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Ghosts in the Machine

13:30-14:30 Tue 19 Mar 2002

ATNF Marsfield Lecture Theatre


Principal Component Analysis (PCA) is a classical statistical technique for dimensionality reduction in signal processing. This talk begins with an intuitive introduction to PCA, showing how a signal can be reconstructed using a small number of PCA eigenvectors, the "ghosts in the machine".

CTIP, in collaboration with the Meudon Observatory, Paris, France, and the High Altitude Observatory (HAO), Boulder, Colorado, USA, has applied PCA inversion to estimate the vector magnetic field in the solar atmosphere from measurements of the Stokes parameters of polarised light in spectral lines split by the Zeeman effect. PCA inversion is over two orders of magnitude faster than previous methods of data inversion. Recent results will be presented using data from HAO’s Advanced Stokes Polarimeter at Sacramento Peak Observatory, New Mexico.


Dr David Rees

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