A survey of two-dimensional electron velocity distributions, f(¾), measured near the earth's bow shock using Los Alamos/Garching plasma instrumentation aboard ISEE 2 is presented. This survey provides clues to the mechanisms of electron thermalization within the shock and the relaxation of both the upstream and downstream velocity distributions. First, near the foreshock boundary, fluxes of electrons having a power law shape at high energies backstream from the shock. Although most often they appear as a monotonically decreasing extension of solar wind distributions in the backward hemisphere along the magnetic field direction, /•, they occasionally appear as a resolved peak in energy. Within the interior of the foreshock, in addition to the hot, isotropic electrons at higher energies, field-aligned depressions in oe (V) are observed at the lowest energies (E • 15 eV) and twin angular peaks centered on/• are observed at intermediate energies (15 eV • E • 45 eV). Such distributions are associated closely with 1-Hz whistler waves. Second, within the shock, cuts through oe(V) along/•, oe(V•), often show single maxima offset toward the magnetosheath by speeds comparable to, but larger than, the upstream thermal speed. When sequences of such distributions ar• observed in a single shock transition, offset speeds increase and peak heights of f(V•) decrease with increasing penetration toward the downstream (magnetosheath) side. Third, magnetosheath distributions generally have flat tops out to an energy, Eo, with maxima substantially lower than that in the solar wind. Occasionally, cuts through f(¾) along/• show one and sometimes two small peaks at the edge of the flat tops making them appear concave upward. The magnetosheath distributions often have strong angular anisotropies which depend on energy. For energies less than Eo, f(V•) > f(V•_) at constant E, whereas for E > Eo, f(V•) < f(V•_). The electron distributions characteristic of these three regions are interpreted as arising from the effects of macroscopic (scale size comparable to or larger than the shock width) electric and magnetic fields and the subsequent effects of microscopic (scale size small in comparison with the shock width) fields. In particular, our results suggest that field-aligned instabilities are likely to be present in the earth's bow shock. 1. INTRODUCTION Much work has been done over the past two decades to understand the physics of collisionless shocks (see e.g., Sagdeer and Galeev [1969], Tidman and Krall [1971], Biskamp [1973], and Galeev [1976]). For any shock above a critical Mach number, Mc, some type of dissipation is necessary to provide a transition between upstream and downstream parameters and satisfy the Rankine-Hugoniot relations [Tidman and Krall , 1971]. Since a collisionless shock has, by definition, a width much less than a mean free path, the dissipation cannot be due to classical collisions. The usual mechanism which is invoked for heating electrons is that of an anomalous, or more precisely, wave-particle dissipation due t...

Large individual differences are commonly found in the behavior of octopuses, even in standardized situations. Octopus rubescens (n = 44) were tested in 3 situations (alerting, threat, and feeding) to quantify this variation. A factor analysis of resulting behaviors isolated 3 orthogonal dimensions of their variability, Activity, Reactivity, and Avoidance, which accounted for 45% of the variance. The similarity of these factors to dimensions of personality in humans and individual differences in animals suggests there may be commonalities in such variation across phyla.

Senescence is a normal stage of an octopus's life cycle that often occurs before death. Some of the following symptoms typify it: lack of feeding, retraction of skin around the eyes, uncoordinated movement, increased undirected activity, and white unhealing lesions on the body. There is inter- and intraspecific variability. Senescence is not a disease or a result of disease, although diseases can also be a symptom of it. Both males and females go through a senescent stage before dying-the males after mating, the females while brooding eggs and after the eggs hatch. There are many aspects of octopus senescence that have not yet been studied. This study discusses the ecological implications of senescence.

Examination of many individual event periods in the ISEE 3 deep tail data set collected in 1982–1983 has suggested that magnetospheric substorms produce a characteristic pattern of effects in the distant magnetotail. ISEE 3 data are appropriate for the study of these effects, since the spacecraft remained relatively fixed within the nominal tail location for long periods. Using auroral electrojet indices (AE and AL) and geostationary orbit particle data to time substorm onsets at earth, we have performed superposed epoch analyses of ISEE 3 and near‐earth data prior to and following substorm expansive phase onsets. Individual events illustrate the wide range of variations possible throughout the magnetosphere, while epoch‐averaged results illustrate the general properties of the deep tail pattern of response to global substorm‐induced dynamical effects. During the growth, or tail energy storage, phase of substorms the distant magnetotail appears to grow diametrically in size, often by many earth radii. Subsequently, about 20–40 min after the substorm expansive phase onset at earth the distant tail undergoes a repeatable sequence of plasma, field, and energetic particle variations as large‐scale plasmoids move rapidly down the tail following their disconnection from the near‐earth plasma sheet.

The principles of oversampling are exploited in a simple beamforming architecture using a single bit delta-sigma (DeltaC) analog to digital converter (A/D) on every channel. The high sampling rate required for the single bit A/D provides adequate delay accuracy for high quality beamforming using elementary sample manipulations. Images produced with this beamformer exhibit significant artifacts directly related to dynamic focusing. However, a simple digital recording technique following delays permits dynamically focused beamforming without degrading image quality. The simplicity of this beamformer compared to conventional methods may facilitate very large channel count or low power beamformers suitable for 1.5-D arrays or portable scanners.