Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 23 April 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 113 Issued at 2200Z on 23 Apr 2021

IA. Analysis of Solar Active Regions and Activity from 22/2100Z to 23/2100Z: 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 23/0252Z from Region 2817 (N18, L=336). There are currently 2 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 (24 Apr, 25 Apr, 26 Apr).

IIA. Geophysical Activity Summary 22/2100Z to 23/2100Z: The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 426 km/s at 23/0246Z. Total IMF reached 10nT at 23/2100Z. The maximum southward component of Bz reached -6 nT at 23/2045Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 19293 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on days one and three (24 Apr, 26 Apr) and quiet to major storm levels on day two (25 Apr).

III. Event probabilities 24 Apr-26 Apr
Class M 10/10/10
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 23 Apr 077
Predicted 24 Apr-26 Apr 077/077/077
90 Day Mean 23 Apr 076

V. Geomagnetic A Indices
Observed Afr/Ap 22 Apr 004/005
Estimated Afr/Ap 23 Apr 011/013
Predicted Afr/Ap 24 Apr-26 Apr 011/012-019/025-013/015

VI. Geomagnetic Activity Probabilities 24 Apr-26 Apr
A. Middle Latitudes
Active 30/35/30
Minor Storm 10/35/15
Major-severe storm 01/10/05
B. High Latitudes
Active 15/05/15
Minor Storm 25/20/30
Major-severe storm 40/75/50