Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 111 Issued at 2200Z on 21 Apr 2023

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 C2 event observed at 20/2230Z from Region 3281 (S22W22). There are currently 7 numbered sunspot regions on the disk.

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

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z: The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 514 km/s at 21/2036Z. Total IMF reached 6 nT at 21/1836Z. The maximum southward component of Bz reached -6 nT at 21/1815Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 131 pfu.

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

III. Event probabilities 22 Apr-24 Apr
Class M 40/40/40
Class X 01/01/01
Proton 05/05/05
PCAF green

IV. Penticton 10.7 cm Flux
Observed 21 Apr 151
Predicted 22 Apr-24 Apr 140/135/130
90 Day Mean 21 Apr 160

V. Geomagnetic A Indices
Observed Afr/Ap 20 Apr 005/004
Estimated Afr/Ap 21 Apr 009/010
Predicted Afr/Ap 22 Apr-24 Apr 014/016-010/012-008/008

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

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