Halo CME MailHalo CME Mail Date: Wed, 21 Jan 2004 13:40 From: Guillermo Stenborg Subject: 'Full' Halo CME on 2004/01/21, frontsided UCMEO 93001 40121 1815/ 40121 60454 81242 0001/ 360// 323// 30852 40121 60336 80536 22525 ///// 2222/ 99999 PLAIN BT LASCO and EIT observed a 'full' halo CME on 2004/01/21. A bright loop front was first seen in C2 at 04:54 UT at the E limb. By 06:30 UT the loop spans ~ 175 deg from PA 45 - 215. By 06:54 UT very faint extensions arounding the rest of the C2 occultor are discernible. The front first appeared in C3 images at 05:18 UT as a bright rim above the E and SE limbs. The mean plane-of-sky speed measured at several PA on C3 data resulted as follows: 365 km/s at PA ~0 708 km/s at PA ~75 852 km/s at PA ~110 619 km/s at PA ~140 The faintness of the front makes it impossible to make reliable measurements on the west. The measurement at PA ~110 is the one taken for the UCMEO code (i.e., the fastest one). The CME was most likely associated with a filament eruption on the visible side of the solar disk. Between 03:36 and 05:36 UT EIT/Fe XII images show the eruption of part of a big filament that extends from roughly the center of the solar disk all along the SE quadrant to the SE limb. At around 04:24 UT post-event loops start to develop (at 07:25 UT the developing of the post-event loops can be well seen in EIT Fe XII data). GOES does not record any significant on-disk events around the time. Neither an EIT wave nor dimming was observed in association with the event. This event has therefore been determined frontsided. Images and movies will shortly be made available at ftp://ares.nrl.navy.mil/pub/lasco/halo/20040121 Best wishes, Guillermo Stenborg ++ Dr. Guillermo A. Stenborg SOHO-LASCO Operations Scientist, CUA, MC 682.3, 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 ++