Cosmic ray investigation for the Voyager missions; energetic particle studies in the outer heliosphere—And beyond

A cosmic-ray detector system (CRS) has been developed for the Voyager mission which will measure the energy spectrum of electrons from 3–110 MeV and the energy spectra and elemental composition of all cosmic-ray nuclei from hydrogen through iron over an energy range from 1–500 MeV/nuc. Isotopes of hydrogen through sulfur will be resolved from 2–75 MeV/nuc. Studies with CRS data will provide information on the energy content, origin and acceleration process, life history, and dynamics of cosmic rays in the galaxy, and contribute to an understanding of the nucleosynthesis of elements in the cosmic-ray sources. Particular emphasis will be placed on low-energy phenomena that are expected to exist in interstellar space and are known to be present in the outer Solar System. This investigation will also add to our understanding of the transport of cosmic rays, Jovian electrons, and low-energy interplanetary particles over an extended region of interplanetary space. A major contribution to these areas of study will be the measurement of three-dimensional streaming patterns of nuclei from H through Fe and electrons over an extended energy range, with a precision that will allow determination of anisotropies down to 1%. The required combination of charge resolution, reliability and redundance has been achieved with systems consisting entirely of solid-state charged-particle detectors.Principal Investigator of the Voyager Cosmic Ray Experiment.     

The Voyager infrared spectroscopy and radiometry investigation

The infrared investigation on Voyager uses two interferometers covering the spectral ranges 60–600 cm^–1 (17–170 m) and 1000–7000 cm^–1 (1.4–10 m), and a radiometer covering the range 8000–25 000 cm^–1 (0.4–1.2 m). Two spectral resolutions (approximately 6.5 and 2.0 cm^–1) are available for each of the interferometers. In the middle of the thermal channel (far infrared interferometer) the noise level is equivalent to the signal from a target at 50 K; in the middle of the reflected sunlight channel (near infrared interferometer) the noise level is equivalent to the signal from an object of albedo 0.2 at the distance of Uranus.For planets and satellites with substantial atmospheres, the data will be used to investigate cloud and gas composition (including isotopic ratios), haze scale height, atmospheric vertical thermal structure, local and planetary circulation and dynamics, and planetary energy balance. For satellites with tenuous atmospheres, data will be gathered on surface and atmospheric composition, surface temperature and thermal properties, local and global phase functions, and surface structure. For Saturn's rings, the composition and radial structure, particle size and thermal characteristics will be investigated. Comparative studies of the planets and their satellite systems will be carried out.Paris Observatory.Cornell University.Jet Propulsion Laboratory.University of Maryland.     

Dual spacecraft observations of energetic particles in the vicinity of the magnetopause,bow shock,and the interplanetary medium

This article presents some of the new and important particle features that have been detected in the energy range 1 keV to 290 keV by the ISEE-1 and -2 spacecraft near the magnetopause, bow shock, and the interplanetary space. Only examples of data from the first few orbits, when the spacecraft were on the front side, are shown.Paper presented at 13th ESLAB Symposium, Innsbruck, Austria (June 5, 1978).     

GEOS-1 observations of electrostatic waves,and their relationship with plasma parameters

In this paper we describe and discuss the occurrence of natural wave emissions detected by GEOS-1 at frequencies above the electron gyrofrequency. The bulk of the data presented comes from the first six months of satellite operation and thus concerns mainly dayside phenomena. The paper is arranged as follows:After some general remarks, a classification of the wave phenomena is developed in Section 2, and experimental evidence and morphological information relevant to this classification are contained in Section 3. Section 4 includes some preliminary comments on nightside observations. The results are discussed in Section 5, where it is argued that they can be understood as manifestations of electron cyclotron harmonic (Bernstein) wave emission in a plasma parameter range which has only very recently received any theoretical examinations. This theme is further developed in a comparison paper (Ronnmark et al., 1978).     

Book reviews

Space Science Reviews -     

Cosmic X-ray observations performed with a gas scintillation spectrometer

Observations of the spectrum of CAS-A in the X-ray energy range 3 to 10 keV have been made using two gas scintillation proportional counters flown on an Aries rocket. Analysis of the data from the 180 second observation has resolved the emission features at 7 keV, which results from transitions in highly ionised iron.     

Observing the Sun at 20–650 MHz at Thermopylae with Artemis

Fine structure of type IV radio solar bursts with a great variety and complexity often give much information in different ways and enable estimation of various coronal characteristics. In this work, we expose our new method for fine structure revealing and separation of two basic kinds of type IV fine structure, as fibers and pulsations. We also estimate frequency drift of fibers from dynamic spectra, clean from continuous background, with a prototype method using 2-D Fourier transform and we estimate periodicities of fibers as well as pulsations with continuous wavelet transform. Working with the last method we found periodicities close to 3 min umbral oscillations and 5 min global solar oscillations.     

CME Theory and Models

This chapter provides an overview of current efforts in the theory and modeling of CMEs. Five key areas are discussed: (1) CME initiation; (2) CME evolution and propagation; (3) the structure of interplanetary CMEs derived from flux rope modeling; (4) CME shock formation in the inner corona; and (5) particle acceleration and transport at CME driven shocks. In the section on CME initiation three contemporary models are highlighted. Two of these focus on how energy stored in the coronal magnetic field can be released violently to drive CMEs. The third model assumes that CMEs can be directly driven by currents from below the photosphere. CMEs evolve considerably as they expand from the magnetically dominated lower corona into the advectively dominated solar wind. The section on evolution and propagation presents two approaches to the problem. One is primarily analytical and focuses on the key physical processes involved. The other is primarily numerical and illustrates the complexity of possible interactions between the CME and the ambient medium. The section on flux rope fitting reviews the accuracy and reliability of various methods. The section on shock formation considers the effect of the rapid decrease in the magnetic field and plasma density with height. Finally, in the section on particle acceleration and transport, some recent developments in the theory of diffusive particle acceleration at CME shocks are discussed. These include efforts to combine self-consistently the process of particle acceleration in the vicinity of the shock with the subsequent escape and transport of particles to distant regions.     

Oxygen Isotope Processes and Transfer Reactions

A unique kinetic isotope effect has been found in the formation process of ozone molecules. Isotope enrichments of about 10% above statistically expected values were first discovered in atmospheric isotopomers ⁴⁹O₃ and ⁵⁰O₃ and later in many other molecular combinations. Most recently the source of this effect was identified through measurement of isotope-specific ozone formation rate coefficients which show a large variability of over 50%. Ozone molecule formation is a complex process since different reaction channels contribute to a specific isotopomer. In addition, fast oxygen isotope exchange reactions determine the abundance of atomic oxygen participating in ozone formation. The isotope enrichments observed are both pressure and temperature-dependent and they decrease at pressures above 100 mbar and toward lower temperatures. Ozone possesses not only one of the most unusual isotope anomalies, it also serves as a mediator by transferring heavy oxygen from the O₂ reservoir to other species. Stratospheric isotope composition of CO₂ has been recently measured with high accuracy and a pronounced isotopic signature was found which shows that ¹⁷O is preferentially transferred from O₃ into CO₂. This revised version was published online in August 2006 with corrections to the Cover Date.