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.
07:31 UT N East Very faint expanding loop front mainly developing toward NE, first seen as a very faint and diffuse front. By 09:06 UT, the angular span of the front in C2 seems to cover from the ESE Limb up up NW Limb (clockwise), though in NW is too faint to define its edge. It is first seen in C3 above the NE Limb at 08:42 UT. The main plane-of-sky speed of the event at PA 35 was ~ 385 km/sec (last frame used: 10:42 UT; LE at ~ 9 solar radii). GOES reported no significant activity by the time prior to the LASCO event. On the other hand, EIT 195 images show a small ejection starting at 06:12 UT, on the southern hemisphere close to the central meridian (far west of AR 10806), just on the border of the southern coronal hole, developing toward SE (see next entry). 07:31 UT S East Diffuse and rather elongated front. 10:06 UT N East Another diffuse front (a little brighter than the one at 07:31 UT on NE). By 11:30 UT, the event seems to span in C2 from ESE well up to the NW limb (clockwise). It is first clearly seen in C3 above the NE Limb at 10:42 UT. This event seem to coalesce with the one at 07:31 UT on NE in the C3 FOV by 12:18 UT (at about 11 solar radii), either because the second event is faster or the first one becomes too faint to be distinguished. The mean plane-of sky speed of the event at PA 40 was ~ 445 km/sec (last frame used: 13:42 UT; LE at ~ 12.5 solar radii). GOES reported no significant activity by the time prior to the LASCO event, except for a B3.2 X-ray flare on NOAA AR 10806 (S17E32) between 09:52 - 10:08 UT with peak emission at 10:02 UT. EIT 195 images show a dimming region just on SE of AR 10806 starting at 10:00 UT, i.e., during the time of the B3.2 X-ray flare. Based on the global appearance on C3 of the events reported to start at 07:30 UT and the present one, the complex event could be classified as a faint and complex Partial (at least) Halo Event. Though the timing of the EIT events reported seem to correlate with the respective LASCO events, the corresponding spatial location on the disk doesn't. Therefore, it is hard to be sure about the location of their source. 11:30 UT W Limb Small brightening just appearing above the W Limb develops as a bright loop front. It is followed (apparently about one hour later) by a fainter and diffuse expanding loop front with faint extensions on E. The C2 occulting disk appears fully covered by 13:31 UT. The "halo" looks rather flat over the poles, and elongated toward W and E. The event is first seen in C3 above the W Limb at 12:42 UT. The C3 occulting disk seems to be fully surrounded by 12:42 UT. The event fades throughout C3. The mean plane-of-sky speed of the outermost edge of the event on W (PA 285) was ~ 860 km/sec. GOES reported a long duration C2.0 X-ray flare on NOAA AR 10803 (N13W13) between 10:26 - 12:51 UT with peak emission at 11:51 UT. EIT 195 images show a brightening on AR 10803 starting at 10:36 UT all along the magnetic inversion line (extending E-W) followed by a dimming region mainly to W and NW of the AR. Post flare loops. In summary, the event has therefore been determined as a faint Full Halo Event, frontsided, associated to a C-class X-ray event on NOAA AR 10803. 17:54 UT WN West Couple of small ragged fronts. 22:30 UT HALO The event appears as a very bright and thick loop front extending all the way from the E limb to the W limb passing over the S Pole with diffuse (though rather bright) extensions ahead (mainly toward S). The thick loop front seems to close the circle around the occulter (all the the way above the N Pole), though not as bright. By 23:06 UT, the event appears brightest on SE. A new expanding loop front follows at 00:54 UT on next day on SE. Another one at 03:06 UT on SSE. The event is first seen in C3 at 23:18 UT, already fully surrounding the occulting disk, the LE of the outermost part of the event on S (diffuse front ahead of the thick loop-like structure) being at 13 solar radii. The mean plane-of sky speed of the LE of several features at various PA is given below: - PA 180: 1870 km/sec (LE of the diffuse front ahead of the loop-like structure, i.e., that of the shock) - PA 180: 1270 km/sec (LE of the loop-like structure) - PA 270: 1225 km/sec (LE of the loop-like structure) - PA 356: 745 km/sec (LE of the loop-like structure) - PA 050: 685 km/sec (LE of the loop-like structure) showing practically no acceleration in all cases. GOES reported no significant X-ray activity by the time of the event. Likewise, EIT 195 running difference images do not show significant activity on the disk by the time prior to the LASCO event. However, they do show signatures of a huge backsided CME all above the S limb starting at 22:24 UT. By 22:36 UT, the CME signature can be seen almost above all around the limb. In summary, the event has therefore been determined as a symmetric and very strong Full Halo Event, backsided.
Time of the last C2 image under analysis: 12:06 UT.