Sequential Chromospheric Brightenings beneath a Transequatorial Halo Coronal Mass Ejection

Analyses of multiwavelength data sets for a solar eruption at 621:30 UT on 2002 December 19 show evidence for the disappearance of a large-scale, transequatorial coronal loop (TL). In addition, coronal manifestations of the eruption (based on SOHO EIT and LASCO images) include large-scale coronal dimming, flares in each associated active region in the northern and southern hemispheres, and a halo CME. We present detailed observations of the chromospheric aspects of this event based on Ha images obtained with the ISOON telescope. The ISOON images reveal distant flare precursor brightenings, sympathetic flares, and, of most interest herein, four nearly cospatial propagating chromospheric brightenings. The speeds of the propagating disturbances causing these brightenings are 600-800 km s super(-1). The inferred propagating disturbances have some of the characteristics of Ha and EIT flare waves (e.g., speed, apparent emanation from the flare site, subsequent filament activation). However, they differ from typical Ha chromospheric flare waves (also known as Moreton waves) because of their absence in off-band Ha images, small angular arc of propagation (