Date: Tue, 31 Oct 2006 12:33
From: Guillermo Stenborg
Subject: Full Halo Event on 2006/10/31, probably backsided
Status: O
UCMEO 93001 61031 1630/
61031 60430 91242 0002/ 360// 113// 20670
61031 ///// ///// ///// ///// 5//2/
99999
PLAIN
LASCO observed a full Halo Event on 2006/10/31. The event was first
seen in the LASCO C2 FOV as a faint and diffuse front all above the
N Pole at 04:30 UT extending up to the E limb (1). A brighter feature
(ragged front) shows up on the W at 05:06 UT with some faint and
diffuse extensions (2) to S up to the E Limb. All together, the event
looks like a full halo event by this time ((elliptical shape), the
signal being barely above the limb on the S Pole. Feature (1) is
first seen in C3 at 05:18 UT, all above the E limb and N Pole. Feature
(2) shows up on W at 06:42 UT, and at 08:18 UT the C3 occulting
disk appears fully surrounded (difficult to establish the relationship
between features (1) and (2)). The mean plane-of-sky speed of the
outermost part of the LE of the complex event at different position
angles is shown below (based on C3 data):
PA 085: ~ 450 km/sec (showing slight deceleration)
PA 310: ~ 670 km/sec (showing slight deceleration)
PA 204: ~ 210 km/sec (showing slight deceleration), most likely
related to Feature (1)
No frontsided signatures prior to the event on EIT 195 images, nor
significant X-ray events were reported by the time. However, EIT 195
images seems to show the apparent slow lift-off of a prominence on NW
between 03:48 - 11:12 UT, though it is really hard to say due to
its faintness and size.
In summary, the event has therefore been determined as a full Halo Event
probably backsided based on the lack of significant frontsided activity.
However please be aware that EIT 195 images did not show signatures
of a backsided event either.
Movies and images of the event will shortly be made available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20061031
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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