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Session 79 - Quiet Solar Photosphere and Chromosphere.
Oral session, Thursday, June 13

[79.06] Limb Observations of He I 1083nm

M. Penn (NSO), H. Jones (NASA/GSFC)

Imaging spectroscopic data of the He I 1083 nm limb emission were taken on several dates in Oct and Nov 1995 with the NASA/NSO Spectromagnetograph at the NSO/Kitt Peak Vacuum Telescope and on 09 Dec 1993 with the Michigan Infrared Camera at the NSO/Sac Peak Vacuum Tower Telescope. Emission line profiles were observed in quiet Sun and coronal hole locations on the northern and southern solar poles and on the east solar limb. The height of the He I 1083 nm shell above the continuum limb at 1083 nm was measured to be 2.11\pm0.12 Mm with the Kitt Peak data, and 1.74\pm0.05 Mm with the Sac Peak data. The Kitt Peak data show within the measurement error there is no significant difference in the height or thickness of the emission shell in coronal holes compared with the quiet Sun, (2) the 1083 nm emission intensity drops by 50% in coronal holes, (3) the line width decreases by about 2 km s^-1 in coronal holes (suggesting less inclined spicules), (4) the line width of the He I 1083 nm line jumps significantly as the line-of-sight crosses the solar limb (consistent with a higher temperature upper shell), (5) a quiescent prominence shows a smaller spectral line width (consistent with a cooler temperature or less velocity broadening), and (6) the entire emission shell and the prominence show a He I spectral component ratio of about 8 (suggesting optically thin emission).

Program listing for Thursday