:Product: Report of Solar-Geophysical Activity
:Issued: 2026 Apr 18 2200 UTC
# Prepared jointly by the U.S. Dept. of Commerce, NOAA,
# Space Weather Prediction Center and the U.S. Air Force.
#
Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 108 Issued at 2200Z on 18 Apr 2026

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.
There are currently 3 numbered sunspot regions on the disk.
IB.  Solar Activity Forecast: Solar activity is likely to be low with a
slight chance for an M-class flare on days one, two, and three (19 Apr,
20 Apr, 21 Apr).

IIA.  Geophysical Activity Summary 17/2100Z to 18/2100Z: The geomagnetic
field has been at quiet to major storm levels for the past 24 hours.
Solar wind speed reached a peak of 601 km/s at 18/1746Z. Total IMF
reached 17 nT at 18/0533Z. The maximum southward component of Bz reached
-14 nT at 18/0533Z.  Electrons greater than 2 MeV at geosynchronous
orbit reached a peak level of 704 pfu.
IIB.  Geophysical Activity Forecast: The geomagnetic field is expected
to be at unsettled to minor storm levels on day one (19 Apr) and quiet
to active levels on days two and three (20 Apr, 21 Apr).

III.  Event probabilities 19 Apr-21 Apr
Class M    15/15/15
Class X    01/01/01
Proton     01/01/01
PCAF       green

IV.  Penticton 10.7 cm Flux
Observed           18 Apr 106
Predicted   19 Apr-21 Apr 105/105/110
90 Day Mean        18 Apr 133

V.  Geomagnetic A Indices
Observed Afr/Ap 17 Apr  003/004
Estimated Afr/Ap 18 Apr  025/038
Predicted Afr/Ap 19 Apr-21 Apr  020/025-014/018-013/015

VI.  Geomagnetic Activity Probabilities 19 Apr-21 Apr
A.  Middle Latitudes
Active                35/35/30
Minor Storm           35/10/05
Major-severe storm    10/01/01
B.  High Latitudes
Active                05/15/15
Minor Storm           20/30/30
Major-severe storm    70/45/35