MAGNETIC FIELDS AND COSMIC RAYS IN GRBs: A SELF-SIMILAR COLLISIONLESS FORESHOCK / Medvedev Mikhail V.,Zakutnyaya Olga V. // ASTROPHYSICAL JOURNAL. - 2009. - V. 696, l. 2. - P. 2269-2274.

ISSN/EISSN:

0004-637X / нет данных

Type:

Article

Abstract:

Cosmic rays accelerated by a shock form a streaming distribution of outgoing particles in the foreshock region. If the ambient fields are negligible compared to the shock and cosmic ray energetics, a stronger magnetic field can be generated in the shock upstream via the streaming (Weibel-type) instability. Here we develop a self-similar model of the foreshock region and calculate its structure, e. g., the magnetic field strength, its coherence scale, etc., as a function of the distance from the shock. Our model indicates that the entire foreshock region of thickness similar to R/(2 Gamma(2)(sh)), being comparable to the shock radius in the late afterglow phase when Gamma(sh) similar to 1, can be populated with large-scale and rather strong magnetic fields (of subgauss strengths with the coherence length of order 10(16) cm) compared with the typical interstellar medium magnetic fields. The presence of such fields in the foreshock region is important for high efficiency of Fermi acceleration at the shock. Radiation from accelerated electrons in the foreshock fields can constitute a separate emission region radiating in the UV/optical through radio band, depending on time and shock parameters. We also speculate that these fields being eventually transported into the shock downstream can greatly increase radiative efficiency of a gamma-ray burst afterglow shock.

Author keywords:

cosmic rays; gamma rays: bursts; magnetic fields; shock waves DIFFUSIVE SHOCK ACCELERATION; PARTICLE-ACCELERATION; ULTRARELATIVISTIC SHOCKS; JITTER RADIATION; BURST SHOCKS; HIGH-ENERGY; AMPLIFICATION; SIMULATIONS; AFTERGLOWS; TURBULENCE

DOI:

10.1088/0004-637X/696/2/2269

Web of Science ID:

ISI:000265762700103

Соавторы в МНС:

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Другие поля

Поле	Значение
Month	MAY 10
Publisher	IOP PUBLISHING LTD
Address	DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
Language	English
Keywords-Plus	DIFFUSIVE SHOCK ACCELERATION; PARTICLE-ACCELERATION; ULTRARELATIVISTIC SHOCKS; JITTER RADIATION; BURST SHOCKS; HIGH-ENERGY; AMPLIFICATION; SIMULATIONS; AFTERGLOWS; TURBULENCE
Research-Areas	Astronomy \& Astrophysics
Web-of-Science-Categories	Astronomy \& Astrophysics
Author-Email	medvedev@ku.edu
Funding-Acknowledgement	NSF {[}AST-0708213]; NASA {[}NNX-08AL39G]; Swift Guest Investigator grant {[}NNX-07AJ50G]; DOE {[}DE-FG02-07ER54940]
Funding-Text	The authors thank colleagues at IKI and RRC ``KI{''} for discussions and Pawan Kumar and the anonymous referee for insightful comments. This work has been supported by NSF grant AST-0708213, NASA ATFP grant NNX-08AL39G, Swift Guest Investigator grant NNX-07AJ50G, and DOE grant DE-FG02-07ER54940.
Number-of-Cited-References	28
Usage-Count-Since-2013	1
Journal-ISO	Astrophys. J.
Doc-Delivery-Number	441IO