Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 18 Oct 2003

By SpaceRef Editor

October 18, 2003

Filed under Space Weather Prediction Center (NOAA), Space Weather Solar-Geophysical Activity, US

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

Updated 2003 Oct 18 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 291 Issued at 2200Z on 18 Oct 2003

IA. Analysis of Solar Active Regions and Activity from 17/2100Z
to 18/2100Z: Solar activity was low. A noticeable increase in flare
activity and background levels was observed during the past 24
hours. Most of this increase was due to newly numbered Region 484
(N05E68) which appears to be a compact D-type group with 240
millionths of area. The region produced numerous C-class flares: the
largest was a C4.9 at 1653 UTC. A partial halo CME was observed off
the southeast limb, beginning at 1554 UTC. The plane of sky velocity
was estimated to be about 700 km/s. Region 483 (S08E55) was assigned
today but so far is a small stable sunspot group. The other active
regions on the disk showed occasional brightenings but were mostly
quiet and stable.

IB. Solar Activity Forecast: Solar activity is expected to be low
for the next three days with Region 484 as the dominant source of
activity. There is a slight chance for an isolated M-class event
during the next three days.

IIA. Geophysical Activity Summary 17/2100Z to 18/2100Z:
The geomagnetic field ranged from unsettled to minor storm levels as
the high speed solar wind stream continues. The solar wind speed did
not show any trend today and the average velocity was around 540
km/s. The interplanetary magnetic field Z-component fluctuated
between -7 nT and + 5 nT but was weakly negative on average. The
greater than 2 MeV electron fluxes were at high levels during the
past 24 hours.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be unsettled to active for the next 24 hours. There
should be a gradual decline in activity sometime tomorrow and
conditions should be mostly unsettled for the second day. An
increase to mostly active with some minor storm periods is expected
on the third day as a new coronal hole rotates into favorable
position at that time. Today’s CME is not expected to directly
impact Earth but might result in a glancing blow that could provide
a boost to activity on the third day.

III. Event Probabilities 19 Oct-21 Oct