Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session GO6: Space Plasma |
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Chair: Earl Scime, West Virginia University Room: Governor's Square 11 |
Tuesday, November 12, 2013 9:30AM - 9:42AM |
GO6.00001: Self-Similar Electron Distribution Functions in the Solar Wind Konstantinos Horaites, Stanislav Boldyrev Although the temperature and density of solar wind electron velocity distribution functions (eVDFs) vary significantly as a function of heliocentric distance, the shape of the distributions---characterized by a thermal core and suprathermal tails---varies only weakly. We suggest that this may be due to the peculiar conditions of the solar wind; specifically, the observed radial density and temperature profiles are such that the ratio between the mean free path $\lambda$ and the characteristic distance $L_T=T/|dT/dr|$ over which the temperature varies is nearly constant. If $\lambda/L_T$ (also known as the temperature Knudsen number) is exactly constant, then the collisional kinetic equation admits self-similar solutions. We discuss these solutions and their applicability to the solar wind near 1 AU. [Preview Abstract] |
Tuesday, November 12, 2013 9:42AM - 9:54AM |
GO6.00002: Progress in iron transmission measurements relevant to the solar convection/radiation boundary J.E. Bailey, T. Nagayama, Guillaume Loisel, G.A. Rochau, C. Blancard, J. Colgan, Ph. Cosse, G. Faussurier, C.J. Fontes, I. Golovkin, S.B. Hansen, C.A. Iglesias, D.P. Kilcrease, J.J. MacFarlane, R.C. Mancini, S.N. Nahar, T.J. Nash, C. Orban, M. Pinsonneault, A.K. Pradhan, M. Sherrill, B.G. Wilson Iron plasma opacity influences the internal structure of the sun. However, opacity models have never been experimentally tested at stellar interior conditions. Recent iron opacity experiments at the Sandia Z facility reached 195 eV temperatures, nearly the same as the solar convection/radiation zone boundary (CZB), at electron densities that are roughly 1/2 the solar CZB value. Progress to solidify these results and use them to examine the physical underpinnings of opacity models will be described. [Preview Abstract] |
Tuesday, November 12, 2013 9:54AM - 10:06AM |
GO6.00003: Induced emission of Alfv\'en waves -- the missing source of solar corona heating and solar wind acceleration Vitaly Galinsky, Valentin Shevchenko The solar corona is considerably hotter than Sun's surface or photosphere. However, the mechanism that heats it to millions of degrees is still under debates. Recent observations revealed presence of the ubiquitous outward-propagating Alfv\'{e}nic motions with amplitudes up to 25~km~s\textsuperscript{-1} and periods of the order of 100--500s throughout the quiescent atmosphere, thus suggesting the possible source of energy for acceleration of the fast solar wind and heating the quiet corona. Nevertheless, the challenge remains to understand how these waves are dissipated in the solar atmosphere, and how that dissipation delivers energy to the ions and electrons that comprise the coronal plasma and solar wind. Here we report a method that extends and extrapolates these observational data up to the level suitable for constraining and verification of heating and acceleration models. The macro-scale instability of the marginally stable particle distribution function compliments the resonant frequency sweeping dissipation of transient Alfv\'en waves by their induced emission in inhomogeneous streaming plasma that provides enough energy for keeping the plasma temperature decaying not faster than $r^{-1}$ -- in close agreement with \textit{in situ} heliospheric observations. [Preview Abstract] |
Tuesday, November 12, 2013 10:06AM - 10:18AM |
GO6.00004: Macro-scale instability of ion shell distribution function and peculiarity of the solar wind turbulence spectra Valentin Shevchenko, Vitaly Galinsky, Roald Sagdeev The ion shell velocity distribution function formed due to resonant cyclotron interaction with Alfv\'en waves in the divergent solar wind is unstable with respect to excitation of Alfv\'en waves with smaller phase velocity at larger distances from the Sun - the macro-scale instability of ion shell distribution [1,2]. It is shown that this instability is responsible for the ``clear peak'' between the inertial and absorption regions in power spectra of the solar wind wave fluctuations propagating parallel to the magnetic field that was recently revealed in observations [3].\\[4pt] [1] V.L. Galinsky \& V.I. Shevchenko, Phys. Rev. Lett. 85, 90, 2000. \newline [2] V.I. Shevchenko et al., Phys. Plasmas, 11, 4290, 2004. \newline [3] R.T. Wicks et al., Mon. Not. R. Astron. Soc., 407, L31, 2010. [Preview Abstract] |
Tuesday, November 12, 2013 10:18AM - 10:30AM |
GO6.00005: Large-Scale Quantization in Plasmas George Livadiotis, David McComas In our recent paper [Livadiotis and McComas, Entropy, 15, 1118; Nature, doi:10.1038/nature.2013.13159], we showed that plasmas are systems characterized by a large-scale phase space quantization, caused by the Debye shielding that structures local correlations between particles. While there is no a priori reason to expect a single value of this phase space minimum across different plasmas, we find a surprisingly constant value of $h* \approx $2$\pi $(1.2 $+$/- 2.4)10$^{-22} $Js, using four independent methods: (1) Ulysses solar wind measurements, (2) a variety of space plasmas spanning a broad range of physical properties, (3) the entropic limit emerging from statistical mechanics, (4) waiting-time distributions of explosive events in space plasmas. Having a phase space minimum $h*$ of 12 orders of magnitude larger than the Planck constant $h$, plasmas are consistent with a larger scale quantization that opens a new areas in theoretical and experimental physics. [Preview Abstract] |
Tuesday, November 12, 2013 10:30AM - 10:42AM |
GO6.00006: Magnetohydrodynamic Turbulence in the Frequency Domain Vladimir Zhdankin, Stanislav Boldyrev, Jean Carlos Perez, Qian Xia We investigate the fluctuations of magnetohydrodynamic (MHD) turbulence in the temporal dimension, in contrast to the more commonly considered spatial dimensions. Such an analysis may be relevant for observations of turbulence in the Earth's magnetotail, where Taylor's hypothesis does not apply. We consider the two-dimensional (wavevector-frequency) energy spectrum, $E(k_\perp,\omega)$, and assess the anisotropy of fluctuations by studying the scaling of the energy-containing region. We find that the form of $E(k_\perp,\omega)$ is strongly indicative of sweeping by the large-scale velocity field. We attempt to remove the effects of sweeping to obtain the local anisotropy, which can be used to test the predictions of critical balance. [Preview Abstract] |
Tuesday, November 12, 2013 10:42AM - 10:54AM |
GO6.00007: Kinetic-Alfven and whistler waves in astrophysical plasma turbulence at subproton scales Stanislav Boldyrev, Konstantinos Horaites, Qian Xia, Jean Carlos Perez The analytical study of sub-proton electromagnetic fluctuations in a collisionless plasma with plasma beta of order unity is presented. In the linear limit, a rigorous derivation from the kinetic equation is conducted focusing on the role and physical properties of kinetic-Alfven and whistler waves. Then, nonlinear fluid-like equations for kinetic-Alfven waves and whistler modes are derived, with the special emphasis on the similarities and differences in the corresponding plasma dynamics. The kinetic-Alfven modes exist in the lower-frequency region of the phase space, $\omega \ll$ k$_{perp}$ v$_{Ti}$, where they are described by the kinetic-Alfven system. These modes exist both below and above the ion cyclotron frequency. The whistler modes, which are qualitatively different from the kinetic-Alfv\'en ones, occupy a different region of the phase space, k$_{perp}$ v$_{Ti} \ll \omega \ll$ k$_{zvTe}$, and they are described by the electron MHD system or the reduced electron MHD system if the propagation is oblique. Here k$_z$ and k$_{perp}$ are the wave numbers along and transverse to the background magnetic field, and v$_{Ti}$ and v$_{Te}$ are ion and electron thermal velocities. The models of sub-proton plasma turbulence are discussed and the results of numerical simulations are presented. Possible implications for solar-wind observations are pointed out. [Preview Abstract] |
Tuesday, November 12, 2013 10:54AM - 11:06AM |
GO6.00008: Simultaneous Multi-angle Measurements of Plasma Turbulence at HAARP Naomi Watanabe, Mark Golkowski, James Sheerin We report the results from a recent series of experiments employing the HAARP HF transmitter to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) located at HAARP, the Super DARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Short pulse, low duty cycle experiments demonstrate control and suppression of artificial field-aligned irregularities (AFAI). This allows the isolation of ponderomotive plasma turbulence effects. For the first time, plasma line spectra measured simultaneously in different spots of the interaction region displayed marked but contemporaneous differences dependent on the aspect angle of the HF pump beam and the pointing angle of the MUIR diagnostic radar. Outshifted Plasma Line (OPL) spectra, rarely observed in past experiments, occurred with sufficient regularity for experimentation. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts. [Preview Abstract] |
Tuesday, November 12, 2013 11:06AM - 11:18AM |
GO6.00009: Observed Local and Conjugate Ionospheric Disturbances from Rare High Peak Current Oceanic Lightning Events Nicholas Gross, Mark Golkowski, Levon Barsikyan, Robert Moore Using VLF remote sensing, we present a rare event in which three distinct and geographically separated ionospheric disturbances, all caused by a single, large (388 kA), positive polarity cloud to ground oceanic lightning discharge. The disturbances include a so-called Early/Fast event caused by a quasi-electrostatic field, along with both a northern and southern hemisphere lightning-induced electron precipitation (LEP) event. The LEP mechanism is driven by cyclotron resonant interactions between the lightning induced whistler waves and radiation belt electrons. Using data from the new GLD360 lightning detection network, we model the electron precipitation characteristics for both hemispheres. Modeling is performed by using the spectral content of the lightning strike to determine the magnetospheric whistler induced particle precipitation, then an atmospheric backscattering model is implemented to account for the geographic dependence of the equatorial loss cone angle. Our findings indicate that future works involving VLF remote sensing need to take into account these multifaceted processes and their unique signatures. [Preview Abstract] |
Tuesday, November 12, 2013 11:18AM - 11:30AM |
GO6.00010: Multi Station Frequency Response and Polarization of ELF/VLF Signals Generated via Ionospheric Modification Ashanthi Maxworth, Mark Golkowski ELF/VLF wave generation via HF modulated ionospheric heating has been practiced for many years as a unique way to generate waves in the ELF/VLF band (3 Hz -- 30 kHz). This paper presents experimental results and associated theoretical modeling from work performed at the High Frequency Active Auroral Research Program (\textit{HAARP}) facility in Alaska, USA. An experiment was designed to investigate the modulation frequency dependence of the generated ELF/VLF signal amplitudes and polarization at multiple sites at distances of 37 km, 50 km and 99 km from the facility. While no difference is observed for X mode versus O mode modulation of the heating wave, it is found that ELF/VLF amplitude and polarization as a function of modulated ELF/VLF frequency is different for each site. An ionospheric heating code is used to determine the primary current sources leading to the observations. [Preview Abstract] |
Tuesday, November 12, 2013 11:30AM - 11:42AM |
GO6.00011: Unified models of E-layer plasma turbulence from density gradients and Hall currents Ehab Hassan, Sandeep Litt, Wendell Horton, Andrei Smolyakov, Fred Skiff The Earth's ionosphere is rich with plasma irregularities of scale-lengths extend from few centimeters to hundreds of kilometers. The combination of small-scale turbulence with large coherent structures is at the forefront of basic plasma turbulence theory. A new unified model for the small-scale plasma turbulence called Type-I and Type-II in the E-region ionosphere is presented. Simulations and a proposed laboratory experiment for these plasma waves in a weakly ionized plasma are reported. The ions [Argon in the lab and NO+ in the ionosphere] are collisional and the electrons ExB drifts produce Hall currents. The dispersion relations are analyzed for both density gradient and electron current driven instabilities. A basic understanding of the turbulence is important for forecasting disruptions in GNSS communication signals from RF signal scattering produced by the E-layer plasma turbulence on the 10cm to 10m scales lengths. [Preview Abstract] |
Tuesday, November 12, 2013 11:42AM - 11:54AM |
GO6.00012: Three-dimensional development of the Kelvin-Helmholtz instability in asymmetric boundary layers T.K.M. Nakamura, W. Daughton, H. Karimabadi, S. Eriksson The Kelvin-Helmholtz instability (KHI) is a key process for the transport of solar wind plasmas into the Earth's magnetosphere. In the presence of both magnetic and velocity shear, the resulting KHI leads to generation of vortices and subsequent triggering of magnetic reconnection. Our initial 3D fully kinetic simulations of this process at the symmetric boundary layers demonstrated the copious formation of oblique flux ropes which leads to enhanced mixing of the plasma. Here, we further consider the density and temperature asymmetries which always exist across the magnetopause. Past 2D simulations in such asymmetric cases showed that these asymmetries lead to an excitation of secondary instabilities along the edge of the vortex. While in the 2D limit, these secondary instabilities are strongly suppressed by the magnetic field component parallel to the k-vector of the KHI which would generally exist at the realistic magnetopause, our recent 3D fully kinetic simulations show that the three-dimensionality allows these instabilities to grow over a range of oblique angles even when a moderate strength of the parallel field exists. The non-linear growth of these instabilities disturbs the structure of the edge layer of the vortex and further enhances the mixing of the plasma. [Preview Abstract] |
Tuesday, November 12, 2013 11:54AM - 12:06PM |
GO6.00013: Propagation of Rossby-Khantadze Electromagnetic Planetary Waves in the Ionospheric E-Layer S. Futatani, T. Kaladze, W. Horton, S. Benkadda Nonlinear vortex propagation of electromagnetic coupled Rossby and Khantadze planetary waves in the weakly ionized E-layer of the ionosphere are investigated with numerical simulations. For each k-vector the linear dispersion relation has two eigenmodes corresponding to the slow magnetized Rossby wave and the fast magnetic Khantadze wave. Both waves propagate westward with speeds of order 10-20 m/s for the slow wave and of order 500-1000km/s for the fast wave. We show that for finite amplitudes there are dipole solitary vortex structures emitted from general initial conditions. These structures are the neutrally stable, nonlinear states that avoid radiating waves by propagating faster than the corresponding linear wave speeds. The condition for these coherent structures to occur is that their amplitudes be such that the nonlinear convection around the core of the disturbance is faster that the linear wave speed for the corresponding dominant Fourier components of the initial disturbance. The presence of the solitary vortex states are indicative of an initial strong disturbance such that arising from a solar storm, a tectonic plate movements or volcanic eruptions. [Preview Abstract] |
Tuesday, November 12, 2013 12:06PM - 12:18PM |
GO6.00014: Double Mid-Latitude Dynamical Reconnection at the Magnetopause Francesco Pegoraro, Francesco Califano, Matteo Faganello, Tommaso Andreussi The interaction between the solar wind and the Earth's magnetosphere can have a non-local character due to the fact that the magnetic field lines, being frozen in the plasma over most of the configuration, can act as rods and transfer momentum and energy very effectively to locations far from the equatorial flank region where the primary Kelvin-Helmohltz instability develops. Eventually external constraints, such as the field lines being tied to the Earth, require that energy be released through the development of field line reconnection. Three-dimensional simulations of the Kelvin-Helmholtz (K-H) instability in a magnetic configuration reproducing typical conditions at the flank Earth's magnetosphere during northward periods show the system ability to generate favorable conditions for magnetic reconnection to occur at mid-latitude. Once these conditions are established, magnetic reconnection proceeds spontaneously in both hemispheres generating field lines that close on Earth but are connected to the solar wind at low-latitude, allowing direct entrance of solar wind plasma into the magnetosphere.\\[4pt] M. Faganello, {\it et al.}, EPL, {\bf 100} 69001 (2012). [Preview Abstract] |
Tuesday, November 12, 2013 12:18PM - 12:30PM |
GO6.00015: The influence of out-of-plane shear flow on Hall magnetic reconnection and FTE generation Chijie Xiao, Yangao Chen, Xiaogang Wang, Zhiwei Ma, Hui Zhang Based on the three-dimensional Hall magnetohydrodynamic (MHD) simulations and in situ measurements of THEMIS spacecraft, magnetic reconnection driven by an out-of-plane shear flow in the symmetric Harris current sheet, asymmetric case with a guide field, specially the parameters in one case based on a vivo flux transfer event (FTE) observed by THEMIS spacecraft, are all calculated. The simulation results show that during the Hall reconnection processes, the out-of-plane shear flow could make the initial single X-line bifurcated, and then a magnetic island (without guide field) or flux rope (with guide field) generated and grown up quickly. In $\sim$240 Alfven time (204 seconds) the flux rope could be reach to one Earth radius (Re), the typical scale of FTE observed in the dayside magnetopause. These results give some clues on the generation mechanism of FTE. References: Chen Y. G., Xiao C. J., Wang X. G., et al., J. Geophys. Res., doi:10.1029/2013ja50417, (2013) [Preview Abstract] |
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