UVCS/SOHO ABSTRACTS

COSPAR MEETINGS

Physical Properties of Coronal Streamers

J. C. Raymond and R. Frazin

Ultraviolet observations with the UVCS instrument aboard SOHO can be used to determine densities, temperatures, outflow speeds and elemental abundances in coronal streamers. These bear upon the in situ measurements of the slow solar wind and upon the the physical mechanisms that heat the coronal plasma and accelerate the solar wind. Here we emphasize the variations in elemental abundances between the closed and open field regions of streamers and O5+ velocity widths and anisotropies. The anisotropies indicate preferential heating of heavy ions in the open field regions, possibly due to wave-particle interactions. The latter results are qualitatively similar to previous findings for coronal holes and may indicate similar heating and acceleration mechanisms for the two structures.

Physical parameters of the source of the fast solar wind

E. Antonucci, S. Giordano

Oxygen abundance in the outer corona during solar minimum

E. Antonucci, D. Marocchi, S. Giordano

Solar wind from high-latitude and equatorial open magnetic field line regions

S. Giordano, E. Antonucci, L.Strachan

POLAR CORONAL JETS

D. Dobrzycka, J.C. Raymond, & S.R. Cranmer

We present ultraviolet spectroscopy of polar coronal jets obtained with UVCS/SOHO. They correlate with the EIT Fe~XII (195\AA) and LASCO white--light jet events.  We found that the jets typically undergo two phases: at the first phase the O~VI lines show a brief intensity enhancement and narrowing, while the H I Ly$\alpha$ line is not enhanced, and the second phase, about 25 minutes later, when the H~I Ly$\alpha$ line shows an intensity enhancement and narrowing, while the O~VI line is relatively unchanged. We modeled the observable properties of the jets from 1997 August 5, detected at $1.71~R_\odot$. We interpret the first phase as the fast, dense centroid of the jet passing by the UVCS slit, and the second phase as a passage of cooler, lower density material following the centroid. Possible scenarios of the electron temperature variations needed to account for observed conditions on 1997 August 5 indicate that some heating is required. We computed models of the temperature and nonequilibrium ionization state of an expanding plasma using various forms for the heating rates. We discuss the model results, the initial electron temperature and heating rate required to reproduce the observed O~VI ionization state. We also place some constraints on the origin of the jet material based on the inferred plasma properties.

Report on The Sun and its Atmosphere

 E.Antonucci 

(COSPAR Symposium E2.1), COSPAR Information Bulletin, 1996, 137,46

Report on The Sun and its Role in the Heliosphere

D.Page and E.Antonucci

 (COSPAR Symposium E2.2), COSPAR Information Bulletin, 1996, 137,46

Measurements of H I and O VI Velocity Distributions in the Extended Solar Corona with Spartan 201 and UVCS/SOHO 

J.L. Kohl, L.D. Gardner, L. Strachan (CfA), G. Noci (U. of Florence), the UVCS/Spartan 201 and UVCS/SOHO teams.

First Results from the SOHO Ultraviolet Coronagraph Spectrometer

 G. Noci (U. of Florence), J.L. Kohl (CfA), E. Antonucci (U. of Turin), G. Tondello (U. of Padua), M.C.E. Huber (ESA), the UVCS/SOHO Team.