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Paper: EUNIS Results on He II 304Å Line Formation
Volume: 368, The Physics of Chromospheric Plasmas
Page: 183
Authors: Jordan, S.D.; Brosius, J.W.
Abstract: The first flight of the Goddard Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) took place from White Sands Missile Range at 18:10 UT on April 12, 2006. Observations of the He II 304 Å principal resonance line were obtained with a cadence of ~ 2 seconds along an eleven arc-minute slit. Corresponding EIT images of this line, and additional EUNIS observations of the strong coronal line of Fe XVI at 335.4 Å, were used to assess the role of the photoionizing coronal flux in the formation of the He II line. In agreement with previous work of these authors and others, the results support formation by the collisional excitation mechanism by thermal electrons in the quiet Sun.
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