SOLAR FINE-SCALE STRUCTURES IN THE CORONA, TRANSITION REGION, AND LOWER ATMOSPHERE

The American Science and Engineering Soft X-ray Imaging Payload and th e Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) were launched from White Sands on 1987 December 11 in coordina ted sounding rocket flights. The goal was to investigate the correspon dence of fine-scale structures from different temperature regimes in t he solar atmosphere, and particularly the relationship between X-ray b right points (XBPs) and transition region explosive events. We present results of the analysis of co-aligned X-ray images, maps of sites of transition region explosive events observed in C IV (10(5) K), HRTS 16 00 angstrom spectroheliograms of the T(min) region, and ground-based m agnetogram and He I 10830 angstrom images. We examined the relationshi p of He I 10830 angstrom dark features and evolving magnetic features which correspond to XBPs. We note a frequent double ribbon pattern of the He i dark feature counterparts to XBPs. We discuss an analysis of the relationship of XBPs to evolving magnetic features by Webb et al., which shows that converging magnetic features of opposite polarity ar e the most significant magnetic field counterparts to XBPs. The magnet ic bipolar features associated with XBPs appear as prominent network e lements in chromospheric and transition region images. The features in C IV observations corresponding to XBP sites are in general bright, l arger scale (approximately 10 arcsec) regions of complex velocity fiel ds of order 40 km s-1, which is typical of brighter C IV network eleme nts. These C IV features do not reach the approximately 100 km s-1 vel ocities seen in the C IV explosive events. Also, there are many simila r C IV bright network features without a corresponding XBP in the X-ra y image. The transition region explosive events do not correspond dire ctly to XBPs. The explosive events appear to be concentrated in the qu iet Sun at the edges of strong network, or within weaker field strengt h network regions. We find a greater number of C IV events than expect ed from the results of a previous Spacelab 2 HRTS disk survey. We attr ibute this at least partly to better spatial resolution with the newer HRTS data. The full-disk X-ray image shows a pattern of dark lanes in quiet Sun areas. The number density of C IV events is twice as large inside as outside a dark lane (4.6 x 10(-3) vs. 2.3 x 10(-3) explosive events per arcsec2). The dark lane corresponds to an old decaying mag netic neutral line. We suggest that this provides an increased opportu nity for small-scale convergence and reconnection of opposite polarity magnetic field features, in analogy with the results of Webb et al. f or XBPs but at a reduced scale of reconnection.