SOLAR ACTIVITY WAS LOW. THE DAY'S LARGEST EVENT WAS A C5 XRAY BURST AT 0329Z. THERE WAS NO ASSOCIATED OPTICAL FLARE. REGION 8462 (N20W40) PRODUCED MOST OF THE C-CLASS EVENTS OBSERVED, AND REGIONS 8458 (S23W36) AND 8459 (S29W80) SPLIT THE REMAINDER. IN GENERAL, ALL SPOTTED REGIONS WERE STABLE OR DECAYING AND THE 10.7 CM RADIO FLUX DROPPED SUBSTANTIALLY FROM YESTERDAY. THE LIMBS WERE QUIET.

SOLAR ACTIVITY IS EXPECTED TO BE LOW TO MODERATE. REGIONS 8458 AND 8462 ARE POTENTIAL SITES FOR M-CLASS ACTIVITY, SHOULD AN INSTABILITY DEVELOP. IIA. GEOPHYSICAL ACTIVITY SUMMARY FROM 17/2100Z TO 18/2100Z: THE GEOMAGNETIC FIELD WAS AT ACTIVE TO SEVERE STORM LEVELS THROUGHOUT THE PERIOD. A SUDDEN STORM COMMENCEMENT MEASURING 43 NANOTESLAS AT BOULDER, OCCURRED AT 0250Z. THE ACE SPACECRAFT MEASURED SOLAR WIND VELOCITIES NEAR 700 KM/S, AND SOUTHWARD IMF OF APPROXIMATELY 20 NT, FOR HOURS FOLLOWING THE PASSAGE OF THE SHOCK. THE SOLAR ORIGIN OF THIS ACTIVITY IS THOUGHT TO BE THE LONG-DURATION M-CLASS EVENT FROM NEAR CENTER DISK, EARLY ON FEBRUARY 16. A FORBUSH DECREASE BEGAN EARLY IN THE DAY, AS SEEN IN NEUTRON MONITOR DATA.

THE GEOMAGNETIC FIELD IS EXPECTED TO BE AT ACTIVE TO MINOR STORM LEVELS FOR THE NEXT 24 HOURS. THE CURRENT STORM SHOULD GRADUALLY WEAKEN, ALTHOUGH EPISODES OF MAJOR STORM MAY OCCUR DURING LOCAL NIGHTTIMES. THE SOLAR WIND SPEED AT ACE IS STILL ABOVE 600 KM/S, BUT THE SOUTHWARD COMPONENT OF THE IMF IS NOW NEAR ZERO. THE RETURN TO MORE BENIGN CONDITIONS SHOULD BRING QUIET TO UNSETTLED LEVELS BY FEBRUARY 21.

  Geobserveerd       18 FEB 168
  Voorspeld   19 FEB-21 FEB  160/155/150
  90 Day Mean        18 FEB 146

OBSERVED AFR/AP 17 FEB  015/016
ESTIMATED AFR/AP 18 FEB  060/050
PREDICTED AFR/AP 19 FEB-21 FEB  030/030-015/015-005/010