A Cosmic-ray Composition Controlled by Volatility and a/q Ratio. snr Shock Acceleration of gas and Dust

The composition of Galactic Cosmic Ray Sources (GCRS) shows the following features: (i) an enhancement of the refractory elements relative to the volatile ones, and (ii) an enhancement of the heavier volatile elements relative to the lighter ones; this mass dependence should reflect a mass-to-charge (A/Q) dependence of the acceleration efficiency; among the refractory elements, there is only a very weak enhancement of heavier species, or none at all. We consider it fortuitous that the GCRS composition resembles that of the solar corona, which is biased according to first ionization potential. In a companion paper by Ellison et al. (1998, this issue), this GCRS composition is interpreted in terms of a supernova shock wave acceleration of interstellar and/or circumstellar (e.g., 22Ne-rich Wolf-Rayet wind) gas phase and especially dust grain material. These two papers summarize and complement the content of two papers that recently appeared in Astrophys. J. (Meyer et al., 1997; Ellison et al., 1997). This revised version was published online in June 2006 with corrections to the Cover Date.     

Cosmic Rays From Supernova Remnants: a Brief Description of the Shock Acceleration of gas and Dust

Space Science Reviews - We summarize our model of galactic cosmic-ray (GCR) origin and acceleration, wherein a mixture of interstellar and/or circumstellar gas and dust is accelerated by a...     

Temperature and altitude of the polar mesopause in summer

A review and summary of 60 in situ experiments is provided which determined the temperature and altitude of the mesopause north of 58°N latitude during the summer months of May through August. These experiments employed 4 experimental techniques; acoustic grenades, rigid and inflatable falling spheres, and Pitot-static tubes. Excellent agreement is found among the results obtained from different techniques. During June and July the average mesopause temperature drops below 130 K, the average mesopause altitude is 88.5 km. The climatological tables of CIRA 1986 indicate, however, a mean mesopause temperature of approximately 140 K at 91 km for corresponding geophysical conditions.     

The Jupiter helium interferometer experiment on the Galileo Entry Probe

We discuss the scientific objective, instrument design, and calibration of a miniaturized Jamin-Mascart interferometer which is to perform an accurate measurement of the refractive index of the Jovian atmosphere in the pressure range 2.5 to 10 bar. The instrument is to perform this measurement in December 1995 aboard the entry probe of the NASA Galileo spacecraft. From the data obtained the mole fraction of helium in the atmosphere of Jupiter is to be calculated with an estimated uncertainty of ± 0.0015. The instrument has a total mass of 1.4 kg and consumes 0.9 W of electrical power.     

Composition of the Venus atmosphere below 100 km altitude

Our current knowledge on the composition of the Venus atmosphere in the altitude range from the surface to 100 km is compiled. Gases that have been measured, and whose mixing ratios are assumed to be constant with altitude, are CO₂, N₂, He, Ne, Ar, and Kr. Gases that have been identified in the lower and/or middle atmosphere, but whose mixing ratios may depend on altitude, latitude and/or local time, are CO, H₂O, HCl, HF, and SO₂. Conflicting data or only upper limits exist on some important trace gases, such as O₂, H₂, and Cl₂. The latter two are key constituents in the photochemistry of the middle atmosphere of Venus. The chapter concludes with a listing of the isotopic abundances of elements measured in the Venus atmosphere.     

Macroscopic Transport Large-scale advection, turbulent diffusion, wave transport

While the solar convection zone is very well mixed by its turbulent motions, chemical composition gradients build up in the radiative interior due to microscopic diffusion and settling, and to nuclear burning. Standard models, which ignore any type of macroscopic transport, cannot explain the depletion of lithium in solar-type stars, as they evolve; neither do they account for the observed profile of molecular weight at the base of the solar convection zone. Such macroscopic transport can be achieved through thermally driven meridian currents, through turbulent diffusion generated by differential rotation and possibly through gravity waves. These processes transport also angular momentum, and therefore the internal rotation profile of the Sun provides a crucial test for their relative importance. So does also the behavior of tidally locked binaries, which appear to destroy less lithium than single stars of the same mass. This revised version was published online in June 2006 with corrections to the Cover Date.     

Vertical density and temperature structure over Northern Europe

During the Energy Budget Campaign, several profiles of the density and temperature of the upper atmosphere were obtained. The measurements were made using rocket-borne instrumentation launched from ESRANGE, Sweden and Andoya Rocket Range, Norway during November and December, 1980. The techniques included meteorological temperature sondes, passive falling spheres, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data within the altitude range from 20 km to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the oscillations and fluctuations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. The geomagnetic storm conditions may be associated with enhanced wave activity and heating observed in the lower thermosphere.     

A differential measurement of the Lyman alpha emission from the giant planets using IUE

The intensity of the resonantly scattered Ly-α line of the gian planets depends on the scattering column length of atomic hydrogen above the methane layer and on the incident solar flux. We have obtained measurements of the Ly-α brightness of Jupiter and Saturn on December 19, 1979, with a time difference of 111 minutes, which is only slightly longer than the additional travel time for solar photons scattered at Saturn compared to those from Jupiter. This observational technique eliminates two major uncertainties — the use of different instruments and solar variability — affecting previous determinations of the relative brightness of the planets. The measured ratio of the brightness of the subsolar points is 3.0 ± 0.4 which agrees well with the ratio of the incident solar flux of 3.4. This implies approximately equal scattering column lengths of H on both planets.