Joint USAF/NOAA Report of Solar and Geophysical Activity 4 Aug 2002

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2002 Aug 04 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 216 Issued at 2200Z on 04 Aug 2002

IA. Analysis of Solar Active Regions and Activity from 03/2100Z
to 04/2100Z: Solar activity was high due to a long duration M6 x-ray
event at 0955 UTC. The event was associated with activity behind the
southwest limb in cotemporaneous solar image data. A faint CME could
be seen in LASCO images associated with the flare with an
approximate plane-of-sky speed of 500 km/s. The CME does not appear
to have any earthward component. The remainder of today’s solar
activity consisted of occasional C-class flares. With the departure
of Regions 39, 44, and 50, Region 57 is now the dominant sunspot
group on the disk. Region 57 has shown growth over the past 24 hours
and possesses some magnetic complexity. The group produced
occasional subflare activity.

IB. Solar Activity Forecast: Solar activity is expected to be
mostly moderate over the next three days. There is a very slight
chance, however, that one of the regions behind west limb could
produce another major flare or proton producing event. Of the
regions on the disk, Region 57 shows the best potential for
producing an M-class event.

IIA. Geophysical Activity Summary 03/2100Z to 04/2100Z:
The geomagnetic field ranged from quiet to minor storm levels. A
period of moderately negative Bz in the solar wind occurred from
about 2300-0300 UTC and led to active to minor storm conditions from
0000-0900 UTC. The source of the enhanced Bz is uncertain, but may
be related to a solar sector boundary crossing from towards
orientation to an away orientation which occurred during the past 24
hours.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly unsettled for the next three days. There is a
possibility, however, for some isolated active periods on the third
and fourth days as a coronal hole will be rotating into favorable
position at that time.

III.  Event Probabilities 05 Aug-07 Aug

Class M    50/45/45

Class X    10/05/05

Proton     10/05/05

PCAF       green

IV.  Penticton 10.7 cm Flux

Observed           04 Aug 151

Predicted   05 Aug-07 Aug  150/145/145

90 Day Mean        04 Aug 167
V.  Geomagnetic A Indices

Observed Afr/Ap 03 Aug  011/020

Estimated Afr/Ap 04 Aug  015/015

Predicted Afr/Ap 05 Aug-07 Aug  010/010-010/010-012/015
VI.  Geomagnetic Activity Probabilities 05 Aug-07 Aug

A.  Middle Latitudes

Active                25/25/35

Minor storm           15/15/20

Major-severe storm    05/05/05

B.  High Latitudes

Active                30/30/35

Minor storm           15/15/20

Major-severe storm    05/05/10