Phase Diagram for Magnetic Reconnection in Heliophysical, Astrophysical and Laboratory Plasmas

Physics of Plasmas (Impact Factor: 2.38). 09/2011; 18. DOI: 10.1063/1.3647505
Source: arXiv

ABSTRACT Recent progress in understanding the physics of magnetic reconnection is
conveniently summarized in terms of a phase diagram which organizes the
essential dynamics for a wide variety of applications in heliophysics,
laboratory and astrophysics. The two key dimensionless parameters are the
Lundquist number and the macrosopic system size in units of the ion sound
gyroradius. In addition to the conventional single X-line collisional and
collisionless phases, multiple X-line reconnection phases arise due to the
presence of the plasmoid instability either in collisional and collisionless
current sheets. In particular, there exists a unique phase termed "multiple
X-line hybrid phase" where a hierarchy of collisional islands or plasmoids is
terminated by a collisionless current sheet, resulting in a rapid coupling
between the macroscopic and kinetic scales and a mixture of collisional and
collisionless dynamics. The new phases involving multiple X-lines and
collisionless physics may be important for the emerging applications of
magnetic reconnection to accelerate charged particles beyond their thermal
speeds. A large number of heliophysical and astrophysical plasmas are surveyed
and grouped in the phase diagram: Earth's magnetosphere, solar plasmas
(chromosphere, corona, wind and tachocline), galactic plasmas (molecular
clouds, interstellar media, accretion disks and their coronae, Crab nebula, Sgr
A*, gamma ray bursts, magnetars), extragalactic plasmas (Active Galactic Nuclei
disks and their coronae, galaxy clusters, radio lobes, and extragalactic jets).
Significance of laboratory experiments, including a next generation
reconnection experiment, is also discussed.

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