Viewing archive of Thursday, 20 May 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 May 20 2200 UTCPrepared by the NOAA © SWPC and processed by SpaceWeatherLive.com
Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 140 Issued at 2200Z on 20 MAY 1999IA. Analysis of Solar Active Regions and Activity from 19-2100Z to 20-2100Z SOLAR ACTIVITY WAS LOW. THE PERIOD WAS CHARACTERIZED
BY A NUMBER OF WEAK, OPTICALLY UNCORRELATED C-CLASS X-RAY FLARES.
REGION 8549 (N25W59) EMERGED AND PRODUCED SEVERAL OPTICAL
SUB-FLARES. REGION 8550 (S14E74) WAS ALSO NUMBERED TODAY.
IB. Solar Activity Forecast
SOLAR ACTIVITY IS EXPECTED TO BE LOW,
WITH A SLIGHT CHANCE OF ISOLATED M-CLASS X-RAY FLARES.
IIA. Geophysical Activity Summary 19-2100Z to 20-2100Z
THE GEOMAGNETIC FIELD WAS QUIET TO UNSETTLED.
IIB. Geophysical Activity Forecast
THE GEOMAGNETIC FIELD IS
EXPECTED TO REMAIN QUIET TO UNSETTLED.
III. Event Probabilities 21 MAY to 23 MAY
| Class M | 20% | 20% | 20% |
| Class X | 01% | 01% | 01% |
| Proton | 01% | 01% | 01% |
| PCAF | GREEN | ||
IV. Penticton 10.7 cm Flux
Observed 20 MAY 143 Predicted 21 MAY-23 MAY 140/140/140 90 Day Mean 20 MAY 128
V. Geomagnetic A Indices
OBSERVED AFR/AP 19 MAY 008/010 ESTIMATED AFR/AP 20 MAY 008/010 PREDICTED AFR/AP 21 MAY-23 MAY 005/008-005/008-008/010
VI. Geomagnetic Activity Probabilities 21 MAY to 23 MAY
| A. Middle Latitudes | |||
|---|---|---|---|
| Active | 20% | 20% | 25% |
| Minor storm | 05% | 05% | 05% |
| Major-severe storm | 01% | 01% | 01% |
| B. High Latitudes | |||
|---|---|---|---|
| Active | 25% | 25% | 25% |
| Minor storm | 10% | 10% | 10% |
| Major-severe storm | 05% | 05% | 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
AR4299 M8.1 CME 2025/12/06 308Growth of Cycle 25 976Ask a powergrid operator anything 45Light pillar 11AR4294 / 4296 / 4298 441
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 | 2025/12/10 | M1.9 |
| Last geomagnetic storm | 2025/12/04 | Kp5 (G1) |
| Spotless days | |
|---|---|
| Last spotless day | 2022/06/08 |
| Monthly mean Sunspot Number | |
|---|---|
| November 2025 | 91.8 -22.8 |
| December 2025 | 157.7 +65.9 |
| Last 30 days | 108.9 +11.4 |