Physics Commons^™

A Model Study Of How Electric Field Structures Affect The Polar Cap F Region, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

A three-dimensional time-dependent ionospheric model was used to study how electric field structures affect the polar F region. The electric field structures are represented by elongated Volland two-cell models whose dimensions range from tens to 1000 km. These model structures are intended to represent the polar cap electric field for IMF B_z northward conditions. A statistical method is used to generate a set of these structures. Their electric field strength and polarity are varied in order to study the F region’s dependence on this magnetospheric input. For electric field structures whose size and electric field strengths are consistent with …

Low-Temperature Ion Beam Mixing In Metals, S J. Kim, M A. Nicolet, R S. Averback, David Peak

All Physics Faculty Publications

A systematic study of ion-beam mixing of tracer impurities in thin metal films at low temperatures has been conducted. We have investigated the dependence of ion mixing on two matrix properties: atomic mass and cohesive energy. We have also studied the dependence of ion mixing on tracer impurity properties: its heat of mixing with the matrix and its thermal diffusivity in the matrix. The matrices investigated were thin films of C, Al, Ti, Fe, Ni, Cu, Mo, Ru, Ag, Hf, Ta, W, Pt, and Au. The tracer impurities, Al, Ti, Cr, Mn, Fe, Ni, Cu, Y, Nb, Mo, Ru, Ag, …

A Photochemical Equilibrium Model For Ionospheric Conductivity, C. E. Rasmussen, Robert W. Schunk, Vincent B. Wickwar

All Physics Faculty Publications

A photochemical equilibrium model of the high-latitude ionosphere has been developed. This model provides densities of the ionospheric constituents, N₂ ⁺, O₂ ⁺, O⁺, and NO⁺, from 85 km to approximately 220 km. These densities are then used to calculate Pedersen and Hall conductivities. A comparison of the model results with Arecibo and Chatanika radar observations was made, covering periods of solar minimum and solar maximum. The comparison showed the model to predict ionospheric densities to within 50% and conductivities to within 40% in the illuminated portion of the ionosphere. In regions …

Observations Of Auroral E Region Plasma Waves And Electron Heating Witheiscat And A Vhf Radar Interferometer, J. Providakes, D. T. Farley, B. G. Fejer, J. Sahr, W. E. Swartz, I. Haggstrom, A. Hedberg, J. A. Nordling

All Physics Faculty Publications

Two radars were used simultaneously to study naturally occurring electron heating events in the auroral E-region ionosphere. During a joint campaign in March 1986 the Cornell University Portable Radar Interferometer (CUPRI) was positioned to look perpendicular to the magnetic field to observe unstable plasma waves over Tromsø, Norway, while EISCAT measured the ambient conditions in the unstable region. On two nights EISCAT detected intense but short lived (< 1 min) electron heating events during which the temperature suddenly increased by a factor of 2–4 at altitudes near 108 km and the electron densities were less than 7 × 104 cm−3. On the second of these nights CUPRI was operating and detected strong plasma waves with very large phase velocities at precisely the altitudes and times at which the heating was observed. The altitudes, as well as one component of the irregularity drift velocity, were determined by interferometric techniques. From the observations and our analysis, we conclude that the electron temperature increases were caused by plasma wave heating and not by either Joule heating or particle precipitation.

Electric Field And Plasmadensity Measurements In The Strongly-Driven Daytime Equatorial Electrojet: 1. The Unstablelayer And Gradient Drift Waves, R. F. Pfaff, M. C. Kelley, E. Kudeki, Bela G. Fejer, K. D. Baker

Bela G. Fejer

Electric field and plasma density instrumentation on board a sounding rocket launched from Punta Lobos, Peru, detected intense electrostatic waves indicative of plasma instabilities in the daytime equatorial electrojet. Simultaneous measurements taken by the Jicamarca radar showed strong 3-m type 1 electrojet echoes as well as evidence of kilometer scale horizontally propagating waves. The in situ electric field wave spectra displayed three markedly different height regions within the unstable layer: (1) a two-stream region on the topside between 103 and 111 km where the electron current was considered to be strongest, (2) a gradient drift region between 90 and 106.5 …

The Condor Equatorial Electrojetcampaign: Radar Results, E. Kudeki, Bela G. Fejer, D. T. Farley, C. Hanuise

Bela G. Fejer

A review of the experimental and theoretical background to the Condor equatorial electrojet campaign is followed by the presentation and discussion of VHF radar interferometer and HF radar backscatter data taken concurrently with two rocket in situ experiments reported in companion papers (Pfaff et al., this issue (a, b). Both experiments were conducted in strongly driven periods with the on-line radar interferometer displaying signatures of what has been interpreted in earlier radar work (Kudeki et al., 1982) as kilometer scale gradient drift waves. Low-frequency density fluctuations detected by in situ rocket sensors confirm the earlier interpretation. VHF radar/rocket data comparisons …

Electric Field And Plasmadensity Measurements In The Strongly-Driven Daytime Equatorial Electrojet: 2. Two-Streamwaves, R. F. Pfaff, M. C. Kelley, E. Kudeki, Bela G. Fejer, K. D. Baker

Bela G. Fejer

Both primary and secondary two-stream (Farley-Buneman) waves have been detected by in situ electric field and plasma density probes in the strongly driven daytime equatorial electrojet over Peru. Simultaneous Jicamarca radar observations showed strong vertical and oblique 3-m type 1 echoes, also indicative of the two-stream mechanism. The rocket data show the two-stream region on the topside of the unstable layer to be situated between 103 and 111 km where the electron current was the strongest. This region was characterized by broadband plasma oscillations extending past 1 kHz in the rocket frame. Furthermore, above 106.5 km, where the electron density …

The O-O Collision Cross-Section: Can It Be Inferred From Aeronomical Measurements?, R G. Burnside, C A. Tipley, Vincent B. Wickwar

All Physics Faculty Publications

No abstract provided.

On The Height Variation Of The Equatorial F-Region Vertical Plasmadrifts, J. E. Pingree, Bela G. Fejer

Bela G. Fejer

We have used improved incoherent scatter radar measurements at the Jicamarca Radio Observatory to study the height variation of the F region vertical plasma drift velocity (driven by the zonal electric field) during moderately quiet conditions. Preliminary results indicate a nearly linear change of the vertical drift velocity with altitude between 200 and 700 km, but with considerable day-to-day variations in the value of the slope. On the average, the velocity gradients are positive in the late night and morning periods and negative during the afternoon and evening hours. Simultaneous vertical and zonal drift measurements confirm that the measured height …

Variational Principles Of Fluid Mechanics And Electromagnetism: Imposition And Neglect Of The Lin Constraint, Ross Roundy Allen Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Variational principles in classical fluid mechanics and electromagnetism have sprinkled the literature since the eighteenth century. Even so, no adequate variational principle in the Eulerian description of matter was had until 1968 when an Eulerian variational principle was introduced which reproduces Euler's equation of fluid dynamics. Although it successfully produces the appropriate equation of motion for a perfect fluid, the variational principle requires imposition of a constraint which was not fully understood at the time the variational principle was introduced. That constraint is the Lin constraint. The Lin constraint has subsequently been utilized by a number of authors who have …

Higher-Dimensional Self-Consistent Solution With Deformed Internal Spaces, T. -C. Shen, J. Sobczyk

T. -C. Shen

We study a system of gravity and free massless scalar fields minimally coupled to gravity in a 7- dimensional background which is a direct product of a 4-dimensional Minkowski space and a 3- dimensional homogeneously deformed three-sphere. Compactification is caused by the vacuum energy of scalar fields. The effective potential as a function of two parameters (scale and deformation) is calculated numerically after dimensional regularization. We find the effective potential decreases rapidly toward negative infinity in both prolate and oblate directions. The classical curvature, however, can balance the quantum effect and yields three extrema. In addition to the round S …

A Theoretical Study Of The Lifetime And Transport Of Large Ionospheric Density Structures, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

Large-scale density structures are a common feature in the high-latitude ionosphere. They have been observed in the dayside cusp, polar cap, and nocturnal auroral region. Relative to background densities, the perturbations associated with large-scale structures vary from about 10% to a factor of 100. The lifetime and transport characteristics of “large” ionospheric structures (factor of 10 to 100) were studied with the aid of a three-dimensional time-dependent ionospheric model. Both density depletions and enhancements were considered. A density structure was created at a specific location in the high latitude F region and the subsequent evolution was followed for different seasonal …

Brst Structure Of General Relativity In Terms Of New Variables, Charles G. Torre

All Physics Faculty Publications

The structure of the Poisson-brackets algebra of constraints of general relativity is reexamined using the recently introduced spinorial variables. Three different combinations of constraints are analyzed and their relative merits are discussed. In each case we construct the corresponding expression of the Becchi-Rouet-Stora-Tyutin charge. These expressions provide a point of departure for a nonperturbative quantization scheme for general relativity.

Theoretical Study Of The Effect Of Ionospheric Return Currents On The Electron Temperature, Robert W. Schunk, Jan Josef Sojka, M. D. Bowline

All Physics Faculty Publications

An electron heat flow can occur in a partially ionized plasma in response to either an electron temperature gradient (thermal conduction) or an electron current (thermoelectric heat flow). The former process has been extensively studied, while the latter process has received relatively little attention. Therefore a time-dependent three-dimensional model of the high-latitude ionosphere was used to study the effect of field-aligned ionospheric return currents on auroral electron temperatures for different seasonal and solar cycle conditions as well as for different upper boundary heat fluxes. The results of this study lead to the following conclusions: (1) The average, large-scale, return current …

Theoretical Study Of The High-Latitude Ionosphere’S Response To Multicell 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 at high latitudes and that a quantitative understanding of their effect requires a knowledge of the plasma convection pattern. When the interplanetary magnetic field (IMF) is southward, plasma convection at F region altitudes displays a two-cell pattern with antisunward flow over the polar cap and return flow at lower latitudes. However, when the IMF is northward, multiple convection cells can exist, with both sunward flow and auroral precipitation (theta aurora) in the polar cap. The characteristic ionospheric signatures associated with multicell convection patterns were studied …

Lower-Thermospheric Winds At High Latitude, R M. Johnson, Vincent B. Wickwar, R G. Roble, J G. Luhmann

All Physics Faculty Publications

Observations made of the high-latitude E-region with the Chatanika, Alaska (65° N), incoherent scatter radar facility during the summer months of 1976 to 1982 are presented. Fourteen 24-h experiments were performed with altitude resolution between 9 and 24 km. Ion drifts measured during these experiments have been analysed to obtain neutral winds at lower-thermospheric heights. Tidal oscillations are the predominant feature of the neutral winds from 90 to 125 km. The semidiurnal oscillation is particularly strong, attaining peak amplitudes of ≈50 m/s at 110 km. Average semidiurnal tidal phases are in good agreement with previous mid- to hight-latitude observations. …

A Substorm Resulting From Energy Storage In The Magnetosphere, T S. Jorgensen, K Larsen, W J. Heikkila, Vincent B. Wickwar, G Haerendel

All Physics Faculty Publications

In order to study the problem whether magnetospheric substorms are directly driven by solar wind energy or result from unloading of such energy temporarily stored in the magnetosphere, it is necessary to investigate substorms following long quiescent periods and to observe solar wind parameters in proximity of the magnetsosphere as well as many high-latitude ionosphere parameters with good temporal resolution.

In this study we present such observations obtained on November 29, 1984 by the AMPTE-IRM spacecraft just outside the bow shock and by the Sondrestrom incoherent scatter radar plus several other instruments in the earth's polar region.

We infer from …

Optical And Radar Characterization Of A Short-Lived Auroral Event At High Latitude, A Vallance-Jones, R L. Gattinger, P Shih, J W. Meriwether, Vincent B. Wickwar, J D. Kelly

All Physics Faculty Publications

Observations of optical emission intensities and incoherent scatter radar returns in the magnetic zenith were compared in a study carried out at Sondre Stromfjord (Λ = 76.1°) in Greenland. The results were used to test the consistency of a theoretical model of ion chemistry and optical emissions in aurora and to explore the accuracy of relations between optical measurements and the average energy of the incident electrons. The incident primary electron spectrum and its temporal variation were inferred from zenith electron density profiles from the radar. The inferred primary energy spectrum at the peak intensity of the event approximated a …

Heterotic String From Four-Dimensional Geometry, James Thomas Wheeler

All Physics Faculty Publications

In any conformally invariant metric-connection theory of 4-dimensional spacetime, there are 26 ways that a body can distort. This follows from the absence of any preferred metric, and is equivalent to the ability of an observer to consider objects on any given world line to be distortion free. Within the simplest conformally invariant theory of distortions that allow metric compatible spaces as trivial solutions, we find the maximal classical solution. This solution corresponds to the bosonic sector of the heterotic string: 26 left-moving fields plus 10 right-moving fields.

A Viable Form Of Weyl’S Theory, James Thomas Wheeler

All Physics Faculty Publications

A reinterpretation of the Weyl vector in a Weyl geometry is shown to yield Dirac’s 1951 classical theory of the electron, thereby avoiding the most obvious problems of measurement inherent in Weyl’s original geometric formulation of electromagnetism. This paves the way for the consistency of recent metric-connection theories, for which similar questions of measurement can arise.

Hemispherical Emissivity Of V, Nb, Ta, Mo, And W From 300 To 1000 K, S. X. Cheng, P. Cebe, L. M. Hanssen, D. Mark Riffe, A. J. Sievers

All Physics Faculty Publications

The hemispherical emissivities of five transition elements, V, Nb, Ta, Mo, and W, have been measured from 300 to 1000 K, complementing earlier higher-temperature results. These low-temperature data, which are similar, are fitted to a Drude model in which the room-temperature parameters have been obtained from optical measurements and the temperature dependence of the dc resistivity is used as input to calculate the temperature dependence of the emissivity. A frequency-dependent free-carrier relaxation rate is found to have a similar magnitude for all these elements. For temperatures larger than 1200 K the calculated emissivity is always greater than the measured value, …

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 most several …

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

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 clusters …

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 …

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.

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

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 with maximum …

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

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 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 …