Date: Thu, 12 May 2005 04:43:21 -0500 (EST) From: Guillermo Stenborg To: stenborg@kreutz.nascom.nasa.gov Subject: Full Halo CME on 2005/05/11, frontsided MIME-Version: 1.0 X-Virus-Scanned: amavisd-new at ucar.edu UCMEO 93001 50512 1040/ 50511 62013 80500 0001/ 360// 123// 30470 50511 61922 81955 35111 10758 1122/ 99999 PLAIN BT LASCO/EIT observed a full halo event on 2005/05/11. The event was first seen clearly in C2 at 20:13 UT above the SW Limb, though in previous frame, i.e. at 19:42 UT, a very small brightening can already be discerned. Diffuse extensions surround completely the C2 occulting disk by 21:05 UT. The event was first seen in C3 at 20:40 UT appearing above the SW Limb. The diffuse (almost) circular extensions are first seen in next frame, at 21:34 UT. By 22:22 UT the C3 occulting disk is well covered. The mean plane-of-sky speed of the LE of the event (based on C3 data) at PA 231 was about 470 km/sec, showing an slight deceleration. GOES reported an M1.1 X-ray flare on NOAA AR 10758 (S11W51) between 19:22 - 19:55 UT with peak emission at 19:38 UT. EIT was in Segment #2 of a Shutterless Campaign, between 17:00 - 19:30 UT, and therefore only subframes (in 195 A) were taken during that time with a cadence of about 1 image/minute. The subframes were centered on AR 10758. Running differences of these images show a strong brightening starting at around 19:21 UT. By 19:24 UT, a ragged structure starts to lift off toward SW. EIT 195 CME watch images resumed at 19:51 UT. An intensity disturbance traveling mainly toward S and SE of the AR is seen by the time. In summary, the event has therefore been determined as a Full Halo event, frontsided, associated with an M-class X-ray flare on NOAA AR 10758. - Mpeg and Quicktime versions of the Shutterless movie are already available on the EIT webpage: http://umbra.nascom.nasa.gov/eit/#SHUTTERLESS - Movies of the event will shortly be made available at: ftp://ares.nrl.navy.mil/pub/lasco/halo/20050511 (I'm still actually abroad and experiencing technical difficulties to make the gif images. They will be ready for sure next week. I do apology for that). NOTE: Please note that another M-class X-ray event occurred on 2005/05/11. That one (an M1.2 X-ray flare) also happened on NOAA AR 10758 (S11W45), between 06:11 - 06:56 UT with peak emission at 06:41 UT. C2 starts to show a big ragged loop front by 07:31 UT, most likely related to the flare. For this event no halo signatures are visible. Best wishes, Guillermo Stenborg +--------------------------------------------------+ Dr. Guillermo A. Stenborg SOHO-LASCO Operations Scientist, CUA, MC 612.5, Bldg 26, Rm 001, F: +1-301-286-0264 NASA Goddard Space Flight Center, Greenbelt, MD 20771. P: +1-301-286-2941 e-mail: stenborg@kreutz.nascom.nasa.gov +--------------------------------------------------+