On estimation of high frequency geophysical signals in Earth rotation by complex demodulation

Polar motion and UT1 contain small geophysical signals (<0.1 milliarcsecond) driven by the daily cycle in the solar heating. These signals are either irregular or quasi-harmonic therefore need to be expressed by the time series and studied using the time domain techniques. This work is focused on the complex demodulation method which seems to be particularly useful for studying high frequency geophysical signals in Earth rotation. After general introduction of the method and its properties, we describe its application for modeling diurnal and subdiurnal components of polar motion and UT1 and of the corresponding excitation functions. We also derive dynamical equations which can be used for direct comparison of the signals demodulated from the Earth rotation and geophysical excitation data.

► This work is focused on application of the complex demodulation method for studying high frequency signals in Earth rotation. ► We describe its use for modeling diurnal and subdiurnal components of polar motion, UT1, and the corresponding geophysical excitation functions. ► We also derive dynamical equations for direct comparison of high frequency signals demodulated from the Earth rotation and geophysical excitation data.