Waves and wave-particle interactions in the magnetosphere: A review

Recent space observations of waves, both electromagnetic and electrostatic, are reviewed and the role which they can play in the dynamics of magnetospheric particles is stressed. Wave particle interactions (WPI) in the exo- and intra-plasmaspheric media depend on the exact process of particle injection under the influence of magnetospheric electric fields, and on the spatial distribution of the cold plasma particles; these two aspects of the problem are studied to some extent. The concepts of optimum cold plasma density, critical energy, limiting flux, marginal stability, steady-state equilibrium are critically discussed. The non-linear aspects — both experimental and theoretical — of WPI's are reviewed and a special section is devoted to active experiments in space. An attempt is made to outline which kind of experiments could be made at high-latitudes, in conjunction with IMS spacecrafts, in order to arrive at a better understanding of magnetospheric processes involving waves and particles.Paper presented at the Esro Symposium on European Sounding Rocket and Scientific Balloon Activity at High Latitudes with Emphasis on the International Magnetospheric Study (Örenäs Slott, Sweden, 1974).     

Fourier spectroscopy in planetary research

The application of Fourier Transform Spectroscopy (FTS) to planetary research is reviewed. The survey includes FTS observations of the Sun, all the planets except Uranus and Pluto, the Galilean satellites and Saturn's rings. Instrumentation and scientific results are considered. The prospects and limitations of FTS for planetary research in the forthcoming years are discussed.     

An Optimal Normalization Scheme

An attitude normalization scheme, based on quaternion updates' of the attitude matrix in a strapdown system, is presented which is optimal in the two-norm sense. Furthermore, the algorithm requires minimal computer time and memory load.     

ATC Beacon Interference Characteristics in the New York Area

An experimental program is described that had the objective of measuring the effects of the time-dependent structure of downlink (air craft to ground) interference generated by the Air Traffic Control Radar Beacon System (ATCRBS) in an active air traffic terminal area that are relevant to system and ground controller response time. The results of this program indicate a number of interesting details concerning the correlation of the level of the downlink interference with changes in the arrival and departure rates of aircraft at the local terminal sites.     

Everyman's Doppler Satellite Navigation System

This paper describes a system of navigation by measurement of the Doppler shift in the radio transmissions from a near-Earth satellite, and simple equipment for making the measurements. It also shows that the current information which is needed by the navigator can be reduced to a number containing six decimal digits. Finally, it shows that the computations needed for the navigator to obtain a fix can be performed witlh the aid of tables that can be prepared at least 18 months in advance. Using these tables and a simple slide rule, but no other computational aids, a fix accurate to about 500 meters can be obtained in about 10 minutes. More accuracy can be obtained at the expense of time, or time can be saved at the expense of accuracy.     

Random Characteristics of the Type II Phase-Locked Loop

The results of a study of the characteristics of the second-order Type II phase-locked loop with a Gaussian noise input, and obtained by digital computer simulation, are presented. The digital simulation is described and the random state variables are defined such that their characteristics can be interpreted in terms of existing phase portraits of autonomous phase-locked loops. The statistics associated with the state variables, which are phase error and a measure of frequency error, and those associated with the number of cycles skipped and the mean time to unlock, are given.     

Diversity of Comets: Formation Zones and Dynamical Paths

The past dozen years have produced a new paradigm with regard to the source regions of comets in the early solar system. It is now widely recognized that the likely source of the Jupiter-family short-period comets (those with Tisserand parameters, T > 2 and periods, P, generally < 20 years) is the Kuiper belt in the ecliptic plane beyond Neptune. In contrast, the source of the Halley-type and long-period comets (those with T < 2 and P > 20 years) appears to be the Oort cloud. However, the comets in the Oort cloud almost certainly originated elsewhere, since accretion is very inefficient at such large heliocentric distances. New dynamical studies now suggest that the source of the Oort cloud comets is the entire giant planets region from Jupiter to Neptune, rather than primarily the Uranus-Neptune region, as previously thought. Some fraction of the Oort cloud population may even be asteroidal bodies formed inside the orbit of Jupiter. These comets and asteroids underwent a complex dynamical random walk among the giant planets before they were ejected to distant orbits in the Oort cloud, with possible interesting consequences for their thermal and collisional histories. Observational evidence for diversity in cometary compositions is limited, at best. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genesis on-board determination of the solar wind flow regime

Some of the objectives of the Genesis mission require the separate collection of solar wind originating in different types of solar sources. Measurements of the solar wind protons, alpha particles, and electrons are used on-board the spacecraft to determine whether the solar-wind source is most likely a coronal hole, interstream flow, or a coronal mass ejection. A simple fuzzy logic scheme operating on measurements of the proton temperature, the alpha-particle abundance, and the presence of bidirectional streaming of suprathermal electrons was developed for this purpose. Additional requirements on the algorithm include the ability to identify the passage of forward shocks, reasonable levels of hysteresis and persistence, and the ability to modify the algorithm by changes in stored constants rather than changes in the software. After a few minor adjustments, the algorithm performed well during the initial portion of the mission. This revised version was published online in August 2006 with corrections to the Cover Date.     

Heliosphere-Geosphere Interactions Using Low Energy Neutral Atom Imaging

Development of the low energy neutral atom (LENA) imager was originally motivated by a need to remotely sense plasma heating in the topside ionosphere, with the goal of greatly enhanced temporal resolution of an otherwise familiar phenomenon. During ground test and calibration, the LENA imager was found to respond to neutral atoms with energies well above its nominal energy range of 10–750 eV, up to at least 3–4 keV, owing to sputtering interactions with its conversion surface. On orbit, LENA has been found to respond to a ubiquitous neutral atom component of the solar wind, to the neutral atoms formed by magnetosheath interactions with the geocorona during periods of high solar wind pressure, and to the interstellar neutral atoms flowing through the heliosphere during the season of maximal relative wind velocity between spacecraft and interstellar medium. LENA imaging has thus emerged as a promising new tool for studying the interplanetary medium and its interaction with the magnetosphere, in addition to the ionospheric heating and outflow that result from this interaction. LENA emissions from the ionosphere consist of a fast component that can be observed at high altitudes, and slower components that evidently create a quasi-trapped extended superthermal exosphere. The more energetic emissions are responsive to solar wind energy inputs on time scales of a few minutes.