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>From: oler@HG.ULeth.CA (CARY OLER)
>Newsgroups: rec.radio.amateur.misc
>Subject: MAJOR SOLAR FLARE ALERT - 21 MARCH - TWO EVENTS
>Message-ID: <910322021108.22401224@HG.ULeth.CA>
>Date: 22 Mar 91 09:11:08 GMT
>Sender: news@ucsd.Edu
>Organization: UCSD Usenet Gateway
>Lines: 84


                        --  MAJOR SOLAR FLARE ALERT  --

                                MARCH 21, 1991

                              Flare Event Summary
                          Potential Impact Assessment


                                    --------



MAJOR ENERGETIC EVENT SUMMARY

     Two major flares erupted from Region 6555 on 21 March.  The first
began at 20:17 UT, peaked at 20:31 UT and ended at 20:34 UT on 21 March.
It was located at S13E29 and attained a class X1.0/1N rating.  It was
associated with rather weak radio bursts and had a low integrated x-ray
flux.  This event was impulsive.  No sweeps were observed.

     The second major flare began at 23:35 UT, peaked at 23:44 UT on 21
March, and ended at 00:01 UT on 22 March.  This event attained a class
M5.4/2B rating and was associated with a fairly strong Type IV event.
However, this flare was impulsive as well.

     Region 6555 (now located at S24E30) remains impressive and is the
largest and most complex region currently visible.  Spot counts have
increased to 75 in this region, which still maintains a magnetic beta
configuration.


POTENTIAL TERRESTRIAL IMPACT ASSESSMENT

     The first major flare (the X-class event) will not have a terrestrial
impact.  It was a high-amplitude event in x-rays, but has not produced any
significant radio emissions and was quite impulsive.

     The second major flare is still being studied and the potential
impacts will not be fully known until later on 22 March.  It presently
appears as though a small risk exists for a light terrestrial impact
(mostly over the higher latitudes) sometime on 24 March.  However, this
flare was not radio rich.  The only truly noteworthy phenomena associated
with this flare was the moderate to strong intensity Type IV which
accompanied the flare.  The integrated x-ray flux of this flare was low.
So there is a higher probability that no terrestrial impacts will be
observed.  A more accurate assessment will be released on 22 March after
all of the data has been analyzed.

     Isolated major flaring will likely continue from Region 6555 over the
next 24 to 72 hours.  Minor M-class flaring will certainly continue at a
fairly frequent rate.  Associated minor SIDs/SWFs could cause momentary
disruptions in HF radio communications.  A total of seven SID's/SWF's were
observed (some are unconfirmed at the present time) on 21 March, associated
with the fairly frequent M-class flaring from Region 6555.

     A period of minor geomagnetic storming occurred between 12:00 UT and
15:00 UT over middle latitudes.  This period was preceded by a sudden impulse
which occurred near 06:00 UT on 21 March over some middle latitude stations.
Locally, the only significant perturbation occurred at 13:45 UT and was
rated as a minor storm level fluctuation with a fairly rapid rise-time and
slow decay.  High latitudes experienced active to severe storming during
this period.  Some high latitude auroral storming was also noted in
conjunction with this increased geomagnetic activity.  It is difficult to
pinpoint the cause of this activity, as there were several events which may
have been responsible.  However, at the present time, it appears as though
the major class M6.7/2B flare of 19 March is most likely responsible.  Auroral
activity remained confined to the high and northerly middle latitudes.  HF
radio conditions during this period of storm activity was degraded to
generally poor levels over middle latitudes and very poor levels over the
high latitudes.  Conditions improved rapidly after 16:00 UT, as did
geomagnetic activity over the middle latitudes.

     A bulletin stating the potential impacts of the last major M-class
flare will be issued later on 22 March.  The POTENTIAL MAJOR SOLAR FLARE
WARNING and the POTENTIAL SATELLITE PROTON EVENT WARNING remain in effect.
Geomagnetic activity should remain at unsettled to active levels over the
next 24 hours.  Auroral activity will remain at low to moderate levels over
the middle and/or northerly middle latitudes on 22 March, with moderate to
high levels of activity likely over the high latitudes.  Low latitudes will
not witness any auroral activity.


**  End of Alert  **
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