  An inverted U burst with equally developed ascending and descending branches
observed by Giant Ukrainian Radio Telescope (GURT) on 18 April 2017 in meter
wavelengths band is discussed. This U burst was attributed to the high coronal
loop above the limb active region NOAA 12651. Under the assumption that,
associated with the burst, the coronal loop confines isothermal plasma
stratified according to a Boltzmann density relation, the geometrical and
physical parameters of the loop were estimated. According to our model coronal
loops may contain plasma which is up to 20 times denser than the surrounding
coronal plasma. In general the proposed model gives the relation between the
plasma temperature and the height of the loop in such a way that under the
given parameters of the associated U burst, higher loops contain cooler plasma
and vice versa. An alternative method of coronal loop height determination was
suggested. Assuming that the observed U burst and the preceding type III burst
were generated by the same exciter we define the height of the loop from the
delay of the former with respect to the latter at certain frequency. We show
that defining of coronal loops heights by another independent method, e.g.
interferometric or tied-array imaging may solve the uncertainty of the
inside-the-loop plasma temperature determination.
