Joint USAF/NOAA Report of Solar and Geophysical Activity 27 Dec 2002

SDF Number 361 Issued at 2200Z on 27 Dec 2002

IA. Analysis of Solar Active Regions and Activity from 26/2100Z
to 27/2100Z: Solar activity reached very low levels this period.
Occasional subflares were observed in decaying Region 230 (S04W77)
as it approached the west limb. New Region 236 emerged today and
produced occasional plage enhancements and a B-class subflare late
in the period The remaining regions are small with simple magnetic
structure.

IB. Solar Activity Forecast: Solar activity is expected to be very
low to low for the next three days.

IIA. Geophysical Activity Summary 26/2100Z to 27/2100Z:
The geomagnetic field was at unsettled to minor storm levels with
isolated major storm periods at higher latitudes. These storm
conditions are a result of a large coronal hole that rotated into a
geoeffective position late yesterday. Solar wind speed ranged from
700 – 800 km/s during the latter half of this period.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to continue at unsettled to minor storm levels in response
to the existing high speed, coronal hole stream. Expect the storming
to gradually subside over days two and three of the period.

III. Event Probabilities 28 Dec-30 Dec
Class M 15/15/15
Class X 01/01/01
Proton 01/01/01
PCAF green

IV. Penticton 10.7 cm Flux

• Observed 27 Dec 117
• Predicted 28 Dec-30 Dec 115/115/115
• 90 Day Mean 27 Dec 166

V. Geomagnetic A Indices

• Observed Afr/Ap 26 Dec 008/015
• Estimated Afr/Ap 27 Dec 025/040
• Predicted Afr/Ap 28 Dec-30 Dec 020/025-015/030-008/020

VI. Geomagnetic Activity Probabilities 28 Dec-30 Dec
A. Middle Latitudes

• Active 60/50/30
• Minor storm 25/20/10
• Major-severe storm 15/05/01

B. High Latitudes

• Active 40/40/40
• Minor storm 40/40/20
• Major-severe storm 20/20/05