LASCO Activity Report for
May 17, 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

Medoc Campaign started on May 16. Since then SOHO is in Telemetry submode 5.
EIT 195 CME watch at half resolution (512x512).

2005/05/16 (Monday)

03:26 UT  S Pole	Another extremely faint (barely discernible) and 
			diffuse loop front. Brightening on SE that could be 
			part of. Nothing can be discerned in C3. GOES reported 
			an M1.4 X-ray flare from NOAA AR 10763 (S16E18) 
			between 02:33 - 02:50 UT with peak emission at 02:43 
			UT. EIT 195 shows a loop brightening at the center of 
			the AR by 02:48 UT. Loops to S of the AR disappear.

06:06 UT  E Limb	Extremely faint slowly-expanding system of loops 
			spanning all above the north eastern limb, up to the 
			N Pole. Also too faint in C3, fading close to its 
			inner edge.

10:50 UT  E Limb	Faint and diffuse fan-like front. It fades throughout
			C2.

13:50 UT  N West	Bright front above the NW limb. By 14:26 UT, a wide 
			and diffuse loop front starts to be visible on NNW,
			partly superposed in the LOS with the former bright
			front. The whole event (hereafter Event #1) expands 
			as it develops. Note that by 14:50 UT, a bright front
			starts to be seen on WSW (hereafter Event#2). The
			development of Event #2 seems to be affected by the
			expansion of Event #1. Infalling material can be seen
			afterward on WSW. The Event #1 (in fact, the event 
			which could be potentially geoeffective) was first 
			seen in C3 at 15:18 UT above the NW Limb. The diffuse
			front on NNW mentioned at the beginning makes its
			appearance at 15:42 UT on NNW. The mean plane-of-sky
			speed of the LE of Event #1 at PA 311 was ~ 390 km/sec
			(based on C3 data). The event spans in C3, at 21:18 UT,
	 		~ 120 deg (form PA 280 - 040), though it is difficult 
			to give an accurate value due to its faintness. GOES
			reported a C1.2 X-ray flare from NOAA AR 10759 (N15W27)
			between 12:46 - 13:12 UT with peak emission at 13:01 UT.
			EIT 195 images show the ejection of material toward NE 
			of the AR by 12:36 UT. An intensity disturbance 
			traveling away from the AR toward NE, N, and NW can be
			seen afterward (all signatures most likely related to
			Event #1). By 13:48 UT, the open up of a system of 
			loops on WSW (barely backsided) starts to develop (EIT
			counterpart of Event #2). In summary, the event (Event
			#1) has therefore been determined as a partial halo 
			CME, frontsided, associated with a C-class X-ray flare
			on NOAA AR 10759.

14:50 UT  WS West	Initially bright ragged front. Development seems to 
			be affected by the expansion of event at 13:50 UT.
			Infalling material (see Event at 13:50 UT).

20:50 UT  NN West	Faint expanding loop front. It fades throughout C3.
		

2005/05/17 (Tuesday)

03:06 UT  WS West	Initially bright ragged front. The event fades close to 
			the inner edge of C3. EIT 195 images show ejection of
			material on the WSW Limb from barely behind the disk
			between 02:24 - 03:36 UT.

03:50 UT  HALO  	Extremely faint and diffuse brightening all around the
			occulting disk (though not very clear at this time).
			Please note that since 03:06 UT an (initially) bright
			ragged front was seen above the WSW Limb, fading out 
			then close to the inner edge of C3. This particular
			feature corresponds to ejection of material seen by 
			EIT 195 on the WSW Limb from barely behind the disk
			between 02:24 - 03:36 UT and should not be confused 
			with the main event. Coming back to the halo event... 
			the event in itself is so faint that is barely
			discernible in C3, where one can say that it is first
			discerned at around 08:18 UT. A very rough estimation 
			of the mean plane-of-sky speed of the LE of the event
			based on C2 data (where at least it is possible to
			measure something) is ~ 300 km/sec (at PA 211). GOES
			reported an M1.8 X-ray flare from NOAA AR 10763 
			(S15W00) between 02:31 - 02:52 UT with peak emission 
			at 02:39 UT. EIT 195 images show a strong brightening 
			at 02:36 UT on the aforementioned AR. A clear wave is
			seen then developing toward N, W, S, and SE of the AR
			between 02:48 - 03:36 UT. Also a dimming region to N 
			and S of the AR. The AR continued flaring afterward 
			(at the time of writing: a C8.4 peaking at 04:03 UT,
			and a C2.8 peaking at 05:53 UT). In summary, the event
			has therefore been determined as a very faint Full
			Halo CME, frontsided, associated with an M-class X-ray
			flare on NOAA AR 10763.

07:27 UT  ES East	Small loop front along streamer. It fades throughout 
			C2.