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From: oler@rho.uleth.ca (Cary Oler)
Message-Id: <9306110032.AA17008@rho.uleth.ca>
Subject: WARNING: Potential Geomagnetic Storm Update - Shock Arrived
To: solar-warnings@lut.fi
Date: Thu, 10 Jun 93 18:32:14 MDT
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                  POTENTIAL MAJOR GEOMAGNETIC STORM WARNING

                         UPDATED: 00:10 UT, 11 JUNE

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NOTE:  A sudden magnetic impulse marked the arrival of the flare shock front
       at 17:27 UTC on 10 June.  A period of minor to major geomagnetic
       storming has been observed in conjunction with the main phase of this
       activity, which commenced at approximately 20:30 UTC.  Minor to major
       storming is expected over the next 24 hours.  High and polar latitude
       regions could see periods of severe storm activity.  Ionospheric
       propagation has shown some minor instabilities over the last few
       hours.  Propagation is expected to become degraded over the polar to
       middle latitude paths, particularly during the local night sectors.
       Strong fading, multipathing, and absorption can be expected if the
       intensity of the activity persists.  Geomagnetic activity should begin
       to subside by 18:00 UTC on 11 June.


    HIGH RISK PERIOD:  11 June         (UT days)
MODERATE RISK PERIOD:  11 Jun - 12 Jun

POTENTIAL LOW-MIDDLE LATITUDE STORM INTENSITY:  MINOR - MAJOR
      POTENTIAL HIGH LATITUDE STORM INTENSITY:  MAJOR

      POTENTIAL DURATION OF GEOMAGNETIC STORM:  24 HOURS

POTENTIAL PEAK LOW-MIDDLE LATITUDE K-INDEX VALUES:  6
      POTENTIAL PEAK HIGH LATITUDE K-INDEX VALUES:  7

  EXPECTED DOMINATING LOW-MIDDLE LATITUDE K-INDEX:  5 - 6
        EXPECTED DOMINATING HIGH LATITUDE K-INDEX:  6

   POTENTIAL FOR LOW LATITUDE HF DEGRADATION:  MODERATE
        POTENTIAL SEVERITY OF HF DEGRADATION:  MINOR
          EXPECTED HF PROPAGATION CONDITIONS:  GOOD - OCCASIONALLY FAIR

POTENTIAL FOR MIDDLE LATITUDE HF DEGRADATION:  HIGH
        POTENTIAL SEVERITY OF HF DEGRADATION:  MINOR - MAJOR
          EXPECTED HF PROPAGATION CONDITIONS:  FAIR - OCCASIONALLY VERY POOR

  POTENTIAL FOR HIGH LATITUDE HF DEGRADATION:  HIGH
        POTENTIAL SEVERITY OF HF DEGRADATION:  MINOR - MAJOR
          EXPECTED HF PROPAGATION CONDITIONS:  POOR TO OCCASIONALLY USELESS

POTENTIAL RISK FOR GEOSYNCHRONOUS MAGNETOPAUSE CROSSINGS:  55% PROBABLE

SUSPECTED SOURCE OF OBSERVED/EXPECTED ACTIVITY:
     Major M5.4/2B tenflare with major Types II and IV sweeps on 07 June.


---------------------------------       ---------------------------------
EST. POTENTIAL GEOMAGNETIC IMPACT       EST. POTENTIAL IONOSPHERIC IMPACT
---------------------------------       ---------------------------------
       SEVERE STORM : 20 %                 LOW LATITUDES : MINOR
        MAJOR STORM : 40 %              MIDDLE LATITUDES : MINOR - MAJOR
        MINOR STORM : 30 %                HIGH LATITUDES : MINOR - MAJOR
     ACTIVE OR LESS : 10 %               POLAR LATITUDES : MINOR - MAJOR
---------------------------------       ---------------------------------
 PROBABLE SI ASSOCIATION : OBSERVED      ESTIMATED GLOBAL IMPACT: MINOR-MAJOR

ESTIMATED FORECAST PEAK PLANETARY 24-HOUR A-INDEX DURING STORM: 42


**  End of Warning  **


