Large electric fields in the magnetosphere

In several regions of the magnetosphere, perpendicular and/or parallel electric fields are found to be orders-of-magnitude larger than expected from simple considerations. Problems associated with these large fields that may be amenable to study through computer simulations are discussed. Regions in which large electric fields are observed include: a) The auroral ionosphere, where Langmuir soliton-like structures have been measured to contain plasma frequency oscillations as large as 500 mV/m, the envelopes of which have parallel electric fields of 100 mV/m lasting for fractions of a millisecond; b) The auroral acceleration region, where electrostatic shocks have been observed to contain perpendicular fields as large as 1000 mV/m and parallel fields as large as 100 mV/m, and where double layers having parallel fields up to 10 mV/m have been observed; c) The high latitude boundary of the plasma sheet, where turbulent electric fields as large as 100 mV/m have been seen along with quasi-static fields of 5–10 mV/m; d) Inside the plasma sheet, where fields of 5–10 mV/m have frequently been observed; e) The bow shock, where turbulent fields as large as 100 mV/m and d.c. fields of 5 mV/m normal to the shock have been seen.also Physics Department     

Super-ion-beams and advanced target concepts for thermonuclear microbomb rocket propulsion

Expected advances in the generation of ultraintense ion beams with currents above the Alfvén limit will make possible the ignition of neutron-poor advanced thermonuclear reactions suitable for thermonuclear microbomb propulsion. The superbeams can be produced by magnetically insulated multistage pulse accelerators. The high thermonuclear yields as they are desirable for an efficient propulsion system can be obtained by target staging and autocatalytic detonation. This will make possible the fast economical transportation of large payloads within the solar system.     

Gravitational effects on human cardiovascular responses to isometric muscle contractions.

Isometric exercise induces profound cardiovascular adaptations increasing mean arterial pressure and heart rate. We investigated effects of simulated +Gz and -Gz respectively on the central and peripheral cardiovascular system. Sustained handgrip exercise was performed at 40% of maximum for 2 minutes in five subjects. This maneuver increased mean arterial pressure by 40-45 mm Hg both during head out water immersion which simulates weightlessness, as well as bedrest during -25, 0, and +25 degrees tilt from the horizontal. Lower body negative pressure (-60 mm Hg for 10 min) attenuated the response to handgrip exercise to 30 mm Hg. It also increased the heart rate minimally by about 20 beats per minute while the water immersion, as well as head up, head down and horizontal bedrest showed increments of about 50 beats per min. It was concluded that the response to isometric contraction is mediated through the high pressure baroreceptors, because similar responses were seen during stresses producing a wide variation in central venous pressure. During lower body negative pressure the increased sympathetic nervous activity itself increased resting heart rate and mean arterial pressure. The responses to static exercise were, therefore, weaker.     

A large area multitechnique experiment for hard X-ray astronomy

A balloon-borne multitechnique large area experiment consisting of 2 co-aligned detectors (3200 cm² NaI and 1800 cm² multiwire proportional counters), is described, which is capble of producing observations of the hard X-ray sky with very high sensitivity and good spectral resolution over the whole operative range (15–300 keV).     

Experimental Study of the Structures of Macroparticles in the Dust Plasma under Microgravity Conditions onboard the MirOrbital Complex

The dynamics of formation of the ordered structures of charged macroparticles under microgravity conditions is investigated. The experimental observations of the behavior of an ensemble of macroparticles were carried out onboard the Mirspace station. The analysis and comparison of results of experimental and theoretical investigations allow us to conclude that under microgravity conditions the formation of elongated, ordered structures of macroparticles, charged by solar radiation, is possible.     

Digitized mapping: the key to achieving a common command and control picture

One of the main goals in transforming the Army is the process of moving away from the use of paper maps and grease pencils into more embedded and computer-oriented forms of command and control. There are currently many weapons platforms trying to achieve this function; however, each platform is developing their own solution to meet individual needs. The Army as a whole needs to standardize on a single path forward to ensure that all systems can communicate across the digitized battlefield, allow for each platform to have a "common picture," and promote software reuse across the Army. Once this "common picture" is achieved, the armed forces will have the information needed to continue domination of the battlefield.     

Multipath Effects on an Azimuthal Monopulse System

The first topic considered is an analysis of the conditions under which the conventional definition of length of the glistening surface, as given by Beckmann and Spizzichino, is not valid. For some conditions, significant amounts of incoherent scattered power can be received from areas beyond the conventional length. A second topic is the investigation of the effect on azimuthal angular tracking accuracy due to such scattering factors as shadowing, surface height distribution, standard deviation in surface height ?, surface correlation length T, unevenness and inhomogeneity of the terrain, antenna heights, and signal polarization. A number of interesting results have been observed. The amount of additional incoherent power not included under the conventional definition depends on the ratio ?/T, except for the case where both transmitter and receiver are very close to the surface. The trends in the behavior of the glistening surface are similar for vertical or horizontal polarization, for Gaussian or exponential surface height distributions, and for different signal frequencies in the S-band to L-band range.     

An imaging telescope for soft gamma-ray astronomy: The preliminary in-flight tests

A large area (6000 cm²) actively shielded low energy gamma-ray telescope is going to be built by an Anglo-Italian collaboration. The telescope, named ZEBRA, will be capable of producing images of the X and gamma ray sky in the energy range 0.015–20 MeV with an intrinsic angular resolution of a few tenths of a degree. A prototype detector has been built in order to experimentally study the main characteristics of the detection plane. The preliminary results obtained during a balloon flight from Trapani, Sicily in July 1981 are presented.     

The position sensitive low energy detector on board the ZEBRA telescope

In order to improve the low energy capability (15 ÷ 150 KeV) of the balloon borne “ZEBRA” low energy gamma imaging telescope (150 KeV-20 MeV), a large area, high spectral resolution (5% at 60 KeV), low background detector has been designed and is now under development.It consists of two MultiWire Spectroscopic Proportional Counter (SPC), escape gated, that have a sensitive area of 6000 cm², and are placed above the large area array of sodiumiodide position sensitive elements.     

Preliminary analysis of shuttle multispectral radiometer data for Southern Egypt

The Shuttle Multispectral Infrared Radiometer (SMIRR) is a spectroradiometer covering the region from 0.5 to 2.5 μm in 10 channels that acquired data from spots 100 m in diameter along the subspacecraft ground track. It was flown aboard the second flight of the space shuttle Columbia, November 12–14, 1981. Data collected during orbit 16 over southern Egypt show that carbonate rocks, kaolinite, and possibly montmorillonite can be identified by their SMIRR spectral signatures and limited knowledge of the lithologic units present. Detailed analysis of SMIRR data for this area indicates that calcite, kaolinite, and montmorillonite rocks give rise to absorption features that result in characteristic 10 channel spectra.