Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 21 September 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 264 Issued at 2200Z on 21 Sep 2021

IA. Analysis of Solar Active Regions and Activity from 20/2100Z to 21/2100Z: Solar activity has been at low levels for the past 24 hours. The largest solar event of the period was a C1 event observed at 21/1153Z from Region 2873 (N26W22). There are currently 3 numbered sunspot regions on the disk.

IB. Solar Activity Forecast: Solar activity is expected to be very low with a chance for a C-class flares and a slight chance for an M-class flare on days one, two, and three (22 Sep, 23 Sep, 24 Sep).

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z: The geomagneticfield has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 344 km/s at 21/0539Z. Total IMF reached 9 nT at 21/1927Z. The maximum southward component of Bz reached -8 nT at 21/1927Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 174 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to unsettled levels on days one and three (22 Sep, 24 Sep) and quiet to active levels on day two (23 Sep).

III. Event probabilities 22 Sep-24 Sep
Class M 10/10/10
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 21 Sep 085
Predicted 22 Sep-24 Sep 085/088/090
90 Day Mean 21 Sep 082

V. Geomagnetic A Indices
Observed Afr/Ap 20 Sep 004/002
Estimated Afr/Ap 21 Sep 007/008
Predicted Afr/Ap 22 Sep-24 Sep 008/008-008/012-007/008

VI. Geomagnetic Activity Probabilities 22 Sep-24 Sep
A. Middle Latitudes
Active 20/30/20
Minor Storm 05/10/05
Major-severe storm 01/01/01
B. High Latitudes
Active 20/15/20
Minor Storm 30/25/30
Major-severe storm 25/40/25