Halo CME Mail

Date: Fri, 25 May 2001 15:49:09 -0400 (EDT)

From: Gareth Lawrence

Subject: Partial halo CME on 2001/05/25 - CLARIFICATION

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This morning's alert contained a typo in the subject (the date was
incorrectly given as 5/15 rather than 5/25) and was described as a
full halo event in the body of the message. Apologies for any
confusion this may have caused. The correct version of the message
appears below. The UCMEO data is correct, as it was in the original.

Best wishes,
        Gareth Lawrence.

UCMEO 93001 10525 1500/
10525 60550 91418 2651/ 135// 213// 30234
10525 60248 90424 42012 09463 4221/
99999

PLAIN

BT

LASCO and EIT observed a partial halo CME on 2001/05/25. The event
was first observed in C2 at 05:50 UT as a narrow loop front in
the NW. By 06:52 this front spanned some 230 deg over the N Pole
from PA 265 to 135. An outflow is discernible around the rest of
the C2 occulting disk, but no identifiable front. The front first
appeared in C3 at 08:18 UT with maximal coverage of the C3 occultor
by 09:42. Note that the event is faint in C3 and hard to
distinguish from two earlier events over the N Pole. The plane of
sky speed of the fastest region of the front was measured as
234 km/s at PA 82 (NE) with significant acceleration
through both coronagraphs.

The CME was most probably associated with an eruptive filament
liftoff which EIT observed from about 02:48 to 04:24, with associated
activity continuing for some hours afterwards including the formation
a bright arcade by 06:00. Note that the timings of the EIT and LASCO
reports are consistent with the slow plane-of-sky speed of the CME.
The eruption disrupted a large region of the disk fairly near disk
center. The region included several active regions and was centered
near AR 9463 at about N12W20. An EIT dimming was seen associated
with the early stages of the disruption, but no EIT wave. X ray
activity was extremely low around the time of the eruption.

Images and movies of this event are available at:

ftp://ares.nrl.navy.mil/pub/lasco/halo/20010525

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       |
++