Max Planck Princeton Center for Plasma Physics

Princeton, NJ, United States

Max Planck Princeton Center for Plasma Physics

Princeton, NJ, United States

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Soto-Chavez A.R.,Princeton University | Wang G.,Princeton University | Wang G.,Max Planck Princeton Center for Plasma Physics | Bhattacharjee A.,Princeton University | And 3 more authors.
Geophysical Research Letters | Year: 2014

Motivated by the fact that geomagnetic field inhomogeneity is weak close to the chorus generation region and the observational evidence that falling-tone chorus tend to have large oblique angles of propagation, we propose that falling-tone chorus start as a marginally unstable mode. The marginally unstable mode requires the presence of a relatively large damping, which has its origins in the Landau damping of oblique waves in this collisionless environment. A marginally unstable mode produces phase-space structures that release energy and produce wave chirping. We show that the present model produces results in reasonable agreement with observations. © 2014. American Geophysical Union. All Rights Reserved.


Teaca B.,Coventry University | Teaca B.,Max Planck Institute for Plasma Physics (Garching) | Teaca B.,Max Planck Princeton Center for Plasma Physics | Navarro A.B.,Max Planck Institute for Plasma Physics (Garching) | And 2 more authors.
Physics of Plasmas | Year: 2014

In magnetized plasma turbulence, the couplings of perpendicular spatial scales that arise due to the nonlinear interactions are analyzed from the perspective of the free-energy exchanges. The plasmas considered here, with appropriate ion or electron adiabatic electro-neutrality responses, are described by the gyrokinetic formalism in a toroidal magnetic geometry. Turbulence develops due to the electrostatic fluctuations driven by temperature gradient instabilities, either ion temperature gradient (ITG) or electron temperature gradient (ETG). The analysis consists in decomposing the system into a series of scale structures, while accounting separately for contributions made by modes possessing special symmetries (e.g., the zonal flow modes). The interaction of these scales is analyzed using the energy transfer functions, including a forward and backward decomposition, scale fluxes, and locality functions. The comparison between the ITG and ETG cases shows that ETG turbulence has a more pronounced classical turbulent behavior, exhibiting a stronger energy cascade, with implications for gyrokinetic turbulence modeling. © 2014 AIP Publishing LLC.


Hatch D.R.,University of Texas at Austin | Hatch D.R.,Max Planck Institute for Plasma Physics (Garching) | Jenko F.,Max Planck Institute for Plasma Physics (Garching) | Jenko F.,Max Planck Princeton Center for Plasma Physics | And 2 more authors.
Physical Review Letters | Year: 2013

A gyrokinetic model of ion temperature gradient driven turbulence in magnetized plasmas is used to study the injection, nonlinear redistribution, and collisional dissipation of free energy in the saturated turbulent state over a broad range of driving gradients and collision frequencies. The dimensionless parameter LT/LC, where LT is the ion temperature gradient scale length and LC is the collisional mean free path, is shown to parametrize a transition between a saturation regime dominated by nonlinear transfer of free energy to small perpendicular (to the magnetic field) scales and a regime dominated by dissipation at large scales in all phase space dimensions. © 2013 American Physical Society.


Bratanov V.,Max Planck Institute for Plasma Physics (Garching) | Jenko F.,Max Planck Institute for Plasma Physics (Garching) | Jenko F.,Max Planck Princeton Center for Plasma Physics | Hatch D.R.,Max Planck Institute for Plasma Physics (Garching) | And 2 more authors.
Physical Review Letters | Year: 2013

Turbulence is generally associated with universal power-law spectra in scale ranges without significant drive or damping. Although many examples of turbulent systems do not exhibit such an inertial range, power-law spectra may still be observed. As a simple model for such situations, a modified version of the Kuramoto-Sivashinsky equation is studied. By means of semianalytical and numerical studies, one finds power laws with nonuniversal exponents in the spectral range for which the ratio of nonlinear and linear time scales is (roughly) scale independent. © 2013 American Physical Society.


Goriely S.,Free University of Colombia | Bauswein A.,Aristotle University of Thessaloniki | Just O.,Max Planck Institute for Astrophysics | Just O.,Max Planck Princeton Center for Plasma Physics | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

We investigate β-interactions of free nucleons and their impact on the electron fraction (Ye) and r-process nucleosynthesis in ejecta characteristic of binary neutron starmergers (BNSMs). For that we employ trajectories from a relativistic BNSM model to represent the density- temperature evolutions in our parametric study. In the high-density environment, positron captures decrease the neutron richness at the high temperatures predicted by the hydrodynamic simulation. Circumventing the complexities of modelling three-dimensional neutrino transport, (anti)neutrino captures are parametrized in terms of prescribed neutrino luminosities and mean energies, guided by published results and assumed as constant in time. Depending sensitively on the adopted νe-ν~e luminosity ratio, neutrino processes increase Ye to values between 0.25 and 0.40, still allowing for a successful r-process compatible with the observed solar abundance distribution and a significant fraction of the ejecta consisting of r-process nuclei. If the νe luminosities and mean energies are relatively large compared to the ν~e properties, the mean Ye might reach values >0.40 so that neutrino captures seriously compromise the success of the r-process. In this case, the r-abundances remain compatible with the solar distribution, but the total amount of ejected r-material is reduced to a fewper cent, because the production of iron-peak elements is favoured. Proper neutrino physics, in particular also neutrino absorption, have to be included in BNSM simulations before final conclusions can be drawn concerning r-processing in this environment and concerning observational consequences like kilonovae, whose peak brightness and colour temperature are sensitive to the composition-dependent opacity of the ejecta. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Pueschel M.J.,University of Wisconsin - Madison | Told D.,Max Planck Institute for Plasma Physics (Garching) | Terry P.W.,University of Wisconsin - Madison | Jenko F.,Max Planck Institute for Plasma Physics (Garching) | And 4 more authors.
Astrophysical Journal, Supplement Series | Year: 2014

A current sheet susceptible to the tearing instability is used to drive reconnection turbulence in the presence of a strong guide field. Through nonlinear gyrokinetic simulations, the dependencies of central quantities such as the heating rate on parameters like collisionality or plasma β are studied, revealing that linear physics tends to predict only some aspects of the quasi-saturated state, with the nonlinear cascade responsible for additional features. For the solar corona, it is demonstrated that the kinetic heating associated with this type of turbulence agrees quantitatively with observational volumetric heating rates. In the context of short particle acceleration events, the self-consistent emergence of plasmoids or flux ropes in the turbulent bath is found to be important: ubiquitously occurring merger events of these objects cause strong bursts in the heating rate, the timescale of which is consistent with nanoflare observations. Furthermore, anisotropy of the temperature fluctuations is seen to emerge, hinting at a new means of generating coronal ion temperature anisotropy in the absence of cyclotron resonances. © 2014. The American Astronomical Society. All rights reserved..


Park J.,Kyung Hee University | Innes D.E.,Max Planck Institute for Solar System Research | Bucik R.,Max Planck Institute for Solar System Research | Bucik R.,Max Planck Princeton Center for Plasma Physics | And 2 more authors.
Astrophysical Journal | Year: 2015

We study the relationship between large gradual solar energetic particle (SEP) events and associated extreme-ultraviolet (EUV) wave properties in 16 events that occurred between 2010 August and 2013 May and were observed by SDO, the Solar and Heliospheric Observatory (SOHO), and/or STEREO. We determine onset times, peak times, and peak fluxes of the SEP events in the SOHO/ERNE and STEREO/LET proton channels (6-10 MeV). The EUV wave arrival times and their speeds from the source sites to the spacecraft footpoints in the photosphere, which are magnetically connected to the spacecraft by Parker spiral and potential fields, are determined by spacetime plots from the full-Sun heliographic images created by combining STEREO-A and STEREO-B 195 Å and SDO 193 Å images. The SEP peak fluxes increase with the EUV wave speeds, and the SEP spectral indices become harder with the speeds. This shows that higher energetic particle fluxes are associated with faster EUV waves, which are considered as the lateral expansions of coronal-mass-ejection-driven shocks in the low corona. © 2015. The American Astronomical Society. All rights reserved.


Kunz M.W.,Princeton University | Kunz M.W.,Max Planck Princeton Center for Plasma Physics | Stone J.M.,Princeton University | Stone J.M.,Max Planck Princeton Center for Plasma Physics | Bai X.-N.,Harvard - Smithsonian Center for Astrophysics
Journal of Computational Physics | Year: 2014

We describe Pegasus, a new hybrid-kinetic particle-in-cell code tailored for the study of astrophysical plasma dynamics. The code incorporates an energy-conserving particle integrator into a stable, second-order-accurate, three-stage predictor-predictor-corrector integration algorithm. The constrained transport method is used to enforce the divergence-free constraint on the magnetic field. A δf scheme is included to facilitate a reduced-noise study of systems in which only small departures from an initial distribution function are anticipated. The effects of rotation and shear are implemented through the shearing-sheet formalism with orbital advection. These algorithms are embedded within an architecture similar to that used in the popular astrophysical magnetohydrodynamics code Athena, one that is modular, well-documented, easy to use, and efficiently parallelized for use on thousands of processors. We present a series of tests in one, two, and three spatial dimensions that demonstrate the fidelity and versatility of the code. © 2013 Elsevier Inc.


Jain N.,Max Planck Princeton Center for Plasma Physics | Jain N.,Max Planck Institute for Solar System Research | Buchner J.,Max Planck Princeton Center for Plasma Physics | Buchner J.,Max Planck Institute for Solar System Research
Physics of Plasmas | Year: 2014

Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =de=c/ωpe), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ∼5de), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow. © 2014 AIP Publishing LLC.


Jain N.,Max Planck Princeton Center for Plasma Physics | Jain N.,Max Planck Institute for Solar System Research | Buchner J.,Max Planck Princeton Center for Plasma Physics | Buchner J.,Max Planck Institute for Solar System Research
Physics of Plasmas | Year: 2014

In collisionless magnetic reconnection, electron current sheets (ECS) with thickness of the order of an electron inertial length form embedded inside ion current sheets with thickness of the order of an ion inertial length. These ECS's are susceptible to a variety of instabilities which have the potential to affect the reconnection rate and/or the structure of reconnection. We carry out a three dimensional linear eigen mode stability analysis of electron shear flow driven instabilities of an electron scale current sheet using an electron-magnetohydrodynamic plasma model. The linear growth rate of the fastest unstable mode was found to drop with the thickness of the ECS. We show how the nature of the instability depends on the thickness of the ECS. As long as the half-thickness of the ECS is close to the electron inertial length, the fastest instability is that of a translational symmetric two-dimensional (no variations along flow direction) tearing mode. For an ECS half thickness sufficiently larger or smaller than the electron inertial length, the fastest mode is not a tearing mode any more and may have finite variations along the flow direction. Therefore, the generation of plasmoids in a nonlinear evolution of ECS is likely only when the half-thickness is close to an electron inertial length. © 2014 AIP Publishing LLC.

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