The parallel electric fields associated with inertial Alfvén waves are investigated using a self-... more The parallel electric fields associated with inertial Alfvén waves are investigated using a self-consistent drift-kinetic simulation code. The simulation code allows for non-linear effects and we show that when the wave energy is large in comparison to the plasma thermal energy, the amplitude and form of the parallel electric field can evolve significantly as the wave propagates throughout the plasma.
Two-dimensional hydrodynamic simulations of laser light self-focusing in a hydrogen plasma are pr... more Two-dimensional hydrodynamic simulations of laser light self-focusing in a hydrogen plasma are presented. The simulation code includes a model for laser beam propagation which accounts for inverse bremsstrahlung absorption, refraction, diffraction, and ponderomotive forces. A Gaussian hot spot, superimposed upon a collimated, spatially uniform laser beam, is used to initiate self-focusing. Intense filaments provide a driving source for ion waves near the axis of the laser beam. The radially propagating ion waves cause spatiotemporal modulations of the flux where it is initially uniform, as well as the more usual focusing that occurs along the axis. Some of the factors affecting the generation of the ion waves are considered. In particular, the effect of changing the amplitude and width of the imposed nonuniformity is investigated. The intensity thresholds for thermal and ponderomotively driven self-focusing have also been determined by artificially turning the ponderomotive force on...
Magnetospheric ULF Waves: Synthesis and New Directions, 2006
We present a review of some theoretical aspects of inertial and kinetic scale Alfven waves in Ear... more We present a review of some theoretical aspects of inertial and kinetic scale Alfven waves in Earth's magnetosphere. The basic elements of two-fluid magnetohydrodynamic theory applied to standing and propagating shear Alfven waves are discussed, and simple estimates of the phase mixing time, latitudinal phase shift, saturation width and timescale are derived. We consider local and nonlocal aspects of the linear dispersion characteristics of dispersive scale Alfven waves, and then discuss important nonlinear processes that arise in the presence of shear wave ponderomotive forces. We review the formation of nonlinear density structures, factors affecting their spatial scale, and the temporal dynamics of Alfven waves excited within them. The process of nonlinear phase mixing is discussed, along with the associated time and spatial scales that lead to fast steepening of Alfven waves inside density fluctuations associated with nonlinearly excited ion acoustic waves. We show how nonlinear structuring of low-frequency waves can lead to a spatial scale comparable to the electron or ion acoustic gyroradius, and consider the consequences of this in terms of explaining electric field-aligned potential drops that might be responsible for aspects of auroral particle acceleration. We then discuss nonlocal kinetic effects related to electrons that mirror along geomagnetic field lines with bounce times that are shorter than the period of low-frequency standing waves. The frequency dependence of kinetic scale processes is briefly discussed, and finally, some results of a model describing self-consistent kinetic scale wave-particle interactions in high-frequency waves are presented.
The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been exami... more The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been examined theoretically and by computer simulation. This conversion is the inverse of resonance absorption exhibiting an identical dependence on magnetic field and density scale length with an optimum conversion efficiency of approximately 60%. Radiation from this source may contribute to the harmonic spectra observed from laser-irradiated plasmas.
Eos, Transactions American Geophysical Union, 2011
The rapidly increasing volume of space science data is leading to a growing need for tools for sc... more The rapidly increasing volume of space science data is leading to a growing need for tools for scientists to access, analyze, and share data. To address this need, the Canadian Space Science Data Portal (CSSDP) provides space scientists with access to a wide range of space data, observations, and investigative tools. CSSDP serves as a one‐stop shop for scientists to discover, gather, and visualize relevant data. The data portal has embedded analysis tools and workflows to simplify common research tasks, along with a rich collaboration framework to develop and share scientific findings (see Figure 1). The data portal is accessible at http://www.cssdp.ca.
Standing and traveling shear Alfvén waves contribute to electron acceleration and parallel electr... more Standing and traveling shear Alfvén waves contribute to electron acceleration and parallel electric field formation on auroral field lines in the Earth’s magnetosphere. In this paper, the self-consistent coupled Vlasov–Maxwell system for shear Alfvén waves is solved in one dimension. The Vlasov equation is gyro-averaged in order to minimize the number of dimensions in the problem, and to avoid numerical problems with the direct evaluation of the parallel electric field, the electron distribution function is described in terms of a spatial coordinate along the field line, the magnetic moment, and the canonical parallel momentum per unit mass. Some preliminary studies of shear Alfvén wave pulses propagating in a uniform magnetic field on model auroral field lines are presented with an emphasis on the kinetic electron response and the parallel electric field. It is shown that when the full parallel electron dynamics are included, wave–particle interactions result in intensification of ...
A model is presented which describes the nonlinear interaction of dispersive shear Alfvén wave (S... more A model is presented which describes the nonlinear interaction of dispersive shear Alfvén wave (SAW) field line resonances (FLRs) and ion acoustic waves (IAWs), with applications to the Earth’s magnetosphere. Two limits are considered: In low-β plasma (β<me/mi), dispersion is dominated by electron inertia (EI), while for higher β it is dominated by the electron thermal effect. In each case, the ponderomotive force steepens the SAW in the radial direction, taken as earthward in the equatorial plane. Following the time of nonlinear steepening, the dynamics strongly depends on dispersion. In the EI case, standing SAWs excited in FLRs exhibit a parametric decay instability (PDI) into secondary SAWs and IAWs. Nonlinearity and dispersion broaden the FLR in the radial direction, leading to rapid density and parallel electric field fluctuations and scale lengths comparable to the EI length. In warm plasmas, SAWs are stable to the PDI, and in this case the FLR emits short perpendicular sc...
Intense laser light filamentation in a hydrogen plasma is investigated using a two-dimensional hy... more Intense laser light filamentation in a hydrogen plasma is investigated using a two-dimensional hydrodynamic simulation code. The laser paraxial wave equation is used to study the focusing which results from a Gaussian hot-spot intensity perturbation. It is found that diffraction increases the scale size of small-scale of-axis filamentation, and significantly raises the ponderomotive self-focusing intensity threshold. Radially propagating density Auctuations, contributing to small-scale focusing, are observed due to the self-consistent treatment of hydrodynamics in the simulations.
We solve the one-dimensional wave equation for high-order mixing of the type h ϭq 0 Ϫl c (qӷlϾϭ1)... more We solve the one-dimensional wave equation for high-order mixing of the type h ϭq 0 Ϫl c (qӷlϾϭ1) using a Keldysh-type model to describe the high-field atomic nonlinear susceptibility. When c is selected to give static phase matching, we show that the conversion efficiency of the mixed field can be increased by about an order of magnitude compared to non-phase-matched high-order harmonic generation but that fundamental limitations are introduced by axial electron-density gradients. ͓S1050-2947͑96͒51108-X͔
The problem of refraction of ultrashort, high-intensity laser pulses in underdense plasmas is dis... more The problem of refraction of ultrashort, high-intensity laser pulses in underdense plasmas is discussed in the context of producing long plasma filaments by high f-number axial focusing of laser beams. For uniform gas targets, it is shown that refraction can clamp the intensity of the focused laser beam at a value near the threshold for multiphoton ionization. In order to make large volumes of underdense plasma with ultrashort pulses, it is necessary to preform a partially ionized filament with a suitable radial electron density profile. Such a structure can act as an indestructible waveguide for ultraintense, subpicosecond laser pulses. Indeed, highly ionized plasma represents the only practical optical material at wavelengths below 50 nm or at intensities above 10(13) W cm(-2).
Journal of Geophysical Research: Space Physics, 2012
Ultra‐low frequency (ULF) field line resonances (FLRs) cause oscillations in F‐region plasma flow... more Ultra‐low frequency (ULF) field line resonances (FLRs) cause oscillations in F‐region plasma flows and can be detected in SuperDARN measured line‐of‐sight (l‐o‐s) velocities. In this paper, we characterize a ULF wave event with coordinated use of SuperDARN HF radars, optical instrumentation, ground based and space based magnetometers. On December 26, 2000 from 00:00–04:00 UT, the SuperDARN Pykkvibaer radar observes first and second harmonic FLR signatures at 0.8 mHz, while the Kodiak and Hankasalmi radars simultaneously observe the driver wave on open field lines at exactly the same 0.8 mHz frequency. These observations show that SuperDARN can provide a diagnostic of MHD wave propagation on open field lines and potentially be used to monitor MHD wave transmission across the magnetopause, and through the outer regions of the magnetosphere. MHD waves in the outer magnetosphere, which couple to FLRs, are seldom observed, and as far as we know this is the first report of a ground based ...
We present results from self-consistent simulations of the electron response to shear Alfve ´n pu... more We present results from self-consistent simulations of the electron response to shear Alfve ´n pulses in the presence of non-uniform magnetic fields and the associated mirror force. We discuss how energies of resonantly accelerated beam particles are affected by the local phase velocity of the pulse, and show that time-of-flight models are inadequate for describing electron acceleration since the acceleration can occur at more than one location along the field line as the pulse propagates toward the ionosphere. We also demonstrate that electron conics in low-altitude satellite observations of electron acceleration can be explained in terms of field-aligned inertial Alfve ´n wave pulses, without the requirement of a static potential drop or a standing Alfve ´n wave structure.
A model is presented that describes the excitation of small-scale density perturbations and elect... more A model is presented that describes the excitation of small-scale density perturbations and electromagnetic fields by standing shear Alfvé n waves in a Cartesian geometry. The model includes the effects of plasma betas and the Hall term effects. The characteristics of magnetospheric density cavities and the formation of the significant peak in density are discussed in the paper.
A model is presented that describes the excitation of small-scale density perturbations and elect... more A model is presented that describes the excitation of small-scale density perturbations and electromagnetic fields by standing shear Alfvé n waves in a Cartesian geometry. The model includes the effects of plasma betas and the Hall term effects. The characteristics of magnetospheric density cavities and the formation of the significant peak in density are discussed in the paper.
Journal of Geophysical Research: Space Physics, 2016
"Zebra stripes" are newly found energetic electron energy-spatial (L shell) distributed structure... more "Zebra stripes" are newly found energetic electron energy-spatial (L shell) distributed structure with an energy between tens to a few hundreds keV in the inner radiation belt. Using high-quality measurements of electron fluxes from Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the twin Van Allen Probes, we carry out case and statistical studies from April 2013 to April 2014 to study the structural and evolutionary characteristics of zebra stripes below L = 3. It is revealed that the zebra stripes can be transformed into evenly spaced patterns in the electron drift frequency coordinate: the detrended logarithmic fluxes in each L shell region can be well described by sinusoidal functions of drift frequency. The "wave number" of this sinusoidal function, which corresponds to the reciprocal of the gap between two adjacent peaks in the drift frequency coordinate, increases in proportion to real time. Further, these structural and evolutionary characteristics of zebra stripes can be reproduced by an analytic model of the evolution of the particle distribution under a single monochromatic or static azimuthal electric field. It is shown that the essential ingredient for the formation of multiple zebra stripes is the periodic drift of particles. The amplitude of the zebra stripes shows a good positive correlation with Kp index, which indicates that the generation mechanism of zebra stripes should be related to geomagnetic activities.
Journal of Geophysical Research: Space Physics, 2013
Primary and secondary Kelvin‐Helmholtz surface wave modes on the Earth's magnetopause are stu... more Primary and secondary Kelvin‐Helmholtz surface wave modes on the Earth's magnetopause are studied within the framework of warm plasma ideal magnetohydrodynamics (MHD) across an infinitely thin magnetopause tangential discontinuity (TD). With the increase of background flow velocity, a Kelvin‐Helmholtz Instability (KHI) unstable boundary separating two uniform semi‐infinite plasma regions is always ultimately stabilized to KHI growth at an upper cut‐off while inclusion of an inner boundary in one plasma region removes this stabilization. Phase velocity Friedrichs diagrams are presented that allow us to identify unstable fast and slow modes that correspond to growing modes of the KHI under different magnetosphere and magnetosheath conditions. On the nightside magnetosphere, and the magnetotail, new KH unstable intermediate‐fast modes are created, which cannot propagate exactly perpendicular to the magnetic field. In the plasma frame, primary unstable KH waves show fast/fast, while...
The Kelvin-Helmholtz instability (KHI) of magnetotail flow channels associated with bursty bulk f... more The Kelvin-Helmholtz instability (KHI) of magnetotail flow channels associated with bursty bulk flows (BBFs) is investigated. MHD oscillations of the channel in both kink and sausage modes are investigated for KHI, and both the primary and secondary KHIs are found that drive MHD waves. These instabilities are likely to be important for flow channel braking where the KHI removes energy from the flow. At flow speeds above the peak growth rate, the MHD modes excited by KHI develop from surface modes into propagating modes leading to the radiation of MHD waves from the flow channel. The coupling of BBF-driven shear flow instabilities to MHD waves presented here represents a new paradigm to explain BBF excitation of tail flapping. Our model can also explain, for the first time, the generation mechanism for the observations of waves propagating toward both flanks and emitted from BBF channels in the magnetotail.
The parallel electric fields associated with inertial Alfvén waves are investigated using a self-... more The parallel electric fields associated with inertial Alfvén waves are investigated using a self-consistent drift-kinetic simulation code. The simulation code allows for non-linear effects and we show that when the wave energy is large in comparison to the plasma thermal energy, the amplitude and form of the parallel electric field can evolve significantly as the wave propagates throughout the plasma.
Two-dimensional hydrodynamic simulations of laser light self-focusing in a hydrogen plasma are pr... more Two-dimensional hydrodynamic simulations of laser light self-focusing in a hydrogen plasma are presented. The simulation code includes a model for laser beam propagation which accounts for inverse bremsstrahlung absorption, refraction, diffraction, and ponderomotive forces. A Gaussian hot spot, superimposed upon a collimated, spatially uniform laser beam, is used to initiate self-focusing. Intense filaments provide a driving source for ion waves near the axis of the laser beam. The radially propagating ion waves cause spatiotemporal modulations of the flux where it is initially uniform, as well as the more usual focusing that occurs along the axis. Some of the factors affecting the generation of the ion waves are considered. In particular, the effect of changing the amplitude and width of the imposed nonuniformity is investigated. The intensity thresholds for thermal and ponderomotively driven self-focusing have also been determined by artificially turning the ponderomotive force on...
Magnetospheric ULF Waves: Synthesis and New Directions, 2006
We present a review of some theoretical aspects of inertial and kinetic scale Alfven waves in Ear... more We present a review of some theoretical aspects of inertial and kinetic scale Alfven waves in Earth's magnetosphere. The basic elements of two-fluid magnetohydrodynamic theory applied to standing and propagating shear Alfven waves are discussed, and simple estimates of the phase mixing time, latitudinal phase shift, saturation width and timescale are derived. We consider local and nonlocal aspects of the linear dispersion characteristics of dispersive scale Alfven waves, and then discuss important nonlinear processes that arise in the presence of shear wave ponderomotive forces. We review the formation of nonlinear density structures, factors affecting their spatial scale, and the temporal dynamics of Alfven waves excited within them. The process of nonlinear phase mixing is discussed, along with the associated time and spatial scales that lead to fast steepening of Alfven waves inside density fluctuations associated with nonlinearly excited ion acoustic waves. We show how nonlinear structuring of low-frequency waves can lead to a spatial scale comparable to the electron or ion acoustic gyroradius, and consider the consequences of this in terms of explaining electric field-aligned potential drops that might be responsible for aspects of auroral particle acceleration. We then discuss nonlocal kinetic effects related to electrons that mirror along geomagnetic field lines with bounce times that are shorter than the period of low-frequency standing waves. The frequency dependence of kinetic scale processes is briefly discussed, and finally, some results of a model describing self-consistent kinetic scale wave-particle interactions in high-frequency waves are presented.
The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been exami... more The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been examined theoretically and by computer simulation. This conversion is the inverse of resonance absorption exhibiting an identical dependence on magnetic field and density scale length with an optimum conversion efficiency of approximately 60%. Radiation from this source may contribute to the harmonic spectra observed from laser-irradiated plasmas.
Eos, Transactions American Geophysical Union, 2011
The rapidly increasing volume of space science data is leading to a growing need for tools for sc... more The rapidly increasing volume of space science data is leading to a growing need for tools for scientists to access, analyze, and share data. To address this need, the Canadian Space Science Data Portal (CSSDP) provides space scientists with access to a wide range of space data, observations, and investigative tools. CSSDP serves as a one‐stop shop for scientists to discover, gather, and visualize relevant data. The data portal has embedded analysis tools and workflows to simplify common research tasks, along with a rich collaboration framework to develop and share scientific findings (see Figure 1). The data portal is accessible at http://www.cssdp.ca.
Standing and traveling shear Alfvén waves contribute to electron acceleration and parallel electr... more Standing and traveling shear Alfvén waves contribute to electron acceleration and parallel electric field formation on auroral field lines in the Earth’s magnetosphere. In this paper, the self-consistent coupled Vlasov–Maxwell system for shear Alfvén waves is solved in one dimension. The Vlasov equation is gyro-averaged in order to minimize the number of dimensions in the problem, and to avoid numerical problems with the direct evaluation of the parallel electric field, the electron distribution function is described in terms of a spatial coordinate along the field line, the magnetic moment, and the canonical parallel momentum per unit mass. Some preliminary studies of shear Alfvén wave pulses propagating in a uniform magnetic field on model auroral field lines are presented with an emphasis on the kinetic electron response and the parallel electric field. It is shown that when the full parallel electron dynamics are included, wave–particle interactions result in intensification of ...
A model is presented which describes the nonlinear interaction of dispersive shear Alfvén wave (S... more A model is presented which describes the nonlinear interaction of dispersive shear Alfvén wave (SAW) field line resonances (FLRs) and ion acoustic waves (IAWs), with applications to the Earth’s magnetosphere. Two limits are considered: In low-β plasma (β<me/mi), dispersion is dominated by electron inertia (EI), while for higher β it is dominated by the electron thermal effect. In each case, the ponderomotive force steepens the SAW in the radial direction, taken as earthward in the equatorial plane. Following the time of nonlinear steepening, the dynamics strongly depends on dispersion. In the EI case, standing SAWs excited in FLRs exhibit a parametric decay instability (PDI) into secondary SAWs and IAWs. Nonlinearity and dispersion broaden the FLR in the radial direction, leading to rapid density and parallel electric field fluctuations and scale lengths comparable to the EI length. In warm plasmas, SAWs are stable to the PDI, and in this case the FLR emits short perpendicular sc...
Intense laser light filamentation in a hydrogen plasma is investigated using a two-dimensional hy... more Intense laser light filamentation in a hydrogen plasma is investigated using a two-dimensional hydrodynamic simulation code. The laser paraxial wave equation is used to study the focusing which results from a Gaussian hot-spot intensity perturbation. It is found that diffraction increases the scale size of small-scale of-axis filamentation, and significantly raises the ponderomotive self-focusing intensity threshold. Radially propagating density Auctuations, contributing to small-scale focusing, are observed due to the self-consistent treatment of hydrodynamics in the simulations.
We solve the one-dimensional wave equation for high-order mixing of the type h ϭq 0 Ϫl c (qӷlϾϭ1)... more We solve the one-dimensional wave equation for high-order mixing of the type h ϭq 0 Ϫl c (qӷlϾϭ1) using a Keldysh-type model to describe the high-field atomic nonlinear susceptibility. When c is selected to give static phase matching, we show that the conversion efficiency of the mixed field can be increased by about an order of magnitude compared to non-phase-matched high-order harmonic generation but that fundamental limitations are introduced by axial electron-density gradients. ͓S1050-2947͑96͒51108-X͔
The problem of refraction of ultrashort, high-intensity laser pulses in underdense plasmas is dis... more The problem of refraction of ultrashort, high-intensity laser pulses in underdense plasmas is discussed in the context of producing long plasma filaments by high f-number axial focusing of laser beams. For uniform gas targets, it is shown that refraction can clamp the intensity of the focused laser beam at a value near the threshold for multiphoton ionization. In order to make large volumes of underdense plasma with ultrashort pulses, it is necessary to preform a partially ionized filament with a suitable radial electron density profile. Such a structure can act as an indestructible waveguide for ultraintense, subpicosecond laser pulses. Indeed, highly ionized plasma represents the only practical optical material at wavelengths below 50 nm or at intensities above 10(13) W cm(-2).
Journal of Geophysical Research: Space Physics, 2012
Ultra‐low frequency (ULF) field line resonances (FLRs) cause oscillations in F‐region plasma flow... more Ultra‐low frequency (ULF) field line resonances (FLRs) cause oscillations in F‐region plasma flows and can be detected in SuperDARN measured line‐of‐sight (l‐o‐s) velocities. In this paper, we characterize a ULF wave event with coordinated use of SuperDARN HF radars, optical instrumentation, ground based and space based magnetometers. On December 26, 2000 from 00:00–04:00 UT, the SuperDARN Pykkvibaer radar observes first and second harmonic FLR signatures at 0.8 mHz, while the Kodiak and Hankasalmi radars simultaneously observe the driver wave on open field lines at exactly the same 0.8 mHz frequency. These observations show that SuperDARN can provide a diagnostic of MHD wave propagation on open field lines and potentially be used to monitor MHD wave transmission across the magnetopause, and through the outer regions of the magnetosphere. MHD waves in the outer magnetosphere, which couple to FLRs, are seldom observed, and as far as we know this is the first report of a ground based ...
We present results from self-consistent simulations of the electron response to shear Alfve ´n pu... more We present results from self-consistent simulations of the electron response to shear Alfve ´n pulses in the presence of non-uniform magnetic fields and the associated mirror force. We discuss how energies of resonantly accelerated beam particles are affected by the local phase velocity of the pulse, and show that time-of-flight models are inadequate for describing electron acceleration since the acceleration can occur at more than one location along the field line as the pulse propagates toward the ionosphere. We also demonstrate that electron conics in low-altitude satellite observations of electron acceleration can be explained in terms of field-aligned inertial Alfve ´n wave pulses, without the requirement of a static potential drop or a standing Alfve ´n wave structure.
A model is presented that describes the excitation of small-scale density perturbations and elect... more A model is presented that describes the excitation of small-scale density perturbations and electromagnetic fields by standing shear Alfvé n waves in a Cartesian geometry. The model includes the effects of plasma betas and the Hall term effects. The characteristics of magnetospheric density cavities and the formation of the significant peak in density are discussed in the paper.
A model is presented that describes the excitation of small-scale density perturbations and elect... more A model is presented that describes the excitation of small-scale density perturbations and electromagnetic fields by standing shear Alfvé n waves in a Cartesian geometry. The model includes the effects of plasma betas and the Hall term effects. The characteristics of magnetospheric density cavities and the formation of the significant peak in density are discussed in the paper.
Journal of Geophysical Research: Space Physics, 2016
"Zebra stripes" are newly found energetic electron energy-spatial (L shell) distributed structure... more "Zebra stripes" are newly found energetic electron energy-spatial (L shell) distributed structure with an energy between tens to a few hundreds keV in the inner radiation belt. Using high-quality measurements of electron fluxes from Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the twin Van Allen Probes, we carry out case and statistical studies from April 2013 to April 2014 to study the structural and evolutionary characteristics of zebra stripes below L = 3. It is revealed that the zebra stripes can be transformed into evenly spaced patterns in the electron drift frequency coordinate: the detrended logarithmic fluxes in each L shell region can be well described by sinusoidal functions of drift frequency. The "wave number" of this sinusoidal function, which corresponds to the reciprocal of the gap between two adjacent peaks in the drift frequency coordinate, increases in proportion to real time. Further, these structural and evolutionary characteristics of zebra stripes can be reproduced by an analytic model of the evolution of the particle distribution under a single monochromatic or static azimuthal electric field. It is shown that the essential ingredient for the formation of multiple zebra stripes is the periodic drift of particles. The amplitude of the zebra stripes shows a good positive correlation with Kp index, which indicates that the generation mechanism of zebra stripes should be related to geomagnetic activities.
Journal of Geophysical Research: Space Physics, 2013
Primary and secondary Kelvin‐Helmholtz surface wave modes on the Earth's magnetopause are stu... more Primary and secondary Kelvin‐Helmholtz surface wave modes on the Earth's magnetopause are studied within the framework of warm plasma ideal magnetohydrodynamics (MHD) across an infinitely thin magnetopause tangential discontinuity (TD). With the increase of background flow velocity, a Kelvin‐Helmholtz Instability (KHI) unstable boundary separating two uniform semi‐infinite plasma regions is always ultimately stabilized to KHI growth at an upper cut‐off while inclusion of an inner boundary in one plasma region removes this stabilization. Phase velocity Friedrichs diagrams are presented that allow us to identify unstable fast and slow modes that correspond to growing modes of the KHI under different magnetosphere and magnetosheath conditions. On the nightside magnetosphere, and the magnetotail, new KH unstable intermediate‐fast modes are created, which cannot propagate exactly perpendicular to the magnetic field. In the plasma frame, primary unstable KH waves show fast/fast, while...
The Kelvin-Helmholtz instability (KHI) of magnetotail flow channels associated with bursty bulk f... more The Kelvin-Helmholtz instability (KHI) of magnetotail flow channels associated with bursty bulk flows (BBFs) is investigated. MHD oscillations of the channel in both kink and sausage modes are investigated for KHI, and both the primary and secondary KHIs are found that drive MHD waves. These instabilities are likely to be important for flow channel braking where the KHI removes energy from the flow. At flow speeds above the peak growth rate, the MHD modes excited by KHI develop from surface modes into propagating modes leading to the radiation of MHD waves from the flow channel. The coupling of BBF-driven shear flow instabilities to MHD waves presented here represents a new paradigm to explain BBF excitation of tail flapping. Our model can also explain, for the first time, the generation mechanism for the observations of waves propagating toward both flanks and emitted from BBF channels in the magnetotail.
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Papers by Robert Rankin