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[55.11] On the Universality of the Leading Orders of PCA. Spectral Eigenprofiles for the Sun.

A. Skumanich, A. López Ariste (HAO-NCAR)

In a previous Principal Component Analysis (PCA) of the spectral region containing the intensity profiles of the FeI \lambda630.15 & \lambda630.25 nm lines for a solar active region, Ref(1), the issue of the universality or invariance of the eigenprofiles (principal components) to changes in the magnetic composition of the studied region was raised. To address this issue we have performed a series of PCA studies in which we incrementally increased the threshold Zeeman polarization for the included profiles for a given region. This reduces the relative roles of the various components such as the quiet sun and elements of the active sun, viz. network, pores, plage and spot.

We find that the Taylor series representation of the highest ranked eigenprofiles in the expansion of the intensity, which yield an estimate of the velocity and magnetic splitting (first and second derivative terms respectively, Ref(1)), continues to hold. However increased eigenprofile 'mixing' occurs. Consequently to obtain eigenprofiles which represent the derivatives of the zeroth order eigenprofile one requires significant rotations of the basis in the PCA space. The implication for derived velocity and magnetic parameters will be discussed.

- Skumanich, A. & López Ariste, A. 2002, "The Physical Content of the Leading Orders of Principal Component Analysis of Spectral Profiles", ApJ 570. In press

The author(s) of this abstract have provided an email address for comments about the abstract: sku@hao.ucar.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.