FROM SPACE ENVIRONMENT SERVICES CENTER, BOULDER, COLORADO
SDF NUMBER 353
JOINT USAF/NOAA REPORT OF SOLAR AND GEOPHYSICAL ACTIVITY.
ISSUED 2200Z 18 DEC 1988
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM 17/2100Z
TO 18/2100Z:  SOLAR ACTIVITY WAS HIGH. REGION 5273 (S30W45)
PRODUCED AN X1/3B FLARE AT 18/1705Z. THE FLARE WAS ACCOMPANIED
BY MINOR DISCRETE FREQUENCY BURSTS ACROSS THE SPECTRUM. A WEAK
TYPE II SWEEP BURST (WITH ESTIMATED VELOCITY BETWEEN 1200-1600
KM SEC-1) ALSO OCCURRED DURING THE FLARE. REGION 5278 (N27E04)
PRODUCED SEVERAL SUBFLARES DURING THE PERIOD. THE LARGEST OF
THESE WAS AN M1/SN FLARE AT 18/0917Z. SLIGHT RELAXATION OF THE
MAGNETIC GRADIENTS OCCURRED WITHIN THIS REGION DURING THE
PERIOD, BUT IT REMAINS IMPRESSIVE IN MORPHOLOGICAL ASPECTS.
REGION 5282 (S21E16) PRODUCED AN M1/1N FLARE AT 18/1640Z. THE
FLARE WAS ACCOMPANIED BY A SIGNIFICANT DISCRETE BURST AT
245 MHZ AND A MAJOR DISCRETE BURST (35000 SFU) AT 410 MHZ.
THREE NEW REGIONS EMERGED TODAY: 5284 (N32E54), 5285 (N20E74),
AND 5286 (N25W48). ALL WERE STRUCTURALLY SIMPLE.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE
MODERATE TO HIGH. REGIONS 5278 AND 5273 ARE THE PRIMARY THREATS
FOR MODERATE OR GREATER LEVELS OF ACTIVITY. REGIONS 5279
(N22W27), 5280 (N27E18), AND 5282 ARE CAPABLE OF PRODUCING
MODERATE LEVELS OF ACTIVITY.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 17/2100Z TO 18/2100Z:
THE GEOMAGNETIC FIELD HAS BEEN AT UNSETTLED TO MINOR STORM
LEVELS. THIS ACTIVITY WAS PROBABLY IN RESPONSE TO THE X4
FLARE OF 16 DECEMBER. THE PROTON EVENT AT GREATER THAN 10 MEV
THAT BEGAN AT 17/2000Z REACHED ITS MAXIMUM OF 29 PFU AT
18/0150Z AND ENDED AT 18/1700Z.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS
EXPECTED TO BE AT ACTIVE TO MINOR STORM LEVELS. MINOR STORMING
IS MOST LIKELY TO OCCUR ON THE SECOND DAY OF THE PERIOD IN
RESPONSE TO THE X1/3B FLARE THAT OCCURRED TODAY. A PROTON
EVENT AT GREATER THAN 10 MEV IS EXPECTED TO BEGIN BEFORE
19/0000Z WITH A MAXIMUM PREDICTED FLUX OF 63 PFU EXPECTED NEAR
19/0000Z. THIS IS ALSO AN EXPECTED RESULT OF TODAY'S X-FLARE.
III.  EVENT PROBABILITIES 19 DEC-21 DEC
CLASS M    90/90/90
CLASS X    50/50/50
PROTON     50/50/50
PCAF       YELLOW
IV.  OTTAWA 10.7 CM FLUX
OBSERVED           18 DEC  253
PREDICTED   19 DEC-21 DEC  258/262/262
90 DAY MEAN        18 DEC  169
V.  GEOMAGNETIC A INDICES
OBSERVED  AFR/AP 17 DEC  024/033
ESTIMATED AFR/AP 18 DEC  024/030
PREDICTED AFR/AP 19 DEC-21 DEC  020/020-030/025-025/025