Magnetic Fields in Astrophysical Jets: From Launch to Termination

Hardcastle, Martin; Gabuzda, D. C.

doi:10.1007/978-1-4614-5728-2_14

Cited by 9 publications

(10 citation statements)

References 193 publications

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“…Strong, collimated, distinct, continuous flows of plasmas known as astrophysical jets have been observed in various astrophysical contexts over the past century and it is now generally believed that astrophysical jets are driven by magnetohydrodynamic (MHD) forces (Pudritz, Hardcastle & Gabuzda 2012). As noted by Livio (2011), these jets exist over an enormous range of parameters and are phenomenologically associated with accretion disks.…”

Section: Introductionmentioning

confidence: 99%

Experiments relevant to astrophysical jets

Bellan

2018

J. Plasma Phys.

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This paper summarizes the results of an experimental program at Caltech wherein magnetohydrodynamically driven plasma jets are created and diagnosed. The theory modelling these jets, the main experimental results and their relevance to astrophysical jets are presented. The model explains how the jets are driven and why they self-collimate. Characteristic kink and Rayleigh–Taylor instabilities are shown to occur and the ramifications of these instabilities are discussed. Extending the experimental results to the astrophysical situation reveals a shortcoming in ideal magnetohydrodynamics (MHD) that must be remedied by replacing the ideal MHD Ohm’s law by the generalized Ohm’s law. It is shown that when the generalized Ohm’s law is used and the consequences of weak ionization are taken into account, an accretion disk behaves much like the electrodes, mass source and power supply used in the experiment.

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Section: Introductionmentioning

confidence: 99%

Experiments relevant to astrophysical jets

Bellan

2018

J. Plasma Phys.

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“…These circumstances indicate the prevalence of large-scale modes of transport. In sub-Eddington sources, large-scale magnetic fields provide natural angular momentum transport agents (Blandford & Payne 1982;Königl 1989;Field & Rogers 1993;Blackman, Frank & Welch 2001;Lynden-Bell 2006;Pudritz, Hardcastle & Gabuzda 2012;Penna et al 2013). In young stars, pre-planetary nebulae, microquasars and active galactic nuclei, jets typically have too much collimated momenta to be driven by mechanisms that do not involve large-scale magnetic fields (Pudritz et al 2012;Blackman & Lucchini 2014).…”

Section: Lessons From Observations Of Jets Coronae and Large-scale Smentioning

confidence: 99%

“…Some use of mean field theory as an input to global simulations is emerging Stepanovs, Fendt & Sheikhnezami (2014), Sadowski et al (2015) but also important is the other direction -informing mean field models with outputs from global simulations. For most of the long history of simulations of jets (Pudritz et al 2012), the magnetic fields have been imposed and the disc treated as a boundary condition but the new generation of simulations is evolving beyond this limitation. A similar evolution between connecting interior to exterior is emerging in solar dynamo simulations as well (Nelson et al 2011;Nelson & Miesch 2014).…”

Section: Role Of Large-scale Dynamos In Mri Simulations and Transportmentioning

confidence: 99%

Motivation and challenge to capture both large-scale and local transport in next generation accretion theory

Blackman

Nauman

2015

J. Plasma Phys.

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Accretion disc theory is less developed than stellar evolution theory although a similarly mature phenomenological picture is ultimately desired. While the interplay of theory and numerical simulations has amplified community awareness of the role of magnetic fields in angular momentum transport, there remains a long term challenge to incorporate the insights gained from simulations into improving practical models for comparison with observations. What has been learned from simulations that can lead to improvements beyond SS73 in practical models? Here, we emphasize the need to incorporate the role of non-local transport more precisely. To show where large-scale transport would fit into the theoretical framework and how it is currently missing, we review why the wonderfully practical approach of Shakura & Sunyaev (Astron. Astrophys., vol. 24, 1973, pp. 337-355, SS73) is necessarily a mean field theory, and one which does not include large-scale transport. Observations of coronae and jets, combined with the interpretation of results from shearing box simulations, of the magnetorotational instability (MRI) suggest that a significant fraction of disc transport is indeed non-local. We show that the Maxwell stresses in saturation are dominated by large-scale contributions and that the physics of MRI transport is not fully captured by a viscosity. We also clarify the standard physical interpretation of the MRI as it applies to shearing boxes. Computational limitations have so far focused most attention toward local simulations, but the next generation of global simulations should help to inform improved mean field theories. Mean field accretion theory and mean field dynamo theory should in fact be unified into a single theory that predicts the time evolution of spectra and luminosity from separate disc, corona and outflow contributions. Finally, we note that any mean field theory, including that of SS73, has a finite predictive precision that needs to be quantified when comparing the predictions to observations.

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“…At the VHE emission region, the typical value of B is in the interval of 0.1-5 G [54,[63][64][65][66][67]. The typical value of the magnetic field in the radio lobes is 10 µG for a coherence length of 10 kpc [48,68]. The magnetic field in the host galactic is poorly known and its strength is approximately equal to µG with coherence lengths of the order of 0.1 to 0.2 kpc [48,54,69].…”

Section: B Magnetic Field Assumptionmentioning

confidence: 99%

Probing $μ$eV ALPs with future LHAASO observation of AGN $γ$-ray spectra

Long,

Chen,

et al. 2021

Preprint

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Axion-like particles (ALPs) are predicted in some well-motivated theories beyond the Standard Model. The TeV gamma-rays from active galactic nuclei (AGN) suffers attenuation by the pair production interactions with the cosmic infrared background light (EBL/CMB) during its travel to the earth. The attenuation can be circumvented through photon-ALP conversions in the AGN and Galaxy magnetic-field, and a flux enhancement is expected to arise in the observed spectrum. In this work, we study the potential of the AGN gamma-ray spectrum for energy up to above 100 TeV to probe ALP-parameter space at around µeV, where the coupling gaγ is so far relatively weak constrained. We find the nearby and bright sources, Mrk 501, IC 310 and M 87, are suitable for our objective. Assuming an intrinsic spectrum exponential cutoff energy at Ec=100 TeV, we extrapolate the observed spectra of these sources up to above 100 TeV by the models with/without ALPs. For gaγ 2×10 −11 GeV −1 with ma 1 µeV, the flux at around 100 TeV predicted by the ALP model can be enhanced more than an order of magnitude than that from the standard absorption, and could be detected by LHAASO. Our result is subject to the uncertainty from the intrinsic spectrum above tens of TeV, which require further observations on these sources by the forthcoming CTA, LHAASO, SWGO and so on.

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Magnetic Fields in Astrophysical Jets: From Launch to Termination

Cited by 9 publications

References 193 publications

Experiments relevant to astrophysical jets

Experiments relevant to astrophysical jets

Motivation and challenge to capture both large-scale and local transport in next generation accretion theory

Probing $μ$eV ALPs with future LHAASO observation of AGN $γ$-ray spectra

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