-----------------Forwarded item dated 11-MAY-1992 14:00:16.68-----------------
From: DECPA::"CREAMER@res1.rd.ray.com" "Jesse Creamer, KC1YZ -- (617)
860-3183 (RAYNET 422-3183)"
To: mast::reisert
Subj: Thought you guys might be interested.
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MAJOR SOLAR FLARE ALERT
ISSUED: 18:45 UT, 08 MAY
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MODERATE TO HIGH IMPACT EXPECTED
PROTON AND PCA WARNING ISSUED
MAJOR ENERGETIC EVENT SUMMARY:
Flare Size: Class M7.4/4B (long-duration, optically large)
Location: S25E10 (Region 7154)
Tenflare: 3,100 sfu at 08/1514 UT. Duration: 102 minutes
245 MHz: 23,000 sfu
Peak Radio: 77,000 sfu at 1415 MHz
SESC Times: Begin=08/1512 UT, Peak=08/1546 UT, End=08/1610 UT
(SESC Times are based on a half-power-point system)
Sweeps: MAJOR TYPE IV SWEEP (IMPORTANCE 3) OBSERVED AT 08/1519 (I/P)
Type II Not reported at the present time (radio activity is
still in-progress).
PRELIMINARY X-RAY TIME PROFILE DATA AND ESTIMATED STATISTICS:
BEGIN (XRAY) MAX (XRAY) END (XRAY) DURATION INTEG. FLUX SWF DUR.
------------ ----------- ----------- -------- ----------- --------
1512 (B6.3) 1546 (M7.4) 1713 (C9.8) 121 MIN. 0.244 J/m^2 112 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.
SYNOPSIS:
This major flare was impressive and somewhat unexpected. It gradually
increased in optical size and appears to have made a 4B rating. X-rays were
also impressive, with a long-duration maximum above the M6.0 level for 30
minutes and a characteristic slow-decay. A strong, long-duration tenflare
of 3,100 sfu accompanied this event. The duration of the tenflare was 102
minutes. The radio burst at 245 MHz was measured at 23,000 sfu. A major
Type IV sweep was observed at 15:19 UT and may be interfering with and/or
obscuring attempts to identify an associated Type II. It is unlikely that a
Type II failed to occur with this event. Final radio reports are not yet
available (consult the daily summary for details).
A PROTON WARNING has been issued. Protons with a peak flux at greater
than 10 MeV of around 100 pfu are expected to begin arriving near 20:00 UT on
08 May. Models indicate protons may vary from approximately 45 pfu to near
170 pfu. As a result, a POTENTIAL POLAR CAP ABSORPTION WARNING has also been
issued. Polar and high latitude regions could be strongly affected by
proton-induced polar ionospheric absorption. Signals over the polar paths
may experience black-out conditions sometime after approximately 20:00 UT,
lasting possibly over 48 hours.
This flare has a high potential for producing a terrestrial impact.
Minor to major geomagnetic storming is anticipated (see below).
POTENTIAL TERRESTRIAL IMPACT ASSESSMENT:
The following tables depict the _preliminary_ estimated potential for
terrestrial impacts in various categories.
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POTENTIAL MAGNITUDE OF DISTURBANCE
----------------------------------
HIGH : 30 %
MODERATE : 40 %
LOW : 20 %
NONE : 10 %
----------------------------------
OVERALL ARRIVAL PROBABILITY : 80 %
ESTIMATED WINDOW OF SHOCK ARRIVAL
---------------------------------------------------------------------
| MINIMUM | EARLY | PREFERRED | LATE | MAXIMUM |
|------------|--------------|-------------|--------------|------------|
| 09/1800 UT | 09/2100 UT | 10/0300 UT | 10/1000 UT | 10/2000 UT |
| APRIL | APRIL | APRIL | APRIL | APRIL |
|------------|---------------------|---------------------|------------|
| 5 % | 45% PROBABILITY | 45% PROBABILITY | 5 % |
---------------------------------------------------------------------
--------------------------------- ----------------------------------
POTENTIAL FOR >10 MEV PROTONS POTENTIAL FOR >100 MEV PROTONS
--------------------------------- ----------------------------------
HIGH FLUX : 40 % > 100 PFU HIGH FLUX : 0 % > 100 PFU
MODERATE FLUX : 40 % > 10 PFU MODERATE FLUX : 0 % > 10 PFU
LOW FLUX : 10 % > 1 PFU LOW FLUX : 20 % > 1 PFU
NONE : 10 % <= 1 PFU NONE : 80 % <= 1 PFU
---------------------------------- ----------------------------------
--------------------------------- ---------------------------------
EST. POTENTIAL GEOMAGNETIC IMPACT EST. POTENTIAL IONOSPHERIC IMPACT
--------------------------------- ---------------------------------
SEVERE STORM : 15 % LOW LATITUDES : MINOR
MAJOR STORM : 40 % MIDDLE LATITUDES : MINOR - MAJOR
MINOR STORM : 40 % HIGH LATITUDES : MAJOR
ACTIVE OR LESS : 5 % POLAR LATITUDES : MAJOR
--------------------------------- ---------------------------------
PROBABLE SI ASSOCIATION : 90 % ESTIMATED GLOBAL IMPACT: MINOR - MAJOR
ESTIMATED POTENTIAL DURATION OF DISTURBANCE AFTER ARRIVAL: 36 TO 48 HOURS
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