Solar activity was low. Only a few low-level C-class subflares occurred. The largest was a C1/Sf at 17/0011 UTC in Region 9581 (S25W42). Although there are several sunspot groups on the visible disk all of them are relatively small and magnetically simple. New Regions 9586 (S15W47) and 9587 (S11E56) were numbered.

Solar activity is expected to be low. Additional low-level C-class flares are possible.

The geomagnetic field was quiet until the occurrence of a sudden impulse observed at ground magnetometers (36 nT at Boulder) at about 17/1103 UTC. The impulse was preceded by a shock observed at the NASA ACE spacecraft at 17/1017 UTC. The geomagnetic field has been at mostly active to minor storm levels since the impulse. A series of magnetopause crossings were observed at the NOAA GOES spacecraft in the interval from about 17/1930--2100 UTC. The greater than 100 MeV proton event which began yesterday has ended (start 16/0105 UTC, 29 pfu peak at 16/0305 UTC, and end 17/1415 UTC). The greater than 10 MeV event remains in progress (start 16/0135 UTC and 493 pfu peak at 16/0355 UTC). The current proton flux (17/2100 UTC) at greater than 10 MeV is about 20 pfu and is slowly decaying.

The geomagnetic field is expected to be at mostly active to minor storm levels for the next 24 hours becoming unsettled to active after that. The greater than 10 MeV proton event is expected to end by 19 August.

  Osservato       17 Aug 145
  Previsto   18 Aug-20 Aug  150/150/155
  Media di 90 Giorni        17 Aug 151

  Osservato Afr/Ap 16 Aug  003/008
  Stimato     Afr/Ap 17 Aug  025/025
  Previsto    Afr/Ap 18 Aug-20 Aug  020/015-015/015-010/018