NOAA/USAF Report of Solar-Geophysical Activity 13 Apr 2000

:Product: Report of Solar-Geophysical Activity

:Issued: 2000 Apr 13 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 104 ISSUED AT 2200Z ON 13 APR 2000

IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  12/2100Z

TO 13/2100Z:  SOLAR ACTIVITY DECREASED TO LOW LEVELS. REGION 8948

(S15W49) SHOWED GRADUAL SIMPLIFICATION OF ITS MAGNETIC STRUCTURE,

BUT MAINTAINED A BETA-GAMMA CLASSIFICATION. IT PRODUCED A C-CLASS

SUBFLARE EARLY IN THE PERIOD. SLIGHT GROWTH WAS REPORTED IN REGION

8959 (S17E14). THE REMAINING REGIONS WERE STABLE INCLUDING NEWLY

NUMBERED REGIONS 8960 (N19W15), 8961 (S25E07), 8962 (N21E76), AND

8963 (N15E74).

IB.  SOLAR ACTIVITY FORECAST:  ACTIVITY IS EXPECTED TO BE AT LOW TO

MODERATE LEVELS. THERE IS A FAIR CHANCE FOR AN ISOLATED M-CLASS

FLARE FROM REGION 8948.

IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 12/2100Z TO 13/2100Z:

GEOMAGNETIC FIELD ACTIVITY RANGED FROM QUIET TO UNSETTLED LEVELS. THE

GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT REMAINED AT

MODERATE TO HIGH LEVELS.

IIB.  GEOPHYSICAL ACTIVITY FORECAST:  GEOMAGNETIC FIELD ACTIVITY IS

EXPECTED TO REMAIN AT QUIET TO UNSETTLED LEVELS DURING MOST OF THE

PERIOD. HOWEVER, BRIEF ACTIVE PERIODS ARE POSSIBLE ON 15 APRIL DUE

TO A SMALL, FAVORABLY POSITIONED CORONAL HOLE. THE GREATER THAN 2

MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS EXPECTED TO DECREASE TO

NORMAL TO MODERATE LEVELS EARLY IN THE PERIOD.

III.  EVENT PROBABILITIES 14 APR-16 APR

CLASS M    40/40/40

CLASS X    05/05/05

PROTON     05/05/05

PCAF       GREEN

IV.  PENTICTON 10.7 CM FLUX

OBSERVED           13 APR 164

PREDICTED   14 APR-16 APR  165/165/160

90 DAY MEAN        13 APR 185

V.  GEOMAGNETIC A INDICES

OBSERVED AFR/AP 12 APR  007/005

ESTIMATED AFR/AP 13 APR  005/008

PREDICTED AFR/AP 14 APR-16 APR  008/010-012/012-007/007

VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 14 APR-16 APR

A.  MIDDLE LATITUDES

ACTIVE                20/30/15

MINOR STORM           05/10/05

MAJOR-SEVERE STORM    01/01/01

B.  HIGH LATITUDES

ACTIVE                25/35/20

MINOR STORM           10/20/10

MAJOR-SEVERE STORM    01/05/01