  The present work is an effort to investigate possible radial variations in
the solar coronal rotation by analyzing the solar radio emission data at 15
different frequencies (275-1755 MHz) for the period starting from July 1994 to
May 1999. We used a time series of disk-integrated radio flux recorded daily at
these frequencies through radio telescopes situated at Astronomical Observatory
of the Jagellonian University in Cracow. The different frequency radiation
originates from different heights in the solar corona. Existing models,
indicate its origin at the height range from nearly $\sim12,000$ km (for
emission at 275 MHz), below up to $\sim2,400$ km (for emission at 1755 MHz).
There are some data gaps in the time series used for the study, so we used
statistical analysis using the Lomb-Scargle Periodogram (LSP). This method has
successfully estimated the periodicity present in time series even with such
data gaps. The rotation period estimated through LSP shows variation in
rotation period, which is compared with the earlier reported estimate using
auto correlation technique. The present study indicates some similarity as well
as contradiction with studies reported earlier. The radial and temporal
variation in solar rotation period are presented and discussed for the whole
period analyzed.
