Wayne Scales

• Virginia Tech

Bayesian optimization has shown promise for the design optimization of inertial confinement fusion targets. Specifically, in Vazirani et al. [Phys. Plasmas 28, 122709 (2021)], optimal designs for double shell capsules with graded inner shells were identified using one-dimensional xRAGE simulation yield calculations. While the machine learning model...

A newly developed three-dimensional electrostatic fluid model solving continuity and current closure equations aims to study phenomena that generate ionospheric turbulence. The model is spatially discretized using a pseudo-spectral method with full Fourier basis functions and evolved in time using a four-stage, fourth-order Runge Kutta method. The...

Scintillation and total electron content (TEC) are the two major examples of the top-side ionospheric parameters that are recorded differently by most Global Positioning System (GPS) receivers. The new GPS sensor created by the Atmospheric and Space Technology Research Associates (ASTRA), Cornell University, and the University of Texas, Austin have...

Plain Language Summary Nonlinear interaction of high‐power electromagnetic waves and magnetized plasmas produces a plethora of fundamental phenomena. Stimulated electromagnetic emissions (SEEs) arises from nonlinear interaction and induces plasma turbulence observable by incoherent scatter radars (ISR). It is important to compare SEE and ISR spectr...

Subauroral polarization streams (SAPS) are regions in the subauroral ionosphere with lower plasma density and large westward flow driven by a poleward electric field. Density irregularities have been observed in the SAPS region; these irregularities can negatively impact radio signals by causing phase and amplitude fluctuations. Previous work ident...

A comprehensive statistical analysis was performed on Global Positioning System scintillation data acquired at high latitudes from 2014 to 2017 after separating phase scintillation events originating from refraction and/or diffraction. Events exceeding a prescribed threshold were identified and analyzed statistically as a function of time, latitude...

Advances in machine learning provide the ability to leverage data from expensive simulations of high-energy-density experiments to significantly cut down on computational time and costs associated with the search for optimal target designs. This study presents an application of cutting-edge Bayesian optimization methods to the one-dimensional (1D)...

Definition The Global Navigation Satellite System (GNSS) plays a pivotal role in our modern positioning, navigation and timing (PNT) technologies. GNSS satellites fly at altitudes of approximately 20,000 km or higher. This altitude is above an ionized layer of the Earth’s upper atmosphere, the so called “ionosphere”. Before reaching a typical GNSS...

In this study, we present the results of an inversion of ionospheric phase scintillation data to characterize the plasma density irregularity parameters for the structures associated with a series of Polar Cap Patches. The parameter estimates obtained during the inversion suggests that the irregularities associated with Polar Cap Patches are predom...

Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fu...

Density irregularities have been observed in subauroral polarization streams (SAPS). One hypothesis of the cause of this ionospheric turbulence, based on the background morphology, is the gradient drift instability (GDI). This work models the GDI using a two‐dimensional electrostatic fluid model to determine if it is a viable cause of turbulence ge...

Studies have shown that in sheared E × B flows in an inhomogeneous ionospheric plasma, the gradient drift (GDI) or the Kelvin–Helmholtz (KHI) instability may grow. This work examines the conditions that cause one of these instabilities to dominate over the other using a novel model to study localized ionospheric instabilities. The effect of collisi...

Studies have shown that in sheared $\mathbf{E}\times\mathbf{B}$ flows in an inhomogeneous ionospheric plasma, the gradient drift (GDI) or the Kelvin-Helmholtz (KHI) instability may grow. This work examines the conditions that cause one of these instabilities to dominate over the other using a novel model to study localized ionospheric instabilities...

Low-earth-orbit (LEO) spacecraft formation flying (SFF) simulated on the Virginia Tech Formation Flying Testbed (VTFFTB) demonstrated the feasibility of detecting simplified ionospheric electron density (Ne) structures (i.e., one-dimensional equatorial plasma bubbles/EPBs) utilizing a differential total electron content (TEC) method. The Thermosphe...

Future space weather missions using spacecraft formation flying can provide more robust, flexible, sustainable, and low-cost observational capability on multi-scale ionospheric plasma structures. The Virginia Tech Formation Flying Testbed (VTFFTB), a hardware-in-the-loop simulation testbed using multi-constellation, multi-frequency global navigatio...

This paper presents the first simultaneous four radar frequency observations of the PMSE region under varying neutral air turbulence conditions. Radar frequencies of 8, 56, 224, and 930 MHz are used in this study. Three days of experimental observations associated with EISCAT are presented. Numerical simulations of mesospheric dusty/ice plasma asso...

This paper presents the first joint observations of multi-frequency SuperDARN (Super Dual Auroral Radar Network) radar of the heated ionosphere by high-power high-frequency (HF) ground-based radio-waves along with the stimulated electromagnetic emissions (SEE) measurements. The unique heating experiment design at EISCAT (The European Incoherent Sca...

The Virginia Tech Formation Flying Testbed (VTFFTB), a GNSS‐based hardware‐in‐the‐loop (HIL) simulation testbed for spacecraft formation flight, is developed and applied to ionospheric remote sensing. The current VTFFTB consists of GNSS RF hardware signal simulators, multi‐constellation multi‐frequency GNSS receivers, a navigation and control syste...

The effect of the August 21, 2017 solar eclipse on the ionosphere is modeled using Sami3 is Also a Model of the Ionosphere (SAMI3). Due to the density gradient geometry that arises from the solar eclipse response, the gradient drift instability (GDI) is hypothesized to develop and grow. The GDI growth rate is calculated using the model data and set...

We narrate our experiences of teaching plasma and fluid mechanics to undergraduate students at Bowie State University and Virgin Tech and comment on possible pathways for future improvements in plasma and fluid education in general. The areas mostly covered are fusion energy science and space sciences with major emphasis on numerical and computatio...

Due to the potential for new diagnostic capabilities, there has been renewed interest in the generation of ionospheric stimulated electromagnetic emissions (SEEs) near the second harmonic of the pump frequency (ω0), a process known as second harmonic generation (SHG). Observations of SHG during experiments at the High Frequency Active Auroral Resea...

The Virginia Tech Formation Flying Testbed (VTFFTB) is a global navigation satellite system (GNSS)-based hardware-in-the-loop (HIL) simulation testbed for spacecraft formation flying with ionospheric remote sensing applications. Past applications considered only the Global Positioning System (GPS) constellation. The rapid GNSS modernization offers...

The stability of a quasi‐static near‐Earth dipolarization front (DF) is investigated with a two‐dimensional electromagnetic particle‐in‐cell model. Strongly localized ambipolar electric fields self‐consistently generate a highly sheared dawnward E→×B→ electron drift on the kinetic scale in the DF. Electromagnetic particle‐in‐cell simulations based...

Subauroral polarization stream (SAPS) is latitudinally narrow flow channels of large westward plasma drifts in the subauroral ionosphere. In this study, the global structure and dynamic evolution of SAPS are investigated by using the Coupled Magnetosphere‐Ionosphere‐Thermosphere model with ring current extension, namely, the Lyon‐Fedder‐Mobarry‐The...

This paper presents results of magnetohydrodynamic (MHD) simulations of flow curvature effects on the parallel velocity shear (PVS) driven instability in a magnetized plasma. Three flow profiles with identical velocity shear but different velocity curvature: positive curvature, no curvature, and negative curvature, are investigated with an MHD mode...

Electromagnetic (EM) and electrostatic (ES) emissions can be generated in the ionosphere by high-power high-frequency (HF) radio waves transmitted from the ground. The signatures of the EM emissions observed on the ground are known as Stimulated Electromagnetic Emissions (SEE) and can be employed for remote measurement of ionospheric parameters. Th...

Stimulated electromagnetic emissions (SEEs) induced by high power electromagnetic waves injected into iono-spheric plasmas provide direct parameter retrieval and assessment of nonlinear wave-particle interaction in the resonance regime. The broad upshifted maximum (BUM) is the most prominent spectral line in ionospheric stimulated electromagnetic r...

First report is made of a holistic investigation of stimulated electromagnetic emission (SEE) during ionospheric electron gyroharmonic heating using a diagnostic approach at the High Frequency Active Auroral Research Program facility (HAARP). The evolution of SEE polarization and plasma irregularities near the third electron gyroharmonic 3fce is de...

The behavior of polar mesospheric summer echoes (PMSEs) during an electron precipitation event is investigated by including dusty plasma effects for the first time. The observational data recorded with the very high frequency (224 MHz) and ultrahigh frequency (930 MHz) radars at the European Incoherent SCATter Scientific Association on 10 and 11 Ju...

Reported herein are first observations of narrowband stimulated electromagnetic emissions (NSEEs) within ±30 Hz of the second harmonic of the pump wave frequency during ionospheric heating experiments at the High Frequency Active Auroral Research Program facility. The observations are juxtaposed with contemporaneous NSEEs observed within ±30 Hz of...

In this paper, a current density convolution finite difference time domain method (JEC-FDTD) is extended to study the electromagnetic wave propagation and absorption in inhomogeneous magnetized plasmas. First of all, we analyze the wave propagation in homogeneous magnetized plasmas for arbitrary magnetic inclination angle. Then, we studied three ty...

Ionospheric signatures of ultralow frequency (ULF) wave in the Pc3-5 band (1.7–40.0 mHz) were surveyed using ∼ 6-s resolution data from Super Dual Auroral Radar Network (SuperDARN) radars in the Northern Hemisphere from 2010 to 2016. Numerical experiments were conducted to derive wave period-dependent thresholds for automated detection of ULF waves...

Artificial ionospheric GPS phase scintillation effects excited during the fourth gyroharmonic (4fce) heating at the High Frequency Active Auroral Research Program along with a theoretical model for the associated ionospheric irregularities are presented in this paper. The generation mechanism and time evolution of artificial GPS phase scintillation...

Initial results of stimulated electromagnetic radiation observed during an ionosphere heating experiment conducted at the High-Frequency Active Auroral Program (HAARP) facility are reported. The frequency of the pump wave used in the heating is in the neighborhood of the third harmonic of the electron cyclotron frequency, and of interest are simula...

The growth and saturation of magnetic fields due to the Weibel instability (WI) have important implications for laboratory and astrophysical plasmas, and this has drawn significant interest recently. Since the WI can generate a large magnetic field from no initial field, the maximum magnitudes achieved can have significant consequences for a number...

The role of solar wind density in the cross polar cap potential (CPCP) response under northward interplanetary magnetic field (IMF) is investigated with observation-based global simulations. A rare event was reported by Clauer et al. [2016] during which the ionospheric electric field EISP does not saturate under extreme interplanetary electric fiel...

We compare observations of stimulated electromagnetic emission (SEE) during ionospheric modification experiments using ground-based high-power high-frequency (HF) radio waves at both the High Frequency Active Auroral Research Program (HAARP) and the European Incoherent scatter (EISCAT). The combined simultaneous observations of SEEs, field-aligned...

Radio wave scintillation can result in severe channel fading and random phase variations that can interfere with the performance of a radar, communication or GPS system. While it is well known that Ionospheric scintillation occurs within the high and low latitude regions, there has been minimal research done within the middle latitudes. However, re...

The growth and saturation of magnetic fields due to the Weibel instability (WI) have important implications for laboratory and astrophysical plasmas, and this has drawn significant interest recently. Since the WI can generate a large magnetic field from no initial field, the maximum magnitudes achieved can have significant consequences for a number...

This paper presents a brief overview of the application of advanced plasma modeling techniques to several space science and engineering problems currently of significant interest. Recent advances in both kinetic and fluid modeling provide the ability to study a wide variety of problems that may be important to space plasmas including spacecraft–env...

This paper presents the first study of the modulation of polar mesospheric winter echoes (PMWE) by artificial radiowave heating using computational modeling and experimental observation in different radar frequency bands. The temporal behavior of PMWE response to HF pump heating can be employed to diagnose the charged dust layer associated with Mes...

This paper presents data from two campaigns at the High Frequency Active Auroral Research Program facility (HAARP) in 2011 and 2012. The measurements of stimulated radio emissions (often called stimulated electromagnetic emissions or SEE) were conducted 15 km from the HAARP site. The potential of Narrowband SEE (NSEE) as a new diagnostic tool to mo...

Dusty (or complex) plasmas in the Earth's middle and upper atmosphere ultimately result in exotic phenomena that are currently forefront research issues in the space science community. This paper presents some of the basic criteria and fundamental physical processes associated with the creation, evolution and dynamics of dusty plasmas in the near-E...

Ionospheric scintillation is caused by irregularities in the ionospheric electron density. The characterization of ionospheric irregularities is important to further our understanding of the underlying physics. Our goal is to characterize the intermediate (0.1-10 km) to medium (10-100 km) scale high latitude irregularities which are likely to produ...

Recent studies reveal that midlatitude ionospheric irregularities are less understood due to lack of models and observations that can explain the characteristics of the observed wave structures. In this paper, the cascading processes of both the temperature gradient instability (TGI) and the gradient drift instability (GDI) are investigated as the...

A variety of statistical studies have shown that the ionospheric polar potential produced by solar wind-magnetosphere-ionosphere coupling is linear for weak to moderate solar wind driving but becomes nonlinear during periods of very strong driving. It has been shown that this applies to the two-cell convection potential that develops during southwa...

Investigation of stimulated radiation, commonly known as stimulated electromagnetic emissions (SEE), produced by the interaction of high-power, high-frequency HF radiowaves with the ionospheric plasma has been a vibrant area of research since the early 1980s. Substantial diagnostic information about ionospheric plasma characteristics, dynamics, and...

Recent studies reveal that midlatitude ionospheric irregularities are less understood due to lack of models and observations that can explain the characteristics of the observed wave structures. In this paper, the Temperature Gradient Instability (TGI) and the Gradient Drift Instability (GDI) are analyzed as the cause of the midlatitude irregularit...

Three-dimensional evolution of the lower hybrid turbulence driven by a spatially localized ion ring beam perpendicular to the ambient magnetic field in space plasmas is analyzed. It is shown that the quasi-linear saturation model breaks down when the nonlinear rate of scattering by thermal electron is larger than linear damping rates, which can occ...

Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Bri...

Joint measurements by the Blackstone SuperDARN radar, and the Millstone Hill Incoherent Scatter Radar (ISR) are analyzed to investigate the generation source responsible for the observed decameter-scale irregularities in the nightside sub-auroral ionosphere during quiet and active geomagnetic periods. In this work, the Temperature Gradient Instabil...

Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world’s largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP e...

Applications of Global Navigation Satellite Systems (GNSS) are ubiquitous in today's society. Their number is expected to grow rapidly for the foreseeable future and well-trained engineers will be needed to exploit the full potential of this technology. GNSS encompasses a broad range of engineering and science disciplines and provides an excellent...

An electrodynamic tether system consists of two satellites connected by a long tether that generates current to produce either power or thrust via the system’s electromagnetic interaction with the space environment. A complete system model for an electrodynamic tether that combines a high-fidelity tether dynamics model and a model for the tether cu...

Observations of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating Magnetized Stimulated Brillouin scatter MSBS and...

The mid-latitude SuperDARN radars have identified quiet-time decameter-scale density irregularities in the night-side sub-auroral ionosphere that have been proposed to be responsible for the observed low-velocity Sub-Auroral Ionospheric Scatter (SAIS). The physical mechanism responsible for such common irregularities is still unknown. Joint collabo...

Use of high frequency (HF) heating experiments has been extended in recent years as a useful methodology for plasma physicists wishing to remotely study the properties and behavior of the ionosphere as well as nonlinear plasma processes. Our recent work using high latitude heating experiments has lead to several important discoveries that have enab...

The interaction between a positively biased body traveling through an ionospheric space plasma has direct application to electrodynamic tether (EDT) systems. A 2-D3v Particle-in-Cell (PIC) model has been developed to study the plasma dynamics near a positively charged EDT system end-body and their impact on the current collected. The results show t...

The midlatitude SuperDARN radars frequently observe quiet time decameter-scale irregularities in the nightside sub-auroral ionosphere. Since opposed temperature and density gradients are a persistent feature in the vicinity of the ionospheric projection of the plasmapause, the temperature gradient instability (TGI) is proposed to explain the observ...

Stimulated Brillouin scattering (SBS) and resonant phenomena are well known in the context of laser fusion, fiber optics and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space experiments using high power high frequency (HF) radio waves may now produce stimulated Brillouin scatte...

The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the EISCAT facility in northern Norway. It is shown that model results are in quali...

SuperDARN radars regularly observe decameter-scale ionospheric irregularities at mid-latitudes during quiet geomagnetic conditions. The mechanism responsible for the growth of such irregularities is still unknown. Previous results based on data from the Wallops SuperDARN HF radar and Millstone Hill Incoherent Scatter Radar have suggested that the T...

Previous joint measurements by the Millstone Hill Incoherent Scatter Radar (ISR) and the SuperDARN HF radar located at Wallops Island, Virginia have identified the presence of opposed meridional electron density and temperature gradients in the region of decameter-scale electron density irregularities that have been proposed to be responsible for l...

Recently, narrowband emissions ordered near the H+ (proton) gyrofrequency (fcH) were reported in the stimulated electromagnetic emission (SEE) spectrum during active geomagnetic conditions. This work presents new observations and theoretical analysis of these recently discovered emissions. These emission lines are observed in the stimulated electro...

Characteristics of the Stimulated Electromagnetic Emission (SEE) spectrum recorded during ionospheric heating near the second electron gyroharmonic frequency, 2fce, have attracted attention due to their possible connection to artificially generated airglow and artificial ionospheric layers. Two newly discovered SEE spectral features within 1 kHz fr...

[1] Stimulated Electromagnetic Emissions (SEEs), secondary electromagnetic waves excited by high power electromagnetic waves transmitted into the ionosphere, produced by the Magnetized Stimulated Brillouin Scatter (MSBS) process are investigated. Data from four recent research campaigns at the High Frequency Active Auroral Research Program (HAARP)...

[1] Results of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power radio waves are reported. These results obtained at the High Frequency Active Auroral Research Program (HAARP) facility specifically considered the generation of Magnetized Stimulated Bril...

Plasma fluctuations arise in the boundary region between charged dust clouds and background plasmas. A self-consistent computational model is developed to study expansion of a charged dust cloud across a magnetic field, creation of the inhomogeneous boundary layer and associated processes. The charging of the dust particulates produces a boundary l...

This work presents the first observations of unique narrowband emissions ordered near the hydrogen ion (H+) gyrofrequency (fcH) in the stimulated electromagnetic emission spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during ionospheric modification experiments. The frequency structuring of these newly...

Stimulated electromagnetic emissions (SEEs) are secondary radiation produced during active space experiments in which the ionosphere is actively heated with high power high frequency (HF) ground-based radio transmitters. Recently, there has been significant interest in ion gyro-harmonic structuring the SEE spectrum due to the potential for new diag...

Stimulated electromagnetic emissions (SEEs) may provide important diagnostic information about space plasma composition, energetics, and dynamics during active experiments in which ground-based high-powered radio waves are transmitted into the ionosphere. The nonlinear plasma processes producing this secondary radiation are not well understood part...

Recently, there has been significant interest in ion gyro-harmonic structuring the Stimulated Electromagnetic Emission SEE spectrum due to the potential for new diagnostic information available about the heated volume and ancillary processes such as creation of artificial ionization layers. These relatively recently discovered emission lines have a...

Features in the Stimulated Electromagnetic Emission (SEE) spectrum during heating near the second electron gyro-harmonic frequency have recently attracted significant attention due to their possible connection to artificial airglow and artificially generated ionization layers. Experimentally, three new phenomenologically related spectral features w...

Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on...

Plasma turbulence associated with the creation of an artificial dust layer in the earth's ionosphere is investigated. The lower hybrid turbulence is considered as the dust is injected across the geomagnetic field into the background plasma, which generates irregularities at times much longer than the dust charging period. A two-dimensional hybrid p...