Halo CME Mail

Date: Wed, 23 Apr 2003 12:06

From: Gareth Lawrence

Subject: Partial Halo CME on 2003/04/23, probably frontsided

Status: O

UCMEO 93001 30423 1800/
30423 60127 90942 1671/ 032// 223// 30667
30423 60113 90125 41719 10338 1212/

LASCO/EIT observed a partial halo CME on 2003/04/23. The 
event was first observed in C2 at 01:27 UT as a bright loop 
front over the NW limb; by 02:26 UT it spanned ~220 deg from
PA 170 - 30. The front first appeared in C3 at 02:18 UT
and reached maximal extension by 03:18 UT. The mean 
plane-of-sky speed for the event was 667 km/s at PA 318, 
with no indication of acceleration. Note that the speed
was indeed measured at the same PA as an earlier event on
2003/04/21 - the PA noted above is not a typo.

EIT had just ended a CCD bakeout by this time; however the 
greater part of the on-disk activity appear to have occurred
during the 01 UT synoptic sequence so coverage is poor. In 
fact, EIT did not observe an eruptive event directly, but an
EIT wave could be seen between 01:25 - 01:48 UT. GOES recorded
a M5.1 X-ray flare between 00:39 - 01:15 UT with peak emission 
at 01:06 UT. SEC records the flare from AR 0338, N22W25, and
a slight brightening can be discerned in this region in the 
EIT 195 A image from 00:48 UT. The region also appears bright 
in the 171 A image from 01:00 UT and the 284 A image from 
01:05 UT. The EIT wave from 01:25 mentioned above appears to
be centered about N20W20. This event has therefore been 
determined most probably frontsided.

Movies and images of this event are available now at: 

Some people may experience difficulties obtaining the images and 
movies at present; this is due to unresolved issues with the 
firewall at NRL. Aplogies to those affected; the problem is being 
worked on. 

The movies and images from the 2003/04/21 event should also now all
be available from their directory. Apologies for the inconvenience
caused by their temporary non-availability which was due to systems
and network problem. Apologies also for any confusion due to the 
typo in the first line of the text, which stated that the CME was
observed on 2003/02/01 - this should of course have read 2003/04/21
as stated in the email subject line, UCMEO code, and ftp site address.

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       |