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

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 115 Issued at 2200Z on 25 Apr 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 C2 event observed at 25/0135Z from Region 2816 (S22W65). There are currently 4 numbered sunspot regions on the disk.

IB. Solar Activity Forecast: Solar activity is likely to be low with a slight chance for an M-class flare on days one, two, and three (26 Apr, 27 Apr, 28 Apr).

IIA. Geophysical Activity Summary 24/2100Z to 25/2100Z: The geomagnetic field has been at quiet to minor storm levels for the past 24 hours. Solar wind speed reached a peak of 503 km/s at 25/2051Z. Total IMF reached 10 nT at 24/2318Z. The maximum southward component of Bz reached -9 nT at 24/2349Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 3082 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on day one (26 Apr) and quiet levels on days two and three (27 Apr, 28 Apr).

III. Event probabilities 26 Apr-28 Apr
Class M 10/10/10
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 25 Apr 079
Predicted 26 Apr-28 Apr 079/078/078
90 Day Mean 25 Apr 076

V. Geomagnetic A Indices
Observed Afr/Ap 24 Apr 010/012
Estimated Afr/Ap 25 Apr 018/021
Predicted Afr/Ap 26 Apr-28 Apr 013/015-006/005-006/005

VI. Geomagnetic Activity Probabilities 26 Apr-28 Apr
A. Middle Latitudes
Active 30/10/10
Minor Storm 15/01/01
Major-severe storm 05/01/01
B. High Latitudes
Active 15/15/15
Minor Storm 30/20/20
Major-severe storm 50/10/10