Viewing archive of Monday, 13 September 1999
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 1999 Sep 13 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 256 Issued at 2200Z on 13 SEP 1999IA. Analysis of Solar Active Regions and Activity from 12-2100Z to 13-2100Z SOLAR ACTIVITY WAS LOW. THE LARGEST EVENT THIS PERIOD
WAS A C4/SF FROM REGION 8699 (N21E01), WHICH OCCURRED AT 13/0846UT.
THE RAPID GROWTH NOTED IN THIS REGION OVER THE PAST 48 HOURS
SUBSIDED DURING THE LATTER HALF OF THIS PERIOD. THE REGION RETAINS A
MODERATELY COMPLEX MAGNETIC STRUCTURE BUT HAS RELATIVELY SMALL WHITE
LIGHT AERIAL COVERAGE. REGION 8690 (N14W06) EXHIBITED GROWTH,
PRODUCED OCCASIONAL SUBFLARES LATE IN THE PERIOD AND WAS THE LIKELY
SOURCE FOR A TYPE II SWEEP AT 13/1622UT. NEW REGION 8701 (N18E13),
WAS NUMBERED TODAY.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW.
SEVERAL EXISTING REGIONS HAVE C-CLASS FLARE POTENTIAL WITH A SMALL
CHANCE OF AN ISOLATED M-CLASS EVENT.
IIA. Geophysical Activity Summary 12-2100Z to 13-2100Z
THE GEOMAGNETIC FIELD WAS AT UNSETTLED TO MINOR STORM CONDITIONS WITH
AN ISOLATED MAJOR STORM PERIOD OBSERVED BETWEEN 13/0000 - 0300Z.
THIS DISTURBANCE IS LIKELY ASSOCIATED WITH A HIGH-SPEED CORONAL HOLE
WIND STREAM.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO CONTINUE AT UNSETTLED TO MINOR STORM LEVELS WITH THE
MOST DISTURBED CONDITIONS EXPECTED DURING LOCAL NIGHTTIME HOURS.
III. Event Probabilities 14 SEP to 16 SEP
| Class M | 20% | 20% | 20% |
| Class X | 05% | 05% | 05% |
| Proton | 05% | 05% | 05% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 13 SEP 155 Predicted 14 SEP-16 SEP 160/165/170 90 Day Mean 13 SEP 164
V. Geomagnetic A Indices
OBSERVED AFR/AP 12 SEP 020/026 ESTIMATED AFR/AP 13 SEP 032/040 PREDICTED AFR/AP 14 SEP-16 SEP 025/025-018/015-018/015
VI. Geomagnetic Activity Probabilities 14 SEP to 16 SEP
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 50% | 50% | 40% |
| Minor storm | 20% | 20% | 15% |
| Major-severe storm | 10% | 10% | 05% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 60% | 60% | 50% |
| Minor storm | 30% | 30% | 25% |
| Major-severe storm | 10% | 10% | 05% |
All times in UTC
Latest news
Sunday, 7 December 2025
M8.1 solar flare with earth-directed CME
Monday, 1 December 2025
X1.9 solar flare, Coronal hole faces Earth
Friday, 14 November 2025
X4.0 solar flare
Latest forum messages
Returning Carrington 14SDO Magnetogram 27Geminid Meteor Shower 23Current Farside Activity 252Coronal Hole 06 50
More topicsSupport SpaceWeatherLive.com!
A lot of people come to SpaceWeatherLive to follow the Solar activity or if there is a chance to see the aurora, but with more traffic comes higher costs to keep the servers online. If you like SpaceWeatherLive and want to support the project you can choose a subscription for an ad-free site or consider a donation. With your help we can keep SpaceWeatherLive online!
Space weather facts
| Last X-flare | 2025/12/08 | X1.1 |
| Last M-flare | 2025/12/12 | M1.1 |
| Last geomagnetic storm | 2025/12/12 | Kp5 (G1) |
| Spotless days | |
|---|---|
| Last spotless day | 2022/06/08 |
| Monthly mean Sunspot Number | |
|---|---|
| November 2025 | 91.8 -22.8 |
| December 2025 | 131.8 +40 |
| Last 30 days | 108.3 +14.5 |