  Properties of type III and type IIIb bursts in the frequency band of 8-80 MHz
observed by the radio telescopes Ukrainian Radio Interferometer of NASU-2
(URAN-2) (Poltava) and Giant Ukrainian Radio Telescope (GURT) (Kharkiv) during
the Parker Solar Probe (PSP) perihelion in April 2019 are discussed. These
correspond of those that were observed by PSP at frequencies <19 MHz. We
analyze dependences of drift rates and durations on frequency for these bursts.
We show that drift rate dependences on frequency agree well with those derived
from the Newkirk corona if source velocities are between 0.17 and 0.2 c for
both type IIIb bursts and type III bursts under the assumption that the first
ones are fundamentals and the second ones are their harmonics. However, all
observational dependences are flatter in comparison with the dependences for a
Newkirk corona. We assume that this can be related with coronal temperature
decreasing at heliocentric distances from 1.35 to 6.5 solar radii. Duration
dependencies of type IIIb and type III bursts on frequency in the range of
10-70 MHz are also obtained. We note that the durations and drift rates of type
III bursts as well as their dependences on frequency differ essentially from
those for type IIIb bursts.
