Stellar Astrophysical Fluid Dynamics: Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between?

A sampling frequency conversion apparatus according to this invention converts an input data string based on an input sampling pulse into a data string based on an output sampling pulse having a frequency different from the frequency of the input sampling pulse. The apparatus reproduces the input sampling pulse based on the input data string, generates interpolation sampling pulses having a frequency corresponding to an integral multiple of the frequency of the input sampling pulse, and generates an interpolated data string from the input data string on the basis of the interpolation sampling pulses. On the other hand, the apparatus phase-modulates the output sampling pulse to diffuse its frequency spectrum, and selects and determines a timing of the interpolation sampling pulse closest to the timing of the phase-modulated output sampling pulse. The apparatus selects data corresponding to the selected timing from the interpolated data string, and outputs the selected data.