LASCO Activity Report for
September 2, 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.

2005/09/01 (Thursday)

00:54 UT  S East	Couple of ragged and expanding loop fronts develop in
			the aftermath of the halo CME reported to start at 
			22:30 UT on previous day.

02:54 UT  SS East	Ragged and expanding loop front followed at 05:30 UT 
			by another one.

11:30 UT  W Limb	Diffuse brightening all above the W Limb (brighter on
			SW). By 12:06 UT, a wide loop front spanning initially
			from NW up to the S Pole (clockwise) develops behind 
			the diffuse front. Pre-existent features on S - SE
			are apparently disturbed by the development of this 
			wide loop front, and hence giving to the event in C2 
			the appearance of a Halo CME. The complex event fades
			throughout C3. EIT 195 running difference images show
			faint rising loops off limb on W - WSW (source on the
			backside) between 10:24 - 12:00 UT. GOES reported no
			significant X-ray activity (A-class) by the time.

12:06 UT  WS West	Loop front along streamer with apparently twisted inner 
			structure is followed at 13:31 UT by a ragged loop 
			front. The trailing (twisted) material of both events
			superposes in the LOS and therefore becomes difficult 
			to distinguish between both events. No clear signatures
			of both events can be distinguish in EIT 195 images.
			GOES reported no significant X-ray activity (A-class) 
			by the time.

20:06 UT  WS West	In the trailing material of previous "complex" event, a
			system of faint expanding loops develops.

23:54 UT  ES East	Diffuse loop front quickly overpassed by big event on 
			NE - E at 00:30 UT on next day (Event #1).

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.

	08:30 - 13:31 UT	Temporary Data Gap.

13:31 UT  W Limb	Loop front developing slightly toward WNW.

Time of the last C2 image under analysis: 16:54 UT.