Plasma Signatures of Small Orbital Debris: LANL Theory and Modeling / Experimental effort.
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Heliospheric and Magnetospheric Physics↗
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Study of debris-plasma interaction in the Earth’s ionosphere
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Heliospheric and Magnetospheric Physics↗
Initial On-Orbit Cross-Calibration of the Electric Propulsion Electrostatic Analyzer Experiment (ÉPÉÉ)
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electrostatic analyzer, ionosphere, space environm↗
The Cross-field Current Instability for Substorm Expansion Onset
A challenging problem in the topic of the nonlinear dynamics of the magnetosphere is the physical process responsible for the onset of magnetospheric substorms. The early collaboration with Dr. K. Papadopoulos has led to the proposal of a kinetic plasma instability, called the cross-field current instability, as the onset process. This has developed into a full-blown research effort, supplementing the initial theoretical analysis with in-depth data analysis and particle simulations. Several theoretical predictions based on this instability are successfully verified in observations. Data from the present NASA THEMIS mission provide some evidence for its validity. Further investigations for this substorm onset process are also discussed.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Rapid enhancement of low energy (<100 eV) ion flux in response to interplanetary shocks based on two Van Allen Probes case studies: Implications for source regions and heating mechanisms
Interactions between interplanetary (IP) shocks and the Earth's magnetosphere manifest many important space physics phenomena including low-energy ion flux enhancements and particle acceleration. In order to investigate the mechanisms driving shock-induced enhancement of low-energy ion flux, we have examined two IP shock events that occurred when the Van Allen Probes were located near the equator while ionospheric and ground observations were available around the spacecraft footprints. We have found that, associated with the shock arrival, electromagnetic fields intensified, and low-energy ion fluxes, including H + , He + , and O + , were enhanced dramatically in both the parallel and perpendicular directions. During the 2 October 2013 shock event, both parallel and perpendicular flux enhancements lasted more than 20 min with larger fluxes observed in the perpendicular direction. In contrast, for the 15 March 2013 shock event, the low-energy perpendicular ion fluxes increased only in the first 5 min during an impulse of electric field, while the parallel flux enhancement lasted more than 30 min. In addition, ionospheric outflows were observed after shock arrivals. From a simple particle motion calculation, we found that the rapid response of low-energy ions is due to drifts of plasmaspheric population by the enhanced electric field. Furthermore, the fast acceleration in the perpendicular direction cannot solely be explained by E × B drift but betatron acceleration also plays a role. Adiabatic acceleration may also explain the fast response of the enhanced parallel ion fluxes, while ion outflows may contribute to the enhanced parallel fluxes that last longer than the perpendicular fluxes.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
The Io Torus and the Jovian magnetosphere
The IUE monitored the physical conditions in the Jovian magnetospheric system using the in situ Voyager measurements as a basis for comparison. Both the Io plasma torus, observable in emission of S(+), S(++), and S(+3), and the Jovian H2 polar aurorae are accessible to the IUE short wavelength spectrograph. Despite significant short-term variations observed, the electron density and temperature structure of the torus has not changed appreciably in the 7 yr since the Voyager encounters. The total radiated power from the polar aurorae remained relatively constant during this period.
Feldman, P. D.↗
Electron Physics in 3‐D Two‐Fluid 10‐Moment Modeling of Ganymede's Magnetosphere
Abstract We studied the role of electron physics in 3‐D two‐fluid 10‐moment simulation of Ganymede's magnetosphere. The model captures nonideal physics like the Hall effect, electron inertia, and anisotropic, nongyrotropic pressure effects. A series of analyses were carried out: (1) The resulting magnetic field topology and electron and ion convection patterns were investigated. The magnetic fields were shown to agree reasonably well with in situ measurements by the Galileo satellite. (2) The physics of collisionless magnetic reconnection were carefully examined in terms of the current sheet formation and decomposition of generalized Ohm's law. The importance of pressure anisotropy and nongyrotropy in supporting the reconnection electric field is confirmed. (3) We compared surface “brightness” morphology, represented by surface electron and ion pressure contours, with oxygen emission observed by the Hubble Space Telescope. The correlation between the observed emission morphology and spatial variability in electron/ion pressure was demonstrated. Potential extension to multi‐ion species in the context of Ganymede and other magnetospheric systems is also discussed.
Wang, Liang↗
ULF waves in the outer magnetosphere of Uranus
ULF waves are ubiquitous in the terrestrial magnetosphere, and play a critical role in the physics of the magnetosphere. A search for similar waves in the Uranian magnetosphere using Voyager 2 magnetometer data reveals ULF waves in the outer magnetosphere near the magnetopause. These waves decrease in amplitude with distance from the magnetopause. In the interior of the magnetosphere the wave level is at or below the noise level of the instrument.
Russell, C. T.↗
Plasma Imaging, LOcal Measurement, and Tomographic Experiment (PILOT): A Mission Concept for Transformational Multi-Scale Observations of Mass and Energy Flow Dynamics in Earth’s Magnetosphere
We currently do not understand the fundamental physical processes that govern mass and energy flow through the Earth’s magnetosphere. Knowledge of these processes is critical to understanding the mass loss rate of Earth’s atmosphere, as well as for determining the role that a planetary magnetic field plays in atmospheric retention, and therefore habitability, for Earth-like planets beyond the solar system. Mass and energy flow processes are challenging to determine at Earth in part because Earth’s planetary magnetic field creates a complex “system of systems” composed of interdependent plasma populations and overlapping spatial regions that perpetually exchange mass and energy across a broad range of temporal and spatial scales. Further, the primary mass carrier in the magnetosphere is cold plasma (as cold as ~0.1 eV), which is invisible to many space-borne instruments that operate in the inner magnetosphere. The Plasma Imaging LOcal and Tomographic experiment (PILOT) mission concept, described here, provides the transformational multi-scale observations required to answer fundamental open questions about mass and energy flow dynamics in the Earth’s magnetosphere. PILOT uses a constellation of spacecraft to make radio tomographic, remote sensing, and in-situ measurements simultaneously, fully capturing cold plasma mass dynamics and its impact on magnetospheric systems over an unprecedented range of spatial and temporal scales. This article details the scientific motivation for the PILOT mission concept as well as a potential mission implementation.
79 ASTRONOMY AND ASTROPHYSICS↗
The Need for Innovations in Instruments and Techniques to Enable Cold Ion and Cold Electron Measurements within the Magnetosphere
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cold plasma, magnetosphere, space physics, ions, e↗
The role of nonlocalities in magnetosphere-ionosphere coupling processes
Microinstabilities are believed to play a crucial role in the physics of magnetosphere-ionosphere coupling. The current driven ion cyclotron instability is a very important microinstability in this respect. A nonlocal formalism is given for studying the ion cyclotron instability in a more realistic magnetospheric environment than is available in the widely used local theory. This formalism includes the magnetic shear produced self-consistently by the field aligned currents and the finite extent of such currents. Significant departures from the local theory are noted.
Ganguli, G.↗
Wave-particle energy exchange directly observed in a kinetic Alfvén-branch wave
Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA’s Magnetospheric Multiscale (MMS) mission, we utilize Earth’s magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. As a result, the investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A new ionospheric electron precipitation module coupled with RAM-SCB within the geospace general circulation model
Electron precipitation down to the atmosphere due to wave-particle scattering in the magnetosphere contributes significantly to the auroral ionospheric conductivity. In order to obtain the auroral conductivity in global MHD models that are incapable of capturing kinetic physics in the magnetosphere, MHD parameters are often used to estimate electron precipitation flux for the conductivity calculation. Such an MHD approach, however, lacks self-consistency in representing the magnetosphere-ionosphere coupling processes. In this study we improve the coupling processes in global models with a more physical method. We calculate the physics-based electron precipitation from the ring current and map it to the ionospheric altitude for solving the ionospheric electrodynamics. In particular, we use the BATS-R-US (Block Adaptive Tree Scheme-Roe type-Upstream) MHD model coupled with the kinetic ring current model RAM-SCB (Ring current-Atmosphere interaction Model with Self-Consistent Magnetic field (B)) that solves pitch angle-dependent electron distribution functions, to study the global circulation dynamics during the 25–26 January 2013 storm event. Since the electron precipitation loss is mostly governed by wave-particle resonant scattering in the magnetosphere, we further investigate two loss methods of specifying electron precipitation loss associated with wave-particle interactions: (1) using pitch angle diffusion coefficients D αα (E,α) determined from the quasi-linear theory, with wave spectral and plasma density obtained from statistical observations (named as “diffusion coefficient method”) and (2) using electron lifetimes τ(E) independent on pitch angles inferred from the above diffusion coefficients (named as “lifetime method”). We found that both loss methods demonstrate similar temporal evolution of the trapped ring current electrons, indicating that the impact of using different kinds of loss rates is small on the trapped electron population. Furthermore, for the precipitated electrons, the lifetime method hardly captures any precipitation in the large L shell (i.e., 4 < L < 6.5) region, while the diffusion coefficient method produces much better agreement with NOAA/POES measurements, including the spatial distribution and temporal evolution of electron precipitation in the region from the premidnight through the dawn to the dayside. Further comparisons of the precipitation energy flux to DMSP observations indicates that the new physics-based precipitation approach using diffusion coefficients for the ring current electron loss can explain the diffuse electron precipitation in the dawn sector, such as the enhanced precipitation flux at auroral latitudes and flux drop near the subauroral latitudes, but the traditional MHD approach largely overestimates the precipitation flux at lower latitudes.
58 GEOSCIENCES↗
Cold Plasma IC Report
This past year we completed the simulation campaign in support of our magnetospheric cold plasma research project. This project aimed to develop the next-generation particle instruments to measure the properties of the cold particle populations in the Earth’s magnetosphere.
58 GEOSCIENCES↗
Coupling of damped and growing modes in unstable shear flow
Analysis of the saturation of the Kelvin-Helmholtz instability is undertaken to determine the extent to which the conjugate linearly stable mode plays a role. For a piecewise-continuous mean flow profile with constant shear in a fixed layer, it is shown that the stable mode is nonlinearly excited, providing an injection-scale sink of the fluctuation energy similar to what has been found for gyroradius-scale drift-wave turbulence. Quantitative evaluation of the contribution of the stable mode to the energy balance at the onset of saturation shows that nonlinear energy transfer to the stable mode is as significant as energy transfer to small scales in balancing energy injected into the spectrum by the instability. The effect of the stable mode on momentum transport is quantified by expressing the Reynolds stress in terms of stable and unstable mode amplitudes at saturation, from which it is found that the stable mode can produce a sizable reduction in the momentum flux.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
The physics of thermal plasma in the magnetosphere; Proceedings of Symposium 9 of the 26th COSPAR Plenary Meeting, Toulouse, France, June 30-July 11, 1986
The conference presents papers on the shape, dynamics, and thermal structure of the plasmasphere and plasmapause; the ionosphere as a supplier of plasma to the earth's magnetosphere; the modeling and remote sensing of thermal plasma in the earth's magnetosphere; and magnetospheric cold plasmas as a medium for wave generation and propagation. Particular attention is given to whistler studies of plasmasphere shape and dynamics, plasmasphere thermal structure as measured by ISEE-1 and DE-1, low-energy ion flows into the magnetosphere, field-aligned flows of ionospheric plasma in the magnetosphere, and field-aligned plasmaspheric flows at moderate latitudes. Papers are also presented on the effects of a tailward stretching geomagnetic field on the drift motion of plasma particles in the magnetospheric equatorial plane, ion cyclotron waves observed near the plasmapause, and the response of energetic particles to nightside magnetic pulsations as seen by AMPTE/CCE.
Chappell, C. R.↗
The Physical Elements of Onset of the Magnetospheric Substorm
During this reporting period effort continued in the areas: (1) understanding the mechanisms responsible for substorm onset, and (2) application of a fundamental description of field-aligned currents and parallel electric fields to the plasma-sheet boundary layer.
Erickson, Gary M.↗
The design and development of a space laboratory to conduct magnetospheric and plasma research
A design study was conducted concerning a proposed shuttle-borne space laboratory for research on magnetospheric and plasma physics. A worldwide survey found two broad research disciplines of interest: geophysical studies of the dynamics and structure of the magnetosphere (including wave characteristics, wave-particle interactions, magnetospheric modifications, beam-plasma interactions, and energetic particles and tracers) and plasma physics studies (plasma physics in space, wake and sheath studies, and propulsion and devices). The Plasma Physics and Environmental Perturbation Laboratory (PPEPL) designed to perform experiments in these areas will include two 50-m booms and two maneuverable subsatellites, a photometer array, standardized proton, electron, and plasma accelerators, a high-powered transmitter for frequencies above 100 kHz, a low-power transmitter for VLF and below, and complete diagnostic packages. Problem areas in the design of a space plasma physics laboratory are indicated.
Rosen, A.↗