scholarly journals Hybrid numerical simulations of pulsar magnetospheres

2019 ◽  
Vol 491 (4) ◽  
pp. 5579-5585 ◽  
Author(s):  
Ioannis Contopoulos ◽  
Jerome Pétri ◽  
Petros Stefanou
Keyword(s):  
Particle Acceleration ◽  
Current Sheet ◽  
Electric Current ◽  
Hybrid Approach ◽  
High Energy ◽  
Basic Premise ◽  
Analytic Approximations ◽  
Polar Caps ◽  
Electron Positron ◽  
Field Lines

ABSTRACT We continue our investigation of particle acceleration in the pulsar equatorial current sheet (ECS). Our basic premise has been that the charge carriers in the current sheet originate in the polar caps as electron–positron pairs, and are carried along field lines that enter the ECS beyond the magnetospheric Y-point. In this work, we investigate further the charge replenishment of the ECS. We discovered that the flow of pairs from the rims of the polar caps cannot supply both the electric charge and the electric current of the ECS. The ECS must contain an extra amount of positronic (or electronic depending on orientation) electric current that originates in the stellar surface and flows outwards along the separatrices. We develop an iterative hybrid approach that self-consistently combines ideal force-free electrodynamics in the bulk of the magnetosphere with particle acceleration along the ECS. We derive analytic approximations for the orbits of the particles, and obtain the structure of the pulsar magnetosphere for various values of the pair formation multiplicity parameter κ. For realistic values κ ≫ 1, the magnetosphere is practically indistinguishable from the ideal force-free one, and therefore, the calculation of the spectrum of high energy radiation must rely on analytic approximations for the distribution of the accelerating electric field in the ECS.

Pulsar magnetospheres

1992 ◽  
Vol 341 (1660) ◽  
pp. 93-104 ◽  
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Photon Emission ◽  
Rotation Period ◽  
Primary Electron ◽  
Rotation Axes ◽  
Polar Caps ◽  
Electron Positron ◽  
Field Lines ◽  
Secular Increase

The energy loss from the neutron star - as inferred from the secular increase in rotation period - is much greater than that emitted in either the radio or the other observed wavelengths. A primary motivation of magnetospheric theory is to trace the mode in which this energy and the associated angular momentum are in fact carried off from active pulsars. This review concentrates on the special case in which the magnetic and rotation axes are aligned. Electrons emitted from the polar caps are accelerated to highly relativistic energies by the electric force and simultaneously pick up angular momentum from the magnetic torque. Some process of angular momentum dissipation occurring beyond the light-cylinder is then required, both to yield the continuous spin-down of the star, and also to allow the electrons to cross magnetic field lines and so complete their circuits back to the star. Within the framework of classical physics, this could occur if most of the spin-down energy is lost through incoherent photon emission in an equatorial domain beyond the lightcylinder, but this would generate y-radiation far in excess of that observed. Transport away of the angular momentum via a relativistic wind requires the generation of a quasi-neutral plasma. Gamma-rays emitted by outflowing electrons will produce electron-positron pairs in the strong magnetic field near the star, and highly energetic electrons returning to the star may also generate a mixed plasma by pair production or by surface spallation. Coupling with the circulating primary electron current may then ensure that the dominant angular momentum loss is via the wind rather than through photon emission.

scholarly journals Jupiter Radio Bursts and Particle Acceleration

1994 ◽  
Vol 142 ◽  
pp. 541-546 ◽  
Author(s):  
Michael D. Desch
Keyword(s):  
Particle Acceleration ◽  
Plasma Wave ◽  
Close Association ◽  
High Energy ◽  
Radio Continuum ◽  
Radio Bursts ◽  
High Energy Electrons ◽  
Planets And Satellites ◽  
Wave Emission ◽  
Field Lines

AbstractParticle acceleration processes are important in understanding many of the Jovian radio and plasma wave emissions. However, except for the high-energy electrons that generate synchrotron emission following inward diffusion from the outer magnetosphere, acceleration processes in Jupiter’s magnetosphere and between Jupiter and Io are poorly understood. We discuss very recent observations from the Ulysses spacecraft of two new Jovian radio and plasma wave emissions in which particle acceleration processes are important and have been addressed directly by complementary investigations. First, radio bursts known as quasi-periodic bursts have been observed in close association with a population of highly energetic electrons. Second, a population of much lower energy (keV range) electrons on auroral field lines can be shown to be responsible for the first observation of a Jovian plasma wave emission known as auroral hiss.Subject headings: acceleration of particles — planets and satellites: individual (Jupiter) — radio continuum: solar system

scholarly journals Anomalous-plasmoid-ejection-induced secondary magnetic reconnection: modeling solar flares and coronal mass ejections by laser–plasma experiments

2013 ◽  
Vol 1 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Quanli Dong ◽  
Dawei Yuan ◽  
Shoujun Wang ◽  
Xun Liu ◽  
Yutong Li ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Theoretical Models ◽  
High Energy ◽  
High Energy Density ◽  
Driving Mechanism ◽  
Secondary Current ◽  
Field Lines

AbstractThe driving mechanism of solar flares and coronal mass ejections is a topic of ongoing debate, apart from the consensus that magnetic reconnection plays a key role during the impulsive process. While present solar research mostly depends on observations and theoretical models, laboratory experiments based on high-energy density facilities provide the third method for quantitatively comparing astrophysical observations and models with data achieved in experimental settings. In this article, we show laboratory modeling of solar flares and coronal mass ejections by constructing the magnetic reconnection system with two mutually approaching laser-produced plasmas circumfused of self-generated megagauss magnetic fields. Due to the Euler similarity between the laboratory and solar plasma systems, the present experiments demonstrate the morphological reproduction of flares and coronal mass ejections in solar observations in a scaled sense, and confirm the theory and model predictions about the current-sheet-born anomalous plasmoid as the initial stage of coronal mass ejections, and the behavior of moving-away plasmoid stretching the primary reconnected field lines into a secondary current sheet conjoined with two bright ridges identified as solar flares.

scholarly journals Reconnection current sheet structure in a turbulent medium

2012 ◽  
Vol 19 (6) ◽  
pp. 605-610 ◽  
Author(s):  
E. T. Vishniac ◽  
S. Pillsworth ◽  
G. Eyink ◽  
G. Kowal ◽  
A. Lazarian ◽  
...  
Keyword(s):  
Current Sheet ◽  
Large Scale ◽  
Transport Coefficients ◽  
Cumulative Effect ◽  
High Energy ◽  
Turbulent Medium ◽  
Laminar Flows ◽  
High Energy Particle ◽  
Mhd Turbulence ◽  
Field Lines

Abstract. In the presence of turbulence, magnetic field lines lose their dynamical identity and particles entrained on field lines diffuse through space at a rate determined by the amplitude of the turbulence. In previous work (Lazarian and Vishniac, 1999; Kowal et al., 2009; Eyink et al., 2011) we showed that this leads to reconnection speeds which are independent of resistivity. In particular, in Kowal et al. (2009) we showed that numerical simulations were consistent with the predictions of this model. Here we examine the structure of the current sheet in simulations of turbulent reconnection. Laminar flows consistent with the Sweet-Parker reconnection model produce very thin and well ordered currents sheets. On the other hand, the simulations of Kowal et al. (2009) show a strongly disordered state even for relatively low levels of turbulence. Comparing data cubes with and without reconnection, we find that large scale field reversals are the cumulative effect of many individual eddies, each of which has magnetic properties which are not very different from turbulent eddies in a homogeneous background. This implies that the properties of stationary and homogeneous MHD turbulence are a reasonable guide to understanding turbulence during large scale magnetic reconnection events. In addition, dissipation and high energy particle acceleration during reconnection events take place over a macroscopic volume, rather than being confined to a narrow zone whose properties depend on microscopic transport coefficients.

scholarly journals Reconnection and particle acceleration in three-dimensional current sheet evolution in moderately magnetized astrophysical pair plasma

2021 ◽  
Vol 87 (6) ◽  
Author(s):  
Gregory R. Werner ◽  
Dmitri A. Uzdensky
Keyword(s):  
Particle Acceleration ◽  
Current Sheet ◽  
Energy Release ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
High Energy ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Wide Range ◽  
Kink Instability

Magnetic reconnection, a plasma process converting magnetic energy to particle kinetic energy, is often invoked to explain magnetic energy releases powering high-energy flares in astrophysical sources including pulsar wind nebulae and black hole jets. Reconnection is usually seen as the (essentially two-dimensional) nonlinear evolution of the tearing instability disrupting a thin current sheet. To test how this process operates in three dimensions, we conduct a comprehensive particle-in-cell simulation study comparing two- and three-dimensional evolution of long, thin current sheets in moderately magnetized, collisionless, relativistically hot electron–positron plasma, and find dramatic differences. We first systematically characterize this process in two dimensions, where classic, hierarchical plasmoid-chain reconnection determines energy release, and explore a wide range of initial configurations, guide magnetic field strengths and system sizes. We then show that three-dimensional (3-D) simulations of similar configurations exhibit a diversity of behaviours, including some where energy release is determined by the nonlinear relativistic drift-kink instability. Thus, 3-D current sheet evolution is not always fundamentally classical reconnection with perturbing 3-D effects but, rather, a complex interplay of multiple linear and nonlinear instabilities whose relative importance depends sensitively on the ambient plasma, minor configuration details and even stochastic events. It often yields slower but longer-lasting and ultimately greater magnetic energy release than in two dimensions. Intriguingly, non-thermal particle acceleration is astonishingly robust, depending on the upstream magnetization and guide field, but otherwise yielding similar particle energy spectra in two and three dimensions. Although the variety of underlying current sheet behaviours is interesting, the similarities in overall energy release and particle spectra may be more remarkable.

scholarly journals The equatorial current sheet and other interesting features of the pulsar magnetosphere

2016 ◽  
Vol 82 (3) ◽  
Author(s):  
Ioannis Contopoulos
Keyword(s):  
Particle Acceleration ◽  
Numerical Simulations ◽  
Current Sheet ◽  
Electric Current ◽  
Large Fraction ◽  
A Priori ◽  
Pulsar Magnetosphere ◽  
Physical Processes ◽  
Equatorial Current

We want to understand what drives magnetospheric dissipation in the equatorial current sheet. Numerical simulations have limitations and, unless we have a clear a priori understanding of the physical processes involved, their results can be misleading. We argue that the canonical pulsar magnetosphere is strongly dissipative and that a large fraction (up to 30–40 % in an aligned rotator) of the spindown luminosity is redirected towards the equator where it is dissipated into particle acceleration and emission of radiation. We show that this is due to the failure of the equatorial electric current to cross the Y-point at the tip of the corotating zone.

scholarly journals Pulsar Emission Physics: The First Fifty Years

2017 ◽  
Vol 13 (S337) ◽  
pp. 52-57 ◽  
Author(s):  
Alice K. Harding
Keyword(s):  
Particle Acceleration ◽  
High Energy ◽  
Pulsar Emission ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
High Energies ◽  
Polar Caps ◽  
History Of ◽  
Emission Models ◽  
High Energy Emission

AbstractOver the last fifty years since the discovery of pulsars, our understanding of where and how pulsars emit the radiation we observe has undergone significant revision. The location and mechanisms of high-energy radiation are intimately tied to the sites of particle acceleration. The evolution of emission models has paralleled the development of increasingly more sensitive telescopes, especially at high energies. I will review the history of pulsar emission modeling, from the early days of gaps at the polar caps, to outer gaps and slot gaps in the outer magnetosphere, to the present era of global magnetosphere simulations that locate most acceleration and high-energy emission in the current sheets.

scholarly journals Penetration of MeV electrons into the mesosphere accompanying pulsating aurorae

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Y. Miyoshi ◽  
K. Hosokawa ◽  
S. Kurita ◽  
S.-I. Oyama ◽  
Y. Ogawa ◽  
...  
Keyword(s):  
High Energy ◽  
Daily Basis ◽  
Maximum Energy ◽  
Energy Electron ◽  
High Energy Electron ◽  
Whistler Mode ◽  
Chorus Waves ◽  
Mesospheric Ozone ◽  
Field Lines ◽  
Eiscat Radar

AbstractPulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.

scholarly journals Resonant Effect of High-Energy Electron–Positron Pairs Production in Collision of Ultrarelativistic Electrons with an X-ray Electromagnetic Wave

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 210
Author(s):  
Georgii K. Sizykh ◽  
Sergei P. Roshchupkin ◽  
Victor V. Dubov
Keyword(s):  
High Energy ◽  
Energy Electron ◽  
Opening Angle ◽  
High Energy Electron ◽  
Scattered Electron ◽  
Differential Probability ◽  
X Ray ◽  
Electron Positron ◽  
Pulsar Radiation ◽  
Resonant Effect

The process of resonant high-energy electron–positron pairs production by electrons in an X-ray pulsar electromagnetic field is studied theoretically. Under the resonance conditions, the second-order process under consideration effectively reduces into two sequential first-order processes: X-ray-stimulated Compton effect and X-ray–stimulated Breit–Wheeler process. The kinematics of the process is studied in detail: the dependencies of the energy of the scattered electron on its outgoing angle and the energies of the particles of the pair on the outgoing angle of the scattered electron and the opening angle of the pair are obtained. The analysis of the number of different possible particles energies values in the entire range of the angles is also carried out, according to which the energies of the particles of the pair can take up to eight different values at a fixed outgoing angle of the scattered electron and opening angle of the pair. The estimate of the resonant differential probability per unit time of the process, which reaches the maximum value of 24 orders of the value of the non-resonant differential probability per unit time, is obtained. The angular distribution of the differential probability per unit time of the process is analyzed, particularly for the case of high-energy positrons presenting in pulsar radiation.

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