:Product: 20000418RSGA.txt :Issued: 2000 Apr 18 2200 UTC # 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 109 ISSUED AT 2200Z ON 18 APR 2000 IA. ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM 17/2100Z TO 18/2100Z: SOLAR ACTIVITY WAS LOW. REGION 8963 (N16E09) RAPIDLY EMERGED AS THE PRIMARY FLARE PRODUCING REGION ON THE VISIBLE DISK AND WAS RESPONSIBLE FOR THE THREE LARGEST EVENTS OF THE PERIOD. THE FIRST AND LARGEST EVENT WAS A C7/SF AT 18/0805UT, FOLLOWED BY A C4 FLARE WITH A TYPE II SWEEP AT 18/1153UT, AND FINALLY A C4/SF AT 18/1415UT. ALL EVENTS WERE ACCOMPANIED BY MINOR CENTIMETRIC BURSTS. THIS REGION, THOUGH QUITE ACTIVE, IS A RELATIVELY SMALL DAO GROUP WITH 80 MILLIONTHS OF WHITE LIGHT AREA. REGION 8955 (S22W19) HAS STABILIZED, PRODUCING ONLY OCCASIONAL MINOR C-CLASS FLARES. NEW REGION 8966 (S13E65) WAS NUMBERED TODAY. REMAINING REGIONS WERE QUIET. IB. SOLAR ACTIVITY FORECAST: SOLAR ACTIVITY IS EXPECTED TO BE LOW. REGIONS 8955 AND 8963 WILL LIKELY CONTINUE TO PRODUCE C-CLASS ACTIVITY. IIA. GEOPHYSICAL ACTIVITY SUMMARY FROM 17/2100Z TO 18/2100Z: THE GEOMAGNETIC FIELD WAS MOSTLY QUIET WITH OCCASIONAL UNSETTLED PERIODS. IIB. GEOPHYSICAL ACTIVITY FORECAST: THE GEOMAGNETIC FIELD IS EXPECTED TO REMAIN AT QUIET TO UNSETTLED LEVELS. III. EVENT PROBABILITIES 19 APR-21 APR CLASS M 35/35/35 CLASS X 05/05/05 PROTON 01/01/01 PCAF GREEN IV. PENTICTON 10.7 CM FLUX OBSERVED 18 APR 160 PREDICTED 19 APR-21 APR 160/165/170 90 DAY MEAN 18 APR 183 V. GEOMAGNETIC A INDICES OBSERVED AFR/AP 17 APR 011/014 ESTIMATED AFR/AP 18 APR 006/010 PREDICTED AFR/AP 19 APR-21 APR 008/012-010/015-005/008 VI. GEOMAGNETIC ACTIVITY PROBABILITIES 19 APR-21 APR A. MIDDLE LATITUDES ACTIVE 25/25/20 MINOR STORM 10/10/05 MAJOR-SEVERE STORM 01/01/01 B. HIGH LATITUDES ACTIVE 30/35/25 MINOR STORM 20/25/15 MAJOR-SEVERE STORM 05/05/01