From: Space Weather Prediction Center (NOAA)
Posted: Tuesday, April 20, 2021
Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 110 Issued at 2200Z on 20 Apr 2021 IA. Analysis of Solar Active Regions and Activity from 19/2100Z to 20/2100Z: Solar activity has been at moderate levels for the past 24 hours. The largest solar event of the period was a M1 event observed at 19/2342Z from Region 2816 (S24E21). There are currently 3 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 and two (21 Apr, 22 Apr) and expected to be very low with a chance for a C-class flares and a slight chance for an M-class flare on day three (23 Apr). IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z: The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Solar wind speed reached a peak of 687 km/s at 19/2348Z. Total IMF reached 6 nT at 20/0222Z. The maximum southward component of Bz reached -5 nT at 19/2342Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 13356 pfu.
IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to unsettled levels on days one and three (21 Apr, 23 Apr) and quiet levels on day two (22 Apr).
III. Event probabilities 21 Apr-23 Apr
Class M 15/15/10
Class X 01/01/01
IV. Penticton 10.7 cm Flux
Observed 20 Apr 080
Predicted 21 Apr-23 Apr 084/082/082
90 Day Mean 20 Apr 076
V. Geomagnetic A Indices
Observed Afr/Ap 19 Apr 015/020
Estimated Afr/Ap 20 Apr 011/012
Predicted Afr/Ap 21 Apr-23 Apr 006/005-005/005-007/008
VI. Geomagnetic Activity Probabilities 21 Apr-23 Apr
A. Middle Latitudes
Minor Storm 01/01/10
Major-severe storm 01/01/01
B. High Latitudes
Minor Storm 25/20/30
Major-severe storm 20/20/40
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