Solar Feature Identification on PSPT Images
Authors: S. R. Walton, A. M. Cookson, D. G. Preminger, G. A. Chapman
We have recently published a series of results on the statistical characteristics of sunspots and faculae (Walton, Preminger and Chapman 2003, Solar Phys. 213, 301) and on the relative contribution of faculae and network to solar irradiance variability (Walton, Preminger and Chapman 2003, Ap. J. 590, 1088). Those results were based primarily on 5” resolution full disk solar photometric images obtained at the San Fernando Observatory (SFO). In this work, we extend those results to photometric images from the Precision Solar Photometric Telescope (PSPT). These images have a substantially higher resolution (1” pixels) and also a better signal-to-noise ratio. Preliminary results indicate that the differential distribution of facular areas, dN/dA, is similar to that found for SFO images for large regions, but that the distribution levels off for smaller regions; that is, the number of small regions is lower than would be expected by extrapolation of the previous results. In particular, we see no evidence for large numbers of previously undetected small regions which could contribute to solar irradiance variability.
This work has been supported by NASA grant NAG5-12905 and NSF grant ATM-9912132. We are grateful to the PSPT team at the High Altitude Observatory for the PSPT images.