- Press Release
- Jun 7, 2023
Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 108 Issued at 2200Z on 18 Apr 2023
IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity has been at low levels for the past 24 hours. The largest solar event of the period was a C4 event observed at 18/1529Z from Region 3280 (S08W94). There are currently 8 numbered sunspot regions on the disk.
IB. Solar Activity Forecast: Solar activity is expected to be low with a chance for M-class flares and a slight chance for an X-class flare on days one, two, and three (19 Apr, 20 Apr, 21 Apr).
IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at quiet to active levels for the past 24 hours. Solar wind speed reached a peak of 624 km/s at 18/2033Z. Total IMF reached 19 nT at 18/1612Z. The maximum southward component of Bz reached -16 nT at 18/1549Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 198 pfu.
IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to minor storm levels on day one (19 Apr), unsettled to minor storm levels on day two (20 Apr) and quiet to active levels on day three (21 Apr).
III. Event probabilities 19 Apr-21 Apr
Class M 40/40/40
Class X 10/10/10
IV. Penticton 10.7 cm Flux
Observed 18 Apr 153
Predicted 19 Apr-21 Apr 150/145/140
90 Day Mean 18 Apr 162
V. Geomagnetic A Indices
Observed Afr/Ap 17 Apr 006/005
Estimated Afr/Ap 18 Apr 012/018
Predicted Afr/Ap 19 Apr-21 Apr 018/020-017/024-015/016
VI. Geomagnetic Activity Probabilities 19 Apr-21 Apr
A. Middle Latitudes
Minor Storm 20/20/10
Major-severe storm 01/01/01
B. High Latitudes
Minor Storm 25/25/25
Major-severe storm 60/60/35