Joint USAF/NOAA Solar Geophysical Activity Report and Forecast 18 May 2013

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 138 Issued at 2200Z on 18 May 2013


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.
The largest solar event of the period was a C6 event observed at
18/0345Z from Region 1748 (N12E11). There are currently 9 numbered
sunspot regions on the disk.

IB.  Solar Activity Forecast: Solar activity is likely to be moderate
with a chance for X-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 to minor storm levels for the past 24 hours.
Solar wind speed, as measured by the ACE spacecraft, reached a peak
speed of 476 km/s at 18/0911Z. Total IMF reached 13 nT at 18/0244Z. The
maximum southward component of Bz reached -13 nT at 18/0146Z. Protons
greater than 10 MeV at geosynchronous orbit reached a peak level of 32
pfu at 17/2245Z. Electrons greater than 2 MeV at geosynchronous orbit
reached a peak level of 131 pfu.

IIB.  Geophysical Activity Forecast: The geomagnetic field is expected
to be at quiet to major storm levels on day one (19 May), quiet to
active levels on day two (20 May) and quiet to unsettled levels on day
three (21 May). Protons are likely to cross threshold on day one (19
May) and have a chance of crossing threshold on days two and three (20
May, 21 May).


III.  Event probabilities 19 May-21 May
Class M    65/65/65
Class X    40/40/40
Proton     60/30/30
PCAF       yellow


IV.  Penticton 10.7 cm Flux
Observed           18 May 132
Predicted   19 May-21 May 135/135/130
90 Day Mean        18 May 121


V.  Geomagnetic A Indices
Observed Afr/Ap 17 May  009/010
Estimated Afr/Ap 18 May  018/020
Predicted Afr/Ap 19 May-21 May  017/035-014/015-007/008


VI.  Geomagnetic Activity Probabilities 19 May-21 May
A.  Middle Latitudes
Active                35/30/15
Minor Storm           30/10/05
Major-severe storm    20/01/01
B.  High Latitudes
Active                05/15/15
Minor Storm           20/30/25
Major-severe storm    75/40/25