Date: Tue, 8 Aug 2006 11:02
From: Guillermo Stenborg
Subject: Very faint Halo Event on 2006/08/07, most probably backsided
Status: O
UCMEO 93001 60808 1505/
60807 60131 82042 0002/ 360// 113// 10170
60807 ///// ///// ///// ///// 5//2/
99999
PLAIN
LASCO observed a faint Halo Event on 2006/08/07. The event was first seen
in C2 at around 01:31 UT, appearing above the NW limb: a faint expanding
loop front apparently preceded by a fainter and expanding front. The
latter fully surrounds the C2 occulting disk by around 07:37 UT. The halo
signature has elliptical shape (by that time the LE on NW is close to the
end of the C2 FOV, and barely above the limb on SE). Note that gusty
outflow (and some ragged fronts) can be seen along the day on SW. The halo
event is first seen in C3 at ~ 08:20 UT on NW, just behind the pylon. The
event is no longer discernible in C3 by 20:42 UT. It didn't reach the end
of the FOV by that time (outermost part at ~ 17 solar radii -on NW-). The
mean plane-of sky speed of the LE at PA 162 was ~ 170 km/sec. The accuracy
of the measurements is poor due to the faintness and diffuseness of the
LE.
GOES recorded no significant X-ray activity during the day (A-level).
Likewise, EIT 195 images do not show significant frontsided activity save
some faint brightenings and apparent outflow to NW of a bright region on
the SW quadrant (signature compatible with the C2 gusty outflow mentioned
in first paragraph).
In summary, the event was catalogued as a very faint and slow Halo Event,
most probably backsided based on the lack of activity at the appropriate
location to be considered frontsided.
LASCO movies and images of the event will shortly be made available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20060807
Best wishes,
Guillermo Stenborg
++
Dr. Guillermo A. Stenborg
SOHO-LASCO Operations Scientist,
CUA, MC 612.5, Bldg 26, Rm 001, F: +1-301-286-0264
NASA Goddard Space Flight Center,
Greenbelt, MD 20771. P: +1-301-286-2941
e-mail: stenborg@kreutz.nascom.nasa.gov
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