Viewing archive of Wednesday, 18 August 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 Aug 18 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 230 Issued at 2200Z on 18 AUG 1999IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z
SOLAR ACTIVITY WAS LOW. A LONG-DURATION C7 EVENT WAS
THE HIGHLIGHT OF THE PERIOD, BUT THE EVENT WAS NOT OPTICALLY
OBSERVED. REGION 8668 (N22E15) REMAINS THE DOMINANT ACTIVE CENTER IN
WHITE LIGHT AND H-ALPHA. NEWLY ASSIGNED REGION 8672 (N12E01) EMERGED
JUST WEST OF 8668 AND PRODUCED A SUBFLARE AT 1154Z.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW.
HOWEVER, REGION 8668 MAY PRODUCE AN ISOLATED M-CLASS EVENT DURING
THE NEXT THREE DAYS.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
THE GEOMAGNETIC FIELD REMAINED AT ACTIVE TO MINOR STORM LEVELS. THIS
DISTURBANCE, RELATED TO A HIGH SPEED SOLAR WIND STREAM, BEGAN IN THE
EARLY PART OF 16 AUGUST. SPEEDS CONTINUED IN THE 600-700 KM/S RANGE
MOST OF TODAY. THE GREATER THAN 2 MEV GEOSYNCHRONOUS ELECTRON FLUX
ATTAINED HIGH LEVELS AROUND 1200Z.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO BE UNSETTLED TO ACTIVE ON 19 AUGUST. SOLAR WIND SPEEDS
SHOULD DIMINISH TO A MORE NORMAL RANGE THEN, AND ACTIVITY SHOULD
DECLINE. UNSETTLED CONDITIONS SHOULD PREVAIL AT THE END OF THE
INTERVAL.
III. Event Probabilities 19 AUG to 21 AUG
| Class M | 15% | 15% | 15% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 18 AUG 131 Predicted 19 AUG-21 AUG 140/155/170 90 Day Mean 18 AUG 163
V. Geomagnetic A Indices
OBSERVED AFR/AP 17 AUG 026/027 ESTIMATED AFR/AP 18 AUG 030/030 PREDICTED AFR/AP 19 AUG-21 AUG 015/020-015/015-015/010
VI. Geomagnetic Activity Probabilities 19 AUG to 21 AUG
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 35% | 25% | 20% |
| Minor storm | 15% | 10% | 10% |
| Major-severe storm | 01% | 01% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 45% | 40% | 40% |
| Minor storm | 30% | 20% | 20% |
| Major-severe storm | 05% | 01% | 01% |
All times in UTC
Latest news
Tuesday, 15 April 2025
CME arrival, G3 storm watch
Friday, 28 March 2025
X1.1 solar flare
Monday, 24 March 2025
Coronal hole faces Earth
Latest forum messages
AR4064 29Filaments and prominences 106AR 4055 115Line chart of indicators on the auror video, animated graph trace 26Unspecified geomagnetic activity 2335
More topicsSupport SpaceWeatherLive.com!
A lot of people come to SpaceWeatherLive to follow the Sun's activity or if there is aurora to be seen, but with more traffic comes higher server costs. Consider a donation if you enjoy SpaceWeatherLive so we can keep the website online!
Latest alerts
07:27 UTC - Hemispheric Power Index
The OVATION model predicts the Hemispheric Power Index to reach 50GW at 08:15 UTC
07:15 UTC - Geomagnetic activity
Active geomagnetic conditions (Kp4) Threshold Reached: 07:03 UTC
06:27 UTC - Coronal mass ejection arrival
CME impact detected - Current Solar Wind Speed 644km/sec - IMF: Bt (strength): 15nT & Bz: 0nT (South).
Space weather facts
| Last X-flare | 2025/03/28 | X1.1 |
| Last M-flare | 2025/04/22 | M1.3 |
| Last geomagnetic storm | 2025/04/21 | Kp5+ (G1) |
| Spotless days | |
|---|---|
| Last spotless day | 2022/06/08 |
| Monthly mean Sunspot Number | |
|---|---|
| March 2025 | 134.2 -20.4 |
| April 2025 | 121.5 -12.7 |
| Last 30 days | 114.6 -22.2 |