Solar activity was moderate. Region 9906 (S14W41) produced a long-duration M2/2n flare at 17/0824 UTC. This flare was associated with a 3000 sfu radio burst at 2695 MHz, Type II/IV radio sweeps, and an Earth-directed "halo" CME visible in LASCO images. The region appears to have retained its size and complexity following the flare. Eruptive limb activity (EPL, BSL, and flare) in the vicinity of Region 9905 (S15W90) occurred during and after the LDE event in 9906.

Solar activity is expected to be moderate. Additional M-class flares, possibly including a major flare, are expected in Region 9906.

The geomagnetic field ranged from quiet to major storm levels. A shock was observed at the NASA ACE spacecraft at 17/1022 UTC and was followed by an SI at ground magnetometers at 17/1109 UTC (57 nT at Boulder). This shock is believed to be associated with the LDE M1/CME which occurred on 15 April. A greater than 10 MeV proton event began at 17/1530 UTC. The maximum flux observed so far was 24 pfu at 17/1540 UTC. This event is believed to be associated with the LDE M2 discussed in Part IA.

The geomagnetic field is expected to be at active to minor storm levels as the current disturbance recovers over the next 24 hours. Another disturbance at minor to major storm levels is expected to begin on 19 April in response to the LDE M2/CME which occurred on 17 April. The greater than 10 MeV proton event currently in progress is expected to end within the next 24 hours.

  觀測的       17 Apr 194
  預測的   18 Apr-20 Apr  190/185/180
  90天平均值        17 Apr 201

  觀測的 Afr/Ap 16 Apr  005/010
  估算值     Afr/Ap 17 Apr  035/055
  預測的    Afr/Ap 18 Apr-20 Apr  020/020-040/040-020/030