The generation of DC and AC electric fields, and electron fluxes in a rocket experiment with barium injection in the auroral ionosphere

The results of an active rocket experiment with barium injection in the auroral ionosphere designed to check possible scenario of the initial phase of substorm are presented and discussed.     

Small Scale Alfvénic Structure in the Aurora

This paper presents a comprehensive review of dispersive Alfvén waves in space and laboratory plasmas. We start with linear properties of Alfvén waves and show how the inclusion of ion gyroradius, parallel electron inertia, and finite frequency effects modify the Alfvén wave properties. Detailed discussions of inertial and kinetic Alfvén waves and their polarizations as well as their relations to drift Alfvén waves are presented. Up to date observations of waves and field parameters deduced from the measurements by Freja, Fast, and other spacecraft are summarized. We also present laboratory measurements of dispersive Alfvén waves, that are of most interest to auroral physics. Electron acceleration by Alfvén waves and possible connections of dispersive Alfvén waves with ionospheric-magnetospheric resonator and global field-line resonances are also reviewed. Theoretical efforts are directed on studies of Alfvén resonance cones, generation of dispersive Alfvén waves, as well their nonlinear interactions with the background plasma and self-interaction. Such topics as the dispersive Alfvén wave ponderomotive force, density cavitation, wave modulation/filamentation, and Alfvén wave self-focusing are reviewed. The nonlinear dispersive Alfvén wave studies also include the formation of vortices and their dynamics as well as chaos in Alfvén wave turbulence. Finally, we present a rigorous evaluation of theoretical and experimental investigations and point out applications and future perspectives of auroral Alfvén wave physics.     

Responses to satellite remote sensing opportunities in East and Southern Africa

Since 1978 the U.S. Agency for International Development (USAID) has funded a regional remote sensing project for East and Southern Africa. The project, hosted by the Regional Centre for Services in Surveying Mapping and Remote Sensing, has provided a programme of training courses, user services and project support. This included the equipping and establishment of a photo-laboratory complex for processing Landsat images and the provision of advice and support for agencies undertaking natural resources analysis.Response to the training programme has been very good. Courses are usually over subscribed and there is a continued demand for training. Assessments of the courses by participants are highly positive and the courses have featured consultants of international calibre. Requests for follow-up courses, and for specialist group training indicate a strong response to this training activity. User services are active, consultations with staff, use of the browse file and interpretation equipment and the purchase of data for project work all produce an average demand of 12 active enquiries per working week. The photo-laboratory is particularly active and demand for products exceeds available capacity.Project work is now being supported but limited resources restrict the range and amount of project activity. Response to the opportunities offered for projects has been favourable and this activity is ripe for expansion. The difficulty in expanding to meet the expressed demand is primarily financial. The east and southern Africa region is not economically strong and has a great need for natural resources data for development work and planning. The responses to satellite remote sensing opportunities will be limited by these financial constraints which effectively means by the level of international aid directed to this activity. For such aid to be effective it must be coordinated and firmly attached to the region. Such coordinated aid programmes would avoid fragmentation of distribution and applications work. Fragmentation could seriously disrupt the present growth in natural resources activity based on remote sensing data from satellites. The lack of financing for a regional ground receiving station is also a significant limiting factor.     

Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity.

Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.     

Immediate and long-term prospects for helioseismology

Recent extensive measurements of frequencies of free oscillation of the Sun have permitted a first direct estimate of the variation of sound speed and angular velocity throughout the Sun. The results hint that the answers to some tantalizing questions concerning the Sun's interior structure and its history are almost within grasp. Optimists like myself believe that in a few years a worldwide network of ground-based observing stations will give us important clues. However, it may be necessary to make observations from space before we can be sure of the answers.     

New architectures for space power systems

Electric power generation and conditioning have experienced revolutionary development over the past two decades. Furthermore, new materials such as high energy magnets and high temperature superconductors are either available or on the horizon. Our work is based on the premise that new technologies are an important driver of new power system concepts and architectures. This observation is borne out by the historical evolution of power systems both in terrestrial and aerospace applications. This paper introduces new approaches to designing space power systems by using several new technologies. Two new architectures are introduced: the current source current intensive system and the articulate system. Basic characteristics of these systems have been investigated. Some aspects of the articulate system architecture, as discussed in this paper can be implemented in the short term. Flexible AC transmission systems which are now undergoing rapid development and implementation, can be regarded as a subset of the family of control methodologies which constitute the realm of articulate systems     

A new facility for fluid sciences: The liquid structure facility

The Liquid Structure Facility (LSF) is presently under development under ESA contract. It will be able to perform a wide range of fluid science experiments taking use of the determination of the velocity, temperature, concentration fields and the interface shape deformation. This facility will be activated by telecommands and/or manually by the crew. The key points of the LSF are the different diagnostic configuration capabilities, the modularity of the facility, and the accuracy of the control at the boundary conditions (and thus of the stimuli). The LSF is structured around four different modules:

• —the cell module which is exchangeable and is dedicated to an experiment or to a group of experiments, it allows to achieve a high accuracy level for the boundary conditions

• —the temperature control module using a liquid cooling loop which can impose a good thermal stability to the cell module

• —the diagnostic module

• —the electronic and data handling module.

The capabilities of the facility are described in terms of stimuli and diagnostic performances.     

The San Andreas fault experiment

Two NASA laser satellite tracking systems on opposite sides of the San Andreas fault will be used in an experiment to measure the gross relative motion of the tectonic plates of North America and the Pacific during the next several years. Initial sites at San Diego on the Pacific Plate and Quincy, California, on the North American Plate, nearly 900 km apart, have already been selected and occupied, and other sites further south are proposed. Each site is occupied for two or three months per year and simultaneous precision laser distance measurements to the Beacon Explorer-C satellite from these sites will be used to determine the relative position of one site with respect to the other. Results of a simulation of this experiment in which a pair of sites are reoccupied annually for about eight years indicate an eventual accuracy of about 0.5 cm/yr in the average plate motion. The results of a preliminary three-month observing period in 1972 indicate a precision of about 15 cm in the chord distance between the San Diego and Quincy sites.