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From: oler@rho.uleth.ca (Cary Oler)
Message-Id: <9306071735.AA25344@rho.uleth.ca>
Subject: ALERT: Major Solar Flare Alert - 07 June
To: solar-warnings@lut.fi
Date: Mon, 7 Jun 93 11:35:23 MDT
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                           MAJOR SOLAR FLARE ALERT

                          ISSUED: 17:15 UT, 07 JUNE

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                     * Low to Moderate Impact Possible *


MAJOR ENERGETIC EVENT SUMMARY:

              ( All times are valid for the UT day of 07 June )

Flare Size: Class M5.4/2N
  Location: S09W30 (Region 7518)
  Tenflare: 1,100 sfu at 1409 UT.  Duration: 42 minutes
SESC Times: Begin=07/1351 UT, Peak=07/1425 UT, End=07/1443 UT
            (SESC Times are based on a half-power-point system)
    Sweeps: Type II (Importance 3).  Estimated shock velocity: 1200 km/sec.
            Type IV (Importance 3).
   Protons: Response observed at > 10 MeV (presently at approx. 4.5 pfu)


PRELIMINARY X-RAY TIME PROFILE DATA AND ESTIMATED STATISTICS:

BEGIN (XRAY)   MAX  (XRAY)   END  (XRAY)   DURATION   INTEG. FLUX   SWF DUR.
------------   -----------   -----------   --------   -----------   --------
 1351 (B5.0)   1425 (M5.4)   1509 (C9.7)   061 MIN.   0.110 J/m^2    056 min

NOTE:  The xray time profile data above is not based on the half-power-point
       system, but is intended to give a general idea of the duration of the
       entire event, from the start to the end when xrays fall below M-class
       levels.  Integrated x-ray flux covers the interval from start to end.


SYNOPSIS:

     Region 7518 (S09W30) spawned a class M5.4/2N tenflare at 14:25 UT.  This
     event was accompanied by major Type II and IV sweeps (both importance 3)
     and a 42 minute tenflare reaching 1,100 sfu at 14:09 UT.  A strong SWF
     was also observed in conjunction with this flare, affecting frequencies
     as high as approximately 12 to 15 MHz.  Protons at greater than 10 MeV
     began arriving around 16:05 UT and are presently running at about 4.5
     particle flux units (pfu).

     Region 7518 did not show any strong signs of producing a major flare.
     It has been associated with the usual internal motions and gradual
     growth over the last several days, although nothing particularly
     significant developed.  This is the first M-class event observed from
     Region 7518. Strong magnetic gradients persist in this group, which
     raises some suspicions regarding its potential future volatility.  Minor
     M-class flares are expected to dominate from this region.  The ability
     of this region to produce additional major-category events is still
     unresolved and of some question.


POTENTIAL TERRESTRIAL IMPACT ASSESSMENT:

     The following tables depict the preliminary estimated potential for
terrestrial impacts in various categories.  These tables are valid only for
the flare described and do not include assessments for previous influential
flare events.


                      ----------------------------------
                      POTENTIAL MAGNITUDE OF DISTURBANCE
                      ----------------------------------
                                 HIGH : 10 %
                             MODERATE : 40 %
                                  LOW : 30 %
                                 NONE : 20 %
                      ----------------------------------
                      OVERALL ARRIVAL PROBABILITY : 75 %


              ESTIMATED WINDOW OF SHOCK ARRIVAL IF SHOCK ARRIVES
    ---------------------------------------------------------------------
   |  MINIMUM   |    EARLY     |  PREFERRED  |     LATE     |  MAXIMUM   |
   |------------|--------------|-------------|--------------|------------|
   | 09/0000 UT |  09/0800 UT  | 09/1800 UT  |  10/0200 UT  | 10/1000 UT |
   |   APRIL    |    APRIL     |   APRIL     |    APRIL     |   APRIL    |
   |------------|---------------------|---------------------|------------|
   |    10 %    |  40%  PROBABILITY   |  40% PROBABILITY    |    10 %    |
    ---------------------------------------------------------------------


---------------------------------       ----------------------------------
  POTENTIAL FOR >10 MEV PROTONS           POTENTIAL FOR >100 MEV PROTONS
---------------------------------       ----------------------------------
    HIGH FLUX :  1 %  > 100 PFU             HIGH FLUX :  0 %  > 100 PFU
MODERATE FLUX : 19 %  >  10 PFU         MODERATE FLUX :  0 %  >  10 PFU
     LOW FLUX : 80 %  >   1 PFU              LOW FLUX :  5 %  >   1 PFU
         NONE :  0 %  <=  1 PFU                  NONE : 95 %  <=  1 PFU
----------------------------------      ----------------------------------
OVERALL ARRIVAL PROBABILITY: Observed   OVERALL ARRIVAL PROBABILITY:  1 %

---------------------------------       ---------------------------------
EST. POTENTIAL GEOMAGNETIC IMPACT       EST. POTENTIAL IONOSPHERIC IMPACT
---------------------------------       ---------------------------------
       SEVERE STORM : 10 %                 LOW LATITUDES : MINOR
        MAJOR STORM : 40 %              MIDDLE LATITUDES : MINOR - MAJOR
        MINOR STORM : 30 %                HIGH LATITUDES : MAJOR
     ACTIVE OR LESS : 20 %               POLAR LATITUDES : MAJOR
---------------------------------       ---------------------------------
 PROBABLE SI ASSOCIATION : 75 %       ESTIMATED GLOBAL IMPACT: MINOR - MAJOR

ESTIMATED PRELIMINARY FORECAST PEAK PLANETARY A-INDEX: 42

ESTIMATED POTENTIAL DURATION OF DISTURBANCE IF IT ARRIVES: 24 HOURS

EST. PROBABILITY FOR GEOSYNCHRONOUS SATELLITE MAGNETOPAUSE CROSSINGS:  55%


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