Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 18 April 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 108 Issued at 2200Z on 18 Apr 2021

IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity has been at very low levels for the past 24 hours. There are currently 1 numbered sunspot regions on the disk.

IB. Solar Activity Forecast: Solar activity is expected to be very low with a slight chance for a C-class flare on days one, two, and three (19 Apr, 20 Apr, 21 Apr).

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at quiet to active levels for the past 24 hours. Solarwind speed reached a peak of 668 km/s at 17/2136Z. Total IMF reached 6 nT at 18/0050Z. The maximum southward component of Bz reached -5 nT at
18/0337Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 14078 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on day one (19 Apr), quiet to unsettled levels on day two (20 Apr) and quiet levels on day three (21 Apr).

III. Event probabilities 19 Apr-21 Apr
Class M 01/01/01
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 18 Apr 078
Predicted 19 Apr-21 Apr 078/075/075
90 Day Mean 18 Apr 076

V. Geomagnetic A Indices
Observed Afr/Ap 17 Apr 020/024
Estimated Afr/Ap 18 Apr 011/014
Predicted Afr/Ap 19 Apr-21 Apr 012/012-009/008-006/005

VI. Geomagnetic Activity Probabilities 19 Apr-21 Apr
A. Middle Latitudes
Active 40/25/15
Minor Storm 15/10/01
Major-severe storm 01/01/01
B. High Latitudes
Active 10/15/15
Minor Storm 25/30/20
Major-severe storm 50/40/20