Solar Physics Division Meeting 2000, June 19-22
Session 2. Corona, Solar Wind, Flares, CMEs, Solar-stellar, Instrumentation, Other
Display, Chair: J. Krall, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[2.18] Prominence Densities as Derived from SOHO/EIT Fe XII (195 Angstrom) Absorption Features

H. Gilbert (NCAR/HAO), L. Mize (Rhodes College), T. Holzer (NCAR/HAO), R. MacQueen (Rhodes College)

Prominences often appear in absorption when the sun is viewed in EUV emission lines formed at coronal temperatures. The coronal EUV radiation at wavelengths less than 504 anstroms undergoes Lyman continuum absorption by both hydrogen and helium (i.e., the coronal radiation ionizes hydrogen and helium atoms from their ground states). We can thus infer prominence column densities by measuring the amount of coronal radiation absorbed by prominence material along the line of sight, and by making assumptions concerning the ionization state and the helium abundance characterizing the prominence plasma. We do so by measuring 195 angstrom intensity along lines of sight inside and outside prominences, both just on the disk and just off the limb. Our absorption measurements are made using Fe XII (195 angstroms) data from the Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft. Initial results using our technique yield prominence densities on the order of 1010 cm-3. This is the first step in reaching our ultimate objective of attaining a quantitative measure of total prominence mass, which may be important in the dynamical processes involved in Coronal Mass Ejection initiation and evolution.

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