reached moderate levels late in the day.

The geomagnetic field is expected to be at predominantly quiet to unsettled levels for day one of the forecast period. A shock passage is expected on day two due to the M2.7 event (discussed in part IA) which may result in active to minor storm conditions. By day three a return to predominantly quiet unsettled levels is expected.

  Pozorováno       20 Dec 197
  Předpovězeno   21 Dec-23 Dec  195/195/185
  90 denní průměr        20 Dec 166

  Pozorováno Afr/Ap 19 Dec  015/021
  Odhadovaný     Afr/Ap 20 Dec  012/015
  Předpovězeno    Afr/Ap 21 Dec-23 Dec  010/015-025/025-012/015