Solar activity was moderate during the past 24 hours. Region 9871 (S18E20) produced today's biggest event, an impulsive M4/Sf at 1931 UTC. The region appears to be growing slowly. An additional M-class event occurred: an M1 at 1019 UTC for which there was no optical report. Region 9866 (S09W33) is decaying gradually, but is still the largest region on the disk. Retrospective analysis of the CME that occurred around 15/2310 UTC shows a full halo event with an estimated plane-of-sky speed somewhere in the 750-850 km/s range. New Region 9873 (S17W09) emerged near the middle of the solar disk during the past 24 hours.

Solar activity is expected to be moderate during the next three days, with Regions 9866 and 9871 being the most likely sources.

The geomagnetic field was quiet during the past 24 hours. The greater than 10 MeV protons began to rise at the very end of the UT day yesterday and crossed event threshold at 17/0820 UTC. The fluxes reached a maximum of 13 PFU at 17/0850 UTC. The fluxes dropped below threshold at 17/1230 UTC, but have been fluctuating and have been on the increase since around 1500 UTC. It seems probable that the current slow climb is related to the approach of an interplanetary shock.

The geomagnetic field is expected to reach active to minor storm levels tomorrow in response to the halo CME event of 15/2310 UTC. A decrease to active is expected on the second day and a further decline to unsettled is expected by the third day. The current trend of the 10 MeV protons and the likely arrival of a shock in the next 12 hours all suggest that the proton fluxes should once again cross threshold.

  觀測的       17 Mar 184
  預測的   18 Mar-20 Mar  190/195/190
  90天平均值        17 Mar 215

  觀測的 Afr/Ap 16 Mar  005/005
  估算值     Afr/Ap 17 Mar  005/005
  預測的    Afr/Ap 18 Mar-20 Mar  030/030-020/020-010/010