Bulletin of the American Physical Society
60th Annual Meeting of the APS Division of Plasma Physics
Volume 63, Number 11
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session JM10: Mini-Conference on Nonlinear Waves and Processes in Space Plasmas I |
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Chair: David Knudsen, University of Calgary Room: OCC C124 |
Tuesday, November 6, 2018 2:00PM - 2:19PM |
JM10.00001: Nonlinear Waves and Processes Observed on the Van Allen Probes Craig Kletzing The physics of the creation, loss, and transport of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field and particle interactions are involved in this physics. To measure these kinds of radiation belt interactions, NASA implemented the two-satellite Van Allen Probes mission. As part of the mission, the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation provides measurements of magnetic fields from DC to 12 kHz and electric fields from 10 Hz to 400 kHz. We show a variety of non-linear waves thought to be important for wave particle interactions in the radiation belts including EMIC wave rising tones and whistler mode waves including upper and lower band chorus. Several of these wave modes could benefit from laboratory studies to further refine our understanding of the detailed physics of the non-linear wave-particle interactions which lead to energization, pitch angle scattering, and cross-field transport. Examples are shown to illustrate some of these wave/particle processes to show relationships between wave activity and particle processes observed in the inner magnetosphere. |
Tuesday, November 6, 2018 2:19PM - 2:38PM |
JM10.00002: Generation of Kinetic Alfven Waves in the Magnetotail Yu Lin, Lei Cheng, Xueyi Wang, Jay R. Johnson, Joseph D Perez Shear Alfven mode waves, including kinetic Alfven waves (KAWs), are often observed around in the tail plasma sheet around fast flows, and they are believed to play important roles in powering the low-altitude auroral acceleration.In this talk, we use the Auburn Global Hybrid Code in 3-D (ANGIE3D) to investigate the generation and propagation of shear Alfven waves in the magnetotail. Our results show that shear Alfven waves/KAWs are generated in magnetic reconnection and present around fast flows. The KAWs are identified, and the Alfvenic energy spectrum is examined. As these waves propagate toward the ionosphere carrying the field-aligned currents and Poynting flux, the flow braking region in front of the strong dipolar magnetic field significantly alters their structure and thus the precipitating Alfvenic energy flux. The subsequent generation of shear Alfven waves in the dipole-like field region of the magnetosphere is also discussed. |
Tuesday, November 6, 2018 2:38PM - 2:57PM |
JM10.00003: Inertial Kinetic-Alfven Turbulence in a Space Plasma Stanislav Boldyrev, Vadim Roytershteyn, Christopher H. K. Chen Observations and analytical models indicate that the electron plasma beta parameter (ratio of the thermal to magnetic energy) becomes relatively small at low heliospheric distances, in the regions close to the solar corona, βe << βi ≤ 1. In such a regime, which is also encountered in the Earth’s magnetosheath and other astrophysical systems, kinetic-scale turbulence may be governed by the so-called inertial kinetic-Alfven modes [1,2]. We discuss the properties of this new regime of nonlinear plasma dynamics, present a phenomenological model of inertial kinetic-Alfven turbulence, and demonstrate that the results are in good agreement with the recent kinetic numerical simulations [3]. [1] Chen, C. H. K. & Boldyrev, S. Astrophys. J. 842 (2017) 122; [2] Passot, T., Sulem, P. L., Tassi, E., Phys. Plasmas 25 (2018) 045107; [3] Roytershteyn, V., Boldyrev, S., Delzanno, G. L., Chen, C. H. K., Grošelj, D., and Loureiro, N. F., Astrophys. J., 2018 (submitted).
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Tuesday, November 6, 2018 2:57PM - 3:16PM |
JM10.00004: The role of advection and advective nonlinearities in the creation of quasi-stationary discrete auroral arcs David Knudsen Discrete auroral arcs are the result of quasi-static magnetic-field-aligned acceleration of electrons to energies of up to tens of keV. They can remain quasi-stationary for tens of minutes, which places a strong constraint on candidate theories. For example, kinetic or inertial Alfven waves can accelerate electrons along B, but only to energies of the order of 1 keV, and then only in short-lived bursts, which excludes them as an explanation for most discrete arcs. One type of theory assumes plasma convection across a stationary arc, which introduces time-dependent effects in the frame of the drifting plasma, including polarization current associated with the advective part of the convective derivative of E. The ion polarization drift velocity can be shown to be of the same order as as the ExB drift across the arc, requiring a fully nonlinear treatment. This talk will show that this mechanism can lead to field-aligned currents having properties consistent with some observations. |
Tuesday, November 6, 2018 3:16PM - 3:35PM |
JM10.00005: Laboratory Scaling Studies of a Shear Alfvén Wave Parametric Instability Seth Dorfman, Troy Carter, Stephen T Vincena, Patrick Pribyl, Yu Lin, Richard Dwayne Sydora Alfvén waves, a fundamental mode of magnetized plasmas, are ubiquitous in space plasmas. The non-linear behavior of these modes is thought to play a key role in important problems such as solar wind turbulence and the heating of the solar corona. Theoretical predictions show that these Alfvén waves may be unstable to various parametric instabilities, but in-situ satellite measurements of these processes are limited. Recent results from the Large Plasma Device at UCLA have recorded the first observation of a sheer Alfvén wave parametric instability in the laboratory [Dorfman and Carter, PRL 2016]. When a single finite ω/Ωi, finite k⊥ Alfvén wave is launched above a threshold amplitude, three daughter waves are observed: two sideband Alfvén waves co-propagating with the pump and a low frequency nonresonant mode. To shed light on the physics responsible, scaling studies are underway to determine how the instability physics changes with plasma and antenna parameters. Parameters required for the instability will be compared to those expected in the near-Sun solar wind region to be visited by Parker Solar Probe. |
Tuesday, November 6, 2018 3:35PM - 3:54PM |
JM10.00006: Extra nonlinear structures and singularity in magnetized plasma T. Kamalam, S. S. Ghosh A novel structure that has been unearthed in recent time is Super Solitary Waves (SSWs). They are extra nonlinear solitary wave pulses with an extra wiggles in their bipolar electric field profile. The theoretical works so far on SSWs are confined to low frequency waves in an unmagnetized plasma. We have extended it to high frequency waves in a magnetized plasma. They occurred in the vicinity of ‘singularity’ in Sagdeev pseudopotential profile. Such singularities are characteristics of a magnetized plasma. In spite of its spiky profile, it was considered as a physical solution due to its finite and physical potential. We presume that there is some association between singularity and SSW solution, as the latter terminates with a singularity. During investigation, we have obtained another novel structure, which shows the signatures of SSW and a Double Layer. We prefer to call this structure as “Folded Double Layer (FDL)”. Here we intend to explore the role of singularity in a magnetized plasma vis a ̀ vis structures like SSW or FDL. Our model comprising of four component magnetized plasma governed by electron dynamics. Incorporating a new analytical tool, we investigate these cusp like solitary waves. We intend to apply our analyses to interpret the observations in magnetosphere. |
Tuesday, November 6, 2018 3:54PM - 4:13PM |
JM10.00007: Alfvén Eigenmode (AE) interactions in Tokamaks: DIII-D Frontier Science Experiments connecting the physics of nonlinear waves and processes in space plasmas M Koepke, S Nogami, G Riggs, G Howes, N Crocker, T Carter, W Heidbrink, M Van Zeeland Measuring nonlinear AE interactions in tokamaks and linear devices, relevant to solar wind, fusion, and magnetospheric physics, may reveal processes that saturate the amplitude of such fluctuations, and thus may explain additional nonlinear physics responsible for particle energization. DIII-D data is being analyzed to identify the nonlinear energy transfer among toroidal AE occurring via three-wave interactions, usually mediated by a much lower frequency mode, such as a zonal flow, an energetic particle mode, or a lower frequency toroidal AE. To understand the influence of such interactions on the saturated amplitudes of driven AE and thereby identify the process that sets the amplitude of kinetic AE in the magnetosphere, we aim to determine the differences in AE amplitudes in the presence or absence of nonlinear interactions in DIII-D plasma. Their linear damping rates, and the rate of energization of the ions, suggest AE would rapidly damp without continual energy injection, so these kinetic AE must be driven by the dynamics of the geomagnetic storm. The nonlinear interaction between counterpropagating AE, i.e., Alfvén wave collision, is believed to be a fundamental building block of Alfvénic turbulence in space and astrophysical plasma environments. |
Tuesday, November 6, 2018 4:13PM - 4:32PM |
JM10.00008: Nonlinear Whistler Wave Physics in the Laboratory and in the Radiation Belts Chris Crabtree, Gurudas Ganguli, Erik M Tejero, Alex Fletcher Recent experiments at NRL on the interaction of electron beams with whistler waves revealed interesting new wave dynamics such as (1) large sub-packet amplitude modulations, (2) discrete changes in frequency between sub-packets, (3) multiple chirping waves at nearby frequencies, and (4) parametric decay of chirping whistlers. These experiments inspired a reanalysis of high time resolution waveform data from the Van Allen Probes of whistler mode chorus in the Earth’s outer radiation belts. We developed a Bayesian spectral analysis technique that uses non-stationary time-domain models for the waves which revealed many features of chorus that are seen in laboratory data. These laboratory and space observations inspired a new finite-dimensional self-consistent Hamiltonian model in which solutions that exhibit sub-packet structuring were found. These solutions exhibit not a single island forming in phase space but a pair of islands. The self-consistent rotation in phase space of the two islands leads to the dramatic amplitude modulations that form sub-packets. These models are tractable enough to incorporate into waveform models of observed time-series to further the development of a self-consistent theory of nonlinear wave-particle interactions. |
Tuesday, November 6, 2018 4:32PM - 4:51PM |
JM10.00009: Drift turbulence, particle transport, and anomalous dissipation at the reconnecting magnetopause Ari Le, William S Daughton, Obioma Ohia, Li-Jen Chen, Yi-Hsin Liu, Shan Wang, William D Nystrom, Robert F Bird Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets observed by NASA’s MMS spacecraft at Earth’s magnetopause are studied [1]. Drift-wave fluctuations are observed in the lower-hybrid frequency range at the steep density gradient across the magnetospheric separatrix. These fluctuations induce cross-field particle transport in agreement with quasi-linear theory and enhanced electron parallel heating compared to 2D simulations. We study three different methods of quantifying the associated anomalous dissipation, based on spatial and temporal averaging, and temporal averaging followed by integration along magnetic field lines. The anomalous dissipation appears weak for each case, and the reconnection rates observed in 3D are nearly the same as in 2D. The 3D simulations show new features consistent with the observations including cold beams of magnetosheath electrons that penetrate into the hotter magnetospheric inflow. |
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