Viewing archive of Thursday, 17 September 1998
Solar activity report
Any mentioned solar flare in this report has a scaling factor applied by the Space Weather Prediction Center (SWPC). Because of the SWPC scaling factor, solar flares are reported as 42% smaller than for the science quality data. The scaling factor has been removed from our archived solar flare data to reflect the true physical units.
Report of Solar-Geophysical Activity 1998 Sep 17 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 260 Issued at 2200Z on 17 SEP 1998IA. 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 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 to 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 to 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% |
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