Computer session on measurement and analysis of waves and turbulence
6th COSPAR Capacity Building Workshop 
Sinaia, Romania, June 4-16, 2007
1. Spectral analysis
Wave measurements are often represented in the frequency domain.
A simple tool to characterize the data is the power spectrum.
It can be obtained from a measured time series of samples of a given quantity (a waveform)
using the Fourier analysis.
The result is the power spectral density
as a function of frequency. For example, if we measure an electric field component in V m-1,
the resulting power spectral density will be given in V2m-1Hz-1.
Note: Non-Fourier methods to estimate the power spectral density are also sometimes used (for example the
autoregressive or maximum entropy models) but these are not discussed here.
Instructions:
- Download the following IDL procedures:
- Read the comments and try to understand the code (the above sequence of files is recommended)
- Run the program example_power_spectrum.pro .
- Modify and re-run the program using different frequency resolutions (controlled by the nfft
parameter) and different waveform data sets.
Reading:
The ISSI book, Chapters 1.1-1.3