Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 261 Issued at 2200Z on 18 Sep 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 C2 event observed at 18/1041Z from Region 3435 (N09E56). There are currently 9 numbered sunspot regions on the disk.
IB. Solar Activity Forecast: Solar activity is expected to be low with a slight chance for an M-class flare on days one, two, and three (19 Sep, 20 Sep, 21 Sep).
IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at quiet to minor storm levels for the past 24 hours. Solar wind speed reached a peak of 598 km/s at 18/1617Z. Total IMF reached 22 nT at 18/1540Z. The maximum southward component of Bz reached -18 nT at 18/1644Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 734 pfu.
IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at unsettled to major storm levels on day one (19 Sep), quiet to active levels on day two (20 Sep) and quiet to unsettled levels on day three (21 Sep).
III. Event probabilities 19 Sep-21 Sep
Class M 20/20/20
Class X 01/01/01
Proton 05/01/01
PCAF green
IV. Penticton 10.7 cm Flux
Observed 18 Sep 155
Predicted 19 Sep-21 Sep 154/154/152
90 Day Mean 18 Sep 162
V. Geomagnetic A Indices
Observed Afr/Ap 17 Sep 014/020
Estimated Afr/Ap 18 Sep 023/029
Predicted Afr/Ap 19 Sep-21 Sep 022/035-014/015-008/008
VI. Geomagnetic Activity Probabilities 19 Sep-21 Sep
A. Middle Latitudes
Active 25/30/20
Minor Storm 40/10/05
Major-severe storm 35/01/01
B. High Latitudes
Active 05/15/15
Minor Storm 20/20/20
Major-severe storm 75/20/20
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