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Session 120 - The Sun.
Oral session, Saturday, January 10
International Ballroom East,

[120.03] Formation of the Helium II 304ÅLine in the Solar Atmosphere

S. D. Jordan, V. Andretta (NASA/GSFC)

The problem of the formation of the principle members of the resonance series of He I and He II at 584Å\ and 304Å\ remains a major unsolved problem of the solar atmosphere. Nevertheless, thanks to observations from the Goddard Solar Extreme Ultraviolet Rocket Telescope and Spectrograph (SERTS) and from the ESA/NASA SOHO mission, we now have a data base to address this problem and, hopefully, to solve it for the quiet atmosphere. This talk will briefly review alternatives for helium resonance line formation in the Sun, and will offer a few examples of observations that promise to help discriminate among them. Specifically, assuming electron collisional excitation is responsible for the 304Å\ line in the quiet Sun, supported by our earlier studies, evidence from SERTS and SOHO will be discussed in support of 'velocity redistribution' of the emitting ions in producing the observed profiles and fluxes.

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Program listing for Saturday