Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session NM10: Mini-Conference: Nonlinear Effects in Geospace Plasmas I |
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Chair: Evgeny Mishin, Air Force Research Laboratory Room: Salon FGH |
Wednesday, October 29, 2014 9:30AM - 9:42AM |
NM10.00001: Interaction of High Frequency Electromagnetic Waves with Vortex Density Structures: Comparison of Analytical and LSP Simulation Results V. Sotnikov, T. Kim, J. Lundberg, I. Paraschiv, T.A. Mehlhorn Interchange or flute type density irregularities in magnetized plasma are associated with Rayleigh-Taylor type instability. In particular, we are interested in the generation of low frequency plasma density irregularities in the form of flute type vortex density structures and interaction of high frequency electromagnetic waves used for surveillance and communication with such structures. These types of density irregularities play an important role in refraction and scattering of high frequency electromagnetic signals propagating in the earth ionosphere, in high energy density physics (HEDP), and in many other applications. We will present PIC simulation results of EM scattering on vortex type density structures using the LSP code and compare them with analytical results. Two cases will be analyzed. In the first case electromagnetic wave scattering will take place in the ionospheric plasma. In the second case laser probing in a high-beta Z-pinch plasma will be presented. [Preview Abstract] |
Wednesday, October 29, 2014 9:42AM - 9:54AM |
NM10.00002: Are the Electromagnetic Whistlers Associated with Magnetotail Reconnection Driven by Temperature Anisotropy or by Electron Phase Space Holes? Martin V. Goldman, David L. Newman, Jonathan Eastwood, Giovanni Lapenta Kinetic simulations of magnetotail reconnection and theoretical analysis have recently been used to show that bipolar fields associated with electron phase space holes on separatrices near an x-point can efficiently emit electromagnetic whistler waves [Goldman, et al., \textit{Phys.~Rev.~Lett}, \textbf{112}, 145002 (2014)]. It is shown here from the same simulation at later times that hole emission of whistlers also occurs near the pile-up front (dipolarization front) associated with magnetotail reconnection. In addition, a more general kinetic theory analysis of \v Cerenkov emission of whistlers by holes is performed which includes electron temperature anisotropy and enables the comparison of \v Cerenkov emission of whistlers by holes with whistler instability due to temperature anisotropy in regions where both anisotropy and holes are present. Observations of whistlers and holes near dipolarization fronts [e.g., Deng, et al., \textit{J.~Geophys.~Res.} \textbf{115}, A09225 (2010)] are discussed in the context of these studies. [Preview Abstract] |
Wednesday, October 29, 2014 9:54AM - 10:06AM |
NM10.00003: A Quantitative Kinetic Theory of Meteor Plasma Formation Yakov Dimant, Meers Oppenheim Every second millions of small meteoroids hit the Earth from space, the vast majority too small to observe visually. Radars easily detect the plasma they generate and use the data they gather to characterize the meteoroids and the atmosphere in which they disintegrate. These diagnostics requires a detailed quantitative understanding of the formation of the meteor plasma and how it interacts with the Earth's atmosphere. Meteors become detectable to radars after they heat due to collisions with atmospheric molecules sufficiently that they begin to sublimate. The sublimated material then collides into atmospheric molecules and forms plasma around and behind the meteoroid. Reflection of radar pulses from the plasma around the descending meteoroid produces a localized signal called a head echo. This research applies kinetic theory to show that the meteoroid plasma develops over a length-scale close to the ion mean free path with a non-Maxwellian velocity distribution. This analytical model will serve as a basis for quantitative interpretation of the head echo radar measurements, the ionization efficiency (called the Beta parameter), and should help us calculate meteoroid and atmosphere parameters from radar head-echo observations. [Preview Abstract] |
Wednesday, October 29, 2014 10:06AM - 10:18AM |
NM10.00004: Turbulent Plasmaspheric Boundary Layer: Observables and Consequences Evgeny Mishin In situ satellite observations reveal strong lower hybrid/fast magnetosonic turbulence and broadband hiss-like VLF waves in the substorm subauroral geospace at and earthward of the electron plasmasheet boundary. These coincide with subauroral ion drifts/polarization streams (SAID/SAPS) in the plasmasphere and topside ionosphere. SAID/SAPS appear in $\sim$10 min after the substorm onset consistent with the fast propagation of substorm injection fronts. The SAID channel follows the dispersionless cutoff of the energetic electron flux at the plasmapause. This indicates that the cold plasma maintains charge neutrality within the channel, thereby short-circuiting the injected plasma jet (injection fronts over the plasmasphere. Plasma turbulence leads to the circuit resistivity and magnetic diffusion as well as significant electron heating and acceleration. As a result, a turbulent boundary layer forms between the inner edge of the electron plasmasheet and plasmasphere. The SAID/SAPS-related VLF emissions appear to constitute a distinctive subset of substorm/storm-related VLF activity in the region co-located with freshly injected energetic ions inside the plasmasphere. Significant pitch-angle diffusion coefficients suggest that substorm SAID/SAPS-related VLF waves could be responsible for the alteration of the outer radiation belt boundary during (sub)storms. [Preview Abstract] |
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