By using HXIS data, the authors studied the further development of the coronal arch extending toward the southeast above active region No. 17255 in Nov. 1980. The arch, studied originally by Svestka ...(1984) disappeared on Nov. 10 (after pronounced revival), but since Nov. 9, HXIS revealed another archlike structure toward the southwest. The development of this new structure was studied, which appeared to be most likely an arch interconnecting AR 17255 with AR 17251, located nearly 30 degrees to the west. This interconnection revived many times during the following days, with intensity varying with the activity in both active regions. The physical characteristics in this coronal structure were estimated and compared with observations of interconnecting loops made at lower energies by Skylab in 1973. The temperature (maximum values 7.5-14 x 10 super(6) K) and the density (1.1-5.0 x 10 super(9) cm super(-) super(3) ) are found to be higher than in the Skylab loops (a result that could be expected because the HXIS energy range was harder than that of Skylab) and similar to the values deduced for the earlier arch system extending to the southeast. However, much shorter decay times of the brightness variations indicate the presence of conduction in contrast to the southeast arch in which conduction was clearly inhibited. This supports the assumption that the southeast and southwest coronal structures were two different phenomena.
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