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91-09-24.DLY
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1991-09-24
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DAILY SUMMARY OF SOLAR GEOPHYSICAL ACTIVITY
24 SEPTEMBER, 1991
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
(Based In-Part On SESC Observational Data)
SOLAR AND GEOPHYSICAL ACTIVITY INDICES FOR 24 SEPTEMBER
-------------------------------------------------------
!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 267, 09/24/91
10.7 FLUX=179.8 90-AVG=203 SSN=166 BKI=1222 2212 BAI=006
BGND-XRAY=C1.5 FLU1=3.6E+05 FLU10=8.8E+03 PKI=2112 2222 PAI=006
BOU-DEV=007,013,014,016,014,016,008,011 DEV-AVG=012 NT SWF=01:018
XRAY-MAX= M6.1 @ 0756UT XRAY-MIN= C1.2 @ 0123UT XRAY-AVG= C2.7
NEUTN-MAX= +004% @ 0520UT NEUTN-MIN= -002% @ 2000UT NEUTN-AVG= +0.7%
PCA-MAX= +0.3DB @ 1510UT PCA-MIN= -3.9DB @ 1425UT PCA-AVG= -0.2DB
BOUTF-MAX=55318NT @ 1322UT BOUTF-MIN=55280NT @ 1806UT BOUTF-AVG=55304NT
GOES7-MAX=P:+124NT@ 1855UT GOES7-MIN=N:-001NT@ 2359UT G7-AVG=+086,+037,+006
GOES6-MAX=P:+135NT@ 1955UT GOES6-MIN=E:-014NT@ 0722UT G6-AVG=+100,-004,+023
FLUXFCST=STD:184,187,195;SESC:182,185,195 BAI/PAI-FCST=010,018,020/015,026,030
KFCST=3233 3233 3445 4334 27DAY-AP=014,039 27DAY-KP=2233 3343 3335 5456
WARNINGS=*MAJFLR
ALERTS=**MAJFLR:M6.1/1N,S10E88(6848),0749-0756-0805,II=1@0759;
**TENFLR:230SFU@0750,DUR:5
!!END-DATA!!
BRIEF SUMMARY OF EVENTS
-----------------------
The highlight of the day was a major class M6.1/1N tenflare which erupted
from Region 6848 (S07E63). The flare was located at S10E88 and was
accompanied by a weak Type II sweep and bright limb surging. Latest imagery
suggests this region may be fairly simple. More will be known over the next
24 to 48 hours as it presents itself in a better position for observations.
Contrary to the statements made in the major flare alert, the region
which erupted with this major event was not old Region 6818. This is
apparently a new area of flux which emerged in front of old Region 6818.
Returning old Region 6818 now appears to be coming into view in the wake of
Region 6848. It has been numbered Region 6850 (S12E81) and is too near to
the limb to discern any details.
Also of interest today were optically uncorrelated Type II and IV
sweeps, which occurred at 00:49 UT and 01:08 UT respectively. The source of
these sweeps is uncertain as there were no optical or x-ray correlated events
which occurred at the time of the observation. However, since Type II and IV
sweeps (together) are usually produced by respectably large energetic events,
there may be additional active regions beyond the east limb capable of
spawning energetic activity.
Solar activity is expected to be low to moderate. The probabilities for
isolated M-class flaring are steadily increasing as new active regions rotate
into view around the east limb. The background x-ray flux has increased
notably today. However, the 10.7 cm solar flux dropped, which was somewhat
of a surprise given the new regions which have rotated into view. An
increase in the solar flux is anticipated over the next several days as the
developing active longitudes continue to return.
Geomagnetic activity and auroral activity have been dormant over the
last 24 hours. A gradual increase to active levels of geomagnetic and
auroral activity are anticipated over the next 48 to 72 hours. Isolated
periods of minor storming may be observed as the disturbance peaks sometime
near 27 or 28 September.
HF propagation conditions have been above normal in almost all regions.
Notably higher MUF levels, combined with low absorption and fading are
responsible for the very good propagation conditions. These conditions are
expected to drop to more normal (or slightly below normal) values as the
coronal-induced geomagnetic disturbance increases ionospheric instability.
Another 24 hours of above normal propagation conditions is possible before
the disturbance begins to affect the ionosphere.
** End of Daily Update **