Neil J. Grossbard

The Alfven-Falthammar formula for the parallel E-field and its analogue in downward auroral-current regions

The authors give an alternative derivation of the Alfven-Falthammar formula for a positive parallel E-field in upward auroral-current regions and its analogue for a negative parallel E-field in downward auroral-current regions. These formulas give new insight into the physics of the Birkeland current system. They find that for downward auroral-current regions, the velocity-space anisotropy in the ion distribution function is such that half the ion energy perpendicular to the magnetic field is greater than the ion energy parallel to the magnetic field. This is just opposite to the case for upward auroral-current regions. These results are compared to recent particle-in cell simulations and FREJA satellite data.

Mesospheric oh airglow temperature fluctuations: A spectral analysis

A field campaign under Project MAPSTAR was conducted in Colorado during May-July 1988. As part of this effort ground based measurements of OH airglow rotational temperatures at 85 km were made by means of an infrared Fourier spectrometer (IRFWI of USU). These measurements employed a least squares spectral fitting technique involving the 3–1 Meinel band. These data and their estimated PSDs will be presented. The latter will be interpreted by means of the relations between gravity wave temperature fluctuations and vertical displacement fluctuations given by Makhlouf et al (1990). The results will be compared with the predictions of the gravity wave model of Dewan (1990, 1991) and shown to be in reasonable agreement thus lending further support to the local wave-cascade hypothesis.

The self-consistent parallel electric field due to electrostatic ion-cyclotron turbulence in downward auroral-current regions of the Earth’s magnetosphere. IV

The physical processes that determine the self-consistent electric field (E∥) parallel to the magnetic field have been an unresolved problem in magnetospheric physics for over 40 years. Recently, a new multimoment fluid theory was developed for inhomogeneous, nonuniformly magnetized plasma in the guiding-center and gyrotropic approximation that includes the effect of electrostatic, turbulent, wave-particle interactions (see Jasperse et al. [Phys. Plasmas 13, 072903 (2006); Jasperse et al., Phys. Plasmas13, 112902 (2006)]). In the present paper and its companion paper [Jasperse et al., Phys. Plasmas 17, 062903 (2010)], which are intended as sequels to the earlier work, a fundamental model for downward, magnetic field-aligned (Birkeland) currents for quasisteady conditions is presented. The model includes the production of electrostatic ion-cyclotron turbulence in the long-range potential region by an electron, bump-on-tail-driven ion-cyclotron instability. Anomalous momentum transfer (anomalous resistivity...

Ion-cyclotron instability in current-carrying Lorentzian (kappa) and Maxwellian plasmas with anisotropic temperatures: A comparative study

Current-driven electrostatic ion-cyclotron instability has so far been studied for Maxwellian plasma with isotropic and anisotropic temperatures. Since satellite-measured particle velocity distributions in space are often better modeled by the generalized Lorentzian (kappa) distributions and since temperature anisotropy is quite common in space plasmas, theoretical analysis of the current-driven, electrostatic ion-cyclotron instability is carried out in this paper for electron-proton plasma with anisotropic temperatures, where the particle parallel velocity distributions are modeled by kappa distributions and the perpendicular velocity distributions are modeled by Maxwellian distributions. Stability properties of the excited ion cyclotron modes and, in particular, their dependence on electron to ion temperature ratio and ion temperature anisotropy are presented in more detail. For comparison, the corresponding results for bi-Maxwellian plasma are also presented. Although the stability properties of the io...

Anomalous momentum and energy transfer rates for electrostatic ion-cyclotron turbulence in downward auroral-current regions of the Earth’s magnetosphere. III

Recently, a new multimoment fluid theory was developed for inhomogeneous, nonuniformly magnetized plasma in the guiding-center and gyrotropic approximation that includes the effect of electrostatic, turbulent, wave-particle interactions (see Jasperse et al. [Phys. Plasmas 13, 072903 (2006); Jasperse et al., Phys. Plasmas13, 112902 (2006)]). In the present paper, which is intended as a sequel, it is concluded from FAST satellite data that the electrostatic ion-cyclotron turbulence that appears is due to the operation of an electron, bump-on-tail-driven ion-cyclotron instability for downward currents in the long-range potential region of the Earth’s magnetosphere. Approximate closed-form expressions for the anomalous momentum and energy transfer rates for the ion-cyclotron turbulence are obtained. The turbulent, inhomogeneous, nonuniformly magnetized, multimoment fluid theory given above, in the limit of a turbulent, homogeneous, uniformly magnetized, quasisteady plasma, yields the well-known formula for th...

Methods for estimating the autocorrelation and power spectral density functions when there are many missing data values

A new method for estimating the autocorrelation and the crosscorrelation has been developed. The resulting estimates are usually more accurate than the classical values. The method is particularly useful when there are many missing data values. For the case when there are many missing data values, it is suggested that a power spectral density (PSD) of the autocorrelation function can be developed. The resulting PSD can easily be mapped into the PSD of the original data. Towards this end, Burgs technique has been applied to the autocorrelation and the results of the application are presented.<<ETX>>

Structure in Middle and Upper Atmospheric Infrared Radiance

An extensive database on spatial structure in the infrared radiance of the middle and upper atmosphere has been collected by the Mid-Course Space Experiment (MSX). The observed radiance contains spatial structure down to the scale of hundreds of meters. This spatial structure results from local fluctuations in the temperature and densities of the radiating states of the emitting molecular species as well as fluctuations in radiation transport from the emitting regions to the observer. A portion of this database has been analyzed to obtain statistical parameters characterizing stochastic spatial structure in the observed radiance. Using simple models, the observed statistics have been shown to agree with prior observations and theoretical models of stochastic spatial structure generated by gravity waves for special viewing geometries. The SHARC model has been extended to predict the statistics of stochastic fluctuations in infrared radiance from the statistics characterizing temperature fluctuations in the middle and upper atmosphere for arbitrary viewing geometries. SHARC model predictions have been compared with MSX data and shown to be in generally good agreement. Additional work is in progress to account for the statistics characterizing small spatial scale fluctuations.

Origin of ion-cyclotron turbulence in the downward Birkeland current region

Linear stability analysis of the electron velocity distributions, which are observed in the FAST satellite measurements in the downward Birkeland current region of the magnetosphere, is presented. The satellite-measured particle (electrons and protons) velocity distributions are fitted with analytic functions and the dispersion relation is derived in terms of the plasma dispersion functions associated with those distribution functions. Numerical solutions of the dispersion relation show that the bump-on-tail structure of the electron velocity distribution can excite electrostatic ion-cyclotron instabilities by the Landau resonance mechanism. Nonlinear evolution of these instabilities may explain the observed electrostatic ion-cyclotron turbulence in the Birkeland current region. Excitation of other types of instabilities by the fitted electron velocity distributions and their relevance are also discussed.

A model for atmospheric background radiance structures

Abstract Infrared radiance fluctuations in the atmosphere result from fluctuations in the density of atmospheric species, individual molecular state populations, and kinetic temperatures along the sensor line of sight (LOS). As part of the SHARC-4 development program, a model for the prediction of atmospheric background radiance fluctuations was constructed. It predicts a two dimensional radiance spatial covariance function and power spectral density (PSD) from the underlying 3D atmospheric structures. Inputs to the model include the parameters of an atmospheric temperature fluctuation model and vertical atmospheric profiles. The model can be applied for arbitrary sensor viewing geometries, including limb viewing. In the upper atmosphere non-equilibrium effects are important. Fluctuations in kinetic temperature can result in correlated or anti-correlated fluctuations in vibrational state temperatures. The model accounts for these effects and predicts spatial covariance functions and PSDs for molecular state number densities and vibrational temperatures. SHARC is used to predict the non-equilibrium dependence of molecular state number density fluctuations on kinetic temperature and density fluctuations, and to calculate mean LOS radiances and radiance derivatives. The goal is to understand the origin of LOS radiance fluctuations and the prediction of fluctuation statistics based on local fluctuations in gas kinetic temperatures, and densities. The modeling capabilities are illustrated with a sample image prediction for the Midcourse Space Experiment (MSX) having an MSX sensor bandpass and field-of-view (FOV).

Analysis Techniques Applied To Balloon-Borne Mosaic Interferometer And Radiometer Measurements

Computational techniques developed for the reduction and analysis of interferometer and radiometer data from the Balloon Altitude Mosaic Measurements (BAMM) program are presented. Emphasis is given to the reduction and analysis techniques developed for mosaic detector interferometer measurements. The presentation includes discussion of techniques to quality check, edit and simulate radiance values. Statistical analyses performed on simulated radiance data is described and examples of raw and edited data and statistical parameters are given. A brief discussion of radiometer reduction and analysis techniques is presented which includes data editing; filtering and decimation; statistical parameter determination; autocovariance estimation; and Fourier Power Spectral estimation of radiance.