Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[1.28] Solar UV Irradiance Variability Observed at High Spatial and Spectral Resolution by HRTS

J. S. Morrill, K. P. Dere, C. M. Korendyke (E. O. Hulburt Center for Space Research, Naval Research Laboratory)

The HRTS-9 rocket flight occured on April 18, 1995 and was configured to study the sources of solar variablity by observing ultraviolet emission patterns near the Mg II h and k lines. These observations include high spatial and spectral resolution spectrograms as well as spectroheliograms in four FUV passbands and H-alpha. The spectrograms cover the wavelength range 2665 to 2885Å\ with a spectral resolution of .2Å\ and a spatial resolution of 1 arc-second along a 900 arc-second slit. Prominent spectral features in this wavelength range include the Mg II h and k lines near 2800 Å, the strong Mg I and Si I Fraunhofer lines near 2850 and 2880Å, respectively, and the line-blanketed quasi-continuum region.

HRTS-9 observations included the quiet sun, quiet limb, plage, and sunspots. The analysis of this data set has focused on the spatial intensity variability of the features as a function of wavelength with particular regard for how these will affect solar variability. Specifically, we examine the contrast variation of the plage and sunspot compared to the quiet sun as well as contrast variation within the quiet sun. The observed sunspot spectrum shows the characteristic decrease in the quasi-continuum, the non-reversed Mg II h and k line shapes as well as the enhancement in the Mg II h and k core emissions over that observed in the quiet sun. In this presentation we will discuss the wavelength dependent contrasts of the plage and quiet sun regions, the characteristics of the observed sunspot spectrum, and the implications on solar variability.

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