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Full-Text Articles in Physics

Auroral E-Region Plasma Waves Andelevated Electron Temperatures, Bela G. Fejer, J. Providakes, D. T. Farley, W. E. Swartz Dec 1986

Auroral E-Region Plasma Waves Andelevated Electron Temperatures, Bela G. Fejer, J. Providakes, D. T. Farley, W. E. Swartz

Bela G. Fejer

We have observed 3-m auroral E region plasma waves with a high-resolution 50-MHz radar interferometer at Ithaca. During postmidnight periods of very strong magnetic activity at Ottawa (L = 3.5), the backscattered power and Doppler spectra vary rapidly with time and range and may have both mean Doppler shifts and half power widths in excess of 200 Hz (600 m/s). In addition, when the radar and magnetometer data imply that the current is approximately parallel to the radar line of sight, sharp spectral peaks corresponding to phase velocities approaching 1 km/s sometimes appear suddenly. These persist for at ...


Symmetric Solutions To The Maximally Gauss-Bonnet Extended Einsteinequations, James Thomas Wheeler Sep 1986

Symmetric Solutions To The Maximally Gauss-Bonnet Extended Einsteinequations, James Thomas Wheeler

All Physics Faculty Publications

The most general gravitational lagrangian which can be constructed from the curvature two-form, the vielbein one-form, and tensors invariant in the tangent space is a linear combination of dimensionally extended Euler characteristics. Several recent studies indicate that superstring lagrangians include such terms. In an arbitrary number of dimensions, with arbitrary torsion, we show that in the most general such extended theory the only static, spherically symmetric, massive solutions to the variational equations of motion contain gravitational singularities. The existence of an event horizon is proved for certain cases, and a bound on the location of singularities is found. A certain ...


On The Kinetics Of Thermal Donor Formation In Silicon, J T. Borenstein, J W. Corbett, David Peak Aug 1986

On The Kinetics Of Thermal Donor Formation In Silicon, J T. Borenstein, J W. Corbett, David Peak

All Physics Faculty Publications

A model for the kinetic growth of oxygen-related thermal donors in Czochralski silicon at about 450°C is presented. The model, which is based on the work of Suezawa and Sumino, derives forward reaction rates for the electrically active species by comparing analytic expressions for the early-time annealing kinetics with the infrared electronic absorption data. The analytic expressions, which are independent of the chemical structure of each species, result from three assumptions: (1) the donor defects beyond the first donor species (TD-1) are chemically stable at the donor formation temperature, (2) the reactions for the TD-1 and those electrically inactive ...


Surface-Reconstruction-Induced Changes In Free-Carrier Scattering From The W(100) Surface: Aninfrared Surface-Electromagnetic-Wave Study, D. Mark Riffe, L. M. Hanssen, A. J. Sievers Jul 1986

Surface-Reconstruction-Induced Changes In Free-Carrier Scattering From The W(100) Surface: Aninfrared Surface-Electromagnetic-Wave Study, D. Mark Riffe, L. M. Hanssen, A. J. Sievers

All Physics Faculty Publications

Using the infrared-absorption technique of surface-electromagnetic-wave spectroscopy (SEWS) we have studied the effects of H2 and D2 chemisorption on the SEW attenuation coefficient α in the 10-μm region between 165 and 350 K. The change in α at room temperature has also been measured for N2, O2, and CO adsorption. The coverage (CTHETA) dependence of α for N2, O2, and CO is fairly simple [either a monotonic increase (N2) or a peak at some intermediate coverage (O2, CO)] and points to changes in free-carrier (FC) surface scattering as the dominant α-changing mechanism ...


Symmetric Solutions To The Gauss-Bonnet Extended Einstein Equations, James Thomas Wheeler May 1986

Symmetric Solutions To The Gauss-Bonnet Extended Einstein Equations, James Thomas Wheeler

All Physics Faculty Publications

Low-energy limits of string theories suggest that gravity lagrangians should include quadratic and higheorder curvature terms, in the form of dimensionally continued Gauss-Bonnet densities. In an arbitrary number of dimensions, we consider the static, spherically symmetric solutions to the lowest order Gauss-Bonnet extended Einstein equations. We also find isotropic, homogeneous cosmological solutions with an ideal fluid source.


Solar- Terrestrial Physics: A Space Age Birth, R. W. Schunk May 1986

Solar- Terrestrial Physics: A Space Age Birth, R. W. Schunk

USU Faculty Honor Lectures

Solar- Terrestrial Physics, in its broadest sense, is concerned with the transport of energy, particles, and fields from the sun to the earth and their consequent effect on the terrestrial environment. Most of the solar energy eventually deposited in our atmosphere, at a rate of approximately a trillion megawatts, arrives in the form of visible light. The study of how this energy affects our environment falls within the purview of meteorology, a discipline that has experienced an independent development and that has sufficiently different problems from solar-terrestrial physics that it can be regarded as a separate but neighboring discipline. In ...


The Condorequatorial Spread-F Campaign: Overview And Results Of The Large-Scale Measurements, M. C. Kelley, J. Labelle, E. Kudeki, Bela G. Fejer, S. Basu, Su. Basu, K. D. Baker, C. Hanuise, P. Argo, R. F. Woodland, W. E. Swartz, D. T. Farley, J. W. Meriwether May 1986

The Condorequatorial Spread-F Campaign: Overview And Results Of The Large-Scale Measurements, M. C. Kelley, J. Labelle, E. Kudeki, Bela G. Fejer, S. Basu, Su. Basu, K. D. Baker, C. Hanuise, P. Argo, R. F. Woodland, W. E. Swartz, D. T. Farley, J. W. Meriwether

Bela G. Fejer

During the Condor campaign a number of instruments were set up in Peru to support the rocket experiments. In this series of papers we report on the results of the experiments designed to study the equatorial F region. In this overview paper we summarize the main results as well as report upon the macroscopic developments of spread F as evidenced by data from backscatter radars, from scintillation observations, and from digital ionosonde meaurements. In this latter regard, we argue here that at least two factors other than the classical gravitational Rayleigh-Taylor plasma instability process must operate to yield the longest-scale ...


Gigahertz Scintillations And Spaced Receiver Drift Measurements During Project Condorequatorial F-Region Rocket Campaign In Peru, S. Basu, Sa. Basu, J. Labelle, E. Kudeki, Bela G. Fejer, M. C. Kelley, H. E. Whitney May 1986

Gigahertz Scintillations And Spaced Receiver Drift Measurements During Project Condorequatorial F-Region Rocket Campaign In Peru, S. Basu, Sa. Basu, J. Labelle, E. Kudeki, Bela G. Fejer, M. C. Kelley, H. E. Whitney

Bela G. Fejer

Radar backscatter at 50 MHz, rocket, and VHF/GHz scintillation measurements of spread F irregularities at the magnetic equator in Peru were made during the Project Condor campaign in March 1983. The paper discusses the coordinated set of observations on two evenings, March 1 and March 14, 1983, when the altitude of the F region peak differed by more than 150 km. The full complement of equatorial spread F phenomena, namely, the occurrence of 3-m plume structures and VHF/GHz scintillations, were recorded on both these evenings. It was found that the radar backscatter with extended plumes occurs in association ...


The Prereversal Enhancement Of Thezonal Electric Field In The Equatorial Ionosphere, D. T. Farley, E. Bonelli, Bela G. Fejer, M. F. Larsen Jan 1986

The Prereversal Enhancement Of Thezonal Electric Field In The Equatorial Ionosphere, D. T. Farley, E. Bonelli, Bela G. Fejer, M. F. Larsen

Bela G. Fejer

The electric fields in the ionospheric E and F regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward (normally) daytime field reverses to westward. Several theoretical models of the low-latitude fields suggest that this enhancement is caused mainly or entirely by F region winds (the F region dynamo), but some authors have suggested that it could be produced solely by E region tidal winds. We give here additional calculations and arguments in support of the F region source. The enhancement of the eastward field for an eastward F region wind turns ...


Comparison Of Simultaneous Chatanika And Millstone Hill Observations With Ionospheric Model Predictions, C. E. Rasmussen, Robert W. Schunk, Jan Josef Sojka, V. B. Wickwar, O. De La Beaujardiere, J. Foster, J. Holt, D. S. Evans, E. Nielsen Jan 1986

Comparison Of Simultaneous Chatanika And Millstone Hill Observations With Ionospheric Model Predictions, C. E. Rasmussen, Robert W. Schunk, Jan Josef Sojka, V. B. Wickwar, O. De La Beaujardiere, J. Foster, J. Holt, D. S. Evans, E. Nielsen

All Physics Faculty Publications

As part of the MITHRAS program, the Chatanika and Millstone Hill incoherent-scatter radars made coordinated observations of the polar ionosphere on June 27 and 28, 1981. We compare these data with predictions made by a high-latitude ionospheric model. Qualitatively, the same features are evident in both the model and the radar data: fairly constant densities on the dayside with a mid-latitude trough forming poleward of 65 degrees around 1900 MLT (magnetic local time). This trough is seen to extend equatorward with increasing MLT, such that the minimum densities occurring in the trough appear just after midnight around 60 degrees dipole ...


Comparison Of Simultaneous Chatanika And Millstone Hill Observations With Ionospheric Model Predictions, C E. Rasmussen, R W. Schunk, J J. Sojka, Vincent B. Wickwar, O De La Beaujardiere, J Foster, J Holt, D S. Evans, E Nielsen Jan 1986

Comparison Of Simultaneous Chatanika And Millstone Hill Observations With Ionospheric Model Predictions, C E. Rasmussen, R W. Schunk, J J. Sojka, Vincent B. Wickwar, O De La Beaujardiere, J Foster, J Holt, D S. Evans, E Nielsen

All Physics Faculty Publications

As part of the MITHRAS program, the Chatanika and Millstone Hill incoherent-scatter radars made coordinated observations of the polar ionosphere on June 27 and 28, 1981. We compare these data with predictions made by a high-latitude ionospheric model. Qualitatively, the same features are evident in both the model and the radar data: fairly constant densities on the dayside with a mid-latitude trough forming poleward of 65 degrees around 1900 MLT (magnetic local time). This trough is seen to extend equatorward with increasing MLT, such that the minimum densities occurring in the trough appear just after midnight around 60 degrees dipole ...


Infrared Surface-Wave Interferometry On W(100), L. M. Hanssen, D. Mark Riffe, A. J. Sievers Jan 1986

Infrared Surface-Wave Interferometry On W(100), L. M. Hanssen, D. Mark Riffe, A. J. Sievers

All Physics Faculty Publications

An IR grating on a clean W(100) surface is shown to generate both homogeneous and inhomogeneous surface electromagnetic waves. An observed interference between these two components, which can be described in terms of a two-beam interferometer with variable arm amplitude and fixed optical path, is used to measure the plasma frequency accurately in the IR.


Crossover From Contact Propagation To Chemical Propagation In First-Passage Percolation, A. R. Kerstein, Boyd F. Edwards Jan 1986

Crossover From Contact Propagation To Chemical Propagation In First-Passage Percolation, A. R. Kerstein, Boyd F. Edwards

All Physics Faculty Publications

On lattices whose bonds are assigned time delays from a bimodal distribution with modes at b and a≫b whose relative weights are p and 1-p, the dependence of the first-passage velocity v on p is investigated by means of scaling arguments and computations. As p increases, v exhibits a sharp rise near the percolation threshold due to a crossover from the contact-propagation regime, in which slow-bond crossings are rate limiting, to the chemical-propagation regime, in which the tortuosity of the shortest path through the fast-bond network is rate limiting. Previous analyses of criticality in the limit a/b→∞ are ...


Problems With Deducing Ionospheric Plasma Convection Patterns, Jan Josef Sojka, Robert W. Schunk Jan 1986

Problems With Deducing Ionospheric Plasma Convection Patterns, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

It is well-known that convection electric fields have an important effect on the ionosphere-thermosphere system at high latitudes and that a quantitative understanding of their effect requires a knowledge of the plasma convection pattern. Consequently, convection electric fields have been measured by a variety of techniques, including satellite, rocket, and balloon-borne probes, optical tracking of ionized barium clouds, incoherent scatter observations of drifting F region plasma, and coherent scatter observations of drifting E region irregularities. Since all of these measurement techniques provide information on only a limited spatial region at any time, the construction of the overall convection pattern requires ...


Formation Kinetics Of Thermal Donors In Silicon, J T. Borenstein, J W. Corbett, David Peak Jan 1986

Formation Kinetics Of Thermal Donors In Silicon, J T. Borenstein, J W. Corbett, David Peak

All Physics Faculty Publications

The kinetics of thermal donor formation in Czochralski-silicon at ca. 450° C are explained by a simple model based on the work of Suezawa and Sumino which derives forward and reverse reaction rates for each electrically active species from the general features of the infrared electronic absorption spectra. The model, which is independent of the chemical nature of the thermal donor core, assumes that all thermal donors beyond the first donor species are chemically stable at the donor formation temperature, and approximates the reactions for species smaller than the first thermal donor as being in chemical equilibrium. The model is ...


Theoretical Study Of The Electron Temperature In The High-Latitude Ionosphere For Solar Maximum And Winter Conditions, Robert W. Schunk, Jan Josef Sojka, M. D. Bowline Jan 1986

Theoretical Study Of The Electron Temperature In The High-Latitude Ionosphere For Solar Maximum And Winter Conditions, Robert W. Schunk, Jan Josef Sojka, M. D. Bowline

All Physics Faculty Publications

The electron temperature (Te) variation in the high-latitude ionosphere at altitudes between 120 and 800 km has been modeled for solar maximum, winter solstice, and strong magnetic activity conditions. The calculated electron temperatures are consistent with the plasma densities and ion temperatures computed from a time-dependent ionospheric model. Heating rates for both solar EUV and auroral precipitation were included. In general, the predicted UT variation of the electron temperature that results from the displacement between the magnetic and geographic poles is only a few hundred degrees. However, in sunlit trough regions, Te hot spots develop, and these hot ...


Effects Of Different Convection Models Upon The High-Latitude Ionosphere, C. E. Rasmussen, Robert W. Schunk, Jan Josef Sojka Jan 1986

Effects Of Different Convection Models Upon The High-Latitude Ionosphere, C. E. Rasmussen, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

It is well known that convection electric fields have an important effect on the ionosphere at high latitudes and that a quantitative understanding of their effect requires a knowledge of plasma convection over the entire high-latitude region. Two empirical models of plasma convection that have been proposed for use in studying the ionosphere are the Volland and Heelis models. Both of these models provide a similar description of two-celled ionospheric convection, but they differ in several ways, in particular, in the manner in which plasma flows over the central polar cap and near the polar cap boundary. In order to ...


A Theoretical Study Of The Production And Decay Of Localized Electron Density Enhancements In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk Jan 1986

A Theoretical Study Of The Production And Decay Of Localized Electron Density Enhancements In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

The origins, transport, and decay of large-scale (≳ 10 km) F region density irregularities were theoretically studied using a high-latitude time dependent ionospheric model. Such density irregularities (blobs) have been found both in the polar cap and the auroral zone. The model study, which focuses on blobs being produced by auroral precipitation, shows that the observed energy fluxes can readily account for the blob densities if a plasma flux tube is exposed to the precipitation for 5-10 min. Once the flux tube is transported away from the source, the F region density profile recovers its shape on a time scale of ...


An Interplanetary Magnetic Field Dependent Model Of The Ionospheric Convection Electric Field, Jan Josef Sojka, C. E. Rasmussen, Robert W. Schunk Jan 1986

An Interplanetary Magnetic Field Dependent Model Of The Ionospheric Convection Electric Field, Jan Josef Sojka, C. E. Rasmussen, Robert W. Schunk

All Physics Faculty Publications

A mathematical model of the magnetospheric electric field imposed upon the ionosphere is presented. The model provides an interplanetary magnetic field (IMF) dependent description of the magnetospheric electric field at ionospheric altitudes for global ionospheric and thermospheric modelers. Although many theoretical and empirical ionospheric convection models have been published, none give both a quantitative and a general Kp, IMF (Bx , By , Bz) dependent description. The need for such a model is particularly pressing with the success of the Dynamic Explorer (DE) mission. As a result of this mission, extensive data sets of thermospheric and ionospheric parameters for ...