Chromospheric Upflow Events Associated with Transition Region Explosive Events

Transition region explosive events are considered to be a manifestation of small scale magnetic reconnection ubiquitously occurring | even in the quiet Sun. In this paper, we report a close association between transition region explosive events and chromo-spheric uppow events seen in H. From a comparison of the Big Bear Solar Observatory (BBSO) H spectrograph data and the Solar and Heliospheric Observatory (SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER) data, we found a succession of chromospheric uppow events at sites where repeated explosive events occurred. Individual chromospheric events appear as compact dark features which are best visible in H-0.5 A, and have a size of 2-3 arc seconds and a lifetime of 1-2 minutes. They are characterized by an upward motion of 15-30 km s ?1 , a temperature of 10 4 K, a mass density of 1 10 ?13 g, and a non-thermal velocity less than 10 km s ?1. Unlike spicules, which display descending motion following their ascending phase, these uppow events are not followed by noticeable redshifts. \H jets" at 1.0 A studied by Wang et al. (1998) appear to be a special case of this kind of chromospheric uppow event. The physical characteristics of chromospheric uppow events and their close association with transition region explosive events suggest that chromospheric uppow events may be the manifestation of cool plasma material owing into magnetically diiusive regions while explosive events represent hot plasma material owing out of the same regions.