FROM SPACE ENVIRONMENT SERVICES CENTER, BOULDER, COLORADO SDF NUMBER 350 JOINT USAF/NOAA REPORT OF SOLAR AND GEOPHYSICAL ACTIVITY. ISSUED 2200Z 15 DEC 1988 IA. ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM 14/2100Z TO 15/2100Z: SOLAR ACTIVITY WAS HIGH. REGION 5278 (N26E44) PRODUCED AN X1/1N FLARE AT 0509Z. THE EVENT LASTED JUST OVER TWO HOURS AND WAS ASSOCIATED WITH SIGNIFICANT RADIO BURSTS, INCLUDING A TENFLARE, A STRONG TYPE II SWEEP, AND A TYPE IV SWEEP. THE ONLY OTHER CLASS M OR GREATER FLARE WAS AN M1 AT 0729Z WHICH WAS NOT OBSERVED OPTICALLY. NUMEROUS ADDITIONAL C-CLASS FLARES WERE PRODUCED WITH CONTRIBUTIONS FROM 5279 (N21E10) AND 5273 (S32W09). THE REMAINDER OF THE SOLAR DISK AND LIMBS WERE STABLE AND QUIET. IB. SOLAR ACTIVITY FORECAST: SOLAR ACTIVITY IS EXPECTED TO BE MODERATE WITH A CONTINUED SLIGHT CHANCE FOR X-CLASS FLARES OR PROTON EVENT PRODUCING FLARES. REGION 5278 CONTINUES TO BE THE PRIMARY THREAT FOR M-CLASS OR GREATER FLARES, AND REGIONS 5273 AND 5279 ARE ALSO CAPABLE OF RAISING ACTIVITY TO MODERATE LEVELS. IIA. GEOPHYSICAL ACTIVITY SUMMARY FROM 14/2100Z TO 15/2100Z: THE GEOMAGNETIC FIELD WAS MOSTLY QUIET TO UNSETTLED, WITH SOME BRIEF ISOLATED PERIODS OF ACTIVE LEVELS. IIB. GEOPHYSICAL ACTIVITY FORECAST: THE GEOMAGNETIC FIELD IS EXPECTED TO ATTAIN ACTIVE TO MINOR STORM LEVELS OVER THE NEXT THREE DAYS IN RESPONSE TO TODAY'S X-CLASS X-RAY EVENT. THE DISTURBANCE IS EXPECTED TO BEGIN LATE TOMORROW, REACH PEAK INTENSITY ON THE SECOND DAY, AND SUBSIDE LATE ON THE THIRD DAY. A PROTON EVENT IS EXPECTED TO BEGIN NEAR MID-DAY TOMORROW IN RESPONSE TO THE FLARE AND IS EXPECTED TO REACH A MAXIMUM OF ABOUT 50 PFU LATE TOMORROW. III. EVENT PROBABILITIES 16 DEC-18 DEC CLASS M 85/85/85 CLASS X 20/20/20 PROTON 20/20/20 PCAF YELLOW IV. OTTAWA 10.7 CM FLUX OBSERVED 15 DEC 219 PREDICTED 16 DEC-18 DEC 218/213/208 90 DAY MEAN 15 DEC 165 V. GEOMAGNETIC A INDICES OBSERVED AFR/AP 14 DEC 012/013 ESTIMATED AFR/AP 15 DEC 010/012 PREDICTED AFR/AP 16 DEC-18 DEC 020/018-035/030-020/018