Joint USAF/NOAA Solar Geophysical Activity Report and Forecast SDF Number 138 Issued at 2200Z on 18 May 2023

IA. Analysis of Solar Active Regions and Activity from 17/2100Z to 18/2100Z: Solar activity has been at moderate levels for the past 24 hours. The largest solar event of the period was a M2 event observed at 18/1147Z from Region 3311 (N18E76). There are currently 8 numbered sunspot regions on the disk.

IB. Solar Activity Forecast: Solar activity is expected to be low with a chance for M-class flares 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 levels for the past 24 hours. Solar wind speed reached a peak of 501 km/s at 18/1058Z. Electrons greater than 2 MeV at geosynchronous orbit reached a peak level of 174 pfu.

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

III. Event probabilities 19 May-21 May
Class M 35/25/25
Class X 05/05/05
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 18 May 151
Predicted 19 May-21 May 145/140/140
90 Day Mean 18 May 153

V. Geomagnetic A Indices
Observed Afr/Ap 17 May 005/004
Estimated Afr/Ap 18 May 004/004
Predicted Afr/Ap 19 May-21 May 006/005-007/008-010/012

VI. Geomagnetic Activity Probabilities 19 May-21 May
A. Middle Latitudes
Active 10/20/25
Minor Storm 01/05/05
Major-severe storm 01/01/01
B. High Latitudes
Active 15/15/15
Minor Storm 20/20/25
Major-severe storm 10/25/40

Space Weather