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Session 73 - Solar Space Observations, SOHO & SERTS.
Display session, Friday, January 09
Exhibit Hall,

[73.01] The Off-Limb Behaviour of the Solar Transition Region FIP Effect

J. M. Laming (NRL/SFA Inc), U. Feldman (NRL), J. J. Drake (SAO), U. Schühle, W. Curdt, K. Wilhelm (MPAe), P. Lemaire (IAS)

We investigate the behaviour of the solar FIP effect (the abundance enhancement of elements with first ionization potential < 10 eV by factor of 3-4 in the corona with respect to photospheric values) with height above the limb in a region of diffuse quiet corona observed by the SUMER instrument on SOHO. Line ratios formed at \log T > 5.8 show coronal abundances for all heights. Line ratios formed at lower temperatures are consistent with coronal abundances well off the limb, with the apparent magnitude of the FIP enhancement decreasing by a factor of 1.5 - 2 as one approaches the solar limb. Thus our observations support a spatial variation in the quiet sun transition region FIP effect inferred previously from studies of the full disk solar spectrum (Laming, Drake, amp; Widing 1995, ApJ, 443, 416 and references therein). This result adds to the probability that emission from the solar disk transition region and corona originates from qualitatively different structures for values of \log T <\atop > 5.8, having different FIP effects.

Program listing for Friday