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

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 137 Issued at 2200Z on 17 May 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 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 and two (18 May, 19 May) and expected to be very low on day three (20 May).

IIA. Geophysical Activity Summary 16/2100Z to 17/2100Z: The geomagnetic field has been at quiet levels for the past 24 hours. Solar wind speed reached a peak of 433 km/s at 17/1057Z. Total IMF reached 8 nT at 17/1954Z. The maximum southward component of Bz reached -7 nT at 17/1921Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 414 pfu.

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

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

IV. Penticton 10.7 cm Flux
Observed 17 May 075
Predicted 18 May-20 May 076/075/074
90 Day Mean 17 May 076

V. Geomagnetic A Indices
Observed Afr/Ap 16 May 004/005
Estimated Afr/Ap 17 May 008/012
Predicted Afr/Ap 18 May-20 May 013/018-017/020-012/012

VI. Geomagnetic Activity Probabilities 18 May-20 May
A. Middle Latitudes
Active 40/30/25
Minor Storm 25/15/05
Major-severe storm 05/01/01
B. High Latitudes
Active 10/10/15
Minor Storm 25/25/30
Major-severe storm 60/40/30