LASCO Activity Report for
September 6, 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

KEYHOLE OPERATIONS:
-------------------
SOHO keyhole #10 telemetry period: Aug 31-Sep 28, 2005.

EIT will go to CCD bakeout between Sep 2 23:00 UT - Sept 23 10:00 UT 
with its mini-cal pre and post sets as folows:
2005/09/02 19:00:00 - 2005/09/03 01:00:00
2005/09/23 20:00:00 - 2005/09/24 00:20:00

During the Telemetry Keyhole LASCO will be in improved synoptic cadence 
of C2 at 12 mins cadence and C3 at 30 mins cadence, including daily 
orange/blue filter fielding images.

The SOHO roll back to 0 deg is scheduled for Thursday Sept 8, 2005.
LASCO will safe for the S/C roll (also Station Keeping and Momentum 
Management) on Wed Sept 7 at 11:00 UT and re-open Saturday Sept 10 
at 12:00 UT.

2005/09/02 (Friday)

00:30 UT  N East	Big and bright feature with its LE close to the end of
(Complex Halo Event)	the C2 FOV all above the NE limb (Event #2). A brighter
			front can be seen also by 00:30 UT on W (Event #3), in 
			the inner part of Event #2 (as projected in the plane 
			of sky). Upon inspection of the C2 movie, one can see
			that Event #1 is quickly surpassed by Event #2 and
			therefore no longer discernible. By 00:54 UT, Event #2
			seems to fully surround the C2 occulting disk (though
			very faint on S). Event #3 develops toward E, followed 
			at 01:31 UT by another ragged front on SE (Event #4,
			though it is difficult to say whether it is really a
			different feature). Event #2 is first seen in C3 at 
			00:42 UT all above the NE Limb. Signatures of Event #3
			are first seen on E at 01:42 UT, followed at 02:18 UT 
			on SE by Event #4. Considered as a whole, the complex
			event covers the C3 occulting disk by 01:42 UT (on W
			still barely above the limb), becoming difficult to
			disentangle the different components. The mean plane-of
			sky speed of the LE of different features is given 
			below:
			- Event #2: PA  63 --> ~ 1450 km/sec
			- Event #3: PA 100 --> ~ 670 km/sec 
			- Event #4: PA 150 --> ~ 660 km/sec
			GOES reported a B4.5 X-ray flare from NOAA AR 10806
			(S17E12) on 2005/09/01 between 22:53 - 23:56 UT with 
			peak emission at 23:21 UT. EIT 195 images show the
			development of a dimming region starting between
			22:36 - 23:12 UT (on 09/01) to N, E, and S of AR 10806.
			Running difference 195 images show signatures of a CME
			developing by the time mainly toward SE and E (this
			signatures are most likely related to Events #3 and #4).
			By 00:24 UT, signature of a huge and apparently 
			backsided CME can be seen all above the E Limb (most
			likely related to Event #2). Though the timing seem to
			match that of the event from AR 10806, the event off 
			limb is most probably from the back side of the Sun.
			In summary, the event as a whole can be determined as 
			an asymmetric full halo CME. Several components
			contribute to the overall shape of the complex event, 
			at least one of them frontsided, which was associated
			with a B-class X-ray flare on NOAA AR 10806. However, 
			the bigger contribution seems to have its origins on 
			the backside.

03:30 UT  W Limb	Ragged loop front.

06:30 UT  E Limb	Faint and asymmetric loop front in the aftermath of the
			halo CME.

11:30 UT  W Limb	Loop front developing along streamer. Twisted trailing 
			material.

12:30 UT  NN East	Diffuse front that quickly fades.

16:06 UT  WS West	Ragged blob-like front.	

17:30 UT  S East	Diffuse loop-like front that fades throughout C3.

20:54 UT  S East	Diffuse and expanding loop-like front. It also fades
			throughout C3.

2005/09/03 (Saturday)

03:12 UT  S East	Bright loop front. Very tenuous and diffuse extensions
			can be then seen around the main loop-like structure.
			Faint extensions fully cover the C2 occulting disk by
			04:12 UT. The event is first seen in C3 at 03:42 UT as 
			a bright loop front above the SE limb with faint and
			diffuse extensions to S. Following frames show the 
			loop-like structure surrounded by a diffuse and faint
			envelope (shock?). This diffuse envelope fully surrounds
			the C3 occulting disk by 05:18 UT (LE at ~ 20 solar 
			radii on SE, while barely above the limb on NW). The 
			mean plane-of-sky speed of the LE of the outermost part 
			of the diffuse front ahead of the main loop-like
			structure (shock) at PA 150 was ~ 1680 km/sec, while 
			that of the LE of the bright loop-like structure at 
			PA 145 was ~ 1390 km/sec. GOES reported no significant
			X-ray activity (A-class) during the day, save for an
			impulsive B6.1 X-ray flare from NOAA AR 10805 (S11W09)
 			between 04:05 - 04:13 UT with peak emission at 04:10 UT.
			No EIT images are available (last EIT 195 image
			available: 19:13 UT, afterward EIT CCD bakeout -->
			2005/09/02 23:00 UT - 2005/09/23 10:00 UT). The event's
			shape and development seem to suggest that the old 
			NOAA AR 10798, which is due to return on 09/07, would
			have likely been associated with the observed Halo.
			In summary, the event has therefore been determined as 
			an asymmetric Full Halo Event, probably backsided
			(according to the lack of X-ray activity reported by 
			GOES and the spatial matching of its likely origin
			with that of old AR 10798). 

20:48 UT  E Limb	Small and elongated front.

2005/09/04 (Sunday)

09:48 UT  EN East	Faint front taht quickly fades.

12:24 UT  N East	Gradual development of a ragged front along streamer 
			(difficult to give an exact time of first appearance)
			followed at 13:24 UT by a faint system of loops that
			quickly vanishes.  

14:48 UT  N East	In the trailing material of previous event, a bright
			loop, top of an elongated twsited structure follows.

14:48 UT  N West	Bright loop front with core and twisted trailing
			material. Very faint extensions to N and S. Gusty 
			outflow afterward in the form of small ragged fronts
			along a current sheet. GOES reported a long duration 
			C2.0 X-ray flare from NOAA AR 10803 (N13W72) between
			14:08 - 16:21 UT with peak emission at 15:06 UT.

22:36 UT  E Limb	Elongated and initially bright loop front. It fades
			throughout C3. Some infalling material.

2005/09/05 (Monday)

09:48 UT  S East	Bright loop front. Diffuse extensions can be then 
			seen around the bright loop-like structure. By 10:12 UT,
			(LE just past the end of the C2 FOV), the total angular
			span of the event -diffuse extensions included- is 
			about 240 deg (from PA 25 - 265). By 10:36 UT, the C2
			occulting disk appears fully covered, though the faint
			feature surrounding the occulting disk seems to be other
			[1] than the faint and diffuse extensions. The event is
			first seen in C3 at 10:18 UT above the SE Limb. 
			Following frames show the loop-like structure surrounded
	 		by a diffuse and faint envelope (shock?). "Apparently",
			the diffuse envelope do not reach to fully cover the
			occulting disk (though it is hard to say due to the
			superposition with [1]); by 11:42 UT, it spans from PA 
			10 - 300 (~ 290 deg). By 11:42 UT, the circular feature
			reported to surround the C2 occulting disk at 10:36 UT
			(i.e., [1]), seems to cover the C3 occulting disk,
			apparently developing (as projected in the plane-of 
			sky) slightly toward NW. The mean plane-of-sky speed 
			of the LE of the outermost part of the diffuse front
			ahead of the main loop-like structure (shock) at PA 
			148 was ~ 2220 km/sec, while that of the LE of the 
			bright loop-like structure at PA 143 was ~ 1895 km/sec,
			showing in both cases practically no acceleration.
			GOES reported a long duration C2.7 X-ray flare on 
			S07E81 between 08:53 - 12:20 UT with peak emission at
			10:41 UT. No EIT images are available (last EIT 195 
			image available: 2005/09/02 @ 19:13 UT, afterward EIT 
			CCD bakeout ** 2005/09/02 23:00 UT - 2005/09/23 
			10:00 UT **). The event's shape and development seem
			to suggest that the old NOAA AR 10798, which is barely
			behind the SE Limb, was likely associated with the
			observed Halo. In summary, the event has therefore been
			determined as a very fast limb event, most likely
			associated to the old AR 10798, just behind the SE limb.
			Its associated shock made it appear in the LASCO FOV as 
			a very asymmetric Full Halo Event. Given the lack of
 			EIT images, it is not clear at this stage the relation 
			of the rather circular structure reported to surround 
			the C2 occulting disk at 10:36 UT with the limb event.

2005/09/06 (Tuesday)

	03:12 - 09:36 UT	Temporary DSN Data Gap.

09:48 UT  S East	Event well under development after data gap.

Time of the last C2 image under analysis: 11:36 UT.