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>Path: infoac!unido!mcsun!uunet!ogicse!ucsd!ucbvax!HG.ULeth.CA!oler
>From: oler@HG.ULeth.CA (CARY OLER)
>Newsgroups: rec.radio.amateur.misc
>Subject: MAJOR SOLAR FLARE ALERT - 17 MARCH - SOLAR INFORMATION UPDATE
>Message-ID: <910318005942.20805548@HG.ULeth.CA>
>Date: 18 Mar 91 07:59:42 GMT
>Sender: daemon@ucbvax.BERKELEY.EDU
>Organization: The Internet
>Lines: 68


                        --  MAJOR SOLAR FLARE ALERT  --

                                MARCH 17, 1991

                              Flare Event Summary
                          Potential Impact Assessment


                                    --------



MAJOR ENERGETIC EVENT SUMMARY

     A very short, impulsive class X1.0/2B Tenflare erupted from Region
6545 beginning at 21:23 UT.  The event peaked at 21:25 UT and ended at
21:31 UT on 17 March.  The flare was associated with a 710 s.f.u. tenflare
and a 245 MHz burst of 5,400 s.f.u..  No sweeps were associated with this
event.  The flare was located at S10W13.  This major category x-ray flare
is characteristic of the short duration events which have originated from
this region over the past week.  However, this event can be considered
rather insignificant considering the low integrated x-ray flux achieved.


POTENTIAL TERRESTRIAL IMPACT ASSESSMENT

     No terrestrial impacts are expected from this latest major flare.  It
was very brief and fairly insignificant, despite the x-ray rating achieved.

     Major flaring is expected to continue, although probably at a reduced
rate from Region 6545.  Another major event is expected within the next 72
hours from this Region.  Some simplification and decay in magnetic
complexity has been observed in this region.  However, it is still
maintaining a delta configuration (although it is now fairly weak) and is
still quite capable of producing a major energetic event.

     New Region 6555 (S22E76) has shown impressive M-class flare activity
since it arrived on the east limb.  It has been responsible for five minor
M-class flares on 17 March and continues to produce frequent M-class
flaring.  Several of these flares have been rated 2B optical types.  Most of
them have lasted average durations of between 20 and 40 minutes.  This
region is still too near the east limb to observe in any detail.  Some
impressive surging has also been observed on the east limb recently.

     A sudden magnetic impulse was observed at many middle latitude
magnetic observatories.  A local SI was not seen, although Boulder reports
a SI measuring 12 gammas at 20:36 UT on 17 March.  This impulse is believed
to be in response to the major flare at 00:52 UT on 16 March.  Geomagnetic
activity has increased to generally unsettled levels since about 02:30 UT
on 18 March.  Activity could reach minor storm levels over high latitudes,
although middle latitudes should remain generally unsettled to active.

     A POTENTIAL SATELLITE PROTON EVENT WARNING continues in progress.
Satellite protons remain enhanced slightly above background levels.  A
major energetic flare could still easily push protons above event
thresholds.

     A POTENTIAL PCA ACTIVITY WARNING also continues in progress and will
likely remain in effect for the next 48 to 72 hours.

     Frequent minor SID's/SWF's can be expected due to the number of
M-class flares occurring from Region 6555.  SID's/SWF's should be fairly
minor and of relatively short duration, unless another major flare erupts
from Region 6545 (which is still very possible, if not likely).


**  End of Alert  **
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