Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 18 April 2014

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 108 Issued at 2200Z on 18 Apr 2014

IA. Analysis of Solar Active Regions and Activity from 17/2100Z to
18/2100Z: Solar activity reached high levels. Region 2036 (S16W41,
Dhc/beta-gamma) produced an M7 flare at 18/1303 UTC, which was the
largest flare of the period. It was accompanied by a Tenflare (1000
sfu), a Castelli-U signature, as well as Type II (851 km/s) and Type IV
radio emissions. An asymmetric halo CME was subsequently observed in
SOHO/LASCO C2 coronagraph imagery at 18/1325 UTC. Analysis suggested the
ejecta was moving at approximately 1000 km/s and Earth-directed.

IB. Solar Activity Forecast: Solar activity is likely to be moderate
with a slight chance for an X-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 levels for the past 24 hours. Solar wind speed,
as measured by the ACE spacecraft, reached a peak speed of 540 km/s at
18/1845Z. Total IMF reached 9 nT at 18/0207Z. The maximum southward
component of Bz reached -8 nT at 18/0243Z. Protons greater than 10 MeV
at geosynchronous orbit reached a peak level of 38 pfu at 18/1955Z.

IIB. Geophysical Activity Forecast: The geomagnetic field is expected
to be at quiet to active levels on day one (19 Apr) and quiet to minor
storm levels on days two and three (20 Apr, 21 Apr) with a chance for
major storm levels on day two (20 Apr). Protons are expected to remain
above the 10 pfu threshold on day one (19 Apr), are expected to cross
threshold on day two (20 Apr) and have a chance of crossing threshold on
day three (21 Apr).

III. Event probabilities 19 Apr-21 Apr
Class M 60/60/60
Class X 10/10/10
Proton 99/75/50
PCAF yellow

IV. Penticton 10.7 cm Flux
Observed 18 Apr 172
Predicted 19 Apr-21 Apr 175/175/175
90 Day Mean 18 Apr 156

V. Geomagnetic A Indices
Observed Afr/Ap 17 Apr 011/011
Estimated Afr/Ap 18 Apr 007/008
Predicted Afr/Ap 19 Apr-21 Apr 009/012-018/025-017/020

VI. Geomagnetic Activity Probabilities 19 Apr-21 Apr
A. Middle Latitudes
Active 40/40/40
Minor Storm 15/35/25
Major-severe storm 01/10/05
B. High Latitudes
Active 10/05/05
Minor Storm 25/20/20
Major-severe storm 55/75/60