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.
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.
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.
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.
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.
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.