MPS and Ionospheric Propagation Codes
This presentation describes diffraction and refraction techniques employed at LLNL for multiple ionospheric propagation scenarios.
97 MATHEMATICS AND COMPUTING↗
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Effect of Density Irregularities on Radio Frequency Wave Propagation in Ionospheric Plasmas
Density irregularities play a vital role in determining how radio frequency (RF) waves travel through plasmas. In the Earth’s ionosphere, these density irregularities also impact radio communication. In this study, we conduct a detailed numerical analysis of RF wave propagation in small-scale ionospheric density irregularities using the advanced Petra-M code. We focus specifically on high-frequency (HF) waves, ranging from 3 to 30 MHz, which are essential for military, amateur radio operators, and emergency communications. By introducing density structures, such as equatorial plasma bubbles derived from fluid simulations, we demonstrate that HF waves can scatter in multiple directions when they encounter these irregularities. Additionally, we observe significant mode conversion, where incoming electromagnetic waves transform into electrostatic modes within the density gradient layer. This shows that smaller density irregularities can greatly weaken signals or cause complete signal loss for receivers, emphasizing the need for increased awareness and innovative solutions in radio communication transmission.
Kim, Eun-Hwa [Princeton Plasma Physics Laboratory ↗
Propagation of an ultrawideband electromagnetic signal in ionospheric plasma
The propagation of an ultrawideband electromagnetic signal in the ionosphere—a plasma medium with spatially nonuniform characteristics—is studied analytically in the high-frequency approximation. The effect of the plasma dielectric properties and angular divergence on the shape and frequency spectrum of the propagating signal is investigated. It is shown that the spectral energy density of the signal is preserved if collisions of ionospheric plasma electrons are neglected.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Ionospheric Transfer Function Tests: Line of Sight and Slab
Ionospheric transfer function (ITF) algorithms determine the effects of the ionosphere on an electromagnetic (EM) signal as it propagates through. In this report, analytic formulas are derived which can be used to compare results of ITF calculations from certain algorithms.
97 MATHEMATICS AND COMPUTING↗
Omission of electron temperature and collisions in DIORAMA ionospheric transfer functions
DIORAMA calculates ionospheric effects on propagating EM signals using a frequency dependent transfer function called the Ionospheric Transfer Function (ITF). The ITF is applied to each of the spatial components of the EM wave, at each frequency in its bandwidth, as it travels through the ionosphere.
42 ENGINEERING↗
Trans-ionospheric signal polarization
An electromagnetic (EM) wave originating at or near the earth’s surface can propagate upwards, traverse the ionosphere, and then be detected at a satellite. While the signal’s magnitude will affect its detectabilty, its polarization will play an important role as well. Furthermore the signal polarization can reveal properties about its source, and the ionospheric conditions through which it traveled. Thus, it is desirable to predict the polarization characteristics of trans-ionospheric EM signals. This situation is complicated by the birefringence imposed on an EM wave propagating in the magnetized plasma of the ionosphere. Each frequency component of the signal can excite two waves that propagate at different phase velocities due to their separate refractive characteristics.For this work, the amplitude and phase of each EM wave field spatial component is followed as it crosses the lower ionospheric boundary, traverses the ionosphere and then crosses the upper boundary. Results are for a single frequency, and can be easily extended to broadband waveforms using fourier transform techniques.
79 ASTRONOMY AND ASTROPHYSICS↗
Assessment of Variability of the TEC in the Equatorial Anomaly Region with a Focus over Africa Using Rz and F10.7 as Input Drivers
This paper mainly intends to address the assessment of altitudinal variability of the vertical total electron content (VTEC) extracted from the Global Positioning System (GPS), the new versions of the International Reference Ionosphere Extended to the Plasmasphere (IRI-Plas 2017), and a quick-run ionospheric electron density (NeQuick 2) model in the equatorial anomaly region with a focus over Africa. This is manipulated employing the daily sunspot number (Rz) and 10.7 cm solar radio flux (F10.7) indices as the driver for the models during 2013–2016. The results show that the GPS-derived VTEC values are generally smaller than the modeled VTEC (IRI-Plas 2017 and NeQuick 2 VTEC) values, especially while utilizing the models with the Rz index. The modeled VTEC values are closer to the GPS VTEC values while using the models with the F10.7 index than Rz. The VTEC values obtained while using both models with the F10.7 index tend to increase while traversing from the high to the low solar activity years (especially in the March equinox and December solstice). The top-side ionospheric and plasmaspheric layers contribute the highest and lowest values to the total VTEC. Hence, the signal propagation through the ionosphere is largely affected when the signal crosses the top-side layer. Unlike other layers, due to the limited impact of the EUV on the ionization of neutral particles in the plasmasphere, the VTEC in the plasmaspheric layer (ECpl) shows smooth pattern with similar hourly values. Moreover, the IRI-Plas 2017 model does not effectively respond to the geomagnetic storm time variability of the VTEC with altitude.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Analytical study of nighttime scintillations using GPS at low latitude station Bhopal
Sporadically structured ionosphere (i.e. in-homogeneities in refractive index) can cause fluctuations (due to refraction effects) on the radio signal that is passing through it. These fluctuations are called ionospheric scintillations. Low latitude region is suitable for studying these scintillations. The influence of the ionosphere on the propagation of the radio wave becomes very marked with reference to communication or navigational radio system at very low frequency (VLF) to a high frequency (HF), which operate over the distances of 1000 km or more. Radio wave communication at different frequencies depends on structure of the ionosphere. With the advent of the artificial satellites, they are used as a prime mode of radio wave communication. Some natural perturbation termed as irregularities, are present in the form of electron density of the ionosphere that cause disruption in the radio and satellite communications. Therefore the study of the ionospheric irregularities is of practical importance, if one wishes to understand the upper atmosphere completely. In order to make these communications uninterrupted the knowledge of irregularities, which are present in the ionosphere are very important. These irregularities can be located and estimated with the help of Ionospheric TEC and Scintillation. Scintillation is generally confined to nighttime hours, particularly around equatorial and low latitudes.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Techniques for Accurate Parallax Measurements for 6.7 GHz Methanol Masers
The BeSSeL Survey is mapping the spiral structure of the Milky Way by measuring trigonometric parallaxes of hundreds of maser sources associated with high-mass star formation. While parallax techniques for water masers at high frequency (22 GHz) have been well documented, recent observations of methanol masers at lower frequency (6.7 GHz) have revealed astrometric issues associated with signal propagation through the ionosphere that could significantly limit parallax accuracy. These problems displayed as a “parallax gradient” on the sky when measured against different background quasars. We present an analysis method in which we generate position data relative to an “artificial quasar” at the target maser position at each epoch. Fitting parallax to these data can significantly mitigate the problems and improve parallax accuracy.
79 ASTRONOMY AND ASTROPHYSICS↗
Mars Dust Storm Effects in the Ionosphere and Magnetosphere and Implications for Atmospheric Carbon Loss
Mars regional and global dust storms are able to impact the lower/upper atmospheres through dust aerosol radiative heating and cooling and atmospheric circulation. Here we present the first attempt to globally investigate how the dust impact transfers from the neutral upper atmosphere to the ionosphere and the induced magnetosphere above 100-km altitude. This is achieved by running a multifluid magnetohydrodynamic model under nondusty and dusty atmospheric conditions for the 2017 late-winter regional storm and the 1971–1972 global storm. In this paper, our results show that the dayside main ionospheric layer (below ~250-km altitude) undergoes an overall upwelling, where photochemical reactions dominate. The peak electron density remains unchanged, and the peak altitude shift is in accordance with the upper atmospheric expansion (~5 and ~15 km for the regional and global storms, respectively). Controlled by the day-to-night transport, the nightside ionosphere responds to the dust storms in a close connection with what happens on the dayside but not apparently with the ambient atmospheric change. At higher altitudes, dust-induced perturbations propagate upward from the ionosphere to the magnetosphere and extend from the dayside to the nightside, within a broad region bounded by the induced magnetospheric boundary. It is found that the global dust storm is able to dramatically enhance the CO⁺₂ loss by a factor of ~3, which amounts to an increase of ~20% or more for total carbon loss (in the forms of neutrals and ions). Strong dust storms are a potentially important factor in atmospheric evolution at Mars.
79 ASTRONOMY AND ASTROPHYSICS↗
Ray Trace Modeling Code
This document gives a brief overview of the basic theory of electromagnetic (EM) wave propagation through an inhomogeneous, non-stochastic plasma and the development of a computer code to model that propagation in three dimensional space. This code has been developed to account for extreme ionospheric refractory conditions, that is, propagation of electromagnetic waves near the geomagnetic poles, and significant electron density gradients in all three directions.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Dust-Acoustic Solitons in Dusty Ionospheric Plasma Containing Adiabatically Captured Electrons
The possible propagation of localized wave structures such as dust-acoustic solitons in dusty ionospheric plasma containing photoelectrons, electrons and ions of the ionosphere, and charged dust particles is considered. Intervals of the possible soliton velocities and amplitudes are determined. Solitary wave solutions for various dimensions and concentrations of particles in dusty ionospheric plasma are found.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Los Alamos Portable Pulser (LAPP) Marx Bank and Digitizer System Characterization
Over the duration of June 22 nd to July 15 th , I interned at Los Alamos National Laboratory within ISR-2 on the Los Alamos Portable Pulser (LAPP) Program. This program concerns a radar dish used for characterizing signal propagation through earth’s ionosphere. The bulk of my internship consisted of characterizing the delay of a Marx Bank Generator and writing hardware-interface C/C++ code for the pulse-recording Digitizer System.
47 OTHER INSTRUMENTATION↗
First tsunami gravity wave detection in ionospheric radio occultation data
After the 11 March 2011 earthquake and tsunami off the coast of Tohoku, the ionospheric signature of the displacements induced in the overlying atmosphere has been observed by ground stations in various regions of the Pacific Ocean. We analyze here the data of radio occultation satellites, detecting the tsunami-driven gravity wave for the first time using a fully space-based ionospheric observation system. One satellite of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) recorded an occultation in the region above the tsunami 2.5 h after the earthquake. The ionosphere was sounded from top to bottom, thus providing the vertical structure of the gravity wave excited by the tsunami propagation, observed as oscillations of the ionospheric Total Electron Content (TEC). The observed vertical wavelength was about 50 km, with maximum amplitude exceeding 1 total electron content unit when the occultation reached 200 km height. We compared the observations with synthetic data obtained by summation of the tsunami-coupled gravity normal modes of the Earth/Ocean/atmosphere system, which models the associated motion of the ionosphere plasma. These results provide experimental constraints on the attenuation of the gravity wave with altitude due to atmosphere viscosity, improving the understanding of the propagation of tsunami-driven gravity waves in the upper atmosphere. They demonstrate that the amplitude of the tsunami can be estimated to within 20% by the recorded ionospheric data.
58 GEOSCIENCES↗
Electromagnetic power of lightning superbolts from Earth to space
Lightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. From burst-triggered measurements, we compute electric and magnetic power spectral density for very low frequency waves driven by superbolts, both on Earth and transmitted into space, demonstrating that superbolts transmit 10-1000 times more powerful very low frequency waves into space than typical strokes and revealing that their extreme nature is observed in space. We find several properties of superbolts that notably differ from most lightning flashes; a more symmetric first ground-wave peak due to a longer rise time, larger peak current, weaker decay of electromagnetic power density in space with distance, and a power mostly confined in the very low frequency range. Their signal is absent in space during day times and is received with a long-time delay on the Van Allen Probes. These results have implications for our understanding of lightning and superbolts, for ionosphere-magnetosphere wave transmission, wave propagation in space, and remote sensing of extreme events.
79 ASTRONOMY AND ASTROPHYSICS↗
EMP-002a Phase Shift through the Ionosphere
In this note we review the derivation and use of the Ionospheric Transfer Function (ITF) in the DIO- RAMA model to calculate the propagation of a broad band ElectroMagnetic Pulse (EMP) through the Ionosphere in the limit of geometric optics. This note is intended to resolve a misunderstanding between the NDS VVA and EMP modeling teams regarding the appropriate use of the phase and group velocities in DIORAMA. The di erent approaches are documented in EMP-002 note, \Phase vs. Group" [1], generated by the LLNL DIORAMA VVA team, and the subsequent response from the DIORAMA EMP modeling team' [2].
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
On the propagation and mode conversion of auroral medium frequency bursts
Abstract Auroral medium frequency (MF) bursts are broadband, impulsive radio emissions associated with local substorm onsets. MF bursts consist of a characteristic fine structure whereby the higher frequencies arrive 10–100 ms before the lower frequencies. LaBelle (2011a) proposed that MF bursts originate as Langmuir/Z mode waves on the topside of the ionosphere that mode‐convert to LO mode waves and propagate to ground level, with the fine structure resulting by propagation delays due to the topside ionospheric density profile. We investigate three aspects of this mechanism. First, full‐wave calculations are used to simulate the MF burst fine structure using a realistic ionospheric density profile. The delay between the highest and lowest frequencies is 21 ms. This value is smaller than the experimentally determined delays of ∼100 ms presented in Bunch and LaBelle (2009), but differences between the topside electron number density profile used in the simulations and the number density profile during disturbed conditions make comparisons only approximate. Second, the Landau damping of Langmuir/Z mode waves on the topside ionosphere is calculated, assuming the electron distribution function consists of a cold background population ( n e 0 ) and a warm secondary population ( n se ). The Landau damping is small when n se / n e 0 = 0.04% (consistent with Maggs and Lotko (1981)) but is significant when n se / n e 0 > 0.4%. Finally, full‐wave calculations are used to determine the mode conversion efficiency from Langmuir/Z mode waves to LO mode waves. These imply that waves would suffer an attenuation of wave energy density of approximately 5–10% if they are generated with their wave vectors in a narrow cone centered around the local magnetic field. Taken together, these calculations suggest that for small values of n se / n e 0 <0.4%, the mechanism proposed by LaBelle (2011a) is a plausible explanation for the origin of MF bursts.
Broughton, M. C.↗
Utilizing the Heliophysics/Geospace System Observatory to Understand Particle Injections: Their Scale Sizes and Propagation Directions
The injection region's formation, scale size, and propagation direction have been debated throughout the years, with new questions arising with increased plasma sheet observations by missions like Cluster and THEMIS. How do temporally and spatially smallscale injections relate to the larger injections historically observed at geosynchronous orbit? How to account for opposing propagation directions—earthward, tailward, and azimuthal—observed by different studies? To address these questions, we used a combination of multisatellite and ground–based observations to knit together a cohesive story explaining injection formation, propagation, and differing spatial scales and timescales. We used a case study to put statistics into context. First, fast earthward flows with embedded small–scale dipolarizing flux bundles transport both magnetic flux and energetic particles earthward, resulting in minutes–long injection signatures. Next, a large–scale injection propagates azimuthally and poleward/tailward, observed in situ as enhanced flux and on the ground in the riometer signal. The large–scale dipolarization propagates in a similar direction and speed as the large–scale electron injection. We suggest small–scale injections result from earthward–propagating, small–scale dipolarizing flux bundles, which rapidly contribute to the large–scale dipolarization. We suggest the large–scale dipolarization is the source of the large–scale electron injection region, such that as dipolarization expands, so does the injection. Here, the >90–keV ion flux increased and decreased with the plasma flow, which died at the satellites as global dipolarization engulfed them. We suggest the ion injection region at these energies in the plasma sheet is better organized by the plasma flow.
79 ASTRONOMY AND ASTROPHYSICS↗