X-rays from quasars and active galaxies

We review some of the most important theoretical ideas and observations for quasars and the nuclei of active galaxies, and suggest areas of future research. Emphasis is on the nature of the power source, the radiation processes, and the mechanism for formation and collimation of jets. Phenomena that produce X-rays are of particular concern. Particular topics discussed are the observed and expected time variability, the gas supply mechanisms and luminosity evolution, thermal and nonthermal radiation processes, observed and theoretical spectra, criteria for thermalization of electrons and ions, effects of electron-positron pairs on relativistic plasmas, hydrodynamic, electrodynamic and inertial methods for producing and confining jets. We conclude with a list of needed observations.Based on a lecture given at the Goddard Workshop on X-ray Astronomy (October 1981).     

On the role of meteoritic impacts in the formation of organic molecules

It is suggested that the UV radiation, and shock and plasma phenomena which accompanied the hypervelocity impacts of solid bodies (meteorites and comets) onto the surface of the young Earth may have contributed to the synthesis of prebiotic organic molecules in the primitive atmosphere in a larger amount than was thought previously. The mechanisms responsible for this synthesis are discussed using information obtained from recent experimental and theoretical work on macroscopic hypervelocity impacts.     

Dynamic considerations for control of closed life support systems

Reliability of closed life support systems will depend on their ability to continue supplying the crew's needs in the face of perturbations and equipment failures. These dynamic considerations interact with the basic static (equilibrium) design through the sizing of storages, the specification of excess capacities in processors, and the choice of system initial state (total mass in the system). This paper uses a very simple system flow model to examine the possibilities for system failures even when there is sufficient storage to buffer the immediate effects of the perturbation. Two control schemes are shown which have different dynamic consequences in response to component failures.     

Advanced regenerative environmental control and life support systems: Air and water regeneration

Extended manned space missions will require regenerative life support techniques. Past U.S. manned missions used nonregenerative expendables, except for a molecular sieve-based carbon dioxide removal system aboard Skylab. The resupply penalties associated with expendables becomes prohibitive as crew size and mission duration increase. The U.S. Space Station, scheduled to be operational in the 1990's, is based on a crew of four to sixteen and a resupply period of 90 days or greater. It will be the first major spacecraft to employ regenerable techniques for life support. The paper uses the requirements for the Space Station to address these techniques.     

The microlesion concept in HZE particle dosimetry.

High energy, high-Z (HZE) particles are present in high-altitude and high-inclination satellite orbits. Most of the HZE dose above LET = 200 keV/micrometer is due to Fe nuclei. Individual HZE particles can damage several cells adjacent to one another along the particle track in tissue. The outcome has been described as a "microlesion" by D. Grahn. The present study attempts to define conditions for microlesions in specific tissues, to seek biological evidence that microlesions are produced, and to evaluate the microlesion as a potentially useful unit of dose in assessing hazards to spaceworkers. Microlesions in individuals cells and hair follicles have been described. Microbial studies have provided some evidence for independent secondary electron action. Whether or not a few hundred microlesions would be damaging to the whole organism depends upon the nature of damage to critical tissues. For example, cancer may occur if microlesions kill several cells in a straight line and mutate other cells alongside the particle track. Fe particle irradiation of the mouse Harderian gland (Fry et al., this issue) produces tumors efficiently. Microlesions in the lens, cornea, and retina need to be considered. Further dialogue is required before a final decision can be made concerning the most appropriate way to assess the HZE hazard.     

Balloon altitude studies of southern hemisphere hard X-ray sources by the Imperial College-University of Tasmania-INPE collaboration

Hard X-ray balloon altitude measurements with a 1600 cm² phoswich array are described. Data from observations on Sco X-1, GX1+4, GX5−1, Nova Oph. 1977, SMC X-1, SS433, IC 4329A and MR 2251-178 are presented. The role of Comptonisation in X-ray production for Sco X-1 and GX1+4 is discussed.     

Physical processes in the strong magnetic fields of accreting neutron stars

The key radiative processes are discussed, numerical methods of magnetized radiative transfer are presented, and these are considered in their application to X-ray pulsar models.     

Long period magnetospheric oscillations at discrete frequencies: The results of a multi-station analysis

A multi-station analysis of geomagnetic field measurements conducted for a remarkable case event, at a European and an American array shows that, although several aspects of the geomagnetic field observations show a clear latitudinal and local time dependence, simultaneous oscillations at discrete frequencies (f ≈ 1.0, 1.3, 2.2 and 3.2 mHz) are almost ubiquitously detected, from low to high latitudes both in the light and dark sector. They are driven by fluctuations of the solar wind density and dynamic pressure at the same frequencies, via the modulation of the magnetopause current. We also report clear evidence for the occurrence of resonant coupling (at f ≈ 2.2 and 3.2 mHz) between such modes and high latitude field lines. Due to the variable length of the field line through the day, oscillation modes at the same frequencies resonate at different latitudes in the daytime and nighttime region, respectively.     

A comparative and numerical study of effects of gravity waves in small miss-distance and miss-time GPS radio occultation temperature profiles

The Global Positioning System (GPS) Radio Occultation (RO) technique has global coverage and is capable of generating high vertical resolution temperature profiles of the upper troposphere and lower stratosphere with sub-Kelvin accuracy and long-term stability, regardless of weather conditions. In this work, we take advantage of the anomalously high density of occultation events at the eastern side of the highest Andes Mountains during the initial mission months of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate). This region is well-known for its high wave activity. We choose to study two pairs of GPS RO, both containing two occultations that occurred close in time and space. One pair shows significant differences between both temperature profiles. Numerical simulations with a mesoscale model were performed, in order to understand this discrepancy. It is attributed to the presence of a horizontal inhomogeneous structure caused by gravity waves.     

The radiation environment in the ISS-USLab measured by ALTEA: Spectra and relative nuclear abundances in the polar,equatorial and SAA regions

We present here the energy spectra relative to different geomagnetic regions as measured by the ALTEA (Anomalous Long Term Effects on Astronauts) detector in the International Space Station – USLab from August 2006 to July 2007.