Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 25 September 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 268 Issued at 2200Z on 25 Sep 2021

IA. Analysis of Solar Active Regions and Activity from 24/2100Z to 25/2100Z: 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 25/1917Z from Region 2871 (S28W13). There are currently 2 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 on days one, two, and three (26 Sep, 27 Sep, 28 Sep).

IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z: The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 574 km/s at 25/0443Z. Total IMF reached 6 nT at 24/2332Z. The maximum southward component of Bz reached -4 nT at 25/0055Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 236 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to minor storm levels on day one (26 Sep), unsettled to major storm levels on day two (27 Sep) and quiet to unsettled levels on day three (28 Sep).

III. Event probabilities 26 Sep-28 Sep
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 25 Sep 088
Predicted 26 Sep-28 Sep 088/086/086
90 Day Mean 25 Sep 082

V. Geomagnetic A Indices
Observed Afr/Ap 24 Sep 006/006
Estimated Afr/Ap 25 Sep 008/008
Predicted Afr/Ap 26 Sep-28 Sep 011/018-020/028-008/008

VI. Geomagnetic Activity Probabilities 26 Sep-28 Sep
A. Middle Latitudes
Active 35/30/20
Minor Storm 35/40/05
Major-severe storm 10/20/01
B. High Latitudes
Active 05/05/15
Minor Storm 25/20/25
Major-severe storm 70/75/25