Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 141 Issued at 2200Z on 21 May 2023

IA. Analysis of Solar Active Regions and Activity from 20/2100Z to 21/2100Z: Solar activity has been at high levels for the past 24 hours. The largest solar event of the period was a M5 event observed at 20/2306Z from Region 3311 (N18E47). There are currently 8 numbered sunspot regions on the disk.

IB. Solar Activity Forecast: Solar activity is expected to be moderate with a chance for X-class flares on days one, two, and three (22 May, 23 May, 24 May).

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z: The geomagnetic field has been at quiet to major storm levels for the past 24 hours. Solar wind speed reached a peak of 632 km/s at 20/2216Z. Total IMF reached 13 nT at 21/1516Z. The maximum southward component of Bz reached -10 nT at 21/1935Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 1084 pfu.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected to be at quiet to major storm levels on day one (22 May), quiet to minor storm levels on day two (23 May) and unsettled to minor storm levels on day three (24 May). Protons have a slight chance of crossing threshold on days one, two, and three (22 May, 23 May, 24 May).

III. Event probabilities 22 May-24 May
Class M 75/75/75
Class X 30/30/30
Proton 15/15/15
PCAF green

IV. Penticton 10.7 cm Flux
Observed 21 May 163
Predicted 22 May-24 May 160/155/150
90 Day Mean 21 May 153

V. Geomagnetic A Indices
Observed Afr/Ap 20 May 026/030
Estimated Afr/Ap 21 May 013/021
Predicted Afr/Ap 22 May-24 May 016/022-014/018-020/022

VI. Geomagnetic Activity Probabilities 22 May-24 May
A. Middle Latitudes
Active 35/35/35
Minor Storm 35/20/30
Major-severe storm 20/05/15
B. High Latitudes
Active 10/15/15
Minor Storm 25/20/25
Major-severe storm 60/20/50

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