EXPLOSIVE EVENTS ASSOCIATED WITH A SURGE

The solar atmosphere contains a wide variety of small-scale transient features. Here, we explore the interrelation between some of them such as surges, explosive events, and blinkers via simultaneous spectral and imaging data taken with the TRACE imager, the SUMER and Coronal Diagnostics Spectrometer (CDS) on board SOHO, and Swedish Vacuum Solar Telescope La Palma. The features were observed in spectral lines with formation temperatures from 10,000 K to 1 MK and with the TRACE Fe IX/X 171 angstrom filter. The H alpha filtergrams were taken in the wings of the H alpha 6365 angstrom line at +/- 700 m angstrom and +/- 350 m angstrom. The alignment of all data in both time and solar XY shows that SUMER line profiles, which are attributed to explosive events, are due to a surge phenomenon. The surge's up- and downflows, which often appear simultaneously, correspond to the blue- and redshifted emission of the transition region N V 1238.82 angstrom and O V 629.77 angstrom lines as well as radiance increases of the C I, S I, and S II and Si II chromospheric lines. Some parts of the surge are also visible in the TRACE 171 angstrom images which could suggest heating to coronal temperatures. The surge is triggered, most probably, by one or more Elerman bombs which are best visible in H alpha +/- 350 angstrom but were also registered by TRACE Fe IX/X 171 angstrom and correspond to a strong radiance increase in the CDS Mg IX 368.07 angstrom line. With the present study, we demonstrate that the division of small-scale transient events into a number of different subgroups, for instance explosive events, blinkers, spicules, surges or just brightenings, is ambiguous, implying that the definition of a feature based only on either spectroscopic or imaging characteristics as well as insufficient spectral and spatial resolution can be incomplete.