Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 17 April 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 107 Issued at 2200Z on 17 Apr 2021

IA. Analysis of Solar Active Regions and Activity from 16/2100Z to 17/2100Z: Solar activity has been at very low levels for the past 24 hours. There are currently 2 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 on days one, two, and three (18 Apr, 19 Apr, 20 Apr).

IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z: The geomagnetic field has been at unsettled to minor storm levels for the past 24 hours. Solar wind speed reached a peak of 612 km/s at 17/0527Z. Total IMF reached 12 nT at 16/2217Z. The maximum southward component of Bz reached -10 nT at 16/2158Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 1092 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on days one and two (18 Apr, 19 Apr) and quiet to unsettled levels on day three (20 Apr).

III. Event probabilities 18 Apr-20 Apr
Class M 01/01/01
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 17 Apr 075
Predicted 18 Apr-20 Apr 078/078/075
90 Day Mean 17 Apr 076

V. Geomagnetic A Indices
Observed Afr/Ap 16 Apr 015/019
Estimated Afr/Ap 17 Apr 020/030
Predicted Afr/Ap 18 Apr-20 Apr 012/016-010/012-009/008

VI. Geomagnetic Activity Probabilities 18 Apr-20 Apr
A. Middle Latitudes
Active 35/35/20
Minor Storm 15/15/05
Major-severe storm 01/01/01
B. High Latitudes
Active 10/10/20
Minor Storm 25/25/25
Major-severe storm 50/50/25