🚀 go-pugleaf

>Path: infoac!unido!math.fu-berlin.de!ira.uka.de!sol.ctr.columbia.edu!lll-winken!elroy.jpl.nasa.gov!swrinde!ucsd!news-mail-gateway
>From: oler@HG.ULeth.CA (CARY OLER)
>Newsgroups: rec.radio.amateur.misc
>Subject: VERY SIGNIFICANT MAJOR SOLAR FLARE - HIGH IMPACT EXPECTED
>Message-ID: <910611004147.272009df@HG.ULeth.CA>
>Date: 11 Jun 91 06:41:47 GMT
>Sender: daemon@ucsd.Edu
>Organization: UCSD Usenet Gateway
>Lines: 96


                        --  MAJOR SOLAR FLARE ALERT  --

                                 JUNE 11, 1991

                              Flare Event Summary
                          Potential Impact Assessment


                                    --------



MAJOR ENERGETIC EVENT SUMMARY

     A very powerful solar flare ripped out of Region 6659 on 11 June.  The
event began at 01:56 UT, peaked at 02:09 UT and ended at 04:40 UT on 11 June.
This event saturated the GOES sensors.  The x-rays surpassed the class X12
level for approximately 4 to 8 minutes before beginning a very slow decay.
The optical component was rated 3B.  The flare was located at a sensitive
position of N31W20.  This class X12+/3B tenflare remained in the X-class
category for almost one full hour.  The rate of decay was very gradual, as
can be seen by the end-time of the event (almost 3 hours from start to end).

This event is a very significant one.  Energetic protons at greater than 100
MeV were observed shortly after the peak x-ray flux was observed.  Protons
at greater than 100 MeV peaked at 18 pfu at 05:25 UT.  Current levels are
near 16 pfu at greater than 100 MeV.  Protons at greater than 10 MeV
skyrocketed from about 10 pfu at 02:30 UT to 980 pfu at 05:15 UT.  10 MeV
protons are currently fluctuating around the 340 to 380 pfu level.

     A major importance 3 Type II sweep and a major importance 3 Type IV
sweep were observed from this event.  Strong radio bursts have also been
observed (most of which are still in progress).  The 15400 MHz burst was
measured at 28,000 sfu, while the 245 MHz burst was measured at 7,500 pfu.
Please note that this is preliminary data and may not be entirely accurate.

     The integrated x-ray flux from this event was high, rated at 1.80 joules
per square meter.  Concurrent with this major flare was a severe geomagnetic
excursion.  The combined effects of the major to severe geomagnetic storming
with the high-intensity x-ray levels produced a major HF blackout locally
despite the low solar zenith angle.  Widespread HF blackouts have been
observed.

     A polar cap absorption event (PCA) has recurred with this most recent
energetic event.  Preliminary data indicates absorption levels are
fluctuating around the 4 dB level.


POTENTIAL TERRESTRIAL IMPACT ASSESSMENT

     This class X12+/3B tenflare will have a major to severe terrestrial
impact.  The impact from this flare could surpass the intensity of the
present disturbance (which is very near severe levels).

     A Major to Severe geomagnetic impact is expected anytime near or after
06:00 UT on 12 June.  Conditions are expected to remain at major to severe
storm levels until 14 June, when conditions should begin to fall to active to
minor storm levels (again, barring additional powerful flaring).

     A Major to Severe auroral storm is expected to accompany this major
interplanetary disturbance.  There is a very high risk (>70%) for significant
low-latitude auroral activity on 12 June and 13 June.  The highest
probabilities for low-latitude auroral activity will occur on 13 June, with a
smaller chance (~ 45%) for residual low-latitude activity on 14 June.  June
12-14 (centered on 13 June) represents a very high risk period for
low-latitude auroral activity.

     A very strong HF radio propagation impact is expected to accompany this
major disturbance.  Despite the fact that we are presently experiencing
significant HF disruptions from the present disturbance (which was caused by
the less powerful X12+/3B flare of 09 June), conditions are expected to
become further disturbed when the interplanetary shock from this last major
flare arrives on 12 June.  Widespread HF blackouts may accompany this
disturbance on 13 June.

     A very high probability (> 80%) for VHF auroral backscatter
communications will exist for 13 June.  We are presently experiencing
conditions very favorable for VHF backscatter.  Conditions should become most
favorable on 13 June.  High latitude regions are not expected to have
particularly good opportunities for VHF backscatter.  This activity is
expected to dominate over the middle and low latitude regions (particularly
the middle latitudes).

     The ionosphere will not recover to significantly useful levels
throughout the remainder of this week.  It will require several quiet days to
strengthen to levels useful for reliable long-distance communication, and
these quiet periods are not expected to occur for the next 7 to 10 days.

     Further major X-class flares are possible from Region 6659, although
over the next 24 hours, predominatly minor M-class flares should be observed.
High energy events are possible from this Region.  White light flares may be
possible.


**  End of Alert  **
-- 
*****************************************************************
   ___  ____  ___    _  _ ___ ___   ___ ___ ___     ___ _  _
  /__/ / / /   /    /\ / /__   /   /__//__//   /__//__ /\ /
 / \  /   / __/_   /  / /__   /   /  //  //__ /  //__ /  /