Date: Mon, 7 Jun 2004 13:13
From: Guillermo Stenborg
Subject: 'Full' halo CME on 2004/06/07, probably frontsided
UCMEO 93001 40607 1730/
40607 60127 81042 0001/ 360// 713// 20596
40606 62226 82314 30007 10624 1222/
99999
PLAIN
BT
LASCO observed a faint asymmetric 'full' halo CME on 2004/06/07.
Several events occurred. The likely signature corresponding to
the 'halo' event was first observed (though still barely
discerned) in C2 at 01:27 UT as a very diffuse front above the
W limb. By 01:50 UT, it is clearly identified as a very diffuse
loop front (1). By this time, a bright loop front (2) starts
developing above the SW limb. Feature (2) develops in C2
exhibiting an apparently twisted inner structure. By 03:50 UT,
extremely faint extensions seem to surround completely the C2
occultor. The diffuse front (1) is first seen in C3 above the
WSW limb at 01:42 UT, while the loop front (2) is first seen in
the next frame, i.e., at 02:18 UT. The front (2) seems to be
confined almost completely within PA 155-295. Meanwhile,
faint extensions, likely belonging to feature (1), completely
surround the C3 occultor by 07:42 UT.
For reference, the mean plane-of-sky speeds at several PA for
the different features involved, is given below (based only on
C3 data):
Feature (1):
PA 238: 596 km/s
PA 266: 487 km/s
PA 297: 388 km/s
PA 348: 380 km/s
Feature (2):
PA 234: 426 km/s
PA 265: 394 km/s
GOES reported the following X_ray events which could likely be
associated with the C2/C3 events mentioned above:
(a) a B3.4 X-ray event at S07W00 (associated to NOAA AR 10624)
between 22:26 - 23:14 UT with peak emission at 22:53 UT (on
2004/06/06).
(b) a C2.7 X-ray event at S17W42 (associated to NOAA AR 10621)
between 00:01 - 01:15 UT with peak emission at 00:44 UT (on
2004/06/07). This event is indeed clearly associated with the
C2/C3 event (2).
A third event was also reported by GOES, but occurred too late:
a B5.2 X-ray event at S11W47 (associated also to NOAA AR 10621)
between 02:34 - 03:14 UT with peak emission at 02:54 UT (on
2004/06/07).
On the other hand, EIT Fe XII running difference images show:
(a') a brightening above NOAA AR 10624 in the frames at 22:36
and 23:12 UT [signature of (a)],
(b') a signature of a CME starting at around 00:12 UT above
NOAA AR 10621, traveling toward SW [EIT counterpart of (2)].
In summary, if (a) and (a') are really associated to the faint
diffuse halo front (2) seen in C2 and C3 images, the event is
to be catalogued as a 'full' halo CME, frontsided.
Should that not be the case, there still seems to be enough
evidence to say that there was at least a partly Earth directed
event.
Movies and images of the complex event will shortly be available
at:
ftp://ares.nrl.navy.mil/pub/lasco/halo/20040607
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
++