Explosive events associated with a surge

Abstract

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 1MK and with the TRACE FeIX/X 171 filter. The Hα filtergrams were taken in the wings of the Hα 6365 line at 700 m and 350 m. 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 NV 1238.82 and OV 629.77 lines as well as radiance increases of the CI, SI, and SII and SiII chromospheric lines. Some parts of the surge are also visible in the TRACE 171 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 Hα 350 but were also registered by TRACE FeIX/X 171 and correspond to a strong radiance increase in the CDS MgIX 368.07 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. © 2009 The American Astronomical Society.