Diffraction pattern analysis of bright trace flares

A study of the diffraction patterns seen in TRACE images of bright flare ke rnels was undertaken to better understand the properties of the telescope. The diffraction pattern caused by light from a bright flare kernel passing through the mesh supporting the filters at the front of the TRACE telescope has been examined, and a method has been developed to use this pattern to determine the zeroth order intensity of hares that cannot be measured direc tly due to saturation of the Analog to Digital Converter (ADC) in the CCD d etection package. The validity of this method is confirmed by testing it on a flare that does not saturate the ADC. The diffraction pattern allows us to measure intensities far brighter than the detection package allows; the range has been effectively increased by at least 41 times. The light scatte red from any point was observed to be approximate to 20%, a significant amo unt which may be affecting the image quality of the telescope. An accurate determination of the ratio of the square slit size to slit spacing of the w ire mesh was obtained. Wavelength dispersion, the phenomenon that as the hi gher-order diffracted peaks lie further from the center, they spread out un til double peaks are observed, has also been examined. This effect is cause d by two principal wavelengths, Fe IX at 171.073 Angstrom and Fe X at 174.5 07 Angstrom in the TRACE 171 Angstrom passband. This study is a part of the TRACE Team educational outreach program.