| Abstract : | Solar radio flux emerge out from different heights of solar atmosphere can be used to estimate the temporal and spatial variation of solar coronal rotation. The solar coronal rotation can also be used as an indicator of the differential rotation of sub-photospheric layers. Disk-integrated concurrent measurement of solar radio flux shows a solid reliance of the coronal rotation period on the heights in the corona. Present work is an effort to find the variation in coronal rotation with altitude in declining phase of solar cycle 21 i.e. for time period (1980-1986). The continuous disk integrated solar radio flux at six different frequencies (430, 606, 810, 1415, 2695 and 2800 MHz) are used to estimate the rotation period. These radio fluxes are originating at different heights of solar corona. Flux modulation method is used to estimate the rotation period. Solar radio flux 430 and 810 MHz are recorded at Jagiellonian University Radio Astronomical observatory, Cracow, Poland; 606, 1415 and 2695 MHz are recorded at Sagamore Hill Radio Observatory Massachusetts, USA and 2800 MHz recorded at Dominion Radio Astrophysical Observatory Pentincton. Using these data sets for each frequency different annual time series is generated from daily radio flux data for study period. Periodic component present in the time series cannot be estimated directly. Statistical technique Lomb Scargle Periodogram able to deal with the time series having permissible data gaps, used here to estimate periodicity present in the time series. Sidereal rotation period thus obtained are plotted against frequency originating from different heights in solar coronal atmosphere. Altitudinal coronal rotation profile in declining phase of solar cycle 21 shows some rigid, temporal and spatial variation in the solar rotation, which may be linked with solar activity cycle. Detail work would be presented in paper. |
