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At least 127 records · Page 7
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NASA NTRS2003

Large- and Small-Scale Ring Current Electrodynamic Coupling

In this talk we will address the two primary issues of ring current (RC) electrodynamic coupling: 1. RC self-consistent magnetosphere-ionosphere coupling that includes calculation of the magnetospheric electric field (large scale electrodynamic coupling); and 2. RC self-consistent coupling with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic coupling). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002] couples the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic coupling processes and provides a self-consistent simulation of RC ions and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale coupling changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale coupling altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned currents and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic coupling processes and to examine their interactions with each other on a global scale.

Khazanov, G. V.↗
NASA NTRS2004

Ring Current Electrodynamic Coupling

In this talk we will address the two primary issues of ring current (RC) electrodynamic coupling: 1. RC self-consistent coupling with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic coupling); and 2. RC self-consistent magnetosphere-ionosphere coupling that includes calculation of the magnetospheric electric field (large scale electrodynamic coupling). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002, 20031 couples the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic coupling processes and provides a self-consistent simulation of RC ions, electrons and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale coupling changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale coupling altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned currents and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic coupling processes and to examine their interactions with each other on a global scale. We also discuss the nonlinear coupling of EMIC and lower hybrid waves in the RC region during the May 2-7, 1998 storm period.

Khazanov, G. V.↗
NASA NTRS2005

Strong Pitch-Angle Diffusion of Ring Current Ions in Geomagnetic Storm-Associated Conditions

Do electromagnetic ion cyclotron (EMIC) waves cause strong pitch-angle diffusion of RC ions? This question is the primary motivation of this paper and has been affirmatively answered from the theoretical point of view. The materials that are presented in the Results section show clear evidence that strong pitch-angle diffusion takes place in the inner magnetosphere indicating an important role for the wave-particle interaction mechanism in the formation of RC ions and EMIC waves.

Khazanov, G. V.↗
NASA NTRS2011

Modeling of Inner Magnetosphere Coupling Processes

The Ring Current (RC) is the biggest energy player in the inner magnetosphere. It is the source of free energy for Electromagnetic Ion Cyclotron (EMIC) wave excitation provided by a temperature anisotropy of RC ions, which develops naturally during inward E B convection from the plasmasheet. The cold plasmasphere, which is under the strong influence of the magnetospheric electric field, strongly mediates the RC-EMIC wave-particle-coupling process and ultimately becomes part of the particle and energy interplay. On the other hand, there is a strong influence of the RC on the inner magnetospheric electric and magnetic field configurations and these configurations, in turn, are important to RC dynamics. Therefore, one of the biggest needs for inner magnetospheric research is the continued progression toward a coupled, interconnected system with the inclusion of nonlinear feedback mechanisms between the plasma populations, the electric and magnetic fields, and plasma waves. As we clearly demonstrated in our studies, EMIC waves strongly interact with electrons and ions of energies ranging from approx.1 eV to approx.10 MeV, and that these waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer RB relativistic electrons. As we found, the rate of ion and electron scattering/heating in the Earth's magnetosphere is not only controlled by the wave intensity-spatial-temporal distribution but also strongly depends on the spectral distribution of the wave power. The latter is also a function of the plasmaspheric heavy ion content, and the plasma density and temperature distributions along the magnetic field lines. The above discussion places RC-EMIC wave coupling dynamics in context with inner magnetospheric coupling processes and, ultimately, relates RC studies with plasmaspheric and Superthermal Electrons formation processes as well as with outer RB physics.

Khazanov, George V.↗
NASA NTRS2011

Global Magnetospheric Response to an Interplanetary Shock: THEMIS Observations

We investigate the global response of geospace plasma environment to an interplanetary shock at approx. 0224 UT on May 28, 2008 from multiple THEMIS spacecraft observations in the magnetosheath (THEMIS B and C) and the mid-afternoon (THEMIS A) and dusk magnetosphere (THEMIS D and E). The interaction of the transmitted interplanetary shock with the magnetosphere has global effects. Consequently, it can affect geospace plasma significantly. After interacting with the bow shock, the interplanetary shock transmitted a fast shock and a discontinuity which propagated through the magnetosheath toward the Earth at speeds of 300 km/s and 137 km/s respectively. THEMIS A observations indicate that the plasmaspheric plume changed significantly by the interplanetary shock impact. The plasmaspheric plume density increased rapidly from 10 to 100/ cubic cm in 4 min and the ion distribution changed from isotropic to strongly anisotropic distribution. Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are most likely excited by the anisotropic ion distributions caused by the interplanetary shock impact. To our best knowledge, this is the first direct observation of the plasmaspheric plume response to an interplanetary shock's impact. THEMIS A, but not D or E, observed a plasmaspheric plume in the dayside magnetosphere. Multiple spacecraft observations indicate that the dawn-side edge of the plasmaspheric plume was located between THEMIS A and D (or E).

Zhang, Hui↗
NASA NTRS2016

Simulation of a Rapid Dropout Event for Highly Relativistic Electrons with the RBE Model

A flux dropout is a sudden and sizable decrease in the energetic electron population of the outer radiation belt on the time scale of a few hours. We simulated a flux dropout of highly relativistic 2.5 MeV electrons using the Radiation Belt Environment model, incorporating the pitch angle diffusion coefficients caused by electromagnetic ion cyclotron (EMIC) waves for the geomagnetic storm events of 23-26 October 2002. This simulation showed a remarkable decrease in the 2.5 MeV electron flux during main phase of the storm, compared to those without EMIC waves. This decrease was independent of magnetopause shadowing or drift loss to the magnetopause. We suggest that the flux decrease was likely to be primarily due to pitch angle scattering to the loss cone by EMIC waves. Furthermore, the 2.5 MeV electron flux calculated with EMIC waves correspond very well with that observed from Solar Anomalous and Magnetospheric Particle EXplorer spacecraft. EMIC wave scattering is therefore likely one of the key mechanisms to understand flux dropouts. We modeled EMIC wave intensities by the Kp index. However, the calculated dropout is a several hours earlier than the observed one. We propose that Kp is not the best parameter to predict EMIC waves.

Kang, S-B.↗
NASA NTRS2017

Marshall Space Flight Center Faculty Fellowship Program

The 2017 Marshall Faculty Fellowship Program involved 21 faculty in the laboratories and departments at Marshall Space Flight Center. These faculty engineers and scientists worked with NASA collaborators on NASA projects, bringing new perspectives and solutions to bear. This Technical Memorandum is a compilation of the research reports of the 2017 Marshall Faculty Fellowship program, along with the Program Announcement (Appendix A) and the Program Description (Appendix B). The research affected the following six areas: (1) Materials (2) Propulsion (3) Instrumentation (4) Spacecraft systems (5) Vehicle systems (6) Space science The materials investigations included composite structures, printing electronic circuits, degradation of materials by energetic particles, friction stir welding, Martian and Lunar regolith for in-situ construction, and polymers for additive manufacturing. Propulsion studies were completed on electric sails and low-power arcjets for use with green propellants. Instrumentation research involved heat pipes, neutrino detectors, and remote sensing. Spacecraft systems research was conducted on wireless technologies, layered pressure vessels, and two-phase flow. Vehicle systems studies were performed on life support-biofilm buildup and landing systems. In the space science area, the excitation of electromagnetic ion-cyclotron waves observed by the Magnetospheric Multiscale Mission provided insight regarding the propagation of these waves. Our goal is to continue the Marshall Faculty Fellowship Program funded by Center internal project offices. Faculty Fellows in this 2017 program represented the following minority-serving institutions: Alabama A&M University and Oglala Lakota College.

Six, N. F.↗
NASA NTRS1986

Transverse acceleration of oxygen ions by electromagnetic ion cyclotron resonance with broad band left-hand polarized waves

Central plasma sheet (CPS) ion conics are oxygen-dominated, with peak energies ranging from tens to hundreds of eV centered around pitch-angles between 115 and 130 degrees. Because of the lack of correlation between the CPS conics and the observed currents and/or electron beam-like structures, it is not likely that all of these conics are generated by interactions with electrostatic ion cyclotron waves or lower hybrid waves. Instead, it is suggested that the observed intense broad band electric field fluctuations in the frequency range between 0 and 100 Hz can be responsible for the transverse energization of the ions through cyclotron resonance heating with the left-hand polarized electromagnetic waves. This process is much more efficient for heating the oxygen ions than hydrogen ions, thus providing a plausible explanation of the oxygen dominance in CPS conics. Simple algebraic expressions are given from which estimates of conic energy and pitch angle can be easily calculated. This suggested mechanism can also provide some preheating of the oxygen ions in the boundary plasma sheet (BPS) where discrete aurorae form.

Chang, T.↗
NASA NTRS1993

Ion acceleration and abundance enhancements by electron beam instabilities in impulsive solar flares

We show that a nonrelativistic electron beam in a hydrogen-helium solar flare plasma will excite H(+) electromagnetic ion cyclotron, shear Alfven, and R-X waves, in addition to waves resulting from the two-stream instability. The H(+) electromagnetic ion cyclotron and shear Alfven waves are able to selectively accelerate ambient He-3 and Fe, respectively, to MeV energies through first harmonic gyroresonance, and thereby account for the large (He-3)/(He-4) and Fe/C ratios seen in the energetic particles from impulsive solar flares. In this model, separate heating and acceleration mechanisms for either He-3 or Fe are not required, and Fe acceleration is quite efficient since it does not need to occur by second harmonic gyroresonance. The combination of the other two unstable modes is able to accelerate ions to hundreds of MeV if the particles become trapped in an electrostatic potential well of a two-stream wave.

Miller, James A.↗
NASA NTRSDate not supplied

Observations of Ion-Scale Cyclotron Waves and Their Relationship with Non-thermal Ion Distributions in the Solar Wind

Introduction - Electromagnetic cyclotron waves (ECWs) near the proton cyclotron frequency (f_pc) and higher than Alfvén wave frequency - Ion cyclotron waves (ICWs): left-hand (LH) polarized in plasma frame - Magnetosonicwaves: right-hand (RH) polarized in plasma frame - They are important because the absorption of fluctuating magnetic field energy starting at f_pc has been demonstrated extensively - Before PSP era, intermittent observations of such ECWs in quiet solar wind have been reported in Behannon (1976), Tsurutani et al. (1994), Jian et al. (2009, 2010, 2014), Boardsen et al. (2015), Wicks et al. (2016), etc

L K Jian↗
NASA NTRS1992

The production of He-3 and heavy ion enrichment in He-3-rich flares by electromagnetic hydrogen cyclotron waves

A new model is presented for the production of He-3 and heavy ion enrichments in He-3-rich flares using a direct single-stage mechanism. In analogy with the production of electromagnetic hydrogen cyclotron waves in earth's aurora by electron beams, it is suggested that such waves should exist in the electron acceleration region of impulsive solar flares. Both analytic and test-particle models of the effect of such waves in a nonuniform magnetic field show that these waves can selectively accelerate He-3 and heavy ions to MeV energies in a single-stage process, in contrast to other models which require a two-stage mechanism.

Temerin, M.↗
NASA NTRS1980

An experimental test of the electromagnetic ion cyclotron instability within the earth's magnetosphere

Examples of propagating electromagnetic Alfven/ion cyclotron waves in plasma particle and magnetic field data observed by the ATS-6 geostationary satellite are discussed. These waves were viewed mainly near the afternoon and dusk regions of the earth's magnetosphere with normalized frequencies in the 0.05 to 0.5 range. Two wave events were analyzed: both appeared coincidentally with the encounter of cool plasma populations which joined the hot populations already present. An electromagnetic ion cyclotron instability was proposed as the wave generation mechanism; this theory was tested by evaluating the linear growth integrals under the measured anisotropic hot ion distribution.

Mauk, B. H.↗
NASA NTRS1994

Semiannual Status Report

During the last six months, we have continued our study of the excitation of electromagnetic waves in the whistler frequency range and the role that these waves will play in the acceleration of electrons and ions in the auroral region. A paper entitled 'Electron Beam Excitation of Upstream Waves in the Whistler Mode Frequency Range' was listed in the Journal of Geophysical Research. In this paper, we have shown that an anisotropic electron beam (or gyrating electron beam) is capable of generating both left-hand and right-hand polarized electromagnetic waves in the whistler frequency range. Since right-hand polarized electromagnetic waves can interact with background electrons and left-hand polarized waves can interact with background ions through cyclotron resonance, it is possible that these beam generated left-hand and right-hand polarized electromagnetic waves can accelerate either ions or electrons (or both), depending on the physical parameters under consideration. We are currently carrying out a comprehensive study of the electromagnetic whistler and lower hybrid like waves observed in the auroral zone using both wave and particle data. Our first task is to identify these wave modes and compare it with particle observations. Using both the DE-1 particle and wave measurements, we can positively identify those electromagnetics lower hybrid like waves as fast magnetosonic waves and the upper cutoff of these waves is the local lower hybrid frequency. From the upper cutoff of the frequency spectrum, one can infer the particle density and the result is in very good agreement with the particle data. Since these electromagnetic lower hybrid like waves can have frequencies extended down to the local ion cyclotron frequency, it practically confirms that they are not whistler waves.

Source record↗
NASA NTRS1994

Proton and helium cyclotron anisotropy instability thresholds in the magnetosheath

Both the protons and the helium ions of the terrestrial magnetosheath typically display T (sub perpendicular) greater than T (sub parallel), where perpendicular to and parallel to denote directions perpendicular and parallel to the background magnetic field. Observations of the highly compressed magnetosheath show an inverse correlation between these ion temperature anisotropies and the parallel proton beta. Computer simulations have demonstrated that these correlations are due to wave-particle scattering by electromagnetic ion cyclotron anisotropy instabilities. These correlations correspond to linear theory thresholds of the proton cyclotron and the helium cyclotron instabilities. This paper uses linear Vlasov theory and the assumption of a constant maximum growth rate to obtain closed-form expressions for these thresholds as a function of the relative helium density and the parallel proton beta in a parameter model of the magnetosheath.

Gary, S. Peter↗
NASA NTRS2021

Prompt Response of the Dayside Magnetosphere to Discrete Structures within the Sheath Region of a Coronal Mass Ejection

A sequence of discrete solar wind structures within the sheath region of an interplanetary coronal mass ejection (ICME) on Nov 06, 2015 caused a series of compressions and releases of the dayside magnetosphere. Each compression resulted in a brief adiabatic enhancement of ions (electrons) driving bursts of electromagnetic ion cyclotron (whistler mode chorus) wave growth across the dayside magnetosphere. Fine-structured rising tones were observed in the EMIC wave bursts, resulting in nonlinear scattering of relativistic electrons in the outer radiation belt. Multipoint observations allow us to study the spatial structure and evolution of these sheath structures as they propagate Earthward from L1 as well as the spatio-temporal characteristics of the magnetospheric response. This event highlights the importance of fine-scale solar wind structure, in particular within complex sheath regions, in driving dayside phenomena within the inner magnetosphere.

L. W. Blum↗
NASA NTRS1992

Kinetic structure of slow shocks - Effects of the electromagnetic ion/ion cyclotron instability

The structure of slow magnetosonic shocks in the low beta regime is analyzed with attention given to ion heating and the effects of waves upstream of the electromagnetic ion/ion cyclotron (EMIIC) instability. Shock formation is assessed by means of three methods - a relaxation method and two based on dynamic flow interactions - to determine the effects of initialization and boundary conditions on the formation. Good solutions are found with the piston method and the similar flow-flow method in which the plasma is injected from two boundaries to form two slow shocks. Plasma parameters and shock normal angle are found to be the key variables dictating the structure of the magnetosonic shocks. Four unique classes of resultant shock structures are described in which classical, steady, or nonsteady behavior is found. The analysis also yields insight into the relationship between EMIIC instability and ion dissipation.

Omidi, N.↗
NASA NTRS1983

Generation of Alfven-ion cyclotron waves on auroral field lines in the presence of heavy ions

Observation of electromagnetic waves in the low-altitude auroral zone at frequencies between the proton and helium gyrofrequencies suggests that Alfven-ion cyclotron waves modified by the presence of helium ions are being excited. Estimates of the growth rates for this mode indicate that the auroral electron beam can provide the free energy for the instability. The effect of the heavy ions is to decrease the group velocity of the waves, leading to larger convective growth. Theoretical wave spectra are computed in the local approximation, which assumes that the gradient scale lengths in density and magnetic field are constant over the ray paths. Narrow banded spectral peaks similar to observations may be produced when the thickness of the electron beam is small (200 m at 3000 km altitude). Narrow beams also limit growth of whistler mode waves, which compete for the free energy of the electron beam.

Lysak, R. L.↗