Halo CME Mail

Date: Thu, 20 Mar 2003 17:30

From: Gareth Lawrence

Subject: Partial Halo CME on 2003/03/18, frontsided - RESEND

Status: O

UCMEO 93001 30319 2215/
30118 61230 91618 2001/ 350// 333// 41384
30118 61200 91248 34814 10314 1112/

** NOTE **

It appears that some (most?) on the list did not receive the
original version of this report, so it is being re-sent 
approximately 24 hours later. It was also noted that some of 
the movies and images on the server were corrupted during 
transfer. These have been remade and/or retransferred.

Apologies for the delay and inconvenience.


LASCO and EIT observed a partial halo CME on 2003/03/18. The 
event was first observed in C2 at 12:30 UT as a bright loop 
front over the W limb; by 12:54 UT the front spanned 152 deg
from PA 200 - 352, though the extensions to the N pole were 
faint. The front first appeared in C3 at 12:42 UT with 
maximal coverage of the C3 occultor by 13:42 UT. The mean 
plane-of-sky speed for this event was 1384 km/s at PA 262, 
with some evidence for acceleration. 

The CME was probably most associated with a flare observed by 
EIT between 12:00 - 12:48 UT with peak emission at 12:12 UT,
centered around S14W48. SEC records a X1.5 X-ray event from 
AR10314 at S15W46 between 11:51 - 12:20 UT with peak emission 
at 12:08 UT. An EIT dimming and wave were observed in
association with this event, largely to the N and W of the
active region.

Movies and images of this event are available now at: 

Note that the LASCO images show a halo CME first appearing 
in the S and SW at 13:54, developing to a full halo CME by
14:30. Careful study of EIT images suggest that this CME was 
backsided in origin, and may be related the the disappearing 
filament noted by SEC between 13:20 - 14:03 UT but without a
given position. Note also that another bright full halo CME, 
visible from 02:30 UT on Feb 19, has also been determined 
backsided following analysis of EIT data. It is worth noting 
here that both of these CMEs caused major disturbances to the 
large streamer in the SW. The predominant motion of this 
streamer within the time frame was clockwise, which is 
indicative of a backsided streamer in the SW.

Best wishes,
        Gareth Lawrence.

| Gareth Lawrence,                   E-mail:grl@kreutz.nascom.nasa.gov |
| SOHO-LASCO Operations Scientist,				       |
| CUA, Mail Code 682.3,                                                |
| NASA Goddard Space Flight Center,      Phone:  +1-301-286-2941       |
| Building 26, Room 001,                         +1-301-286-3447       |
| Greenbelt, MD 20771.                   Fax:    +1-301-286-0264       |