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91-10-27.DLY
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1991-10-27
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DAILY SUMMARY OF SOLAR GEOPHYSICAL ACTIVITY
27 OCTOBER, 1991
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
(Based In-Part On SESC Observational Data)
SOLAR AND GEOPHYSICAL ACTIVITY INDICES FOR 27 OCTOBER
-----------------------------------------------------
!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 300, 10/27/91
10.7 FLUX=249.4 90-AVG=195 SSN=339 BKI=6464 3434 BAI=037
BGND-XRAY=C2.7 FLU1=*.*E*** FLU10=7.6E+03 PKI=5455 4544 PAI=036
BOU-DEV=132,050,127,040,039,066,033,040 DEV-AVG=065 NT SWF=06:209
XRAY-MAX= X6.1 @ 0548UT XRAY-MIN= C1.8 @ 2223UT XRAY-AVG= M1.5
NEUTN-MAX= +003% @ 2350UT NEUTN-MIN= -003% @ 0600UT NEUTN-AVG= +0.1%
PCA-MAX= +0.3DB @ 2130UT PCA-MIN= -0.2DB @ 0230UT PCA-AVG= +0.0DB
BOUTF-MAX=55309NT @ 0537UT BOUTF-MIN=55248NT @ 1845UT BOUTF-AVG=55288NT
GOES7-MAX=E:+121NT@ 0837UT GOES7-MIN=N:-042NT@ 0133UT G7-AVG=+062,+062,+003
GOES6-MAX=P:+125NT@ 2316UT GOES6-MIN=N:-107NT@ 0143UT G6-AVG=+074,-002,+018
FLUXFCST=STD:250,250,245;SESC:250,245,240 BAI/PAI-FCST=030,040,030/035,045,040
KFCST=3466 5543 5567 5444 27DAY-AP=046,046 27DAY-KP=3454 3366 5556 5543
WARNINGS=*MAJFLR;*PROTFLR;*PROTON;*PCA;*GSTRM;*AURMIDWRN;*AURLOWWCH
ALERTS=**MAJFLR:X1.9/2B,S11E20(6891),0206-0212-0240;**MINFLR:M3.3@1301;
**MAJFLR:X6.1/3B,S13E15(6891),0537-0548-0600,II=3@0540,IV=2@0545;
**TENFLR:3800SFU@0539;**MINFLR:M2.3@0035;**SWEEP:IV@0035;
**TENFLR:410SFU@1301;**245STRM:0000-2400UT
!!END-DATA!!
NOTE: Protons failed to arrive as predicted by the models. However, a
strong threat for proton activity associated with future major flaring
still exists. Further major flares are anticipated. Region 6891 has
not significantly altered its structure. In fact, magnetic shear
appears to be somewhat greater today was observed yesterday.
BRIEF SUMMARY OF EVENTS
-----------------------
Solar activity remained high today. Two major flares occurred early in
the UT day. The first was an impulsive class X1.9/2B flare at 02:12 UT.
This event was not particularly radio-impressive. No sweeps were observed
and the event failed to generate a tenflare. The second major flare occurred
at 05:48 UT and was rated a powerful class X6.1/3B tenflare. The tenflare
measured 3,800 sfu at 05:39. This event was accompanied by a major Type II
sweep and a moderate Type IV sweep. This Type IV lasted almost 5 hours.
This X6.1/3B event was expected to generate a fairly high proton flux in the
near Earth environment, but failed to do so. Protons at greater than 10 MeV
have been stable at background levels.
Aside from these two major flares, the only other energetic events were
minor flares. A Class M2.3/1N with a Type IV sweep occurred at 0035 UT. A
class M3.3/1N tenflare (410 sfu) also occurred at 13:01 UT. Following this
last minor flare, conditions abated and have been fairly stable since then.
Despite this, the region remains very hot, large and complex (clearly a
strong beta-gamma-delta configuration).
Structurally, Region 6891 has not changed very much over the last 24
hours. In fact, its neutral line filaments seem to be even more twisted and
frayed today. Magnetic shear and gradients remain high. This region shares
a common neutral line with Region 6892 (S20E08) which produced only
occassional subflares today.
Region 6891 will almost certainly generate other major flares in the M
or X-class range. Potential proton activity is continuing to become an
increasing threat as the region moves into the western solar hemisphere. Any
major flares over the next 4 to 5 days could have strong terrestrial impacts,
both geomagnetically and with regards to proton and PCA activity. Watch for
future alerts for impact assessments.
The geomagnetic field ranged from unsettled to major storm levels today.
Two primary episodes of major storming were observed over the middle latitude
regions, while high latitudes have observed mostly minor to major storming.
Conditions should remain similar until later in the UT day of 28 October or
early on 29 October when impacts from the recent major solar flares are
anticipated. We are anticipating minor to major geomagnetic storming with a
risk for brief periods of severe geomagnetic storming, particularly over the
high latitude regions. This activity should begin to decay later in the UT
day of 29 October or sometime on 30 October, barring other influential major
events.
Auroral storm warnings have been issued for the middle and high latitude
regions. Activity should become high over the middle and high latitude
regions. There is a fair chance for auroral observations during the moonless
hours of the evening over the low latitude regions, although this depends on
the intensity of the storming during the moonless hours, among other things.
Consult the recent auroral activity warnings and watches for more
information.
HF propagation conditions have been slightly below normal today. High
and polar latitude signal paths were most notably degraded due to geomagnetic
storming. Conditions should become increasingly disturbed, particularly
after the interplanetary shock from the recent major flares arrives later on
28 October or early on 29 October. Conditions should begin to improve on 30
or 31 October, barring further major solar flares.
** End of Daily Update **