Date: Tue, 20 Jul 2004 15:39
From: Guillermo Stenborg
Subject: 'Partial' Halo CME on 2004/07/20, frontsided
UCMEO 93001 40720 1945/
40720 61331 91742 2801/ 084// 123// 30740
40720 61222 81245 13310 10652 1112/
99999
PLAIN
BT
LASCO/EIT observed a complex event on 2004/07/20, composed
of apparently two partial 'halo' CMEs with almost simultaneous
development. One of the events (#1) - and the most important
one - was first seen in C2 at 13:31 UT as a bright loop front
rising above the N Pole. By 15:06 UT the front spans in C2
~ 164 deg, from PA ~ 280 - 084. Please note also the very
faint extensions (hereafter Event #2) developing mainly toward
S and SE. The Event #1 is first seen in the C3 FOV at 14:18 UT,
while a much fainter front (Event #2) is also seen, developing
toward S and SE (already farther out), though quickly fading.
The mean plane-of-sky speed for Event #1, as measured on C3
data at its leading edge (LE), was:
at PA ~358: ~550 km/sec
at PA ~330: ~740 km/sec
Both events were associated with complex solar activity reported
by GOES on the visible side of the solar disk, more precisely,
related to activity above the NOAA AR 0652. That AR produced
several C-class flares during the last 24 hours and one M-class
flare. In particular, GOES recorded an M8.6 X-ray flare (N10E33)
between 12:22 - 12:45 UT with peak emission at 12:32 UT, which
was associated with Event #1. EIT Fe XII images show a strong
brightening on the aforementioned AR starting at 12:24 UT and
reaching its peak at 12:36 UT. Afterward, an intensity disturbance
(wave) is seen traveling across the disk mainly toward NW.
The Event #1 has therefore been determined as a 'partial' halo
CME, frontsided.
Despite the faintness of Event #2, it is worth to mention that,
before the brightening recorded by EIT at 12:24 UT, material
is seen to be ejected from the AR 0652 mainly toward SW (more
precisely, starting at ~ 11:12 UT). The time coincides with a
C6.0 X-ray flare recorded by GOES from NOAA AR 0652 (N03E34)
between 11:01 - 11:37 UT with peak emission at 11:26 UT.
Therefore, the faint extensions seen in C2 (and hence referred
to as Event #2) could probably be associated with these events.
Images and movies of the events will shortly be made available
at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040720
Best wishes,
Guillermo Stenborg
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Dr. Guillermo A. Stenborg
SOHO-LASCO Operations Scientist,
CUA, MC 682.3, Bldg 26, Rm 001, F: +1-301-286-0264
NASA Goddard Space Flight Center,
Greenbelt, MD 20771. P: +1-301-286-2941
e-mail: stenborg@kreutz.nascom.nasa.gov
++