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91-10-30.DLY
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1991-10-30
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DAILY SUMMARY OF SOLAR GEOPHYSICAL ACTIVITY
30 OCTOBER, 1991
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
(Based In-Part On SESC Observational Data)
SOLAR AND GEOPHYSICAL ACTIVITY INDICES FOR 30 OCTOBER
-----------------------------------------------------
!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 303, 10/30/91
10.7 FLUX=261.7 90-AVG=197 SSN=342 BKI=1313 4443 BAI=016
BGND-XRAY=C2.0 FLU1=*.*E*** FLU10=1.1E+06 PKI=2324 5544 PAI=024
BOU-DEV=005,037,009,022,068,067,057,025 DEV-AVG=036 NT SWF=02:205
XRAY-MAX= X2.5 @ 0634UT XRAY-MIN= C1.6 @ 0214UT XRAY-AVG= M1.2
NEUTN-MAX= +000% @ 2335UT NEUTN-MIN= -010% @ 0050UT NEUTN-AVG= -4.7%
PCA-MAX= +1.3DB @ 1650UT PCA-MIN= -0.2DB @ 0140UT PCA-AVG= +0.3DB
BOUTF-MAX=55320NT @ 2345UT BOUTF-MIN=55259NT @ 1810UT BOUTF-AVG=55300NT
GOES7-MAX=P:+105NT@ 1906UT GOES7-MIN=N:-007NT@ 2358UT G7-AVG=+077,+057,+004
GOES6-MAX=P:+123NT@ 2104UT GOES6-MIN=E:-022NT@ 0607UT G6-AVG=+088,+001,+026
FLUXFCST=STD:260,260,255;SESC:265,260,255 BAI/PAI-FCST=035,045,030/042,047,045
KFCST=3445 5654 4556 6654 27DAY-AP=027,014 27DAY-KP=2453 4354 4333 2222
WARNINGS=*MAJFLR;*PROTFLR;*PROTON;*PCA;*GSTRM;*AURMIDWRN;*AURLOWWCH
ALERTS=**MAJFLR:X2.5/3B,S08W25(6891),0610-0634-0935,II=3@0625,IV=3@0630;
**MINFLR:M4.3@1916;**PROTN10:94PFU@0810;**PCAENH;**FORBUSH;
**TENFLR:5200SFU@0615
!!END-DATA!!
IMPORTANT NOTE: Estimated target shock arrival time from the last major
flare has been adjusted to 15:00 UT on 31 Oct.
BRIEF SUMMARY OF EVENTS
-----------------------
Solar activity was high today. Region 6891 (S12W32) spawned another
powerful solar flare. Rated a class X2.5/3B tenflare, this event was
associated with major Type II and IV sweeps as well as strong radio bursts
across the spectrum. The estimated velocity of the Type II sweep was an
impressive 1,600 km/sec. This event occurred at 06:34 UT and was located at
S08W25. Within approximately 30 minutes from the maximum of the flare, 10
MeV and energetic 100 MeV protons arrived at near relativisitic speeds. 10
MeV protons immediately climbed to a peak flux of 94 pfu at 08:10 UT. 10 MeV
protons then fell back down to about the 20 pfu level and slowly declined
throughout most of the UT day. Recent observations show proton levels to be
climbing yet again as the interplanetary shockwave begins to approach the
Earth. Shortly after the shock arrives between 12:00 UT and 18:00 UT, proton
levels should quickly drop below the event threshold.
Other solar activity included a very impulsive class M4.3/1B event at
19:16 UT. Region 6891 (S12W32) appears to be continuing to fragment. It
appears as though this region is now in a decay phase. However, minor and/or
major flaring will remain very possible from this region over the next 72
hours. The decaying may further destabilize the region.
Region 6892 (S19W33) was the only other region to produce a noteworthy
minor flare, rated a class C9/2F event at 04:35 UT.
A minor PCA event was associated with this major flare. PCA levels are
currently enhanced but are just below the event threshold. Polar latitude
absorption of HF signals has been high today.
The geomagnetic field rapidly stabilized early in the UT day.
Conditions became mostly quiet to unsettled by 06:00 UT, which is somewhat
unusual considering conditions less than six hours earlier were at storm
levels. A slight increase in activity was noted later in the UT day,
although no storming has been observed thus far. However, conditions will
definitely change for the worse later this UT day when the interplanetary
shockwave from the last major flare is expected to arrive.
The shock arrival is anticipated to occur anytime between approximately
12:00 UT and 18:00 UT on 31 October. We have adjusted our impact arrival
time from 18:00 UT to near 15:00 UT based on recent observations, although
these estimates could be in error by up to approximately six hours.
Following the shock arrival, we are anticipating major geomagnetic storming
with possible periods of severe storming, particularly over the high latitude
regions and during the local evening/early morning hours.
Auroral activity is expected to become impressively high over the middle
and high latitude regions during the local evening and early morning hours of
31 October/01 November. There is a distinct possibility for low latitude
observations of auroral activity. The most intense phase of the storming is
expected to last approximately 6 to 12 hours, followed by less persistent
(yet strong) geomagnetic and auroral storming for another 18 to 24 hours
thereafter. It is during the intense phase of the storm (the 6 to 12 hour
period during the main phase) when low latitude observations will be most
favorable.
HF propagation conditions continue below normal. Low latitude regions
have observed mostly good to fair propagation conditions, while many middle
latitude regions have witnessed generally fair to poor propagation conditions
with high noise levels and reduced MUFs. Conditions will become notably
degraded with the arrival of the interplanetary shock (provided it arrives as
expected) on 31 October. Conditions should become poor to extremely poor
(with possible frequent blackout periods) over the high and northerly middle
latitude regions. Middle latitude regions should observe mostly fair to very
poor propagation conditions. Low latitudes are expected to witness generally
fair conditions with some poor periods interspersed.
There is a moderate to high probability for middle (and possibly low)
latitude VHF auroral backscatter associated with this storming. The last
severe geomagnetic storm was associated with numerous backscatter reports.
The storm anticipated for 31 October and 01 November should produce similar
results. Barring further major flares, conditions should begin to improve
late in the UT day of 01 November or sometime on 02 November.
** End of Daily Update **