NOAA / Space Weather Prediction Center

Solar Flare 3-day Report of Solar and Geophysical Activity
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Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Weather Prediction Center and the U.S. Air Force.
Updated 2017 Apr 22 2200 UTC

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 112 Issued at 2200Z on 22 Apr 2017

IA.  Analysis of Solar Active Regions and Activity from 21/2100Z to
22/2100Z: Solar activity has been at very low levels for the past 24
hours. There are currently 2 numbered sunspot regions on the disk.

IB.  Solar Activity Forecast: Solar activity is expected to be very low
with a chance for a C-class flares on days one, two, and three (23 Apr,
24 Apr, 25 Apr).

IIA.  Geophysical Activity Summary 21/2100Z to 22/2100Z: The geomagnetic
field has been at active to major storm levels for the past 24 hours.
Solar wind speed reached a peak of 776 km/s at 22/2043Z. Total IMF
reached 9 nT at 22/1221Z. The maximum southward component of Bz reached
-8 nT at 22/0804Z. Electrons greater than 2 MeV at geosynchronous orbit
reached a peak level of 7466 pfu.

IIB.  Geophysical Activity Forecast: The geomagnetic field is expected
to be at active to major storm levels on day one (23 Apr), active to
minor storm levels on day two (24 Apr) and unsettled to minor storm
levels on day three (25 Apr).

III.  Event probabilities 23 Apr-25 Apr
Class M    01/01/01
Class X    01/01/01
Proton     01/01/01
PCAF       green

IV.  Penticton 10.7 cm Flux
Observed           22 Apr 084
Predicted   23 Apr-25 Apr 084/084/084
90 Day Mean        22 Apr 078

V.  Geomagnetic A Indices
Observed Afr/Ap 21 Apr  011/018
Estimated Afr/Ap 22 Apr  033/050
Predicted Afr/Ap 23 Apr-25 Apr  028/040-023/030-015/020

VI.  Geomagnetic Activity Probabilities 23 Apr-25 Apr
A.  Middle Latitudes
Active                30/40/40
Minor Storm           45/30/25
Major-severe storm    15/05/01
B.  High Latitudes
Active                05/05/10
Minor Storm           15/20/25
Major-severe storm    80/65/60