LASCO Activity Report for
November 21, 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

2005/11/18 (Friday)

00:30 UT  E Limb	Jet-like front.

14:54 UT  ES East	Faint and diffuse loop-like front that fades close to 
			the inner edge of C3.

19:31 UT  W Limb	Ragged loop front. It fades close to the inner edge
			of C3.

2005/11/19 (Saturday)

	  SS West	Slow development of a system of faint loops since late
			on previous day. Difficult to give an exact time of
			first appearance.

05:54 UT  SS West	Complex Partial Halo Event. Signatures of the complex
			event started to be seen in C2 at 05:54 UT barely above
 			SSW limb (hereafter Feature #1), developing behind a
			rather faint system of faint loops that started to be
			discerned late on previous day. Feature #1 develops as 
			an asymmetric and expanding loop front. It is followed 
			by a system of wide and expanding (faint) loops 
			(Feature #2) developing above the S Pole (it starts to 
			be discerned at around 08:30 UT). By 14:54 UT, an
			apparently distinct (expanding) loop front (Feature #3)
			follows on the S Pole. A relatively bright and narrow
			loop front, first seen at 15:06 UT, develops on the ESE
			superposed in the LOS with the corresponding leg of
			Feature #3. By the time, and still a little bit to N 
			(on E limb) an elongated front developing apparently 
			faster can also be discerned. The complex event is 
			first seen in C3 around 12:18 UT above the WSW limb
			(Feature #1) developing as a ragged loop front, not 
			wide at all. By 16:42 UT, Feature #3 starts to be
			discerned above the S Pole. As seen in C3, it is 
			Feature #3 the one that clearly develops as a Partial 
			Halo Event. Feature #2 is to faint to be properly
			distinguished. Feature #3 spans in C3 at 21:18 UT 
			about 170 deg (from PA 95 - 265). The mean plane-of-sky
			speed of Feature #3 at PA 185 was ~ 325 km/sec. For
			completeness, the mean plane-of-sky speed of Feature #1
			at PA 245 was 225 km/sec. Both cases show practically 
			no acceleration. GOES recorded by the time just a 
			couple of B-class X-ray flares from NOAA AR 10822: i) a
			B6.0 peaking at 04:16 UT at S07W02, and ii) a B8.2
			peaking at 09:42 UT at S07W05. EIT 195 images do not 
			show any significant activity on the disk, other than
			small brightenings on AR 10822 associated to the B-class
			X-ray flares. In summary, although several components
			were described, it is Feature #3 the one that apparently
			shows up with all the characteristics of a Partial Halo
			Event. And based on EIT, it looks like Feature #3 was
			originated on the backside of the Sun.

14:54 UT  S Pole	Expanding loop front (see Feature #3 in previous event).

15:06 UT  ES East	Loop front superposed in the LOS with the leg of 
			previous event on the eastern hemisphere. At the same
			time, an elongated and ragged front develops a little 
			to N (on the E limb).

18:31 UT  WS West	Ragged loop front.

2005/11/20 (Sunday)

01:54 UT  EN East	Elongated and narrow fan-like front.

09:30 UT  E Limb	Elongated front "pushed" toward the equator during
			its early development.

17:54 UT  SS West	Faint and ragged wide front. Barely visible in C3.

17:54 UT  ES East	Slow development of a system of faint loops. Difficult
			to give an exact time of first appearance.

21:30 UT  S Pole	Complex Partial Halo Event. Signatures of the event
			started to be seen in C2 at 21:30 UT barely above the 
			S Pole (Feature #1). By 21:54 UT, an apparently new 
			loop starts to be seen above the SSW limb (Feature #2).
			The latter develops mainly toward SW followed by a 
			system of expanding loops, moving apparently faster
 			than Feature #1, and hence disturbing its development
			(Feature #1 appears to be pushed from behind). Note 
			that since earlier, i.e. starting at around 17:30 UT, 
			the slow development of system of faint loops can be
			discerned on ESE. By the end of the day, it superposes 
			in the LOS with the development of Feature #1, showing 
			up later developing as an expanding loop front. It is
			worth to mention that Feature #1 seems to be also
			disturbed by this other event. The complex event spans 
			in the C2 FOV at 00:54 UT (on 11/21) about 205 deg 
			(from PA 60 - 265). The complex event is first seen in 
			C3 on 11/21 at 00:18 UT above the SSW limb. During its
			development in C3, it becomes difficult to disentangle
			features #1 and #2. The mean plane-of-sky speed of the
			outermost front of the complex event at PA 204 was 
			390 km/sec, showing practically no acceleration. GOES
			recorded a couple of C-class X-ray events on 11/20 from
			NOAA AR 10822. They peaked at 07:36 UT (S09W17), and
			15:20 UT (S08W22). Hence, their time frame does not 
			match that of the LASCO events. On the other hand, a
			couple of B-class X-ray flares from AR 10822 occurred
			later in the day, i.e. a B2.8 peaking at 21:55 UT
			(S07W26), and a B7.5 peaking at 23:55 UT (S06W29). EIT
			195 images do not show significant activity by the 
			time of the LASCO event, save the small brightenings 
			on AR 10822 associated to the B-class X-ray flares. In
		 	summary, the complex event has therefore been 
			determined as at least a Partial Halo Event, most
			probably backsided, based on the lack of a likely EIT
			counterpart of the LASCO events on the solar disc.

2005/11/21 (Monday)

Complex Partial Halo aftermath.

Last C2 image available by the time of writing: 08:30 UT.