Juan G. Roederer

Global problems in magnetospheric plasma physics and prospects for their solution

Selected problems of magnetospheric plasma physics are critically reviewed. The discussion is restricted to questions that are ‘global’ in nature, i.e., involve the magnetosphere as a whole, and that are beyond the stage of systematic survey or isolated study requirements. Only low-energy particle aspects are discussed. The article focuses on the following subjects: (i) Effect of the interplanetary magnetic field on topography, topology and stability of the magnetospheric boundary; (ii) Solar wind plasma entry into the magnetosphere; (iii) Plasma storage and release mechanisms in the magnetospheric tail; (iv) Magnetic-field-aligned currents and magnetosphere-ionosphere interactions. A brief discussion of the prospects for the solution of these problems during and after the International Magnetospheric Study is given.

On the relationship between human brain functions and the foundations of physics, science, and technology

The objective of this paper is to discuss the relationship between the functional properties and information-processing modes of the human brain and the evolution of scientific thought. Science has emerged as a tool to carry out predictive operations that exceed the accuracy, temporal scale, and intrinsic operational limitations of the human brain. Yet the scientific method unavoidably reflects some fundamental characteristics of the information-acquisition and -analysis modes of the brain, which impose a priori boundary conditions upon how science can develop and how the physical universe can be “understood.” A brief description of physical and biological interactions is given, with emphasis on the defining role played by the concept of information. Current views on the information-processing and information-generating mechanisms of the human brain are briefly reviewed. It is shown how some particular features of superstition, natural philosophy, physical thought, and intuition can be linked to certain characteristic information-processing modes of the brain. A discussion is given of how greatly expanded knowledge of brain functions might affect the future of science and technology.

The international magnetospheric study

Abstract During the past 15 years, the study of the earths magnetosphere—mans immediate plasma and radiation environment—has undergone a successful stage of discovery and exploration. We have obtained a morphological description of the magnetospheric field, the particle population embedded in it, and its interface with the solar wind, and we have identified and are beginning to understand many of the physical processes involved. Quite generally, the magnetosphere reveals itself as a region where we can observe some of the fundamental plasma processes at work that are known to occur elsewhere in the universe. Time has come now for a transition from the exploratory stage to one in which satellite missions and ground-based, aircraft, balloon, and rocket observations are planned with the specific objective of achieving a quantitative understanding of the physical processes involved. Some of the principal targets of current research are: the electric field in the magnetosphere, the dynamics of the two main plasma reservoirs (plasmasphere and plasmasheet) and their boundaries, the interaction between trapped particles and waves, the transfer of particles, energy and momentum from the solar wind to the magnetosphere and from there into the ionosphere, and the development of a fundamental instability, the magnetospheric “substorm.” It is expected that the International Magnetospheric Study 1976–1978 will solve many of the problems involved, particularly those related to the timing of dynamical changes during substorms, the identification of spatial locations for these changes, the nature of magnetospheric boundaries and the energy budget in the solar wind-magnetosphere-ionosphere system.

Auditory Processing in the Nervous System

In this review we shall discuss some relevant aspects of the auditory nervous system and the mechanisms which are believed to play a role in the processing of acoustical information. We will mainly focus on the effects of musical tones,1 leaving out speech and noise forms. As compared to language, musical tones are simpler input signals, and their processing requires fewer cooperative actions by, and associations in, other regions of the brain. Hence, they are more appropriate stimuli for the exploration of the fundamental primary processes that operate in the auditory system from periphery to the cortex.

Superposition and Successions of Complex Tones and the Perception of Music

In the course of Chapters 2, 3, and 4 we have been moving gradually up the ladder of neural processing of acoustical signals, from the mechanisms leading to the perception of primary pitch, loudness, subjective pitch, and timbre, and to the recognition of a musical instrument. On the physical side, we have analyzed how the sound characteristics leading to these sensations are actually generated in musical instruments. These psychological attributes are necessary, but by no means sufficient, ingredients of music. Music is made of successions and superpositions of tones that convey certain meanings (Gestalt) which can be analyzed, stored, and compared in the brain. An objective study of the neuropsychology of these higher order processes is practically nonexistent. The reader no doubt already has sensed how much guesswork was involved in the discussion of the perception of timbre (Section 4.8). We are in much worse shape when it comes to the higher psychological attributes such as consonance, dissonance, the sense of tonality and return, and, in the end, the whole gamut of emotional reactions to music.

Music, Physics, and Psychophysics: An Interdisciplinary Approach

Imagine yourself in a concert hall listening to a soloist performing. Let us identify the systems that are relevant to the “music” you hear. First, obviously, we have the player and the instrument that “makes” the music. Second, we have the air in the hall that transmits the sound into all directions. Third, there is you, the listener. In other words, we have the chain of systems: instrument→air→listener. What links them while music is being played? A certain type and form of vibrations called sound which propagate from one point to another in the form of waves and to which our ear is sensitive. (There are many other types and forms of vibrations that we cannot detect at all, or that we may detect, but with other senses such as touch or vision.)

The Magnetospheric Electric Field

Considerable progress has been made in recent years in the study of the electric field of the magnetosphere. This electric field is quite difficult to measure because of its weakness (millivolts per meter or less) and high variability in time and space. Direct measurements from satellites have begun only in recent years (Heppner, 1972a); indirect techniques based on the study of energetic particle motion (McDiarmid et al., 1969; Roederer and Hones, Jr., 1970; DeForest and McIlwain, 1971) and drifts of natural (Carpenter et al., 1972) for artificial (Haerendel, 1972) plasmas have been historically the first to provide information on the electric field. Balloon-borne measurements (Mozer, 1971) of the horizontal component of the stratospheric electric field — assumed to be roughly proportional to the horizontal electric field in the overlying ionosphere — are becoming an increasingly popular and relatively cheap technique, particularly useful if carried out simultaneously over periods of many hours at different geographic locations.

Trapped Particle Population Changes Associated with Solar Events

Trapped particle population changes associated with solar events are caused by the effects of solar wind discontinuities on the magnetosphere. The most drastic sequence of such time variations occurs during a magnetospheric storm.