Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 21 April 2013

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 111 Issued at 2200Z on 21 Apr 2013

IA. Analysis of Solar Active Regions and Activity from 20/2100Z to
21/2100Z: Solar activity has been at low levels for the past 24 hours.
The largest solar event of the period was a C4 event observed at
21/1839Z from Region 1726 (N12W22). There are currently 3 numbered
sunspot regions on the disk.
IB. Solar Activity Forecast: Solar activity is expected to be low with
a chance for M-class flares and a slight chance for an X-class flare on
days one and two (22 Apr, 23 Apr) and expected to be low with a chance
for M-class flares on day three (24 Apr).

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z: The geomagnetic
field has been at quiet levels for the past 24 hours. Solar wind speed,
as measured by the ACE spacecraft, reached a peak speed of 412 km/s at
21/0728Z. Total IMF reached 7 nT at 21/1656Z. The maximum southward
component of Bz reached -1 nT at 21/0145Z. Protons greater than 10 MeV
at geosynchronous orbit reached a peak level of 3 pfu at 21/1640Z.
IIB. Geophysical Activity Forecast: The geomagnetic field is expected
to be at quiet to unsettled levels on day one (22 Apr) and quiet to
active levels on days two and three (23 Apr, 24 Apr). Protons greater
than 10 Mev have a slight chance of crossing threshold on days one and
two (22 Apr, 23 Apr).

III. Event probabilities 22 Apr-24 Apr
Class M 40/40/40
Class X 15/15/05
Proton 15/15/01
PCAF green

IV. Penticton 10.7 cm Flux
Observed 21 Apr 109
Predicted 22 Apr-24 Apr 115/115/115
90 Day Mean 21 Apr 111

V. Geomagnetic A Indices
Observed Afr/Ap 20 Apr 002/004
Estimated Afr/Ap 21 Apr 002/003
Predicted Afr/Ap 22 Apr-24 Apr 006/008-008/012-011/012

VI. Geomagnetic Activity Probabilities 22 Apr-24 Apr
A. Middle Latitudes
Active 15/25/25
Minor Storm 05/05/05
Major-severe storm 01/01/01
B. High Latitudes
Active 15/15/15
Minor Storm 20/30/30
Major-severe storm 20/30/30