Search Publications

Solar EUV and UV Emission Line Observations Above a Polar Coronal Hole

Wilhelm, K.; Bodmer, R.

The roll manoeuvre of SOHO on September 3, 1997 provided the opportunity to study the northern coronal hole with SUMER slits in east-west orientation, so that polar plumes and inter-plume lanes could be observed simultaneously. A preliminary analysis of the observations shows that lines emitted by ions with the lowest formation temperatures (with …

Elemental Abundances in Coronal Structures

Kohl, John L.; Noci, Giancarlo; Raymond, John C. +1 more

A great deal of evidence for elemental abundance variations among different structures in the solar corona has accumulated over the years. Many of the observations show changes in the relative abundances of high- and low-First Ionization Potential elements, but relatively few show the absolute elemental abundances. Recent observations from the SOH…

Deuterium Observations in the Galaxy

Ferlet, R.; Vidal-Madjar, A.; Lemoine, M.

An accurate measurement of the primordial value of D/H would provide one of the best tests of nucleosynthesis models for the early Universe and the baryon density. Such evaluations have been traditionally made using present estimations of the deuterium abundance in the interstellar medium, extrapolated backwards in time with the use of galactic ev…

Epilogue: Cosmic Rays in the Active Heliosphere

Wibberenz, G.; Jokipii, J. R.

The Solar Wind - Inner Heliosphere

McComas, D. J.; Goldstein, B. E.; Neugebauer, M. +3 more

The solar wind in the inner heliosphere, inside ~ 5 AU, has been almost fully characterized by the addition of the high heliographic latitude Ulysses mission to the many low latitude inner heliosphere missions that preceded it. The two major omissions are the high latitude solar wind at solar maximum, which will be measured during the second Ulyss…

Composition and Opacity in the Solar Interior

Turck-Chieze, Sylvaine

Detailed abundances of elements from hydrogen up to iron are necessary to perform a precise model of the solar structure. Most of them have been deduced from photospheric observed values, some others from the meteoritic composition. Nowadays, thanks to helioseismic constraints, they seem more and more under control.

UVCS/SOHO: The First Two Years

Cranmer, S. R.; Noci, G.; Kohl, J. L.

The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) has observed the extended solar corona between 1 and 10 R· for more than two years. We review spectroscopic and polarimetric measurements made in coronal holes, equatorial streamers, and coronal mass ejections, as well as selected non-solar targets. UVCS/SOHO has provided a great amount of …

Structure of the Solar Wind and Compositional Variations

Bochsler, P.

The composition of the solar wind is largely determined by the composition of the source material, i.e. the present-day composition of the outer convective zone. It is then modified by the processes which operate in the transition region and in the inner corona. In situ measurements of the solar wind composition give a unique opportunity to obtain…

Magnetic Fields in the Inner Heliosphere

Balogh, A.

The structure of Heliospheric Magnetic Field (HMF) is a function of both the coronal conditions from which it originates and dynamic processes which take place in the solar wind. The division between the inner and outer regions of the heliosphere is the result of dynamic processes which form large scale structures with increasing heliocentric dist…

Primordial Helium and DeltaY/DeltaZ from H II Regions and from Fine Structure in the Main Sequence Based on HIPPARCOS Parallaxes

Girardi, L.; Høg, E.; Pagel, B. E. J. +3 more

The primordial helium abundance YP is important for cosmology and the ratio DeltaY/DeltaZ of the changes relative to primordial abundances constrains models of stellar evolution. While the most accurate estimates of YP come from emission lines in extragalactic H II regions, they involve an extrapolation to zero metallicity which itself is closely …