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

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 138 Issued at 2200Z on 18 May 2021

IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity has been at low levels for the past 24 hours. The largest solar event of the period was a C1 event observed at 18/0209Z from Region 2824 (N19E65). There are currently 2 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 May, 20 May, 21 May).

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic field has been at quiet to active levels for the past 24 hours. Solar wind speed reached a peak of 410 km/s at 18/0316Z. Total IMF reached 10 nT at 18/0142Z. The maximum southward component of Bz reached -9 nT at 18/0130Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 177 pfu.

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

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

IV. Penticton 10.7 cm Flux
Observed 18 May 076
Predicted 19 May-21 May 075/074/073
90 Day Mean 18 May 076

V. Geomagnetic A Indices
Observed Afr/Ap 17 May 006/006
Estimated Afr/Ap 18 May 012/014
Predicted Afr/Ap 19 May-21 May 015/016-012/012-008/008

VI. Geomagnetic Activity Probabilities 19 May-21 May
A. Middle Latitudes
Active 35/25/15
Minor Storm 15/05/01
Major-severe storm 01/01/01
B. High Latitudes
Active 10/15/15
Minor Storm 25/30/25
Major-severe storm 50/30/20