Digital Commons Network^™

Equatorial F-Regionvertical Plasma Drifts During Solar Maxima, Bela G. Fejer, E. R. De Paula, I. S. Batista, E. Bonelli, R. F. Woodman

Bela G. Fejer

Incoherent scatter radar measurements at Jicamarca are used to study the effects of large solar fluxes and magnetic activity on the F region vertical plasma drifts. The average drifts from the two last solar maxima are almost identical except in the late afternoon-early evening sector where their variations with solar flux and magnetic activity are strongly season dependent. The average evening winter (May-August) drifts appear to remain almost constant after a certain solar flux level is reached but increase with magnetic activity. The equinoctial evening drifts increase systematically with solar-flux but decrease with magnetic activity. Very large prereversal enhancement velocities, …

Nife Invar Alloys: Theoretical Insights Into The Underlying Mechanisms Responsible For Their Physical Properties, Duane D. Johnson, F. J. Pinski, J. B. Staunton, B. L. Gyorffy, G. M. Stocks

Duane D. Johnson

What are the "driving forces" responsible for various physical properties of alloys? What causes alloy systems to order chemically and/or magnetically? To answer these questions, we have been using a quantum mechanical (QM) method to calculate cohesive energies, magnetic properties, and thermodynamic phase instability of alloys. This scheme directly incorporates the inherent disorder of the high-temperature solid solution and in this sense goes beyond traditional "band theory." Although approximations have been made at various steps in the thermodynamical averaging, and in the QM treatment of the electrons, adjustable parameters have not been used. Recently, for FCC NiFe (INVAR) alloys, we …

Phase Transitions In A Driven Lattice Gas With Repulsive Interactions, K.-T. Leung, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

We study a lattice gas with repulsive nearest-neighbor interactions driven to steady state by an external electric field E. Using Monte Carlo techniques on a two-dimensional system, we find, in the E-T plane, a line of second-order transitions joining a line of first-order ones, at a point which is probably tricritical. From a field theoretical model, we show that the operator associated with E is naively irrelevant for critical behavior. This expectation is borne out by the Monte Carlo result β=(1/8.

Effects Of Pollution On Critical Population Dynamics, R. Kree, B. Schaub, Beate Schmittmann

Beate Schmittmann

We investigate the effects of pollution on a population that is on the brink of extinction. In the vicinity of the associated critical point, the temporal scales of the population density fluctuations are found to be completely governed by the diffusive behavior of the pollution density fluctuations. Moreover, the mean value of the population density is found to vanish with a larger power-law exponent in the presence of pollution density fluctuations. Results are obtained within a renormaliza- tion-group calculation to O(ε) (ε=4-d, d being the spatial dimension).

Pitch Of Complex Tones With Many High‐Order Harmonics, Adrianus J. M. Houtsma, J. Smurzynski

Jacek Smurzynski

A Simple Monochromatic Spark Discharge Light-Source, Chin Oi Hoong

Chin Oi Hoong

Spark light illumination has been used in high-speed photog-raphy since the beginning ofthe century and various designs ofthe spark discharge light source have since been reportedr with spark duration ranging from nanoseconds to millisec-onds. We report here a simple and easy to build spark dis-charge tube for operation as a monochromatic point light source. The design and construction ofthe spark discharge tube is shown in Fig. 1. The sharp-tip solid cone anode is made of stainless steel which is screwed onto a brass rod connected A compact spark discharge tube operated as a monochromatic light source at 587.5 nm is …