| Texto completo | |
| Autor(es): |
Lazarian, A.
[1]
;
Vlahos, L.
[2]
;
Kowal, G.
[3]
;
Yan, H.
[4]
;
Beresnyak, A.
[5, 6]
;
de Gouveia Dal Pino, E. M.
[3]
Número total de Autores: 6
|
| Afiliação do(s) autor(es): | [1] Univ Wisconsin, Dept Astron, Madison, WI 53706 - USA
[2] Univ Thessaloniki, Dept Phys, Thessaloniki 54124 - Greece
[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil
[4] Peking Univ, Kavli Inst, Beijing 100871 - Peoples R China
[5] Los Alamos Natl Lab, Los Alamos, NM 87545 - USA
[6] Ruhr Univ Bochum, D-44789 Bochum - Germany
Número total de Afiliações: 6
|
| Tipo de documento: | Artigo de Revisão |
| Fonte: | SPACE SCIENCE REVIEWS; v. 173, n. 1-4, p. 557-622, NOV 2012. |
| Citações Web of Science: | 54 |
| Resumo | |
Turbulence is ubiquitous in astrophysics. It radically changes many astrophysical phenomena, in particular, the propagation and acceleration of cosmic rays. We present the modern understanding of compressible magnetohydrodynamic (MHD) turbulence, in particular its decomposition into Alfv,n, slow and fast modes, discuss the density structure of turbulent subsonic and supersonic media, as well as other relevant regimes of astrophysical turbulence. All this information is essential for understanding the energetic particle acceleration that we discuss further in the review. For instance, we show how fast and slow modes accelerate energetic particles through the second order Fermi acceleration, while density fluctuations generate magnetic fields in pre-shock regions enabling the first order Fermi acceleration of high energy cosmic rays. Very importantly, however, the first order Fermi cosmic ray acceleration is also possible in sites of magnetic reconnection. In the presence of turbulence this reconnection gets fast and we present numerical evidence supporting the predictions of the Lazarian and Vishniac (Astrophys. J. 517:700-718, 1999) model of fast reconnection. The efficiency of this process suggests that magnetic reconnection can release substantial amounts of energy in short periods of time. As the particle tracing numerical simulations show that the particles can be efficiently accelerated during the reconnection, we argue that the process of magnetic reconnection may be much more important for particle acceleration than it is currently accepted. In particular, we discuss the acceleration arising from reconnection as a possible origin of the anomalous cosmic rays measured by Voyagers as well as the origin cosmic ray excess in the direction of Heliotail. (AU) | |
| Processo FAPESP: | 06/50654-3 - Investigação de fenômenos de altas energias e plasmas astrofísicos: teoria, observação e simulações numéricas |
| Beneficiário: | Elisabete Maria de Gouveia Dal Pino |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |
| Processo FAPESP: | 09/50053-8 - Magnetic reconnection and particle acceleration in astrophysical sources and diffuse media |
| Beneficiário: | Grzegorz Kowal |
| Modalidade de apoio: | Bolsas no Brasil - Pós-Doutorado |