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91-09-17.DLY
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1991-09-18
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/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
DAILY SUMMARY OF SOLAR GEOPHYSICAL ACTIVITY
17 SEPTEMBER, 1991
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
(Based In-Part On SESC Observational Data)
SOLAR AND GEOPHYSICAL ACTIVITY INDICES FOR 17 SEPTEMBER
-------------------------------------------------------
!!BEGIN!! (1.0) S.T.D. Solar Geophysical Data Broadcast for DAY 260, 09/17/91
10.7 FLUX=176.9 90-AVG=202 SSN=145 BKI=1222 1322 BAI=007
BGND-XRAY=B8.0 FLU1=2.6E+05 FLU10=8.6E+03 PKI=1212 2322 PAI=007
BOU-DEV=008,012,015,014,008,020,014,012 DEV-AVG=012 NT SWF=01:004
XRAY-MAX= M1.3 @ 1904UT XRAY-MIN= B6.6 @ 0324UT XRAY-AVG= C1.0
NEUTN-MAX= +003% @ 2220UT NEUTN-MIN= -001% @ 1455UT NEUTN-AVG= +1.1%
PCA-MAX= +0.3DB @ 1450UT PCA-MIN= -0.1DB @ 2105UT PCA-AVG= +0.1DB
BOUTF-MAX=55317NT @ 2251UT BOUTF-MIN=55282NT @ 1555UT BOUTF-AVG=55306NT
GOES7-MAX=P:+105NT@ 1652UT GOES7-MIN=N:-002NT@ 2217UT G7-AVG=+083,+044,+005
GOES6-MAX=P:+114NT@ 1911UT GOES6-MIN=E:-012NT@ 0850UT G6-AVG=+098,-001,+025
FLUXFCST=STD:182,187,193;SESC:175,175,180 BAI/PAI-FCST=006,010,010/010,012,012
KFCST=2133 3111 2134 4111 27DAY-AP=043,019 27DAY-KP=5664 4434 4444 3222
WARNINGS=
ALERTS=**MINFLR:M1.3@1904
!!END-DATA!!
BRIEF SUMMARY OF EVENTS
-----------------------
Solar activity became moderate today in response to a class M1.3 x-ray
flare at 19:04 UT. An optical classficiation for this flare was unavailable.
However, no significant radio emissions were observed. No sweep frequency
events were associated with this event either.
Region 6832 (N07E17) was responsible for spawning this M-class flare
today. This region has shown some increased growth and an enhancement in
magnetic complexity. The trailer spot complex became a little better defined
today in white-light. Growth within this region is not characterized as
rapid, but rather as steady and fairly stable. Signs of increasing
instability may be materializing.
The only other notable region was Region 6827 (S21W31) which managed to
spawn two C-class subflares during the UT day. These were both low-level
C-class events, not exceeding a class C2.0/SF level.
Region 6824 (S20W47) continued to decay during the day and is now a
small bipolar group. This region has remained dormant throughout the period
and is not expected to produce anything more significant than subflares or an
isolated low-level C-class event.
A large hedge row prominence which was visible yesterday (as should have
been easily discerned in the full-disk H-alpha image sent out to image
subscribers yesterday), disappeared sometime today (the time is uncertain).
The large prominence was visible on the southeast limb between S30 and S50.
The actual eruption of this prominence was not observed.
Solar activity should remain mostly low, with only a very slight chance
for an isolated M-class flare from Region 6832. The solar disk is still
dormant. The background x-ray flux has increased over the last 6 to 12
hours and may approach or surpass the class C1.0 level on 18 September.
Geomagnetic activity remained quiet today. Conditions are expected to
remain quiet to unsettled over the next 72 hours at least.
Auroral activity has likewise been dormant and should remain dormant
over the next 72 hours.
HF propagation conditions were above normal over most regions. Northern
hemisphere reports have indicated very good propagation conditions over the
low, middle and high latitude paths, with good stability in polar path
signals also noted. Southern hemisphere stations have reported generally
good propagation conditions, with some periods of fading and distortion on
equatorial and high latitude paths. Global propagation conditions are
characterized as above normal for 17 September. Normal to above normal
conditions may be expected over the next 48 to 72 hours.
** End of Daily Update **