A parametric study of electron multiharmonic instabilities in the magnetosphere

Ashour‐Abdalla, M.; Kennel, C. F.; Livesey, W. A.

doi:10.1029/ja084ia11p06540

Cited by 55 publications

(35 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[3][4][5][6]. On the other hand, self-consistent particle-in-cell (PIC) simulations of loss cone distributions, which can be used to analyze nonlinear effects are difficult to carry out.…”

Section: Introductionmentioning

confidence: 99%

A numerical electromagnetic linear dispersion relation for Maxwellian ring-beam velocity distributions

et al. 2012

View full text Add to dashboard Cite

A positive slope in a velocity distribution function perpendicular to the ambient magnetic field, such as due to a loss cone or ring velocity distribution, can become a free energy source for the excitation of various plasma waves. Since there exists no analytic expression for integrals of Maxwellian ring velocity distribution functions, their linear properties have previously been studied using several approximations or modeled distributions. In this paper, a numerical method for analyzing the linear dispersion relation for Maxwellian ring-beam velocity distributions is developed. The obtained linear properties are confirmed by direct comparison with full particle simulation results. V C 2012 American Institute of Physics. [http://dx.

show abstract

“…[3][4][5][6]. On the other hand, self-consistent particle-in-cell (PIC) simulations of loss cone distributions, which can be used to analyze nonlinear effects are difficult to carry out.…”

Section: Introductionmentioning

confidence: 99%

A numerical electromagnetic linear dispersion relation for Maxwellian ring-beam velocity distributions

et al. 2012

View full text Add to dashboard Cite

show abstract

“…For the electrostatic instability, the electron velocity distribution function F ( v ∥ , v ⊥ ) (where v ∥ and v ⊥ are the velocity components parallel and perpendicular to the ambient magnetic field, respectively) must have a region of positive gradient, i.e., ∂ F /∂ v ⊥ > 0. Thus a loss cone or ring distribution is likely to drive ECH waves unstable, and the presence of the cold background electrons strongly affects the growth rates [ Fredricks , 1971; Young et al , 1973; Young , 1975; Ashour‐Abdalla et al , 1975, 1979; Ashour‐Abdalla and Kennel , 1978a, 1978b; Kennel and Ashour‐Abdalla , 1982], which may explain the enhancement of such waves near the plasmapause. Electromagnetic whistler mode waves, on the other hand, can be excited by a temperature anisotropy in the velocity distribution functions whereby T ⊥ > T ∥ .…”

Section: Introductionmentioning

confidence: 99%

Particle‐in‐cell simulation of Maxwellian ring velocity distribution

et al. 2007

View full text Add to dashboard Cite

[1] Electrostatic electron cyclotron harmonic (ECH) and electromagnetic whistler wave emissions are sometimes observed simultaneously in the near-Earth nightside equatorial magnetotail region. The excitation mechanism for these two wave emissions, however, is quite different with ECH waves excited by a positive slope in the velocity distribution function perpendicular to the ambient magnetic field (such as due to a loss cone or ring velocity distribution), while whistler waves are excited by a temperature anisotropy whereby the perpendicular temperature is larger than the parallel temperature. Here we examine, using a two-dimensional electromagnetic particle-in-cell computer simulation, the excitation of both waves as a consequence of a warm electron ring distribution in the presence of cold background electrons. Initially, ECH waves are excited by the ring distribution in the linear stage, which results in heating of the cold electrons and smearing of the ring distribution. During a nonlinear consequence of the ECH excitation and ensuing electron wave-particle interactions, whistler waves are also excited by the different instability. Thus both waves are excited during the same simulation run, which may account for the magnetospheric observations of both ECH and whistler waves at the same location where electron loss cone distributions form in the equatorial magnetotail at about 6-9 RE from the Earth.

show abstract

“…Young et al (1973), Ashour-Abdalla et al (1979) and Birmingham et al 0981) and references therein) suggest that the presence of these emissions can be understood if 1) the electron phase space is more complicated than a simple Maxwellian and 2) that varying patterns in the gyro-harmonic: structure can be produced depending on the thermal to suprathermal density and temperature ratios. that the system is demonstrably removed from local thermal equilibrium, 2) that the electron bulk parameters posses: important and sizeable macroscopic and microscopic variation: with radius and magnetic latitude within the torus, and 3) that a rsample of there regime: arc, compatible with selectively inferred properties of the plasma torus made by essentially indirect methods.…”

Section: Plasma Sheet Gyro-harmonic Emissionsmentioning

confidence: 99%

A survey of the plasma electron environment of Jupiter: A view from Voyager

Sittler²,

1981

View full text Add to dashboard Cite

A survey of the plasma environment within Jupiter's bow shock is presented in terms of the in situ, calibrated electron plasma measurementa made between 10 eV and 5. c .5 keV by the Voyager Plasma Science Experiment (PLS). These measurements have been analyzed and corrected for spacecraft potential variations; the :'.ata have been reduced to nearly model independent macroscopic parameters of the local electron density and temperature. The electron parameters are derived without reference to or internal calibration from the positive ion measurements made by the PL$ experiment. Extensive statistical and direct comparisons with other determinations of the local plasma charge density clearly indicate that the analysis procedures used have successfully and routinely discriminated between spacecraft sheath and ambient plasmas. These statistical cross correlations have been performed over the density range of 10-3 to 2 x 10 2 /cc. These data clearly define the bow shock, the magnetosheath (30-50 eV) the magnetosphere (10 -2 /cc, 2-3 keV) as well as the periodic appearances of the plasma sheet which are illustrated to be routinely cooler than the surroundings. The proximity of the plasma sheet define:. a regime in the magnetosphere where very cold electron plasma (as low as 50 eV) at 40 R can be seen in unexpected density enhancements. These plasma "spikes" in the density can often represent an order of magnitude enhancement above the ambient density and are correlated with diamagnetic depressions. These features have been seen at nearly all magnetic latitudes within the plasma sheet. The temperature within these spikes is lowered by similar factors indicating that the principal density enhancements are of cold plasma. The plasma sheet when traversed in the outer magnetosphere has a similar density and temperature morphology as that seen in these 11 3pikes". In all oases the plaama sheet crossing lasts for intervals commensurate with that defined by the diamagnetic depression in the simultaneously measured and uisplayed magnetic field. The electron temperatures in the plasma sheet in the outer and middle magnetosphore appear to have a positive radial gradient with jovicentric distance. The electron temperature is observed to be lower on the centrifugal, side of the minimum magnetic field strength seen in each sheet, while the suprathermal, electron density is enhanced symmetrically about the locally indicated magnetic equator. The electron distribution functions within the plasma sheet are markedly non-Maxwellian; during the density enhancemeW s of the plasma sheet tie thermal sub-population is generally enhanced more than the suprathermal population. The suprathermal fraction of the electron densf..y within the plasma sheet is an increasing function of jovicentric distance.Direct, in situ sampling of the electron plasma environment of lo's torus clearly illustrates that the system is demonstrably removed from local, thermodynamic equilibrium; these measurements illustrate that between 5.5 and 8.9 R, there are s...

show abstract

A parametric study of electron multiharmonic instabilities in the magnetosphere

Cited by 55 publications

References 25 publications

A numerical electromagnetic linear dispersion relation for Maxwellian ring-beam velocity distributions

A numerical electromagnetic linear dispersion relation for Maxwellian ring-beam velocity distributions

Particle‐in‐cell simulation of Maxwellian ring velocity distribution

A survey of the plasma electron environment of Jupiter: A view from Voyager

Contact Info

Product

Resources

About