Peter J. Palmadesso

Kinetic theory for electrostatic waves due to transverse velocity shears

A kinetic theory in the form of an integral equation is provided to study the electrostatic oscillations in a collisionless plasma immersed in a uniform magnetic field and a nonuniform transverse electric field. In the low temperature limit (kyρi ≪1, where ky is the wave vector in the y direction and ρi is the ion gyroradius) the dispersion differential equation is recovered for the transverse Kelvin–Helmholtz modes for arbitrary values of k∥, where k∥ is the component of the wave vector in the direction of the external magnetic field assumed in the z direction. For higher temperatures (kyρi>1) the ion‐cyclotron‐like modes described earlier in the literature by Ganguli, Lee, and Palmadesso [Phys. Fluids 28, 761 (1985)] are recovered. In this article the integral equation is reduced to a second‐order differential equation and a study is made of the kinetic Kelvin–Helmholtz and the ion‐cyclotron‐like modes that constitute the two branches of oscillation in a magnetized plasma including a transverse inhomoge...

Electrostatic ion-cyclotron instability caused by a nonuniform electric field perpendicular to the external magnetic field

A new mechanism that can destabilize kinetic ion‐cyclotron waves in the presence of a nonuniform electric field perpendicular to the uniform ambient magnetic field is given. In the absence of the electric field, the mode energy is positive, while in the presence of a uniform electric field the mode energy could be negative. However, when the electric field is nonuniform, it is possible for a finite region to be a negative wave energy surrounded by regions of positive wave energy. A nonlocal wave packet couples the two regions so that a flow of energy from the region of negative wave energy to the region of positive wave energy will cause the mode to brow. This gives rise to the instability.

Wave Instabilities in Space Plasmas

I: Natural Noise in Space.- ELF and VLF Noise Intensity and Spectra in the Magnetosphere.- ELF and VLF Activity Associated with High Latitude Hole.- Effects of Power Line Radiation into the Magnetosphere.- Ariel 3 and 4 Studies of Power Line Harmonic Radiation.- Does ELF Chorus Show Evidence of Power Line Stimulation?.- Chorus, Energetic Electrons and Magnetospheric Substorms.- II: Plasma Turbulence.- Magnetospheric Multiharmonic Instabilities.- Some Theoretical Aspects of Electrostatic Double Layers.- Formation of Double Layers in Laboratory Plasmas.- Laboratory Simulation of Ionospheric Double-Layers.- Anomalous Transition from Buneman to Ion Sound Instability.- Marginal Plasma Waves in the Equatorial Electrojet Observed by HF Coherent Radar Techniques.- III: Nonlinear Effects.- Nonlinear Whistler-Mode Interactions and Triggered Emissions in the Magnetosphere: A Review.- Siple Station Experiments on Wave-Particle Interactions in the Magnetosphere.- Non Linear Wave Particle Interaction Theory Applied to Siple Triggered Emissions.- Quenching of Natural Cyclotron Instability by Large Amplitude Monochromatic Waves Propagating in an Inhomogeneous Medium.- Nonlinear Effects Involved in the Generation of Type III Solar Radio Bursts.- A Theory of Solar Type III Radio Bursts.- IV: Ionospheric F-Region Irregularities.- A Review of Recent Results on Spread F Theory.- Equatorial Spread F: A Review of Recent Experimental Results.- Index of Subjects.

Use of filter vectors in hyperspectral data analysis

We report recent progress using a filter vector technique to analyze the data from a hyperspectral image. The filter vector technique finds the optimal filter vectors for demixing the complex patterns found in the hyperspectral image. The method has the potential to be implemented in real time since it is fully parallel. Computation of the filter vectors for a given family of known species vectors is fast and direct and improved algorithms for developing of the algorithm which may be updated as conditions change is possible. Advantages of using the filter vector techniques over the technique of pattern matching will be discussed. The portable hyperspectral images for low light spectroscopy (PHILLS) instrument has been used on a number of depolyments in the last year. Typically, the instrument files on the Naval Research Laboratorys P-3 Orion aircraft. Currently, the PHILLS instrument records over 1000 wavelength bands between UV and near IR. Results from a number of deployment and test situations is shown.

Behavior of ionized plasma in the high latitude topside ionosphere: The polar wind

Abstract : We have developed a numerical model to study the steady state behavior of a fully ionized plasma (H+, O+ and the electrons) encompassing the geomagnetic field lines. The theoretical formulation is based on the 16-moment system of transport equations. The electron gas is collision is dominated below 2500 km. Above this altitude electron temperature anisotropy develops with temperature perpendicular to the field line being higher than that parallel to the field line. The H+ ion temperature anisotropy shows H+ temperature parallel to the field line being higher than that perpendicular to the field line. H+ ion temperature also exhibits adiabatic cooling as to the supersonic ion gas cools down as it expands in a diverging magnetic field. Our results are in good agreement with the pervious theoretical studies of the polar wind and recent experimental observations. This is the first successful steady state solution to the 16-moment set of transport equations. Keywords include: Polar wind, Temperature anisotropy, and Adiabatic cooling.

Tearing instability in an anisotropic neutral sheet

A study is made of the collisionless tearing‐mode stability properties of a neutral sheet whose temperature distribution is anisotropic. A kinetic description is used for both ions and electrons. The wave vector k of the perturbation is taken to be parallel to the equilibrium magnetic field B0 and perpendicular to the equilibrium current J0. The analysis is carried out for the low‐frequency perturbation (‖ω‖≪ωci). It is found that the conventional technique of matching the inner and outer asymptotic solutions at the electron inner region (two‐region approximation), thus neglecting the axis‐crossing ion orbits outside the electron inner region, is inadequate for the anisotropic case. An intermediate region in which the axis‐crossing ion orbits make the dominant contribution is identified. The eigenvalue equation is solved using both analytic approximations and numerical methods to obtain the eigenmode structure and the linear dispersion relation. Specializing primarily to anisotropic ions with isotropic or...

Electron–ion hybrid mode due to transverse velocity shear

It has been established that electrostatic ion‐cyclotron‐like and Kelvin–Helmholtz modes can be sustained by a transverse velocity shear for L>ρi, where L is the velocity shear scale length and ρi is the ion gyroradius. Here it is shown that if ρe<L≪ρi, where ρe is the electron gyroradius, then a short wavelength electron–ion hybrid mode can be excited around the lower hybrid frequency. Like the Kelvin–Helmholtz instability, an explicit dependence on the second derivative of the dc electric field is essential for the growth of this mode.

Simulation of ion‐cyclotron‐like modes in a magnetoplasma with transverse inhomogeneous electric field

Ion‐cyclotron turbulence has been observed with shocks and double layers in the magnetosphere where strongly localized electric fields perpendicular to the magnetic field are present. Theoretical analysis suggests that electrostatic waves with frequencies of the order of the ion‐cyclotron frequency can be destabilized as a result of the coupling of regions of positive and negative‐energy ion waves. The nonlocal theory for a smooth profile of transverse inhomogeneous electric fields shows that localized ion waves grow in the region where the electric fields are present. Using a spatially two‐dimensional electrostatic code, we investigate this instability in plasma conditions characterized by a localized transverse electric field L≪Lx, where Lx is the simulation length in the x direction; and distinguish it from the transverse kinetic Kelvin–Helmholtz instability. The simulation results show that the growing ion waves are associated with the small vortices in the linear state, which evolve into a nonlinear ...

Electron–ion hybrid instabilities driven by velocity shear in a magnetized plasma

The stability of a magnetized plasma is investigated in which a sheared electron flow channel is present. The flow’s peak velocity and shear scale length are denoted by V and L, respectively. If the velocity channel is perpendicular to the confining magnetic field and L≤ ρi (ρi is the ion Larmor radius) an electrostatic instability develops whose frequency is on the order of the lower hybrid frequency. For V/(ΩeL) ≳ 0.02 (Ωe denotes the electron cyclotron frequency), the peak growth rate is on the order of the lower hybrid frequency when k∥ = 0 (in here, k∥ is the wave number along the magnetic field). For V/(ΩeL) ≳ 0.1 and k∥ = 0, the spectrum peaks when kyL ∼ 1, where ky is the wave number in the direction of the flow velocity. For this mode it is shown that (i) a net cross‐field current is not required for the onset of instability and (ii) the growth rate is not reduced by a velocity profile with no net flow (spatially averaged). Hence we conclude that velocity shear is the only source of free energy. ...

Excitation of lower hybrid waves in a plasma by electron beams

The linear theory of excitation of electrostatic lower hybrid waves by electron beams is presented. The importance of such waves in tokamaks with runaway electrons is discussed. (Author) (GRA)