A s t r o  A l e r t
                               Sun-Earth Alert

                          Solar Terrestrial Dispatch
                            http://www.spacew.com

                              25 September 2001

               1. POTENTIAL SIGNIFICANT AURORAL STORM WARNING.
               2. WHITE LIGHT FLARE NOTIFICATION.
               3. POTENTIAL SATELLITE ANOMALY WARNING.
               4. COPY OF THE MIDDLE LATITUDE AURORAL ACTIVITY WARNING.

1. POTENTIAL SIGNIFICANT AURORAL STORM WARNING

     A significant major class X2.6 solar flare was observed from a sunspot
complex identified by NOAA as sunspot complex number 9632. This solar flare
was associated with a strong Earthward directed coronal mass ejection. It is
expected to impact the Earth late in the UTC day of 25 September (anytime
near 18:00 UTC on 25 September or 2 pm EDT on 25 September). The impact of
this disturbance could produce periods of major auroral storm activity
("northern lights") that may become visible from many middle and low latitude
regions. In response to this potential activity, a Middle Latitude Auroral
Activity Warning has been issued together with a Low Latitude Auroral
Activity Watch for the days of 25 and 26 September. A copy of the middle
latitude warning announcement has been included below (see item 4).

2. Todays major X2.6 solar x-ray flare was reportedly observed in
white-light by Jure Zakrajsek of Slovenia. Additional white-light flares are
possible in this region. See: http://www.spacew.com/aurora/mdi_sunspots.jpg

3. A strong category S3 (rated from S1 to S5) solar radiation storm was
observed following the eruption of todays strong solar flare. Energetic
protons travelling at near relativistic speeds (near the speed of light) have
produced heavy ionospheric absorption of high frequency radio signals through
the polar ionospheric regions. Spacecraft in geosynchronous orbits may
experience increased incidences of SEU's (single event upsets), which are
caused when an energetic proton impacts a spacecraft and releases some of
its energy in semiconductors components on the spacecraft. SEU's can result
in "phantom commands" on spacecraft that may (or may not) require operator
intervention to correct. Strong proton events such as this can also
permanently degrade the performance of solar arrays on spacecraft. In
situations where spacecraft power levels are already low, energetic proton
events can force spacecraft operators to shut down instruments in order to
preserve power. Atmospheric drag on lower orbiting spacecraft is also
expected to increase following the arrival of the coronal mass ejection and
the ensuing geomagnetic storm. Spacecraft with cameras are already observing
the effects of the heightened proton activity in the form of increased cosmic
ray noise produced as protons impact spacecraft imaging sensors and trace
out streaks of light. These conditions can confuse star tracking systems used
to maintain accurate spacecraft orientations.

4.

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                   MIDDLE LATITUDE AURORAL ACTIVITY WARNING

                     ISSUED: 04:20 UTC, 25 SEPTEMBER 2001

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                  *** POTENTIAL FOR HIGH ACTIVITY EXISTS ***

VALID BEGINNING AT: 15:00 UTC 25 SEPTEMBER
VALID UNTIL: 19:00 UTC ON 28 SEPTEMBER

    HIGH RISK PERIOD: 25 - 26 SEPTEMBER (UTC DAYS)
MODERATE RISK PERIOD: 25 - 28 SEPTEMBER

PREDICTED ACTIVITY INDICES: 30, 100, 40, 12 (25 - 28 SEPTEMBER)

POTENTIAL MAGNITUDE OF MIDDLE LATITUDE AURORAL ACTIVITY: HIGH

POTENTIAL DURATION OF THIS ACTIVITY: MAIN BELT = 24 TO 36 HOURS
                                    MINOR BELT = 36 TO 48 HOURS

ESTIMATED OPTIMUM OBSERVING CONDITIONS: NEAR AND AFTER LOCAL MIDNIGHT

EXPECTED LUNAR INTERFERENCE: MODERATE, BECOMING NIL AFTER MOONSET NR MIDNIGHT

OVERALL OPPORTUNITY FOR OBSERVATIONS FROM MIDDLE LATITUDES: GOOD TO VERY GOOD

AURORAL ACTIVITY *MAY* BE OBSERVED APPROXIMATELY NORTH OF A LINE FROM...

   CENTRAL/SOUTHERN CALIFORNIA TO ARIZONA TO NEW MEXICO TO TEXAS TO LOUISIANA
   TO MISSISSIPPI TO ALABAMA TO GEORGIA AND POSSIBLY NORTHERN REGIONS OF
   FLORIDA TO SOUTH CAROLINA.

ACTIVITY *MAY* ALSO BE OBSERVED APPROXIMATELY NORTH OF A LINE FROM...

   EXTREME NORTHERN MOROCCO TO EXTREME NORTHERN ALGERIA TO NORTHERN TUNISIA
   TO SOUTHERN ITALY TO GREECE TO EXTREME NORTHERN TURKEY TO GEORGIA TO
   NORTHERN AZERBAIJAN TO SOUTHWESTERN KAZAKSTAN TO NORTHERN UZBEKISTAN TO
   CENTRAL KAZAKSTAN TO EAST-CENTRAL KAZAKSTAN TO EXTREME NORTHERN MONGOLIA
   TO EXTREME NORTHEASTERN CHINA TO CENTRAL SAKHALIN. THERE IS A SMALL
   POSSIBILITY EXTREME NORTHERN JAPAN MAY WITNESS ACTIVITY.

   IN AUSTRALIA, ACTIVITY *MAY* BE OBSERVED APPROXIMATELY *SOUTH* OF A LIHE
   FROM NORTHERN NEW SOUTH WALES TO NORTHERN SOUTH AUSTRALIA TO CENTRAL
   WESTERN AUSTRALIA.

   ALL OF NEW ZEALAND HAS MAY OBSERVE ACTIVITY.

   IN SOUTH AFRICA, THE EXTREME SOUTHERN TIP OF SOUTH AFRICA (NEAR CAPE TOWN
   AND PORT ELIZABETH) *MAY* OBSERVE SOME ACTIVITY DURING THE HEIGHT OF THE
   STORM, IF PREDICTIONS HOLD TRUE.

   IN SOUTH AMERICA, SOUTHERN REGIONS OF CHILE AND ARGENTINA *MAY* SPOT
   PERIODS OF ACTIVITY SOUTH OF A LINE OF ROUGHLY 50 DEGREES SOUTH LATITUDE.
   THE FALKLAND ISLANDS MAY ALSO SPOT PERIODS OF ACTIVITY.

SYNOPSIS...

     A strong solar flare and high velocity Earthward directed coronal mass
ejection were observed at 10:38 UTC (6:38 am EDT) on 24 September. The
coronal mass ejection is expected to impact the Earth near 18:00 UTC (2 pm
EDT) on 25 September, give or take several hours.

     The arrival of this disturbance is expected to produce periods of major
to severe geomagnetic and auroral storm activity. This disturbance has the
potential to be one of the largest observed this solar cycle. Observations
well into the low latitude regions may be possible if predictions hold true.

     Observations will be best after local midnight in the northern
hemisphere when the moon sets (or after about 3 am in Australia/New Zealand).

     Forecasters suggest this disturbance has the potential to last as long
as perhaps 48 hours. As a result, most middle latitude regions of the world
should have at least one chance to observe activity. Whether this holds true
remains to be seen. Forecasts of storm durations are an inexact science.

     This warning will remain in effect until 19:00 UTC on 28 September. It
will then be updated or allowed to expire.

              PLEASE REPORT OBSERVATIONS OF AURORAL ACTIVITY TO:
                  http://solar.spacew.com/www/auroras.html

                                    * OR *

        Use the STD AURORA MONITOR Software to monitor conditions and
                    report sightings. It is available at:
                         http://www.spacew.com/aurora

  For Real-Time News and Discussions with Experienced Aurora Enthusiasts:
                          http://www.spacew.com/irc
              and join the #aurora channel (type /join #aurora)

    WE HAVE A USEFUL DISCUSSION FORUM FOR AURORA ENTHUSIASTS AVAILABLE AT:
                   http://www.spacew.com/aurora/forum.html

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