Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 20 September 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 263 Issued at 2200Z on 20 Sep 2021

IA. Analysis of Solar Active Regions and Activity from 19/2100Z to 20/2100Z: Solar activity has been at very low levels for the past 24 hours. 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 on days one, two, and three (21 Sep, 22 Sep, 23 Sep).

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z: The geomagnetic field has been at quiet levels for the past 24 hours. Solar wind speed reached a peak of 327 km/s at 20/0346Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 124 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to unsettled levels on days one and two (21 Sep, 22 Sep) and quiet to active levels on day three (23 Sep).

III. Event probabilities 21 Sep-23 Sep
Class M 05/05/05
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 20 Sep 079
Predicted 21 Sep-23 Sep 075/075/077
90 Day Mean 20 Sep 082

V. Geomagnetic A Indices
Observed Afr/Ap 19 Sep 002/002
Estimated Afr/Ap 20 Sep 004/004
Predicted Afr/Ap 21 Sep-23 Sep 007/008-008/008-008/012

VI. Geomagnetic Activity Probabilities 21 Sep-23 Sep
A. Middle Latitudes
Active 20/20/30
Minor Storm 05/05/10
Major-severe storm 01/01/01
B. High Latitudes
Active 20/20/15
Minor Storm 30/30/25
Major-severe storm 25/25/40