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T. Q. Donaghy (Stanford University, Department of Physics), J. W. Harvey (National Solar Observatory)
Daily full-disk measurements of the chromospheric magnetic field have been made using the 854.2 nm Ca II line and the NSO/Kitt Peak Vacuum Telescope since June 1996. These observations have revealed previously unobserved features of the solar magnetic field, chief of which are fields associated with filament channels. These fields are apparent in the chromosphere, but do not appear in the photosphere. They are diffuse, unipolar fields that exhibit a reversal of sign as solar rotation carries them across the disk, indicating a predominant horizontal component to the field.
We explore the changes in these fields before and after a prominence eruption and we study six strong events, showing the chromospheric and photospheric magnetic fields both before and after an eruptive event. In the cases where we could detect the filament channel fields, we were also able to detect noticeable change in the fields with the advent of the prominence eruption. Many more events need to be studied before a consistent pattern of field changes can be considered as certain. Such a extensive study should also help elucidate the mechanisms of filament eruption.
The NSO is one of the National Optical Astronomy Observatories which are sponsored by the National Science Foundation. The NSO data used here are produced cooperatively by NSF/NOAO, NASA/GSFC, and NOAA/SEC.