The 3s-3p and 3p-3d lines of MG II observed above the solar limb from SKYLAB

Absolute intensities and full widths at half-maximum are given for the Mg II 3s--3p and 3p--3d lines observed above the limb of a quiet Sun region and an active region. The data were recorded by the NRL normal-incidence spectrograph on Skylab. The intensity ratio of the 3p--3d lines to the 3s--3p lines is shown to be very sensitive to electron temperature. An upper limit of 1.4 x 10/sup 4/ K is derived for the Mg II emitting regions at heights approximately-greater-than8'' (6000 km) above the limb in the quiet Sun, for an electron pressure of 2 x 10/sup 15/ cm/sup -3/ K. A similar result is found for the active region. The widths of the optically thin 3p--3d lines increase with height above the limb. Nonthermal velocities from 14 to 25 km s/sup -1/ are derived from the line widths, for both the quiet and the active region. These velocities are the same as previously found by us for Si II and C II intersystem lines observed above the limb of a quiet Sun region.