Date: Tue, 13 Jul 2004 12:33
From: Guillermo Stenborg
Subject: Faint 'full' halo CME on 2004/07/13, frontsided
UCMEO 93001 40713 1630/
40713 60054 81118 0001/ 360// 713// 20406
40713 60009 80023 44514 10646 1112/
99999
PLAIN
BT
LASCO & EIT observed a couple of at least partly Earth-directed
events on 2004/07/13, which showed up in the LASCO coronagraphs
FOV as rather faint 'full' Halo CMEs. This report refers to the
first of them. In short the second event will be reported.
The first event was first observed in C2 at 00:54 UT above the
NW Limb as a bright loop front with faint extensions to S. By
01:31 UT the faint extensions seem to cover the C2 occultor,
though due to their faintness, they are difficult to follow
after a couple of frames. The halo extensions are barely visible
in C3. During the evolution of the event in C2, at least two
parts can be distinguished: i) a bright ragged loop front, and
ii) a fainter and diffuse front to N and also ahead of the other
front. At 01:31 UT, bright material appears to N, below the
faint front previously mentioned, developing toward NNW. An
apparently twisted (and rather circular) structure develops
below the bright material. The circular structure seems to
surpass later, while still in C2, the bright material. By
05:30 UT more bright material appears above the NNW limb. By
09:08 UT, what I refer as the second event appears in C2 just
above the WNW Limb, developing much faster than the bright
material (see next report).
The mean plane-of-sky speed for the event as measured at the LE
of the ragged front [i)], at PA ~289, was ~406 km/sec (based on
C3 data).
The event was 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 0646. That AR produced
several C- and M-class X-ray flares during the day. For
completness, the list of the X-ray events reported at the time
of writing is given below:
Start Peak End Flare Location
00:09 00:17 00:23 M6.7 N14W45
05:21 05:33 05:40 C6.7 N14W49
06:26 06:33 06:48 C4.1 N14W51
07:10 07:14 07:19 C2.6 N14W50
08:40 08:48 08:55 M5.4 N14W51
Most likely, the X-ray event reported to start at 00:09 UT is
the one associated to the start of the C2 event. On the other
hand, EIT Fe XII images show a brightening above the AR mentioned
starting at 00:12 UT. A CME signature is seen traveling toward
NW afterward, originated on or nearby the AR. Likewise, an
intensity disturbance is seen traveling across the disk (wave).
Starting at 00:24, material (seen in absorption in EIT/Fe XII)
is ejected from nearby the AR apparently toward N and NE.
The complex event has therefore been determined as, at least,
partly Earth-directed.
Images and movies will shortly be made available at (for both,
the event reported in this message and what I referred as
the second event):
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040713
Best wishes,
Guillermo Stenborg
++
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
++