Comparison of Transient Network Brightenings and Explosive Events in the Solar Transition Region

The relation between transient network brightenings, known as blinkers, and explosive events is examined based on coordinated quiet Sun observations in the transition region line O V λ630 recorded by the Coronal Diagnostic Spectrometer (CDS), in the transition region line Si IV λ1402 recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, and in photospheric magnetograms taken by the Big Bear Solar Observatory videomagnetograph. From these observations, we find that (1) explosive events, which are traditionally defined as features with very broad UV line profiles, tend to keep away from the centers of network brightenings and are mostly located at the edges of such brightenings, (2) CDS blinkers consist of many small-scale, short-lived SUMER "unit brightening events" with a size of a few arcseconds and a lifetime of a few minutes, and most importantly (3) each SUMER unit brightening event is characterized by a UV line profile that is not as broad as those of explosive events, but still has significantly enhanced wings. Our results imply that, like explosive events, individual unit brightening events involve high velocities, and, hence, blinkers may have the same physical origin as explosive events. It is likely that transient network brightenings and explosive events are both due to magnetic reconnection—but with different magnetic geometries.