Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Plasma Physics
Volume 64, Number 11
Monday–Friday, October 21–25, 2019; Fort Lauderdale, Florida
Session TM9: Mini-conference: Magnetic Reconnection |
Hide Abstracts |
Chair: Dmitri Uzdensky, University of Colorado, Boulder Room: Grand C/E |
Thursday, October 24, 2019 9:30AM - 9:50AM |
TM9.00001: Explosive Reconnection and Particle Acceleration in Relativistic Plasma Maxim Lyutikov We develop a model of particle acceleration during explosive reconnection events in relativistic highly magnetized plasma and apply the model to explain the Crab gamma-ray flares. The most rapid acceleration occurs during the early stages of X-point collapse. Ensuring flux mergers proceed with lower rates, and eventually dissipates a large fraction of the magnetic energy. We argue that magnetic reconnection is an important (and dominant in some cases) process of particle acceleration in high energy astrophysical sources. [Preview Abstract] |
Thursday, October 24, 2019 9:50AM - 10:10AM |
TM9.00002: The interplay of magnetically-dominated turbulence and reconnection in producing non-thermal particles Luca Comisso, Lorenzo Sironi Magnetized turbulence and reconnection are often invoked to explain the observed non-thermal emission from a wide variety of astrophysical sources. With fully-kinetic particle-in-cell simulations, we study the interplay between turbulence and reconnection in generating non-thermal particles in magnetically-dominated (or equivalently, “relativistic”) pair plasmas. We find that magnetic reconnection, which self-consistently occurs in the turbulent plasma, is efficient in injecting particles out of the thermal pool. The particles are then further accelerated to high energies by stochastic scattering off turbulent fluctuations. As a result, the turbulent plasma produces an extended non-thermal particle energy spectrum with a power-law energy range. The power-law slope is harder for larger magnetizations and higher turbulence fluctuations, while the initial plasma temperature enters only as an overall energy shift --- everything else being fixed. The non-thermal tail typically contains a large fraction of particles and extends up to the limit set by the size of the largest turbulent eddies. These results have important implications for the origin of non-thermal particles in high-energy astrophysical sources. [Preview Abstract] |
Thursday, October 24, 2019 10:10AM - 10:30AM |
TM9.00003: ABSTRACT WITHDRAWN |
Thursday, October 24, 2019 10:30AM - 10:50AM |
TM9.00004: Pulsar radio nanoshots as a low-frequency afterglow of relativistic magnetic reconnection Alexander Philippov, Dmitri Uzdensky, Anatoly Spitkovsky In this talk we propose that coherent radio emission of young energetic pulsars and some millisecond pulsars is produced in the magnetospheric current sheet. Magnetic reconnection in the pulsar sheet proceeds in the plasmoid-dominated regime. Collisions of plasmoids with each other and with the upstream magnetic field eject fast-magnetosonic waves, which escape from the plasma as electromagnetic waves in radio band. We illustrate this mechanism with first-principles kinetic plasma simulations, which allow us to compute the radiation spectrum. This model explains many features of observed short bursts of radio emission: their phase coincidence with the gamma-ray emission, nano-second duration, and extreme instantaneous brightness. [Preview Abstract] |
Thursday, October 24, 2019 10:50AM - 11:10AM |
TM9.00005: 3D Effects in Magnetic Reconnection in Collisionless Relativistic Pair Plasma with Moderate Magnetization Gregory Werner, Dmitri Uzdensky Magnetic reconnection is a plasma process that can efficiently harness stored magnetic energy to energize particles, resulting in heating and nonthermal particle acceleration (NTPA). Reconnection has been much studied in 2D, but it remains an important task to establish the extent to which 2D models apply to real 3D phenomena, with the prohibitive expense of 3D simulations allowing relatively few studies of 3D effects, typically in a limited range of regimes. We have recently observed significant 2D/3D differences in first-principles electromagnetic particle-in-cell (EM-PIC) reconnection simulations---in perhaps the most expedient regime for EM-PIC, viz., relativistic pair plasma with moderate magnetization (i.e., with plasma beta around 1). Reconnection in this regime may power intense high-energy flares from astrophysical sources such as pulsar wind nebulae and jets of accreting black holes. We find that, in 3D, the rates of reconnection and magnetic energy conversion slow down, flux ropes no longer merge and grow ad infinitum in neatly hierarchical fashion, and plasma and magnetic flux no longer stay trapped in those flux ropes---thus allowing more magnetic energy to be dissipated overall. Nevertheless, NTPA is remarkably similar in 2D and 3D. [Preview Abstract] |
Thursday, October 24, 2019 11:10AM - 11:25AM |
TM9.00006: Plasmoid formation in jets and accretion disks Bart Ripperda, Alexander Philippov, Lorenzo Sironi, Fabio Bacchini, Oliver Porth, Jordy Davelaar Black hole accretion disks and jets, consisting of charged particles, regularly emit high-energy radiation.~Macroscopic plasma dynamics of such systems is described by general relativistic magnetohydrodynamics (GRMHD), coupling the charged particle fluid to electromagnetic fields. Despite outstanding results achieved with GRMHD, current studies are affected by a lack of information on microscopic physics. Nonthermal radiation is governed by the interaction between micro- and macroscopic physics and to interpret observations both scales need to be resolved. Magnetic energy can be transferred from the macroscale through turbulent magnetic reconnection and plasmoid formation, accelerating radiating particles on the microscale. In GRMHD models, reconnection is caused by finite resistivity allowing magnetic energy to dissipate and heat the plasma. We employ a novel resistive GRMHD code BHAC (Black Hole Accretion Code) to study reconnection and plasmoid formation in accretion disks and jets. Modeling nonthermal radiation is the main uncertainty in interpreting observations of the accretion disk and jet of M87 by the Event Horizon Telescope and flaring emission from Sgr A* by the GRAVITY collaboration. [Preview Abstract] |
Thursday, October 24, 2019 11:25AM - 11:40AM |
TM9.00007: 3D Collisionless Reconnection with Strong Guide Field Yu Lin, Xueyi Wang, Liu Chen, Zhifang Guo 3D physics of magnetic reconnection under a strong guide field with $B_G/B_0 \gg 1$, as in the solar and laboratory plasmas, is investigated using the gyrokinetic electron and fully-kinetic ion (GeFi) particle simulation model. Here, $B_G$ and $B_0$ are the guide and the anti-parallel components of the magnetic field, respectively. Using the GeFi model, 3D physics of reconnection with a realistically large ion-to-electron mass ratio, $m_i/m_e$, can be calculated. In the computation, the time variation of background magnetic field for gyrokinetic electrons must be taken into account. Turbulence spectrum, wave properties, and electron heating in the high guide field reconnection are analyzed. Secondary instabilities, which are excited near the separatrix region of the magnetic island associated with the primary reconnection, are also studied. [Preview Abstract] |
Thursday, October 24, 2019 11:40AM - 11:55AM |
TM9.00008: Magnetic Reconnection Experiments on the MAGPIE Pulsed Power Generator Jack Halliday, Lee Suttle, Jack Hare, Sergey Lebedev, Daniel Russell, Eleanor Tubman, Vicente Valenzuela Villaseca Magnetic reconnection is a relaxation mechanism through which energy stored in magnetic flux is dissipated, leading to bulk plasma heating, plasma acceleration, and the generation of fast particles. In this presentation we will provide an overview of results obtained using a versatile, pulsed power driven platform for magnetic reconnection experiments [1, 2]. The platform uses the MAGPIE generator to produce plasma inflows (u$_{\mathrm{in}}$ $\approx $ 50 kms$^{\mathrm{-1}})$ that carry a strong azimuthal magnetic field (B$_{\mathrm{in}}$ \textasciitilde 3 T) and persist for many hydrodynamic timescales (T$_{\mathrm{total\thinspace \thinspace }}\approx $ 500 ns \textgreater \textgreater T$_{\mathrm{hydro}} \quad \approx $ 10 ns). Experiments are diagnosed with a suite of high spatial and temporal resolution diagnostics including laser interferometry, Thomson scattering, and Faraday rotation imaging.Notable results obtained using this platform include observation of the semi-collisional plasmoid instability, anomalous heating within the reconnection layer, and measurements of a power balance which demonstrates that magnetic energy is efficiently dissipated by the reconnection process. [1] L. G. Suttle et al. PRL 2016, [2] J. D. Hare et al. PRL 2017 [Preview Abstract] |
Thursday, October 24, 2019 11:55AM - 12:10PM |
TM9.00009: Kinetic Beaming in Radiative Magnetic Reconnection: A Mechanism for Rapid Variability in Gamma-Ray Flares John Mehlhaff, Gregory Werner, Dmitri Uzdensky, Mitchell Begelman Relativistic collisionless magnetic reconnection may power rapid gamma-ray flares---as observed, for example, in pulsar wind nebulae, blazars, and radio galaxies---by accelerating electrons to sufficient energies to produce the observed emission. When the particles radiate efficiently, the back-reaction force they experience influences the reconnection dynamics: the so-called radiative regime. Using a series of particle-in-cell simulations self-consistently incorporating radiation reaction, we study the impact of radiative cooling on kinetic beaming, wherein the highest energy particles are preferentially focused into beams when accelerated through the reconnection layer. We find that cooling plays a crucial role in allowing these beams to radiate their energy before decohering. Hence, only radiatively efficient reconnection produces highly collimated photon beams that can cause abrupt flares as they cross an observer's line of sight. These findings paint a remarkably compelling picture for many spectacular gamma-ray flares in astrophysics, where magnetic reconnection underlies not only the flares' energetics, but also, via kinetic beaming, their extremely short observed timescales. [Preview Abstract] |
Thursday, October 24, 2019 12:10PM - 12:25PM |
TM9.00010: Plasma Dynamics and Particle Acceleration in Relativistic Turbulent Magnetic Reconnection Fan Guo, Hui Li, William Daughton, Xiaocan Li, Patrick Kilian Past years have seen an active development on relativistic magnetic reconnection. A major uncertainty of the reconnection studies is the role of three-dimensional physics and turbulence. This study is designed to explore these aspects when magnetic reconnection occurs in a turbulent state. These large scale three-dimensional fully kinetic simulations are carried out using the LANL's VPIC code on the Trinity machine. Different from typical kinetic studies, we have added a new set of long-wavelength perturbation to drive external turbulence in the simulation domain. Because of this, the reconnection layer quickly evolves into a turbulent state. The flux ropes evolve quickly after their generation, and can completely disrupt due to the secondary kink instability. We find that the while the reconnection is strongly modified by the injected fluctuations and self-generated fluctuation due to secondary tearing and kink instabilities, the acceleration of high particles is robust and not dependent on the injected turbulence. In addition, we show that for the anti-parallel reconnection case the Fermi-like mechanism is still the dominant acceleration process. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700