:Product: 19980917RSGA.txt
:Issued: 1998 Sep 17 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 260 ISSUED AT 2200Z ON 17 SEP 1998
IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  16/2100Z
TO 17/2100Z:  SOLAR ACTIVITY HAS BEEN VERY LOW FOR THE PAST 24 HOURS.
TWO NEW REGIONS WERE NUMBERED: REGION 8339 (S17E42), A B-TYPE SPOT
GROUP, AND REGION 8340 (N20E76), A SINGLE H-TYPE SPOT WHICH IS THE
QUIET RETURN OF OLD ACTIVE REGION 8319. REGION 8319 PRODUCED FIVE
M-CLASS FLARES DURING ITS LAST ROTATION. NUMEROUS TYPE III RADIO
SWEEPS WERE REPORTED THROUGHOUT THE DAY, AS WELL AS A RADIO NOISE
STORM AT 410 MHZ BEGINNING AT 1839 UT. MINOR SURGING ACCOMPANIED THE
EAST LIMB APPEARANCE OF REGION 8340.  THE REMAINDER OF THE LIMBS,
AND THE DISK, WERE QUIET.
IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE LOW
BASED ON EXPECTATIONS OF C-CLASS FLARES FROM REGIONS DEVELOPING IN
ACTIVE LONGITUDES IN THE EASTERN SOLAR HEMISPHERE. ISOLATED M-CLASS
FLARES ARE POSSIBLE.
IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 16/2100Z TO 17/2100Z:
THE GEOMAGNETIC FIELD HAS BEEN QUIET FOR THE PAST 24 HOURS.
IIB.  GEOPHYSICAL ACTIVITY FORECAST:  GEOMAGNETIC ACTIVITY IS
EXPECTED TO PERSIST AT QUIET LEVELS TOMORROW, BUT INCREASE FROM
QUIET TO UNSETTLED LEVELS IF THE SOLAR WIND CHANGES FROM ITS PRESENT
STATE OF LOW SPEEDS, NORMAL DENSITIES, AND NORMAL MAGNETIC FIELD
INTENSITIES. HIGHER SPEEDS AND FLUCTUATING MAGNETIC FIELDS
ASSOCIATED  SMALL DISAPPEARING FILAMENTS, OR FROM A POSITIVE
NORTHERN CORONAL HOLE SHOULD ARRIVE AT EARTH DURING THE 3-DAY
FORECAST PERIOD.
III.  EVENT PROBABILITIES 18 SEP-20 SEP
CLASS M    10/10/10
CLASS X    01/01/01
PROTON     01/01/01
PCAF       GREEN
IV.  PENTICTON 10.7 CM FLUX
OBSERVED           17 SEP 117
PREDICTED   18 SEP-20 SEP  130/130/135
90 DAY MEAN        17 SEP 127
V.  GEOMAGNETIC A INDICES
OBSERVED AFR/AP 16 SEP  002/004
ESTIMATED AFR/AP 17 SEP  004/010
PREDICTED AFR/AP 18 SEP-20 SEP  005/010-010/012-010/012
VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 18 SEP-20 SEP
A.  MIDDLE LATITUDES
ACTIVE                10/20/25
MINOR STORM           05/10/10
MAJOR-SEVERE STORM    05/05/05
B.  HIGH LATITUDES
ACTIVE                20/25/25
MINOR STORM           10/10/15
MAJOR-SEVERE STORM    05/05/05