LASCO Activity Report for
January 20, 2005 SOHO Science Daily Meeting

Event times are first frame seen in C2 camera unless otherwise noted.
These are preliminary observations for the daily SOHO science discussions.
Final analysis is reported on the Lasco CME list.
An archive of these reports is available.

Points Of Interest

2005/01/19 (Wednesday)

	LASCO/EIT observed a couple of events on 2005/01/19 that, considered
	together, look like an asymmetric and complex full halo event. 
	However, closer inspection show that apparently, at least two 
	different events occurred: i) a very asymmetric full halo CME, and 
	ii) a relatively slow asymmetric full halo event.

08:29 UT  N West	The event i) was first seen in C2 at 08:29 UT as a 
			very bright loop front above the NW limb surrounded by 
			a tenuous and diffuse excess intensity. By 09:06 UT, 
			the LE on NW already exited the C2 FOV, trailing 
			material coming out toward WNW followed by much gusty 
			outflow. Streamers on NE and SW are pushed away by 
			the event. By that time, an apparently new faint and
09:28 UT  N East	ragged structure [ii)] develops towards NE. Faint
			extensions to E up to the  S Pole surround the C2
			occulting disk by 09:39 UT. Please also note that a
10:54 UT  N West	bright front starts developing toward NW. 
			The event i) is first seen in C3 at 09:16 UT above the 
			NW Limb as a clear loop front surrounded by a faint
			envelope, while event ii) is first seen appearing 
			above the NE Limb by 10:10 UT. By that time, the C3
			occulting disk is completely covered. The mean plane-
			of-sky speed of the different features involved was
			(based on C3 data):
		      * LE of the outermost front of the diffuse envelope
			surrounding the loop front i): ~ 1960 km/sec at PA 321.
		      * LE of the outermost feature of the bright loop i): ~ 
			1855 km/sec at PA 311.
		      * LE of ii) at PA 056: 614 km/sec
			GOES reported the following X-ray events by the time, 
			on NOAA AR 10720:
		      * an M6.7 X-ray flare (N16W53) between 06:58 - 07:55 UT
			with peak emission at 07:31 UT, 
		      * an X1.3 X-ray flare (N15W51) between 08:03 - 08:40 UT
			with peak emission at 08:22 UT, and
		      * an M2.7 X-ray flare (N17W52) between 10:19 - 10:29 UT
			with peak emission at 10:24 UT.
			EIT 195 images show a strong increase in intensity on 
			AR 10720 since around 07:17 UT peaking at 07:29 UT, 
			08:12 UT, and then again at 10:27 UT. After first
			peaking, the brightening is followed by ejection of
			material toward NW until around 09:00 UT. A big wave 
			can be seen mainly to NE, N, NW and SW of the AR. 
			Later, at 10:05 UT, more material can be seen ejected,
			this time mainly toward NE-NNE of the AR. This happen 
			at the same time as an apparently backsided CME on the 
			E Limb. It is difficult to associate temporally any 
			of the signatures seen in EIT with the event ii) 
			observed in C2/C3. Even though, considering the events
			on NOAA AR 10720, the X-ray flares, and the signatures 
			in C2/C3, the event can be be determined as a very
			asymmetric and complex 'full' halo event, frontsided. 

11:16 UT  EN East	Bright spray-like front.

14:02 UT  ES East 	Elongated and aparently twisted structure with a 
			diffuse front.

20:06 UT  WN West	Faint and not-well-defined front followed by another
			one, a little bit brighter, at 21:54 UT. They fade
			throughout C3. Some infalling material on W.

2005/01/20 (Thursday)

00:06 UT  N East	Ragged front along streamer. Barely visible in C3.

03:30 UT  S West	Slow development of a system of loops along the s
			treamer.

04:06 UT  N West	Faint spray-like front.

	LASCO/EIT observed a major proton event most likely associated to
	an X7.9(GOES10)/7.1(GOES12) X-ray flare that started at 06:36 UT and 
	peaked at 07:01 UT. Signatures of a full halo CME can be guessed
	in the highly degraded LASCO data. Here comes the report:

06:54 UT  N west 	Extremely bright loop front above the WNW-NW limb. 
			An intense proton storm starts affecting by that time 
			the LASCO images. The next C2 frame (07:34 UT) shows 
			up 100 % contaminated and therefore practically 
			useless. The same occurs with the following frames 
			(at least up to the time of the last C2 frame at hand,
			i.e., 16:00 UT. The proton event is first seen in C3 
			at 07:54 UT, hiding any potential CME signatures that
			could be present. The next frame allows to guess a 
			ragged loop front all above the SE Limb. By 10:24 UT 
			the C3 occulting disk seems to be completely covered. 
			If, the LE is what I guess it is, the mean plane-of-
			sky speed of that front at PA 141 would be around 
			571 km/sec (based on C3 data). However, given the
			projected development of this guessed halo (apparently
			mainly toward SE), it is difficult to be sure about 
			its association with the X7 X-ray event. Maybe there 
			is a front already farther out on NW, but the 
			degradation of the data prevents telling anything.
			GOES(10) reported an X7.1 X-ray flare on NOAA AR 10720
			(N14W61) between 06:36 - 07:26 UT with peak emission 
			at 07:01 UT. EIT 195 images show between 06:36 - 
			06:48 UT a well-defined loop eruption toward NW above 
			the AR 10720, clearly under way before the X7 flare. 
			At 06:48 UT a strong brightening starts to be seen on 
			the aforementioned AR, peaking in the frame at 
			07:14 UT. Many particle hits by that time. Maximum
			particle counts occur by 07:27 UT. Given the data
			degradation due to the particle hits nothing can be 
			said about potential dimming/wave  associated to the
			event. It is difficult to be sure that the 'halo' 
			guessed in C3 is really a halo or if it is really
			associated with the big event. However, due to the
			location of the source region of the event on the 
			disk, is likely that the associated CME can at least 
			be partly directed toward Earth.