Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 21 April 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 111 Issued at 2200Z on 21 Apr 2021

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 C1 event observed at 21/0129Z from Region 2817 (N18W79). 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 and a slight chance for an M-class flare on day one (22 Apr) and expected to be very low with a chance for a C-class flares on day two (23 Apr) and expected to be very low with a slight chance for a C-class flare on day three (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 605 km/s at 20/2101Z. Total IMF reached 5 nT at 21/0109Z. The maximum southward component of Bz reached -3 nT at 21/0548Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 12719 pfu.

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

III. Event probabilities 22 Apr-24 Apr
Class M 10/05/01
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 21 Apr 078
Predicted 22 Apr-24 Apr 080/078/078
90 Day Mean 21 Apr 076

V. Geomagnetic A Indices
Observed Afr/Ap 20 Apr 010/012
Estimated Afr/Ap 21 Apr 007/008
Predicted Afr/Ap 22 Apr-24 Apr 005/005-009/010-009/010

VI. Geomagnetic Activity Probabilities 22 Apr-24 Apr
A. Middle Latitudes
Active 15/40/40
Minor Storm 01/15/15
Major-severe storm 01/01/01
B. High Latitudes
Active 15/10/10
Minor Storm 20/25/25
Major-severe storm 20/50/50