Halo CME Mail

Date: Fri, 28 Sep 2001 11:36

From: Gareth Lawrence

Subject: Partial Halo CME on 2001/09/28, frontsided

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UCMEO 93001 10928 1530/
10928 60842 91418 0201/ 200// 233// 30625
10928 60824 80912 11810 09636 1222/
99999

PLAIN

BT

LASCO and EIT observed a partial halo CME on 2001/09/28. The
event was first observed in C2 at 08:42 UT as a bright loop
front over the E limb. By 09:30 UT this front spanned some
180 deg over the S Pole from PA 20 to PA 200. The front first
appeared in C3 at 09:42 UT with maximal coverage of the C3
occultor by 10:20 UT. Note that the C3 images show a faint
emission around the rest of the occulting disk - this is
probably existing coronal material being compressed somewhat
by the shock. This faint emission is also visible in C2
images but only extremely faintly. The plane of sky speed of
the front was measured as 625 km/s at PA 91 (E) with a slight
deceleration through the coronagraphs' fields of view.

The CME was most probably associated with an M3.3 X-ray flare in
AR9636 between 08:10 and 09:10 UT with peak emission at 08:30.
EIT also observed this flare between 08:25 and 09:36, peaking at
18:36. SEC places the flare at N10E18. Both a dimming and an
EIT wave were observed in association with this event. Bright
post-eruption loops are clearly visible from about 10:12 UT.

Images and movies of this event are available at:

ftp://ares.nrl.navy.mil/pub/lasco/halo/20010928

All the movies clearly show a later event, a wide CME in the
SW which is probably associated with a later M2.2 flare from
AR9632 at S17W24. While this CME alone might not normally
merit a partial halo alert, we note that since the locations,
timings and speed of the CMEs are relatively close it is
likely that a certain amount of interacting and/or merging
could occur, possibly increasing the magnitude and complexity
of the earth-directed component.

Best wishes,
        Gareth Lawrence.

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| 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 G-1,                         +1-301-286-3447       |
| Greenbelt, MD 20771.                   Fax:    +1-301-286-0264       |
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