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The Linear Instability of Dilute Ultrarelativistic e± Pair Beams

Chang, Philip and Broderick, Avery E. and Pfrommer, Christoph and Puchwein, Ewald and Lamberts, Astrid and Shalaby, Mohamad and Vasil, Geoffrey (2016) The Linear Instability of Dilute Ultrarelativistic e± Pair Beams. Astrophysical Journal, 833 (1). Art. No. 118. ISSN 0004-637X.

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The annihilation of TeV photons from extragalactic TeV sources and the extragalactic background light produces ultrarelativistic e± beams, which are subject to powerful plasma instabilities that sap their kinetic energy. Here we study the linear phase of the plasma instabilities that these pair beams drive. To this end, we calculate the linear growth rate of the beam-plasma and oblique instability in the electrostatic approximation in both the reactive and kinetic regimes, assuming a Maxwell–Jüttner distribution for the pair beam. We reproduce the well-known reactive and kinetic growth rates for both the beam-plasma and oblique mode. We demonstrate for the oblique instability that there is a broad spectrum of unstable modes that grow at the maximum rate for a wide range of beam temperatures and wave-vector orientations relative to the beam. We also delineate the conditions for applicability for the reactive and kinetic regimes and find that the beam-plasma mode transitions to the reactive regime at a lower Lorentz factor than the oblique mode due to a combination of their different scalings and the anisotropy of the velocity dispersions. Applying these results to the ultrarelativistic e± beams from TeV blazars, we confirm that these beams are unstable to both the kinetic oblique mode and the reactive beam-plasma mode. These results are important in understanding how powerful plasma instabilities may sap the energy of the ultrarelativistic e± beams as they propagate through intergalactic space.

Item Type:Article
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URLURL TypeDescription Paper
Chang, Philip0000-0002-2137-2837
Broderick, Avery E.0000-0002-3351-760X
Pfrommer, Christoph0000-0002-7275-3998
Lamberts, Astrid0000-0001-8740-0127
Shalaby, Mohamad0000-0001-9625-5929
Additional Information:© 2016 The American Astronomical Society. Received 2016 August 17; revised 2016 September 27; accepted 2016 September 30; published 2016 December 12. We thank A. Bret for sharing his notes of the oblique instability and for extensive and enlightening discussions. P.C. is supported by the UWM Research Growth Initiative, the NASA ATP program through NASA grant NNX13AH43G, and NSF grant AST-1255469. A.E.B. and M.S. receive financial support from the Perimeter Institute for Theoretical Physics and the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation. C.P. gratefully acknowledges support by the European Research Council under ERC-CoG grant CRAGSMAN-646955 and by the Klaus Tschira Foundation. E.P. gratefully acknowledges support by the Kavli Foundation. Support for A.L. was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. G.V. acknowledges support from the Australian Research Council, project number DE140101960.
Funding AgencyGrant Number
University of Wisconsin-MilwaukeeUNSPECIFIED
Perimeter Institute for Theoretical PhysicsUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Industry CanadaUNSPECIFIED
Ontario Ministry of Research and InnovationUNSPECIFIED
European Research Council (ERC)CRAGSMAN-646955
Klaus Tschira FoundationUNSPECIFIED
Kavli FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Australian Research CouncilDE140101960
Subject Keywords:BL Lacertae objects: general – gamma rays: general – instabilities – magnetic fields – plasmas
Issue or Number:1
Record Number:CaltechAUTHORS:20161214-100859234
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Official Citation:Philip Chang et al 2016 ApJ 833 118
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72807
Deposited By: Tony Diaz
Deposited On:14 Dec 2016 18:26
Last Modified:03 Oct 2019 16:21

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