scholarly journals Kinetic ‘jets’ from fast-moving pulsars

2019 ◽  
Vol 485 (2) ◽  
pp. 2041-2053 ◽  
Author(s):  
Maxim V Barkov ◽  
Maxim Lyutikov ◽  
Noel Klingler ◽  
Pol Bordas
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Interstellar Medium ◽  
Fast Moving ◽  
Thermal Emission ◽  
Pulsar Wind Nebulae ◽  
Ambient Magnetic Field ◽  
Ram Pressure ◽  
Pulsar Wind ◽  
Ism Magnetic Fields

AbstractSome fast-moving pulsars, such as the Guitar and the Lighthouse, exhibit asymmetric non-thermal emission features that extend well beyond their ram pressure confined pulsar wind nebulae (PWNe). Based on our 3D relativistic simulations, we analytically explain these features as kinetically streaming pulsar wind particles that escaped into the interstellar medium (ISM) due to reconnection between the PWN and ISM magnetic fields. The structure of the reconnecting magnetic fields at the incoming and outgoing regions produces highly asymmetric magnetic bottles therefore and result in asymmetric extended features. For the features to become visible, the ISM magnetic field should be sufficiently high, BISM > 10 $\mu$G. We also discuss archival observations of PWNe displaying evidence of kinetic jets: the Dragonfly PWN (PSR J2021 + 3651), G327.1–1.1, and MSH 11–62, the latter two of which exhibit symmetric ‘snail eyes’ morphologies. We suggest that in those cases the pulsar is moving along the ambient magnetic field in a frisbee-type configuration.

scholarly journals Lepton-driven Nonresonant Streaming Instability

2021 ◽  
Vol 923 (2) ◽  
pp. 208
Author(s):  
Siddhartha Gupta ◽  
Damiano Caprioli ◽  
Colby C. Haggerty
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetized Plasma ◽  
Ion Current ◽  
Pulsar Wind Nebulae ◽  
Particle In Cell ◽  
Streaming Instability ◽  
Electrons And Positrons ◽  
Pulsar Wind ◽  
The Magnetic Field

Abstract A strong super-Alfvénic drift of energetic particles (or cosmic rays) in a magnetized plasma can amplify the magnetic field significantly through nonresonant streaming instability (NRSI). While the traditional analysis is done for an ion current, here we use kinetic particle-in-cell simulations to study how the NRSI behaves when it is driven by electrons or by a mixture of electrons and positrons. In particular, we characterize the growth rate, spectrum, and helicity of the unstable modes, as well the level of the magnetic field at saturation. Our results are potentially relevant for several space/astrophysical environments (e.g., electron strahl in the solar wind, at oblique nonrelativistic shocks, around pulsar wind nebulae), and also in laboratory experiments.

scholarly journals A corrugated termination shock in pulsar wind nebulae?

2016 ◽  
Vol 82 (4) ◽  
Author(s):  
Martin Lemoine
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
Radiation Reaction ◽  
Termination Shock ◽  
Pulsar Wind Nebulae ◽  
Order Unity ◽  
Poynting Flux ◽  
Electron Positron ◽  
Pulsar Wind ◽  
The Crab Nebula

Successful phenomenological models of pulsar wind nebulae assume efficient dissipation of the Poynting flux of the magnetized electron–positron wind as well as efficient acceleration of the pairs in the vicinity of the termination shock, but how this is realized is not yet well understood. This paper suggests that the corrugation of the termination shock, at the onset of nonlinearity, may lead towards the desired phenomenology. Nonlinear corrugation of the termination shock would convert a fraction of order unity of the incoming ordered magnetic field into downstream turbulence, slowing down the flow to sub-relativistic velocities. The dissipation of turbulence would further preheat the pair population on short length scales, close to equipartition with the magnetic field, thereby reducing the initial high magnetization to values of order unity. Furthermore, it is speculated that the turbulence generated by the corrugation pattern may sustain a relativistic Fermi process, accelerating particles close to the radiation reaction limit, as observed in the Crab nebula. The required corrugation could be induced by the fast magnetosonic modes of downstream nebular turbulence; but it could also be produced by upstream turbulence, either carried by the wind or seeded in the precursor by the accelerated particles themselves.

scholarly journals Magnetic Field Evolution in Neutron Star Crusts: Beyond the Hall Effect

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 130
Author(s):  
Konstantinos N. Gourgouliatos ◽  
Davide De Grandis ◽  
Andrei Igoshev
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Hall Effect ◽  
Thermal Emission ◽  
Ohmic Dissipation ◽  
Field Evolution ◽  
The Universe ◽  
The Magnetic Field ◽  
Maxwell Stresses

Neutron stars host the strongest magnetic fields that we know of in the Universe. Their magnetic fields are the main means of generating their radiation, either magnetospheric or through the crust. Moreover, the evolution of the magnetic field has been intimately related to explosive events of magnetars, which host strong magnetic fields, and their persistent thermal emission. The evolution of the magnetic field in the crusts of neutron stars has been described within the framework of the Hall effect and Ohmic dissipation. Yet, this description is limited by the fact that the Maxwell stresses exerted on the crusts of strongly magnetised neutron stars may lead to failure and temperature variations. In the former case, a failed crust does not completely fulfil the necessary conditions for the Hall effect. In the latter, the variations of temperature are strongly related to the magnetic field evolution. Finally, sharp gradients of the star’s temperature may activate battery terms and alter the magnetic field structure, especially in weakly magnetised neutron stars. In this review, we discuss the recent progress made on these effects. We argue that these phenomena are likely to provide novel insight into our understanding of neutron stars and their observable properties.

scholarly journals Searching for X-ray counterparts of Fermi Gamma-ray pulsars in Suzaku observations

2011 ◽  
Vol 7 (S279) ◽  
pp. 317-318 ◽  
Author(s):  
Yu Aoki ◽  
Takahiro Enomoto ◽  
Yoichi Yatsu ◽  
Nobuyuki Kawai ◽  
Takeshi Nakamori ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Flux Ratio ◽  
Radio Pulsars ◽  
Pulsar Wind Nebulae ◽  
X Ray ◽  
Absorbed Power ◽  
Pulsar Wind ◽  
Error Circle

AbstractWe report the Suzaku follow-up observations of the Gamma-ray pulsars, 1FGL J0614,13328, J1044.55737, J1741.82101, and J1813.31246, which were discovered by the Fermi Gamma-ray observatory. Analysing Suzaku/XIS data, we detected X-ray counterparts of these pulsars in the Fermi error circle and interpreted their spectra with absorbed power-law functions. These results indicate that the origin of these X-ray sources is non-thermal emission from the pulsars or from Pulsar Wind Nebulae (PWNe) surrounding them. Moreover we found that J1741.82101 exhibits a peculiar profile: spin-down luminosity vs flux ratio between X- and gamma-rays is unusually large compared to usual radio pulsars.

scholarly journals Using Herschel and Planck observations to delineate the role of magnetic fields in molecular cloud structure

2019 ◽  
Vol 629 ◽  
pp. A96 ◽  
Author(s):  
Juan D. Soler
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Thermal Emission ◽  
Relative Orientation ◽  
Young Stellar Objects ◽  
Circular Statistics ◽  
Stellar Objects ◽  
Submillimeter Wavelengths ◽  
The Magnetic Field

We present a study of the relative orientation between the magnetic field projected onto the plane of sky (B⊥) on scales down to 0.4 pc, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the distribution of gas column density (NH) structures on scales down to 0.026 pc, derived from the observations by Herschel in submillimeter wavelengths, toward ten nearby (d < 450 pc) molecular clouds. Using the histogram of relative orientation technique in combination with tools from circular statistics, we found that the mean relative orientation between NH and B⊥ toward these regions increases progressively from 0°, where the NH structures lie mostly parallel to B⊥, with increasing NH, in many cases reaching 90°, where the NH structures lie mostly perpendicular to B⊥. We also compared the relative orientation between NH and B⊥ and the distribution of NH, which is characterized by the slope of the tail of the NH probability density functions (PDFs). We found that the slopes of the NH PDF tail are steepest in regions where NH and B⊥ are close to perpendicular. This coupling between the NH distribution and the magnetic field suggests that the magnetic fields play a significant role in structuring the interstellar medium in and around molecular clouds. However, we found no evident correlation between the star formation rates, estimated from the counts of young stellar objects, and the relative orientation between NH and B⊥ in these regions.

scholarly journals Pulsar Wind Nebulae

1996 ◽  
Vol 160 ◽  
pp. 393-399 ◽  
Author(s):  
James M. Cordes
Keyword(s):  
Neutron Stars ◽  
Radial Velocity ◽  
Velocity Component ◽  
Pulsar Wind Nebulae ◽  
Radial Velocity Component ◽  
Ram Pressure ◽  
Pulsar Wind ◽  
Pulsar Winds

AbstractI discuss pulsar wind nebulae for which ram pressure from the neutron star’s motion is a key element of the morphology. These PWN are tools for determining the pulsar distance, radial velocity component, and interaction of pulsar winds with surrounding media. The Guitar Nebula pulsar (B2224+65) also represents a ‘smoking gun’ for velocity kicks from asymmetric supernovae or other rocket effects. The detectability of wind nebulae from pulsars and from as-yet unknown neutron stars is discussed.

scholarly journals Dynamically dominant magnetic fields in the diffuse interstellar medium

2008 ◽  
Vol 4 (S259) ◽  
pp. 87-88 ◽  
Author(s):  
Andrew Fletcher ◽  
M. Korpi ◽  
A. Shukurov
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Interstellar Medium ◽  
Numerical Simulations ◽  
Hydrodynamic Model ◽  
Mass Conservation ◽  
Unstable Flow ◽  
Gas Density ◽  
The Magnetic Field

AbstractObservations show that magnetic fields in the interstellar medium (ISM) often do not respond to increases in gas density as would be naively expected for a frozen-in field. This may suggest that the magnetic field in the diffuse gas becomes detached from dense clouds as they form. We have investigated this possibility using theoretical estimates, a simple magneto-hydrodynamic model of a flow without mass conservation and numerical simulations of a thermally unstable flow. Our results show that significant magnetic flux can be shed from dense clouds as they form in the diffuse ISM, leaving behind a magnetically dominated diffuse gas.

scholarly journals Modelling multiwavelength emissions from PSR B1259–63/LS 2883: Effects of the stellar disc on shock radiations

2019 ◽  
Vol 627 ◽  
pp. A87 ◽  
Author(s):  
A. M. Chen ◽  
J. Takata ◽  
S. X. Yi ◽  
Y. W. Yu ◽  
K. S. Cheng
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Orbital Plane ◽  
Light Curves ◽  
Double Peak ◽  
Stellar Disc ◽  
X Ray ◽  
Pulsar Wind ◽  
Star Binary

PSR B1259–63/LS 2883 is an elliptical pulsar/Be star binary that emits broadband emissions from radio to TeV γ-rays. The massive star possesses an equatorial disc that is inclined with the orbital plane of the pulsar. Non-thermal emission from the system is believed to be produced by pulsar wind shock and double-peak profiles in the X-ray, and TeV γ-ray light curves are related to the phases of the pulsar passing through the disc region of the star. In this paper, we investigate the interactions between the pulsar wind and stellar outflows, especially with the presence of the disc, and present a multiwavelength modelling of the emission from this system. We show that the double-peak profiles of X-ray and TeV γ-ray light curves are caused by the enhancements of the magnetic field and soft photons at the shock during the disc passages. As the pulsar is passing through the equatorial disc, the additional pressure of the disc pushes the shock surface closer to the pulsar, which causes the enhancement of magnetic field in the shock, and thus increases the synchrotron luminosity. The TeV γ-rays due to the inverse-Compton (IC) scattering of shocked electrons with seed photons from the star are expected to peak around periastron, which is inconsistent with observations. However, the shock heating of the stellar disc could provide additional seed photons for IC scattering during the disc passages, and thus produces the double-peak profiles as observed in the TeV γ-ray light curve. Our model can possibly be examined and applied to other similar gamma-ray binaries, such as PSR J2032+4127/MT91 213, HESS J0632+057, and LS I+61°303.

scholarly journals PARTICLE ACCELERATION AT THE TERMINATION SHOCK OF STRIPED PULSAR WINDS

2012 ◽  
Vol 08 ◽  
pp. 144-150 ◽  
Author(s):  
LORENZO SIRONI ◽  
ANATOLY SPITKOVSKY
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Magnetic Energy ◽  
Termination Shock ◽  
Larmor Radius ◽  
Pulsar Wind Nebulae ◽  
Field Polarity ◽  
Particle In Cell ◽  
Post Shock ◽  
Pulsar Wind

The relativistic wind of pulsars consists of toroidal stripes of opposite magnetic field polarity, separated by current sheets of hot plasma. By means of multi-dimensional particle-in-cell simulations, we investigate particle acceleration and magnetic field dissipation at the termination shock of a relativistic striped pulsar wind. At the shock, the flow compresses and the alternating fields annihilate by driven magnetic reconnection. Irrespective of the stripe wavelength λ or the wind magnetization σ (in the regime σ ≫1 of magnetically dominated flows), shock-driven reconnection transfers all the magnetic energy of alternating fields to the particles. In the limit λ/(rL σ) ≫ 1, where rL is the relativistic Larmor radius in the wind, the post-shock spectrum approaches a flat power-law tail with slope around -1.5, populated by particles accelerated by the reconnection electric field. Our findings place important constraints on the models of non-thermal radiation from Pulsar Wind Nebulae.

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