:Product: Report of Solar-Geophysical Activity :Issued: 2000 Apr 16 2200 UT # Prepared jointly by the U.S. Dept. of Commerce, NOAA, #Space Environment Center and the U.S. Air Force. # JOINT USAF/NOAA REPORT OF SOLAR AND GEOPHYSICAL ACTIVITY SDF NUMBER 107 ISSUED AT 2200Z ON 16 APR 2000 IA. ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM 15/2100Z TO 16/2100Z: SOLAR ACTIVITY WAS LOW. REGION 8955 (S21E07) ENDURES AS THE MOST COMPLEX AND ACTIVE REGION ON THE SUN. THIS REGION PRODUCED A C6/SF AT 15/2143UT AND A C6/1N AT 16/0015UT. BOTH EVENTS WERE ACCOMPANIED BY MINOR CENTIMETRIC BURSTS. NO SIGNIFICANT CHANGES WERE OBSERVED IN THE OVERALL SIZE OF THIS REGION, BUT SOME DECREASE IN COMPLEXITY WAS NOTED. REGIONS 8957 (S12W90) AND 8959 (S17W25) ALSO PRODUCED MINOR C-CLASS X-RAY FLARES. NEW REGION 8964 (N34E21) WAS NUMBERED TODAY. IB. SOLAR ACTIVITY FORECAST: SOLAR ACTIVITY IS EXPECTED TO BE LOW TO MODERATE. ISOLATED M-CLASS EVENTS ARE STILL POSSIBLE FROM REGION 8955. IIA. GEOPHYSICAL ACTIVITY SUMMARY FROM 15/2100Z TO 16/2100Z: THE GEOMAGNETIC FIELD WAS AT UNSETTLED TO MINOR STORM LEVELS. MINOR STORMING BEGAN AFTER A WEAK SHOCK WAS OBSERVED PASSING THE ACE SPACECRAFT AT 16/0951UT. IIB. GEOPHYSICAL ACTIVITY FORECAST: THE GEOMAGNETIC FIELD SHOULD REMAIN PREDOMINANTLY UNSETTLED TO ACTIVE WITH OCCASIONAL MINOR STORMING AT HIGH LATITUDES. ACTIVE CONDITIONS MAY BE PROLONGED THROUGH DAYS TWO AND THREE BY THE ARRIVAL OF A DISTURBANCE FROM THE M4/CME EVENT ON 15/1018UT. III. EVENT PROBABILITIES 17 APR-19 APR CLASS M 50/50/50 CLASS X 10/10/10 PROTON 05/05/05 PCAF GREEN IV. PENTICTON 10.7 CM FLUX OBSERVED 16 APR 159 PREDICTED 17 APR-19 APR 160/160/165 90 DAY MEAN 16 APR 184 V. GEOMAGNETIC A INDICES OBSERVED AFR/AP 15 APR 007/007 ESTIMATED AFR/AP 16 APR 022/024 PREDICTED AFR/AP 17 APR-19 APR 015/015-015/018-012/012 VI. GEOMAGNETIC ACTIVITY PROBABILITIES 17 APR-19 APR A. MIDDLE LATITUDES ACTIVE 40/40/30 MINOR STORM 20/20/15 MAJOR-SEVERE STORM 05/05/01 B. HIGH LATITUDES ACTIVE 50/50/35 MINOR STORM 30/30/20 MAJOR-SEVERE STORM 15/15/05