Properties of the first-order Fermi acceleration in fast magnetic reconnection driven by turbulence in collisional magnetohydrodynamical flows
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| Author(s): |
del Valle, Maria V.
;
de Gouveia Dal Pino, E. M.
;
Kowal, G.
Total Authors: 3
|
| Document type: | Journal article |
| Source: | Monthly Notices of the Royal Astronomical Society; v. 463, n. 4, p. 4331-4343, DEC 2016. |
| Web of Science Citations: | 8 |
| Abstract | |
Fast magnetic reconnection can occur in different astrophysical sources, producing flare-like emission and particle acceleration. Currently, this process is being studied as an efficient mechanism to accelerate particles via a first-order Fermi process. In this paper, we analyse the acceleration rate and the energy distribution of test particles injected into three-dimensional magnetohydrodynamical (MHD) domains with large-scale current sheets where reconnection is made fast by the presence of turbulence. We study the dependence of the particle acceleration time with the relevant parameters of the embedded turbulence: the Alfven speed V-A, the injection power P-inj and scale k(inj) (k(inj) = 1/l(inj)). We find that the acceleration time follows a power-law dependence with the particle kinetic energy: tacc. Ea, with 0.2 < alpha < 0.6 for a vast range of values of c/V-A similar to 20-1000. The acceleration time decreases with the Alfven speed (and therefore with the reconnection velocity) as expected, having an approximate dependence t(acc) proportional to (V-A/c)(-kappa), with kappa similar to 2.1-2.4 for particles reaching kinetic energies between 1 and 100 m(p)c(2), respectively. Furthermore, we find that the acceleration time is only weakly dependent on the P-inj and l(inj) parameters of the turbulence. The particle spectrum develops a high-energy tail, which can be fitted by a hard power law already in the early times of the acceleration, consistent with the results of kinetic studies of particle acceleration by magnetic reconnection in collisionless plasmas. (AU) | |
| FAPESP's process: | 13/04073-2 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources |
| Grantee: | Grzegorz Kowal |
| Support type: | Research Grants - Young Investigators Grants |
| FAPESP's process: | 09/54006-4 - A computer cluster for the Astronomy Department of the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences and for the Cruzeiro do Sul University Astrophysics Center |
| Grantee: | Elisabete Maria de Gouveia Dal Pino |
| Support type: | Multi-user Equipment Program |
| FAPESP's process: | 13/10559-5 - Investigation of high energy and plasma astrophysics phenomena: theory, numerical simulations, observations, and instrument development for the Cherenkov Telescope Array (CTA) |
| Grantee: | Elisabete Maria de Gouveia Dal Pino |
| Support type: | Research Projects - Thematic Grants |
| FAPESP's process: | 13/18815-0 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources |
| Grantee: | Grzegorz Kowal |
| Support type: | Scholarships in Brazil - Young Researchers |