  The paper analyzes the structure and dynamics of a quiescent prominence that
occurred on October 22, 2013. We aim to determine the physical characteristics
of the observed prominence using MgII k and h, CII (1334 and 1336 A), and SiIV
(1394 A) lines observed by IRIS. We employed the 1D non-LTE modeling of MgII
lines assuming static isothermal-isobaric slabs. We selected a large grid of
models with realistic input parameters and computed synthetic MgII lines. The
method of Scargle periodograms was used to detect possible prominence
oscillations. We analyzed 2160 points of the observed prominence in five
different sections along the slit averaged over ten pixels due to low signal to
noise ratio in the CII and SiIV lines. We computed the integrated intensity for
all studied lines, while the central intensity and reversal ratio was
determined only for both MgII and CII 1334 lines. We plotted several
correlations: time evolution of the integrated intensities and central
intensities, scatter plots between all combinations of line integrated
intensities, and reversal ratio as a function of integrated intensity. We also
compared MgII observations with the models. Results show that more than
two-thirds of MgII profiles and about one-half of CII 1334 profiles are
reversed. Profiles of SiIV are generally unreversed. The MgII and CII lines are
optically thick, while the SiIV line is optically thin. The studied prominence
shows no global oscillations in the MgII and CII lines. Therefore, the observed
time variations are caused by random motions of fine structures with velocities
up to 10 km/s. The observed average ratio of MgII k to MgII h line intensities
can be used to determine the prominence's characteristic temperature. Certain
disagreements between observed and synthetic line intensities of MgII lines
point to the necessity of using more complex 2D multi-thread modeling in the
future.
