Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 18 September 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 261 Issued at 2200Z on 18 Sep 2021

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 18/0827Z from Region 2871 (S28E73). There are currently 1 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 (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 426 km/s at 18/0408Z. Total IMF reached 15 nT at 17/2125Z. The maximum southward component of Bz reached -5 nT at 18/0738Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 179 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to unsettled levels on days one and three (19 Sep, 21 Sep) and quiet levels on day two (20 Sep).

III. Event probabilities 19 Sep-21 Sep
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 18 Sep 074
Predicted 19 Sep-21 Sep 076/076/076
90 Day Mean 18 Sep 082

V. Geomagnetic A Indices
Observed Afr/Ap 17 Sep 019/021
Estimated Afr/Ap 18 Sep 010/011
Predicted Afr/Ap 19 Sep-21 Sep 006/008-006/005-007/008

VI. Geomagnetic Activity Probabilities 19 Sep-21 Sep
A. Middle Latitudes
Active 20/10/20
Minor Storm 05/01/05
Major-severe storm 01/01/01
B. High Latitudes
Active 20/15/20
Minor Storm 30/20/30
Major-severe storm 25/20/25