Solar activity was high. The long duration X-flare, which was in progress at the beginning of the period, ended at 29/2132 UTC. This impressive X3.4 east limb event (located near S23) was accompanied by a 1600 sfu tenflare, type-II radio sweeps, and bright post-flare loops visible in H-alpha and EIT imagery for several hours following the event. A large CME was also evident in LASCO imagery, with an estimated plane-of-sky velocity reported at 2170 km/s. Other activity included a west limb CME, with an M9.3 x-ray enhancement peaking at 29/0945 UTC, and associated type-II and type-IV radio sweeps. An associated subfaint optical flare was also observed from Region 9748 (S11W90), but is presumed to be only a sympathetic indicator of the bulk of the activity from an apparent nearby source region behind the west limb. Several other M-class flares occurred throughout the period, though most were optically uncorrelated and presumed to be from limb sources, except for an M1/1f from Region 9751 (N04W38) at 29/0545 UTC.

Solar activity is expected to persist at moderate to high levels for the next three days.

The geomagnetic field was quiet to active. An L1 shock passage was observed at approximately 29/0440 UTC, and followed by a sudden impulse of 44 nT at 29/0538 UTC. Predominantly northward IMF orientation following the shock passage mostly mitigated the potential geomagnetic response to this event, presumed to have originated from the CME activity of 26 December. The 10 MeV integral proton flux at geosynchronous orbit followed a slow rising trend shortly after the end of the east limb X-flare, and exceeded event threshold at 29/0510 UTC. Further enhancement in possible association with the shock passage resulted in a peak flux observation of 76 pfu at 29/0815 UTC, and the event remains in progress.

Geomagnetic field activity is expected to be mostly quiet to unsettled for the next 24-48 hours. Increased activity with possible minor storming is expected on 31 December and 1 January, due to model predictions of a trailing flank shock passage from the east limb X-flare event discussed in section 1A above.

  Observé       29 Dec 264
  Prévisionnel   30 Dec-01 Jan  255/255/250
  Moyenne des 90 derniers jours        29 Dec 218

  Observé Afr/Ap 28 Dec  009/005
  Estimé     Afr/Ap 29 Dec  013/011
  Prévisionnel    Afr/Ap 30 Dec-01 Jan  010/008-015/015-020/020