Solar activity was low. Region 978 (S10W78) produced today's only C-class event, a C2 at 0716Z. The region appears to be decaying as it approaches west limb.

Solar activity is expected to be very low, although there continues to be a chance for an isolated C-class event.

The geomagnetic field ranged from quiet to minor storm levels. The field was initially quiet but became disturbed after a sudden impulse was observed at 0300Z. The sudden impulse was preceded by a weak shock in the solar wind observed at ACE at 0204Z. The shock was followed by an increase in velocity and magnetic field at ACE consistent with a corotating interaction region which was then followed by a high speed stream. Active to minor storm conditions prevailed from 0600-1200Z, followed by mostly active conditions. As of forecast issue time the solar wind velocity remains elevated with values around 550-600 km/s.

Geomagnetic activity is expected to be unsettled to active for the next three days (18-20 December), due to continued influence of the high speed stream.

  觀測的       17 Dec 080
  預測的   18 Dec-20 Dec  075/070/070
  90天平均值        17 Dec 071

  觀測的 Afr/Ap 16 Dec  001/002
  估算值     Afr/Ap 17 Dec  022/025
  預測的    Afr/Ap 18 Dec-20 Dec  015/015-015/015-015/015