Halo CME Mail

Date: Thu, 26 Apr 2001 16:02:48 -0400 (EDT)

From: Gareth Lawrence

Subject: Full halo CME on 2001/04/26

  ------------------------------------------------------------------------

UCMEO 93001 10426 2000/
10426 71230 91718 0001/ 360// 123// 30918
10426 61148 91418 42317 09433 1222/
99999

PLAIN

BT

LASCO and EIT observed a full halo CME on 2001/04/26. The event
was first observed in C2 at 12:30 UT as a wide bright front in
the NE. By 12:54 this bright front spanned some 220 deg from
PA 290 to 150, with faint extensions around the rest of the C2
occulting disk. The bright front first appeared in C3 at
12:42 UT with the C3 occultor surrounded by 14:18. The plane
of sky speed of the fastest region of the front was measured
as 918 km/s at PA 24 (NE) with no significant deceleration
through either coronagraph. This speed should not be considered
especially accurate due to the sparse data available, and to
problems tracking features in uneven-cadence running difference
movies.

The CME was probably associated with an M7.8 X-ray flare in
AR 9433. GOES records the flare between 11:26 and 13:19 UT with
peak emission at 13:12. The flare was poorly observed by EIT,
partly due to its timing - when EIT was not running the 195 A
CMEwatch program - and partly due to ground station problems
mean that some of the data from around this time is yet to
arrive and is unlikely to do so before tomorrow. Nevertheless,
some motions and brightenings can be seen prior to 12:36, and
bright post-flare loops are evident after 14:06 UT. Dimming
and EIT waves were not evident in association with this
event, though analysis of a complete dataset is required
for a more confident statement.

Images and movies of this event are available at:

ftp://ares.nrl.navy.mil/pub/lasco/halo/20010426

and improved versions will be generated as soon as the
additional data is available.

Best wishes,
        Gareth Lawrence.

++
| Gareth Lawrence,                 E-mail:grl@ajcannon.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 G-1,                         +1-301-286-3447       |
| Greenbelt, MD 20771.                   Fax:    +1-301-286-0264       |
++