Date: Thu, 9 Dec 2004 11:34
From: Guillermo Stenborg
Subject: Potential 'Full' Halo CME on 2004/12/08, frontsided
UCMEO 93001 41209 1625/
41208 62026 92126 0001/ 360// 122// 10360
41208 61934 82044 40701 10709 1112/
99999
PLAIN
BT
LASCO C2/EIT observed what it could have been a Full Halo CME
Event on 2004/12/08. Signatures of the potential event were first
observed in C2 at 20:26 UT above the SE and NW limbs (i.e., faint
brightenings). By 21:26 UT the C2 occulting disk is fully
surrounded by a feature that shows up elongated towards NW and SE,
and barely above the NE Limb. A LASCO data Gap occurred afterward
(see Spacecraft Status [*] below). The mean plane-of-sky speed as
measured only on a couple of C2 images was about 360 km/sec at
PA 314.
GOES reported a long duration X-ray event (C2.5) originating from
NOAA AR 10709 (N01W07) between 19:34 - 20:44 UT with peak emission
at 19:59 UT, associated to the event seen on LASCO. EIT 195 images
show a brightening on the AR mentioned above starting at 19:36 UT.
A filament erupts at least partially. Post flare loops form later
across the old filament location. Relatively large dimming region
to E and W of the AR. Last EIT image before Data Gap taken at
21:36 UT.
For completeness, also note that a second X-ray flare (C1.1) was
reported, this time originating on NOAA AR 10710 (S09E49) on
2004/12/09 between 00:09 - 00:15 UT with peak emission at 00:10 UT
(No corresponding LASCO/EIT images).
In summary, the event has therefore been determined as a potential
'full' halo CME, frontsided.
Movies and images (only C2 and EIT 195) of the event will shortly
be made available at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20041208
[*] Spacecraft Status:
At 21:58 UT telemetry was lost. It was recovered at 22:12 UT in low
rate showing that SOHO is in ESR (Emergency Sun Reacquisition)
mode. The indicated trigger cause is the CSPAAD (Coarse Sun Pointing
Attitude Anomaly Detector). Since all pointing was nominal up to
the point where telemetry was lost this is obviously a false
trigger. The cause is currently unknown. As part of a nominal
recovery from ESR mode, SOHO entered CRP (Coarse Roll Pointing)
mode at 04:44 UT on 2004/12/09. SOHO is still in low rate telemetry.
Recovery is under way.
Best wishes,
Guillermo Stenborg
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Dr. Guillermo A. Stenborg
SOHO-LASCO Operations Scientist,
CUA, MC 682.3, 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
++