Climate Observations - The Instrumental Record

A survey is given of the available instrumental data for monitoring and analysis of climatic variations. We focus on temperature measurements, both over land and ocean, at the surface and aloft.Over land, the older observations were subject to exposure changes which may not have been fully compensated. The effects of urbanization have been largely avoided in studies of climatic change over the last 150 years. There are few records for pre-1850 outside Europe and eastern North America, and the global network shows a recent decline. Over the ocean, sea surface temperature (SST) has been measured using buckets, engine intakes, hull sensors, buoys, and satellites. Many of these data have been effectively homogenized, but new challenges arise as observing systems evolve. Available SST and marine air temperature datasets begin in the 1850s. The data are concentrated in shipping lanes especially before 1900, and very sparse during the world wars, but additional historical data are being digitized.The radiosonde record is short (40 years) and has major gaps over the oceans, tropics and Southern Hemisphere. Instrumental heterogeneities are beginning to be assessed and removed using physical and statistical techniques. The MSU record is complete but only began in 1979, and is not highly resolved in the vertical: major biases, mainly affecting the lower-tropospheric retrieval, have been reduced as a result of recent analyses.Advanced interpolation or data-assimilation techniques are being applied to these data, but the results must be interpreted with care.     

Initial observations of low energy charged particles near the Earth's bow shock on ISEE-1

We report initial measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-1. ULECA is an electrostatic deflection — total energy sensor consisting of a collimator, deflection analyzer and an array of solid state detectors. The position of a given detector, which determines the energy per charge of an incident particle, together with the measured energy determine the particle's charge state. We find that a rich variety of phenomena are operative in the transthermal energy regime (10 keV/Q to 100 keV/Q) covered by ULECA. Specifically, we present observations of locally accelerated protons, alpha particles, and heavier ions in the magnetosheath and upstream of the Earth's bow shock. Preliminary analysis indicates that the behavior of these locally accelerated particles is most similar at the same energy per charge.     

σ-stability analysis of hydromagnetic instabilities in stars with toroidal magnetic fields

-stability analysis is used to investigate the adiabatic stability of a star containing an axisymmetric toroidal magnetic field. Necessary and sufficient conditions for -stability are derived. Special attention is devoted to the typical hydromagnetic instabilities that can be introduced by a weak toroidal magnetic field in a star that is stably stratified in the absence of any magnetic field. An expression for the maximum growth rate of instability is derived and the basic properties of the displacement fields associated with the instabilities are indicated.     

Crossarray Beamforming with a Parametric Receiving Array and a Line Array

A beamforming technique involving cross correlation of the outputs of two directional arrays is investigated. The performance characteristics of the crossarray system are determined and related to the characteristics of the two individual arrays. It is found that the crossarray beam pattern is the average (in decibels) of the beam patterns of the individual arrays, and that the crossarray gain (rejection of spatially distributed noise) is 1.5 dB greater than the average (in decibels) of the individual array gains. The most interesting applications for this system may be those where the two arrays are quite different, as in the case of a parametric acoustic receiving array (PARRAY) and a broadside line array.     

X-Ray spectroscopic investigation of the coronal structure of capella

The binary system Capella (G6 III + F9 III) has been observed on 1979 March 15 and on 1980 March 15–17 with the Objective Grating Spectrometer (OGS) onboard theEinstein Observatory. The spectrum measured with the 1000 l/mm grating covers the range 5–30 Å with a resolution < 1 Å. The spectra show evidence for a bimodal temperature distribution of emission measure in an optically thin plasma with one component 5 million degrees and the other one 10 million degrees. Spectral features can be identified with line emissions from O VIII, Fe XVII, Fe XVIII, Fe XXIV, and Ne X ions. Good spectral fits have been obtained assuming standard cosmic abundances. The data are interpreted in terms of emission from hot static coronal loops rather similar to the magnetic arch structures found on the Sun. It is shown that the conditions required by this model exist on Capella. Mean values of loop parameters are derived for both temperature components.     

Self-Cohering an Airborne e Radio Camera

By distributing antenna elements or small subarrays throughout the skin of an aircraft, a large portion of the airframe can act as an electromagnetic transducer. The basic problem associated with such a design is that uncertainties in element locations due to the nonrigidness of the airframe induce phase errors. Self-cohering techniques are required to compensate for those errors. Four such techniques are presented here.     

The long term variability of 4U 1258-61 (GX304-1)

We present optical spectroscopy and photometry of 4U 1258-61 obtained over the course of six years. Evidence for the evolution of a circumstellar envelope throughout the course of the observations is presented.     

Voyager 2 Solar Wind Observations in the Outer Heliosphere

We discuss the solar wind parameters measured in the distant heliosphere from the Voyager 2 spacecraft. Periodic variations in the speed of the wind observed at roughly the solar rotation period may correspond to interaction regions between slower and faster streams of wind. Since the interplanetary magnetic field is enhanced in such regions, they are important for the study of modulation of cosmic rays. Unfortunately, direct observation of the enhanced magnetic field from Voyager 2 has been made difficult by spacecraft-associated noise since 1989.     

Experiments in Adaptive Estimation of Unknown Binary Waveforms

A special-purpose adaptive machine is described which carries out estimation in real time of an unknown binary waveform which is perturbed with additive Gaussian noise. Unknown waveforms of over 103 samples in duration can be recovered. The unknown waveforms are of unknown epoch and can reappear at either random or periodic time intervals. The observed signal is received at moderate or low signal-to-noise ratios so that a single observation of the received data (even if one knew the precise signal arrival time) is not sufficient to provide a good estimate of the signal waveshape. Experimental results are described which show transient behavior waveform estimate. The transient behavior is expressed as the number of errors in the current estimate of the signal plotted vs. time. In a noisy environment, each ``learning' transient is a random time function. These learning transients are shown for several different signal-to-noise ratios and indicate the threshold noise levels for various types of initial states of the machine memory.