:Product: Weekly Highlights and Forecasts
:Issued: 2001 Sep 04 2112 UT
Highlights of Solar and Geomagnetic Activity
27 August - 02 September 2001

Solar activity was at moderate levels during most of the period.
Region 9591 (S19, L = 295, class/area Fki/740 on 25 August) produced
isolated C- and M-class flares (for flare times and magnitudes,
please refer to the Energetic Events listing). Region 9591 was large
and magnetically complex with magnetic delta structures observed
within its interior and trailer spots as the period began. The
interior delta dissipated during 27 August as the region began to
gradually decay, but the trailer delta persisted through the rest of
the period. Region 9599 (S18, L = 238, class/area Dai/220 on 30
August) produced an isolated low-level M-class flare on 30 August
during a relatively brief period of growth, which included the
formation of a weak delta magnetic structure within its interior
spots. The delta structure dissipated on 31 August as Region 9599
began to gradually decay. Region 9601 (N14, L = 213, class/area
Fai/760 on 31 August) also produced isolated C- and M-class flares
(Note: Regions 9600 and 9601 were combined on 30 August and
designated as Region 9601). Region 9601 was large with a moderate
degree of magnetic complexity through most of the period. It entered
a brief growth phase on 01 September and developed a delta magnetic
structure in its trailer spots. Region 9601 lost its delta structure
on the following day as it began to gradually decay.

Solar Wind data were available from the Advanced Composition Explorer
(ACE) spacecraft for most of the period. A coronal mass ejection
(CME) passed the spacecraft at approximately 27/1920 UTC and was
likely associated with the X5/3b flare observed on 25 August. The
passage was accompanied by abrupt increases in temperature, density,
and velocity (peak to around 600 km/sec late on 25 August). IMF Bz
turned mostly northward following the shock. Another possible
transient signature was observed on 30 August, characterized by
abrupt, but relatively minor increases in temperature, total IMF
field intensity, density, and velocity (peaks to 520 km/sec). A
possible high-speed stream began late on 02 September and was in
progress as the period ended.

There were no proton events detected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels through 30 August, then decreased to
normal levels for the rest of the period.

The geomagnetic field was disturbed on 27 August following a sudden
impulse at 27/1952 UTC (37 nT, as measured by the Boulder USGS
magnetometer). Active periods occurred during this disturbance. A
few active periods also occurred during 30 - 31 August, possibly due
to a CME passage. Quiet to unsettled levels prevailed during the
remainder of the period.

Forecast of Solar and Geomagnetic Activity
05 September - 01 October 2001

Solar activity is expected to be at low to moderate levels. Isolated
M-class flares are possible. There will be a chance for a major
flare until Region 9601 departs the west limb on 10 September.

There will be a chance for a solar proton event from Region 9601
until it departs the west limb.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at normal to moderate levels during most of the
period.

Active geomagnetic field conditions will be possible around 18 and 30
September due to coronal hole effects. Otherwise, quiet to unsettled
levels are expected.


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