Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 20 May 2021

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 140 Issued at 2200Z on 20 May 2021

IA. Analysis of Solar Active Regions and Activity from 19/2100Z to 20/2100Z: 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 day one (21 May) and expected to be very low on days two and three (22 May, 23 May).

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z: The geomagnetic field has been at quiet to minor storm levels for the past 24 hours. Solar wind speed reached a peak of 575 km/s at 20/2042Z. Total IMF reached 18 nT at 20/1201Z. The maximum southward component of Bz reached -14 nT at 20/1027Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 117 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to active levels on day one (21 May), quiet to unsettled levels on day two (22 May) and quiet levels on day three (23 May).

III. Event probabilities 21 May-23 May
Class M 01/01/01
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 20 May 072
Predicted 21 May-23 May 072/072/072
90 Day Mean 20 May 076

V. Geomagnetic A Indices
Observed Afr/Ap 19 May 005/005
Estimated Afr/Ap 20 May 020/024
Predicted Afr/Ap 21 May-23 May 008/010-008/008-006/005

VI. Geomagnetic Activity Probabilities 21 May-23 May
A. Middle Latitudes
Active 30/15/10
Minor Storm 10/01/01
Major-severe storm 01/01/01
B. High Latitudes
Active 15/15/15
Minor Storm 30/25/20
Major-severe storm 40/20/20