Hard Radio Spectra from Reconnection Regions in Galactic Nuclei

Birk, G. T.; Crusius-Wätzel, A. R.; Lesch, H.

doi:10.1086/322394

Cited by 27 publications

(25 citation statements)

References 34 publications

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“…Relativistic reconnection in ion-electron plasmas has been studied less. We find a test-particle simulation (Romanova & Lovelace 1992), a resolution of the diffusion equation (Birk et al 2001), and a discussion by Sakai et al (2002) in a 2D PIC simulation of laser fusion beams.…”

Section: Introductionmentioning

confidence: 82%

“…Such attributes made it attractive for high-energy astrophysics to explain, for example, radiation (Romanova & Lovelace 1992) and flares (Giannios et al 2009) in active galactic nuclei (AGNs) jets or in gamma-ray bursts (Lyutikov 2006a;Lazar et al 2009), the heating of AGN and microquasar coronae and associated flares (Di Matteo 1998;Merloni & Fabian 2001;Goodman & Uzdensky 2008;Reis & Miller 2013), the flat radio spectra from galactic nuclei and AGNs (Birk et al 2001), the heating of the lobes of giant radio galaxies (Kronberg et al 2004), the σ-paradox and particle acceleration at pulsar wind termination shocks (Kirk & Skjaeraasen 2003;Pétri & Lyubarsky 2007;Sironi & Spitkovsky 2011), GeV flares from the Crab nebula (Cerutti et al 2012a(Cerutti et al ,b, 2013, transient outflow production in microquasars and quasars (de Gouveia dal Pino & Lazarian 2005;de Gouveia Dal Pino et al 2010;Kowal et al 2011;Dexter et al 2014), gamma-ray burst outflows and non-thermal emissions (Drenkhahn & Spruit 2002;McKinney & Uzdensky 2012), X-ray flashes (Drenkhahn & Spruit 2002), soft gamma-ray repeaters (Lyutikov 2006b;Uzdensky 2011), flares in double pulsar systems (Lyutikov & Lazarian 2013), or energy extraction in the ergosphere of black holes (Koide & Arai 2008).…”

Section: Introductionmentioning

confidence: 99%

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Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

Melzani

Walder

Folini

et al. 2014

A&A

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Magnetic reconnection is a leading mechanism for magnetic energy conversion and high-energy non-thermal particle production in a variety of high-energy astrophysical objects, including ones with relativistic ion-electron plasmas (e.g., microquasars or AGNs), a regime where first principle studies are scarce. We present 2D particle-in-cell (PIC) simulations of low β ion-electron plasmas under relativistic conditions, i.e., with inflow magnetic energy exceeding the plasma restmass energy. We identify outstanding properties: (i) For relativistic inflow magnetizations (here 10 ≤ σ e ≤ 360), the reconnection outflows are dominated by thermal agitation instead of bulk kinetic energy. (ii) At high inflow electron magnetization (σ e ≥ 80), the reconnection electric field is sustained more by bulk inertia than by thermal inertia. It challenges the thermal-inertia paradigm and its implications. (iii) The inflows feature sharp transitions at the entrance of the diffusion zones. These are not shocks but results from particle ballistic motions, all bouncing at the same location, provided that the thermal velocity in the inflow is far lower than the inflow E × B bulk velocity. (iv) Island centers are magnetically isolated from the rest of the flow and can present a density depletion at their center. (v) The reconnection rates are slightly higher than in non-relativistic studies. They are best normalized by the inflow relativistic Alfvén speed projected in the outflow direction, which then leads to rates in a close range (0.14-0.25), thus allowing for an easy estimation of the reconnection electric field.

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Section: Introductionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

Melzani

Walder

Folini

et al. 2014

A&A

View full text Add to dashboard Cite

show abstract

“…It is a candidate for explaining (i) particle acceleration at pulsar wind termination shocks (Kirk & Skjaeraasen 2003;Pétri & Lyubarsky 2007;Sironi & Spitkovsky 2011a); (ii) the flat radio spectra from galactic nuclei and AGNs (Birk et al 2001) and from extragalactic jets (Romanova & Lovelace 1992); (iii) GeV flares from the Crab nebula (Bednarek & Idec 2011;Uzdensky et al 2011;Cerutti et al 2012aCerutti et al ,b, 2013; (iv) flares in active galactic nuclei (AGN) jets (Giannios et al 2009) or in gamma-ray bursts (Lyutikov 2006a;Lazar et al 2009); (v) the heating of AGN and microquasar coronae and the observed flares (Di Matteo 1998;Merloni & Fabian 2001;Goodman & Uzdensky 2008;Reis & Miller 2013;Romero et al 2014;Zdziarski et al 2014); (vi) the heating of the lobes of giant radio galaxies (Kronberg et al 2004); (vii) transient outflow production in microquasars and quasars (de Gouveia dal Pino & Lazarian 2005;de Gouveia Dal Pino et al 2010;Kowal et al 2011;Dexter et al 2014); (viii) gamma-ray burst outflows and non-thermal emissions (Drenkhahn & Spruit 2002;Giannios & Spruit 2007;McKinney & Uzdensky 2012); (ix) X-ray flashes (Drenkhahn & Spruit 2002); or (x) soft gamma-ray repeaters (Lyutikov 2006b;Uzdensky 2011).…”

Section: Introductionmentioning

confidence: 99%

The energetics of relativistic magnetic reconnection: ion-electron repartition and particle distribution hardness

Melzani

Walder

Folini

et al. 2014

A&A

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Collisionless magnetic reconnection is a prime candidate to account for flare-like or steady emission, outflow launching, or plasma heating, in a variety of high-energy astrophysical objects, including ones with relativistic ion-electron plasmas. But the fate of the initial magnetic energy in a reconnection event remains poorly known. What are the amounts assigned to kinetic energy, the ion and electron distribution, and the hardness of the particle distributions? We explored these questions with 2D particle-in-cell simulations of ion-electron plasmas. We find that 45 to 75% of the total initial magnetic energy ends up in kinetic energy, this fraction increasing with the inflow magnetization. Depending on the guide field strength, ions get from 30% to 60% of the total kinetic energy. Particles can be separated into two populations that mix only weakly: (i) particles initially in the current sheet heated by its initial tearing and subsequent contraction of the islands, and (ii) particles from the background plasma that primarily gain energy via the reconnection electric field when passing near the X-point. Particles of (ii) tend to form a power law with an index p = −dlog n(γ)/dlog γ that depends mostly on the inflow Alfvén speed V A and magnetization σ s of species s. For electrons p = 5 to 1.2 for increasing σ e . The highest particle Lorentz factor for ions or electrons increases roughly linearly with time for all the relativistic simulations. This is faster, and the spectra can be harder, than for collisionless shock acceleration. We discuss applications to microquasar and AGN coronae, to extragalactic jets, and to radio lobes. We point out situations where effects, such as Compton drag or pair creation, are important.

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“…Magnetic reconnection has been invoked as an explanation of the rapid variability observed in active galactic nuclei (Di Matteo 1998). Particle acceleration in the reconnection process has been proposed as operating in radio jets (Romanova & Lovelace 1992;Birk et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection

Watanabe

Yokoyama

2006

ApJ

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It has been recognized that the magnetic reconnection process is of great importance in high-energy astrophysics. We develop a new two-dimensional relativistic resistive magnetohydrodynamic (R 2 MHD) code and carry out numerical simulations of magnetic reconnection. We find that the outflow velocity reaches the Alfvén velocity in the inflow region and that a higher Alfvén velocity provides a higher reconnection rate. We also find that Lorentz contraction plays an important role in enhancement of the reconnection rate.

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Hard Radio Spectra from Reconnection Regions in Galactic Nuclei

Cited by 27 publications

References 34 publications

Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

The energetics of relativistic magnetic reconnection: ion-electron repartition and particle distribution hardness

Two-dimensional Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection

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