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>From: oler@HG.ULETH.CA (CARY OLER)
>Newsgroups: rec.radio.shortwave
>Subject: MAJOR SOLAR FLARE ALERT - STORM WARNING UPDATES - 16 MARCH
>Message-ID: <910316000554.2080472a@HG.ULeth.CA>
>Date: 16 Mar 91 07:05:54 GMT
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>Reply-To: CARY OLER <oler@HG.ULETH.CA>
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                        --  MAJOR SOLAR FLARE ALERT  --

                                MARCH 16, 1991

                              Flare Event Summary
                          Potential Impact Assessment
                      Storm Warning Informational Update


                                    --------



MAJOR ENERGETIC EVENT SUMMARY

     Another major X-class flare exploded from Region 6545 early this UT
day.  The event was rated as a major class X1.8/2B Tenflare.  The
event began at 00:44 UT on 16 March, peaked at 00:52 UT and ended at 01:02
UT on 16 March.  This event, like all of the other major events originating
from this region, was of short duration.  However, it was rich in radio
emissions, with significant Type II AND IV bursts.  The estimated shock
velocity of the Type II is near 1000 km/s.  The flare was associated with a
910 s.f.u. Tenflare and an 18,000 s.f.u. burst at 245 MHz.  The flare was
located at S10E08, easily within range of producing significant terrestrial
impacts (however, see the impact assessment below).


POTENTIAL TERRESTRIAL IMPACT FORECAST

     There is some uncertainty at the present time with regards to the
potential impact this latest flare might have on the earth.  The strong
Type II and IV sweeps indicate some expulsion of mass was likely.  At the
present time, we think there is a fairly good chance that an interplanetary
shock may be associated with this event.  If so, magnetic storming is not
out of the question.  Any impacts from this flare are likely to be observed
late on the 17th or on 18 March.  The extent of the potential activity (if
it occurs) is still to be determined.  An additional update will be posted
later on 16 March (with the warning update near 18:00 UT on 16 March).


STORM WARNING INFORMATIONAL UPDATE

     A POTENTIAL GEOMAGNETIC STORM WARNING REMAINS IN EFFECT FOR 16 MARCH
and may be extended to 17 March if an interplanetary shock arrives within
the next 12 to 18 hours.  A shock has not yet been observed.  It is late
now by almost 12 hours.  It is possible this shock could still arrive and
produce some respectable storm conditions.  However, as time passes by, the
potential magnitude of any activity is diminishing.  Major geomagnetic
storming is still possible.  The Pioneer Venus data indicated that some
significant activity was out there near the Venusian environment.  However,
this satellite is a fair distance east of the earth-sun line and would have
been more prone to flare-induced activity.  There is a possibility the
ejected mass will not impinge on the earth.  But we believe there is still
a fairly high possibility for a shock impact with the earth within the next
12 to 24 hours.  Hence, the Potential Major Geomagnetic Storm Warning will
be continued for the next 12-24 hours.  If nothing materializes by then, it
may be cancelled (or updated depending on further analysis of the recent major
flare).  These shocks have been known to be rather tardy.

     Please note that if storming does materialize, auroral activity will
not likely become visible until the evening of 16 March (local time) for
observers in North America.

     Geomagnetic activity has diminished substantially over the past 6 to 9
hours.  Very quiet geomagnetic activity has been observed at almost all
middle latitude stations as of 06:30 UT on 16 March.  This could change
abruptly, however, if a shock arrives as expected.

     ALL PREVIOUS ALERTS ARE STILL IN EFFECT FOR 16 MARCH.  An update will
be posted near 18:00 UT on 16 March.  Warning cancellations or extensions
will be issued then.

     Satellite level protons are still very near event thresholds.  They
are hovering between the 5 and 9 p.f.u. level (10 is the event threshold).
If an interplanetary shock arrives, protons could easily surpass the event
threshold briefly.  A polar cap disturbance is currently in progress.  The
cause is the elevated proton fluence levels in progress.

     If a shock arrives, a bulletin will be posted immediately (provided
the shock arrives during manned hours).  If the shock arrives during
unmanned hours, a bulletin will be posted immediately thereafter.


**  End of Alert  **
-- 
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