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  
  
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              and join the #aurora channel (type /join #aurora) 
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**  End of AstroAlert  **